L8148a 1090 Aquastat Relay Wiring Diagram

Honeywell L8148 Aquastat Controllers
Install, set-up, wire & Troubleshoot L8148 aquastats

• POST a QUESTION or COMMENT about Aquastats controls used on Heating Boilers

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Guide to the Honeywell L8148-series aquastat controls on heating equipment:

Features & applications for the L8148 Aquastat and links to product features & wiring or installation instructions for this and other Honeywell aquastats in current use for oil or gas fired heating equipment as well as some electric boiler equipment.

This article series explains how aquastats work and what the different aquastat controls are, what they do, and how they are set. We define the HI LO and DIFF controls on heating boiler aquastats and explains what they do and how they work. We explain the location and use of the heating boiler reset button found on aquastats.

We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Honeywell L8148 Series Aquastats

Excerpting from Honeywell's manual for this controller,

The L8148 Aquastat® Relays are immersion type hydronic controllers that combine high limit protection with switching relay control of burner and circulator motors.

This Honeywell L8124-series aquastat

• Is used with a 24VAC thermostat
• Provides a high-limit control that is set using a dial with settings in the range of 180F to 240F (82C to 116C) with optional models available with a scale range of 140F to 240F (60C to 116C)
• Uses a differential that is not adjustable
• Includes models supporting addition of a remote low limit temperature control
• Includes models that can operate 2 zone valves or 4 relays such as the Honeywell R8320C. To add additional relays you'll need to add an additional transformer to power them in groups of 4.

[Click to enlarge any image]

Question: L4148e 1257, L4148E 1265 & L4148e 1299 aquastat model differences -> L8148 Aquastat models & manual

2016/11/10 Gary said:

Would like to know what the difference is between the L4148e 1257, L4148E 1265 and the L4148e 1299 model aqua stats. Thanks

Reply: Honeywell L8148-series aquastat model differences

Gary, I have not found an L4148 series such as in your question. Guessing you meant L8148 I note:

Honeywell offers aquastat controllers for both oil and gas fired heating equipment such as hydronic (hot water) heating boilers and water heaters. Both single function (high limit or low limit are separate controls) and multi-function aquastats are provided.

The photo shows a Honeywell L8148E installed on a gas fired heating boiler, courtesy of reader Paul, July 2018. The data tag on the aquastat interior (red arrow) can help identify which version of the L8148 Aquastat is installed.

The Honeywell L8148 series aquastats are used on hydronic heating equipment and use an immersion-well sensor to inform the aquastat of the boiler temperature.

• Honeywell L8148A aquastat switches line voltage to the burner, mounts horizontally, contains a HI limit only, uses a 24VAC thermostat
• Honeywell L8148A-1017 is a horizontal-mount aquastat with a 8deg DIFF control. The controller switches both burner and circulators.
• Honeywell L8148E-1265 is a vertical-mount aquastat with a 15deg DIFF control using a 24VAC transformer. Its high limit opens the burner circuit only. A remote low limit controller can be added.
• Honeywell L8148E-1299 is a vertical-mount aquastat with an 15deg DIFF control and a 50VAC transformer. The limit control can switch both burner and circulator. This unit is designed for a low-voltage burner circuit.
• Honeywell L8148J is a vertical or horizontal-mount aquastat switching a millivolt circuit (such as found on gas control valves)

Often an alternative case is available to convert vertical to horizontal mount for these controllers.

A link to the Installation and Operating guide and cross reference manual from Honeywell is give in the article above.

Diagnostics for the Honeywell L8148 series Aquastat Relays

Question: I shorted some wires and now the aquastat doesn't work - do I need a new one?

2019/11/15 Anon2 said

Hi, I am a homeowner. My Utica boiler has L8148 aquastat.

I was changing the Taco circulator pump and I made a mistake while power is on and I caused a short with line going to taco pump.

Now the aquastat has stopped working after the electric short.

So do I have to replace the aquastat?

Reply: Steps in Troubleshooting the Honeywell L8148 Aquastat & Similar

If you shorted the power wires to any heating control including the Honeywell L8148 Aquastat then it's quite possible that the control has been damaged or destroyed and will need replacement.

Basics of What the Aquastat is Doing

In the U.S. the way heating boilers are wired, the thermostat turns on the circulator pump and it is the temperature in the boiler that separately, by cooling down, tells the Aquastat to Turn on the oil or gas burner to re-heat the boiler.

So our general approach in diagnosing an aquastat is to see if first the thermostat successfully causes the aquastat to turn on the circulator(s) and then to see if second when the boiler is cool or cold whether the aquastat turns on the oil or gas burner.

Watch out: in Canada many heating systems are wired so that the circulator runs all the time during the heating season and the thermostat (and thence the aquastat) turn the boiler on and off. (The reason for this is that in a colder climate house temperature will be kept more even and the risk of frozen heating zone or other pipes is reduced.)

In any event if the L8148 Isn't turning on the circulator (s) and thus is never causing the boiler to run, here are some diagnostic steps, starting with what a homeowner can do and continuing with what a service technician might do.

Homeowner Checks at the Aquastat

1 .Look at the Aquastat for Obvious Damage

Remove the gray cover on the L8148 Aquastat at the boiler. You may need to loosen two screws at two of the cover edges to remove it from the aquastat body. Don't fully remove the screws, just loosen them.

Now DO NOT TOUCH anything inside the aquastat; there is live voltage here including 120VAC that could shock or kill you.

JUST LOOK at the aquastat internals; if you see brown or black burn marks on the circuit board or on any other components the aquastat is probably damaged beyond economical repair.

Above we show brown and overheating marks on the green circuit board of a Honeywell heating system control. This controller was shot and needed to be replaced. If you see burn marks like this don't bother with costly diagnostics.

If there is no obvious visual evidence of a burn-up nor smell of burned electrical components, the heating system and possibly even the control still needs diagnostic service and repair.

2. Check that the thermostats are calling for heat

While you listen at and look at the aquastat, have an accomplice turn all of your thermostats all the way up.

You should hear a "click" at the aquastat and if you were watching closely, the aquastat relay switch may have "closed" by clicking "down" to turn on the circulator pump(s).

If not the call for heat isn't being relayed to the circulator(s).

3. Check that the Aquastat electrical circuit power is on

Check at your electrical panel for the fuse or circuit breaker powering your heating system - be sure that electrical power is on.

If in doubt, switch the breaker fully to OFF position then turn it back on, or replace the fuse (if it's a fuse pane) with a new one.

Watch out: do not remove the panel or fuse box cover and don't stick a finger or any tool inside the electrical panel as you could be shocked or killed.

Heating Service Technician Aquastat Diagnosis & Repair Steps

Call your heating service company. Most heating service techs will simply replace a bad aquastat even though a new Honeywell L8148 is costly - about $175. U.S. - because their time to run detailed diagnostics is expensive too.

However a service technician might elect to try some of the following steps to be sure that her diagnosis of a bad Aquastat L8148 is the right guess.

In the text below "you" refers to "the service technician, not the homeowner.

At the L8148 Aquastat the technician may check for supply voltage and may check the thermostat circuit voltage using a DMM or VOM as follows:

Watch out: Safety details are at DMMs VOMs SAFE USE OF

1. Check that the thermostat(s) are calling for heat

And check that and that room temperature is below the set temp in the thermostat. (I turn the TTs all the way up - and leave my truck keys atop one of them so I don't forget to set them back to the homeowner setting before I leave.)

2. Check for line voltage at the power terminals in the Aquastat

There should be 120VAC at terminals L1 and L2 where by convention L1 is the "hot" or "black" wire and L2 the neutral or "white" wire.

If there is no voltage supplied to the aquastat then the problem begins at the electrical panel - blown fuse, tripped breaker, or in a wiring short or disconnect between the electrical panel and the electrical box powering the aquastat and heating boiler or furnace.

[Click to enlarge any image]

If there is voltage then let's be sure the thermostat's call for heat shows up at the Aquastat

3. Check the thermostat wires

On the Honeywell L8148A Aquastat relay these two terminals to which the two thermostat wires connect are simply marked "THERMOSTAT" and are found next to the transformer in the control.

On the Honeywell L8148E Aquastat (used to control separate, multiple zone valves or zone circulator relay switches) the two thermostat wires will be connected to terminals marked T and TV.

• Call for heat, no voltage: Turn the thermostat(s) all the way UP and confirm that room temperature is below the thermostat SET temperature; the thermostat should call for heat.

  If there is NO voltage at the TT wires at the Aquastat and the Wall Thermostat IS calling for heat then it is possible that there is a break in the thermostat wiring.

• No call for heat, Voltage detected: Turn the thermostat(s) all the way DOWN and confirm that room temperature is above the thermostat SET temperature; the thermostat should not be calling for heat.

  If there IS voltage at the TT wires at the Aquastat when the thermostat IS NOT calling for heat then the wires are shorted together somewhere in their route.

If you need to rule out the thermostat itself as the problem, simply remove the wall thermostat and jump or tie together the two heat wires - usually red and white - to call for heat. This is the same as turning the thermostat all the way up.

Details of troubleshooting thermostats and thermostat wiring are at

• THERMOSTAT WON'T TURN OFF
• THERMOSTAT WON'T TURN ON
• LOW VOLTAGE WIRING SYSTEM COMPONENTS
• LOW VOLTAGE LIGHTING & CONTROL RELAYS
• LOW VOLTAGE TRANSFORMERS, TRANSVERTERS, CONVERTERS
• LOW VOLTAGE TRANSFORMER, TRANSVERTER DIAGNOSIS
• LOW VOLTAGE TRANSFORMER TEST

Watch out: Before leaving the job don't forget to restore the thermostat wires to the terminals wherever you've disconnected them.

If you've ruled out a problem at the thermostat itself and at the thermostat wires, continue below.

4. Check the Aquastat Relay Switch & Voltage at Circulator Terminals C1 - C2

On a call for heat the relay switch should click and should "close" or be in the "down" position on the circuit board.

At the Aquastat, at terminals C1 and C2 check for line voltage (120VAC) supplied to the circulator pump.

Watch out: I have seen techs just push down the relay to confirm that voltage is then produced and the circulator pump runs, but if the thermostat is calling for heat and the relay doesn't close on its own then either the control board or the relay is bad.

Watch out: there is live voltage here. You can be shocked or killed.

If the relay closes as it should and there is voltage at the circulator terminals then the problem is downstream from the aquastat.

5. Check thermostat wires at zone valves or zone circulator relays

If the heating system uses multiple zones each will be controlled by a zone valve (that opens or closes a loop of heating water pipe and that turns a common circulator pump on)

OR each zone may be controlled by individual heating zone circulator pumps that are in turn switched on or off by a separate heating zone circulator relay control.

When a thermostat controlling an individual heating zone calls for heat in this design either an end switch on the zone valve OR a relay switch in the circulator relay turns on the circulator for that zone.

At the zone valve or at the circulator relay control check the thermostat terminals for 24VAC at that control and check line voltage at the common circulator or at the line voltage terminals in the circulator relay if one is used.

On a zone valve system if the zone valve doesn't operate when there is voltage across the thermostat wire terminals (24VAC) at the zone valve, then the problem is at the valve - the control head itself, or the actual hot water line valve (could be jammed).

If there's no voltage at the TT terminals on the zone valve then we're back to diagnosing the thermostat itself or the thermostat wires or the low voltage transformer - topics we listed earlier.

On a multiple circulator system if the circulator relay doesn't close when there is voltage across the thermostat wire terminals (24VAC) at the circulator relay, then the problem is a bad relay or relay control board.

If the circulator relay closes and produces line voltage at the circulator terminals C1 C2 in the relay, but the circulator doesn't run then the problem is in the circulator or circulator power circuit.

If the relay has closed and there is voltage on the C1 C2 terminals but the circulator(s) won't run then

see CIRCULATOR PUMP WON'T START

6. Canadian systems: circulators always on:

At the L8184 Aquastat check for line voltage to the burner - Terminals B1 B2 (or between L1 and B2 on some models.)

When the thermostat is calling for heat the burner will nevertheless remain OFF until the boiler temperature falls to or below the CUT-IN temperature on the limit control on the Aquastat (typically 15 deg. below the HI LIMIT) so you may need to run heat in the building long enough to cool down the boiler to see the burner turn on.

Once the boiler temperature drops below the cut-in the burner should run.

[Click to enlarge any image]

At AQUASTAT CONTROLS, our home page for this control, we explain in more detail, from which I excerpt:

The boiler Cut-on temperature or burner turn-on temperature for the boiler, AS LONG AS THE THERMOSTAT IS CALLING FOR HEAT is fixed at 10 deg. F. below wherever the HI is set. (Green in our edited version of Honeywell's drawing.) On some controls this hard-wired fixed gap may be 15 °F.

On some controls this hard-wired fixed gap may be 15 °F.

IF voltage is being supplied to the burner (to turn it on) and the burner never runs, the the problem is probably not the aquastat but the burner itself, such as a burner that has tripped off a cad cell relay or other safety control.

or on an LP or natural gas burner system the burner is turned on by a low voltage circuit

Gas burners on a heating boiler typically used a Honeywell L814B like the L8148E1257/B that has an isolated burner circuit typically used with powerpile systems. That aquastat is replaced by the L8148J1009/U Aquastat Relay, a universal replacement offering 120 – 240 F range with 8 degree F fixed differential, low volt/millivolt

See gas fired boiler troubleshooting details starting at

DIAGNOSE & FIX HEATING PROBLEMS-BOILER  at https://inspectapedia.com/heat/Heating-Boiler-Diagnosis.php

Same diagnostics and same electrocution shock warnings as above.

Manuals for the Honeywell L8148 series Aquastat Relays

• Honeywell L8148A,E,J AQUASTAT® RELAY SERIES MANUAL (Controllers) [PDF] (2001) product data & installation, operation manual including L8148 wiring diagrams
• Honeywell L8148A E J AQUASTAT RELAYS MANUAL [PDF] (2002)
  Description Excerpts:
  
  The L8148A,E,J Aquastat Relays are immersion-type controllers for use with forced hydronic heating systems.

  The combination high limit and intermediate switching relay works with a low voltage (24V) thermostat to control burner and circulator circuits.

  A call for heat by the thermostat starts both the burner and the circulator. When boiler-water temperature exceeds the high-limit settings, the burner circuit is broken; the circulator continues to operate during the thermostat call for heat.

  The L8148A controls line-voltage burner circuits;

  The L8148E is available with a plug and 50 VA transformer for use with Honeywell Smart Valve SV9500/SV9600.

  The L8148J controls millivoltage burner circuits.

  The L8148E,J control low-voltage burner circuits

  The L8148E,J can power valves in multizone systems.

  The L8148A,E,J have provisions for adding low-limit controllers;

  
  All models control line-voltage circulator circuits.
• Note: As their numbers can be confusing and are sometimes transposed, don't confuse the Honeywell L8148 -series Aquastats with the Honeywell R8184 G,N or R4194 D Protectorelay oil burner controls (cad cell flame sensor control).

Reader Comments & Q&A

Don

Having replaced the aquastat and noting that the noise has stopped sounds reasonable and might well confirm our guess at a bad aquastat relay. Better to fix a problem like this before it fails hard and leaves your building with no heat in freezing weather.

While it's technically possible to do so, we will virtually never find a heating service tech trying to replace just the relay on the control board of a failed HVAC control; the time and trouble and risks just don't add up for the service company; it's quicker and easier to replace the whole control.

@Don Hardcastle, they replaced the Aquastat, even though it was new, and the noise seems to have disappeared.

@Don Hardcastle,

A buzzing aquastat is usually a failing relay or on occasion a failing low voltage transformer. That's disappointing on a new aquastat - so check for a bad transformer first.

See details about buzzing aquastats and relays and our suggestions at

AQUASTAT TROUBLESHOOTING https://inspectapedia.com/heat/Aquastat_Diagnosis_Repair.php

and at

HEATING SYSTEM BUZZING NOISE https://inspectapedia.com/heat/Heater-Buzzing-Noise.php

and don't hesitate to ask follow-up questions as needed;

please also keep me posted on your repair.

Also see WHITE RODGERS CONTROLS - all

My Aquastat L8148A sometimes makes a loud humming type sound. It appears to be coming from the switch relay. When I push the relay the noise stops.

The plumbing company wants to replace the White Rodgers zone valves with Honeywell zone valves.

They think that is the solution to the noise. The noise occurs when any of the 4 zone valves comes on. One of the zone valves is only a couple of months old. The Aquastat is only a couple months old also.

@MICHAEL, sometimes when you have a known good gas valve but the pilot won't stay lit, AND if you're sure the pilot assembly is also new and good, And the problem is that the sensor is not placed properly and the flame or That the other end of the thermocouple is not fully seated in the gas valve. I've been fooled on this myself a couple of times. I found if I didn't screw the little fitting sufficiently tightly into the bottom of the gas valve the pilot never opened the valve.

I have a slant fin hot water furnace. I have had continued issues with my pilot going out. I replaced the honeywell thermocouple on a number of occasions with an additional honeywell brand thermocouple. When the burner does run the gas flame height is normal and the gas pressure appears good.

I then assumed it was the pilot mechanism in a defective gas valve that was the problem. I replaced the gas valve with a new valve. The pilot light continues to go out periodically. It is a mystery. Can I rule out any connection between the pilot failing and the aquastat control for the burner? Thank

@Ken, Nice; I'd like to see the diagram; you can use the "Add Image" button if you want to try posting that.

1k ad 2k are relays. The expanded circuit diagram was in my boiler instruction manual

Lc

I can only guess with just a tiny bit of information in your note but it's possible that your aquastat relay has burned contact super that the relay itself has failed. If after checking all of the electrical connections to be sure there's nothing simple like a loose wire, or a bad thermostat, you may have to replace the relay or the control itself.

I have an honeywell aquastat relay l8148e and the relay switch won't turn on the ignitor. I have to click it and then it turns the ignitor on. What can I do to fix the problem?

I have a resideo L8148j1009 which is replacing a Honeywell aquastat. I have wired it in and can not get the contactor switch to pull in or burner to light. what am I doing wrong ?

Most technicians just replace the control entirely rather than attempting a field repair. I think they figured that they had a labor and the risk of an unsuccessful repair calculate out to that conclusion.

Is it better to replace the whole circular relay or can i do it peice by peice and wich would be cheaper

Grn

Take a look at NEST THERMOSTAT INSTALLATION & WIRING https://inspectapedia.com/heat/Nest_Thermostat_Wiring.php

and you'll see several examples of smart thermostats that I've installed that needed only the two original R and W themostat wires at the old room thermostat.

And at THERMOSTAT WIRE CONNECTIONS - https://inspectapedia.com/heat/Thermostat_Wiring_Instructions.php we cover how to wire up all types and brands of heating & cooling thermostats- how to wire up all types and brands of heating & cooling thermostats

such as THERMOSTAT WIRE CONNECTIONS - 2-WIRE like the T87F https://inspectapedia.com/heat/Thermostat_Wiring_Instructions.php#2w

To provide a C-wire for you rnew thermostat where none is found at your old wall thermostat, see the procedures we describe

at COMMON WIRE at THERMOSTATS

I am considering an upgrade to a Smart Thermostat designed for Hot Water Boilers. My boiler is controlled by the L8148E model Aquastat which has a 2-wire control up to an old "not-so-smart" digital thermostat that runs on 2 AA batteries. All of the smart thermostats require a C-wire. Since there is no terminal on the Aquastat labeled Common, How or where do I run the new wire from?

OK still I'm concerned about those overheated wires; And there should not be more than 24VAC across those terminals.

Watch out: if you are not familiar with safe and proper electrical wiring you could get shocked or start a fire. - as I warn everyone.

I jut wired it based on the one I removed. Same red wires with black spots on the one that had been running for years.

Crystal:

Watch out: I see burned wires at the top of your controls, those two red wires

- I suspect there is a wiring error or a voltage error at this aquastat, and it's possible that the control has been damaged as a result.

Those wires are connected to what are supposed to be the Thermostat terminals, normally low-voltage 24VAC - so I think something's wrong here.

Who wired this up for you?

See the HONEYWELL L8148 AQUASTAT WIRING INSTRUCTIONS given as a PDF found linked-to in our section title

Manuals for the Honeywell L8148 series Aquastat Relays

near the end of the article above, and also note this excerpt - below

Hi everyone,

I just installed a new AquatatL8418J on my boiler (along with a new expansion tank, pressure relieve valve nut and automatic pressure vent) and I can't get heat.

The boiler turns on, the water heats up but I can't get it to send out the water when the thermostats call for it.

I have 2 zones with separate thermostats and it isn't working for either so I am fairly sure it is not the thermostats or the zone valves causing the problem.

I labeled all my wires and rewired it based on the labels but I am wondering if I messed up.

I am thinking it is the T and TV connections that would be causing this particular issue but I don't know enough about it to be sure.

For fun both wires are red so its difficult to tell which is which and they both lead out to red wires on the zone valve motor boxes.

The relay doesn't engage when the thermostat is turned on, and if I manually press the relay the pump seems to come on so I think that rules out the pump as the issue either.

Side note, the replacement was technically L8148J1009 and my original one did not have 1009 on the model number but they looked exactly alike so I was guessing they updated the model number in the decades since the original was installed.
Thanks for any help you can give, its getting cold tonight :)

Ed

First check the settings in your control to be sure that your high limit is set below 200 degrees. Make sure that the low limit is at least 20 degrees lower than that.

If the settings are correct then I suspect either that the sensor in the sensor well is not correctly sensing boiler temperature or has failed, or the control itself has failed. Those are repairs that can be done by your heating service tech

I have an aquastat L8148E and when I call for heat it fires up and when it reaches set temperature the circulator pumps keep running and the temp just keeps rising until I have to turn the power switch off because it gets like a sauna? Please help

Angelina

In the ARTICLE INDEX links or at CONTINUE READING near the end of this page please see the live link

AQUASTAT L6006A HONEYWELL GUIDE - for proper wiring instructions for that limit control.

Typically R and W are the two thermostat wire connecrtions

Watch out: if you are not trained on safe and proper electrical wiring you could be shocked or killed or could damage the equipment or cause a fire.

When wiring a hi limit aquastat to my gas boiler valve do I use the r,w terminal?

Or r,b?

Also the line feeds from a transformer, to gas valve, to L4006A thermostat then to the hi limit( L6006C)

If the relay won't pull in when voltage is applied to the terminals then it is probably defective (unusual in new equipment)

Check first for a wiring error.

Don't forget to confirm that the problem isn't an open or broken thermostat wire

Bought a new honeywell aqua stat L814J1009. The relay is not pulling in?

Travis

I suspect the problem is in a connection or wire right on the aquastat control board or relay.

I'm assuming that you've checked or can check that
- the supply voltage to your building is around 120VAC at the same time that you are seeing 90VAC at the aquastat B1 B2 (burner) terminals

- there is no problem with under-sized wiring

- the circuit itself is not overloaded

- there are no obvious loose wiring connections

Largely, my aquastat seems to be operating in accordance with what is described above, but for the fact that I get a 90 VAC reading between B1 and B2.

I have 117 VAC between L1 & L2, and interestingly enough that same 117 VAC between L2 (L2 as common) and B1 (boiler line output).

The conclusion is there is some voltage drop... having 90 VAC on the boiler supply output (B1/B2)

I assume is not enough to fire the boiler... not sure on that. Can anyone confirm? Any ideas what would be causing the voltage drop?

Thanks for the follow-up; do keep us posted.

Yes it's disappointing that as business models shift to very high volumes customer service is on the wane.

Thanks for the prompt reply Dan. Honeywell doesn't seem to have the chat option anymore, so I guess I'll call their 800 support number this coming week.

I'll come back & let you know how I make out and what they say.

Gee Jim I hope your confidence in me will increase when I admit I don't know something. Rather than guess I'd feel safer if we (that really means you) give Honeywell a call or chat directly with this schematic and question. [Click to enlarge any image]

Honeywell Technical Support: 1-877-841-2840 or (800) 645-7492 or for international customers 00 1 480-353-3020

Website: www.honeywellaidc.com/working-with-us/contact-technical-support

Honeywell Chat:
honeywell.com/Pages/contact-us.aspx

Honeywell Email:
sales@HoneywellStore.com

Corporate Office Address:
Honeywell International
101 Columbia Road Mailstop - M6/LM
Morristown , NJ 07962
USA

let me know how you're treated and what you're told as that will surely help other readers.

In general, at the zone valve the thermostat operates the valve from the two T- terminals (not polarized) and the zone motor's end-switch will turn on the circulator wired to two C terminals.

I don't know, without more reading, what the 1K1 & 1K3 are.

I find myself re-wiring my Honetwell zone valves/Honeywell Aquastat/and thermostat wiring at my gas boiler furnace. (It's a long story!).

My burner uses a low voltage (24v AC) gas valve, and it is a 4 zone valve system with 2 additional 24v AC transformers for the thermostats and Honeywell zone valves.

I also have 3 Honeywell V8043E and 1 V8043F valves. I'm an ex-auto tech and trainer so I "get" DC schematics, and have done a fair amount of 110/220 AC electrical wiring & fixes to be knowledgeable but by no means an authority.

I find the Honeywell schematics to be very helpful, but at the same time lacking and since none of the diagrams in either the Aquastat or zone valve sheets matched my system,

I re-drew what I thought my system schematic should look like, in a format that I was familiar with. Can someone have a look to see if what I have drawn is theoretically correct? The two things I had the most problem with were properly

isolating the 3 AC transformer circuits, and

which 2 Aquastat terminals on the AC circuit going to the zone end switches and back to close the burner & circulator relay (specifically TV and T- Does it matter if what I show connected to T were connected to either W or TP?)

Thanks to anyone having a look at my diagram and offering advice or corrections.

One last puzzle to me .. what the heck are the 1K2 & 1K3 items on the Honeywell sheets? Switches or capacitors?

Image lost, our foul-up; please re-post it if you can.

Thank you for your generous words Fred and for the posting which will certainly help other readers.

First off, THANK YOU for this awesome website! It was very helpful in diagnosing an intermittent problem with my L8148 1090 Aquastat. The Aquastat was not always firing the burner correctly. I'll describe it here, in case anyone in the future has a similar issue: It would initially fire correctly, but sometimes cut out at a mid-range temperature say 120F or so, or sometimes not re-fire after reaching the high-temp limit and then cooling past the normal low "limit". Hitting the side of the box, or sometimes carefully pushing on areas of the board, would then cause the burner to fire. There are videos on YouTube stating that on these models, some solder joints on the backside might go bad. I believe that was the case with mine. Replacing the Aquastat fixed the issue. I inspected the back of the board of the old one, and there were no obvious bad solders, but I'm still pretty confident that was the culprit. Thanks for this page. It gave me a much better understanding of the function and proper operation of the Aquastat.

Right its AC

AC Voltage has no "polarity" - so you can connect either wire to either side of the control.

Technical note: this is even true right at the low-voltage transformer. The high and low voltage sides within the transformer are isolated from one another. The low-voltage transformer used on heating and ventilating equipment and controls is an alternating-current or "AC" device.

Details are at LOW VOLTAGE BUILDING WIRING and at other links in our discussion, given below.

Danjoe, the low voltage transformer that I would like to use is that which is built into the L8148A boiler aquastat which sends 24 VAC to the T-T terminals. As you are aware, Honeywell doesn't label them R-W so I don't know how to tell which T is R and which is W, if it even matters since AC goes both ways.

Maybe I can't use the aquastat transformer because it seems that connecting the R & W lwco wires to T-T would, in effect, complete the circuit & trip the relay to run the boiler & circulator. With a separate 24 VAC power supply, wiring the Normally Closed lwco switch yellow wires in series with the thermostat makes perfect sense. What do you think? Have a Happy Turkey day.

Thanks for the follow-up, Tight.

I think our confusion (mine perhaps) with your question is about just where we're obtaining the two thermostat wires.

at THERMOSTAT WIRING HONEYWELL https://inspectapedia.com/heat/Honeywell_Thermostat_Wiring_Guide.php

we describe a simple two-wire thermostat wiring hook-up

On a simple traditional thermostat such as the Honeywell T87 the Red wire is the lead coming to the thermostat from the heater.

IN THE THERMOSTAT this wire connects to the "R" terminal.

On that same thermostat the White wire coming to the thermostat from the heater connects to the W terminal IN THE THERMOSTAT.

The thermostat itself is simply operating as an on-off switch that, on a call for heat, joins R to W to turn on the heater.

Now

Let's back up to the low voltage transformer in, on, or near your heating equipment. At the transformer itself the R and W wires originate.

At LOW VOLTAGE TRANSFORMER TEST

we describe how one can use a VOM or DMM to identify which of those two R and W wires is which.

Perhaps that will help.

I get that but I just don't want to connect the lwco wires for 24vac power incorrectly (as you said, it might not matter). The attached image (if it's visible) should explain. Thanks again.

[Click to enlarge any image]

Tight

At the control the two thermostat wires that reach that point are acting as an on-off switch.

So it doesn't matter which wire connects to which of the two T Terminals

The L8148A 24 VAC terminals are both labelled "T". Shouldn't one be Hot/Red and the other Common? I ask because I'm trying to use this as a power source for a GuardDog RB-24 low water cut-off. It wants the red wire to go t 24 V+ and the white wire to Common. I don't want to fry it. Thanks.

Steps in Troubleshooting the Honeywell L8148 Aquastat

If you shorted the power wires to any heating control including the Honeywell L8148 Aquastat then it's quite possible that the control has been damaged or destroyed and will need replacement.

In any event if the L8148 Isn't turning on the circulator (s) and thus is never causing the boiler to run, here are some diagnostic steps starting with what a homeowner can do and continuing with what a service technician might do.

Please now find your question and my very detailed reply giving some step by step suggestions in the article above on this page starting t

AQUASTAT L8148 CONTROL DIAGNOSTICS

Hi,
I am a homeowner. My Utica boiler has L8148 aquastat. I was changing the taco pump and I made a mistake while power is on and I caused a short with line going to taco pump. And aquastat stop working after electric short. So do I have to replace the aquastat?

Anon

I'd start diagnosis at

NO HEAT - BOILER https://inspectapedia.com/heat/Heating-Boiler-Diagnosis.php

or see

CIRCULATOR PUMP WON'T START

I had a problem with my heat not working on 1 st floor I replaced my circulator pump thinking that was the problem however it was not I hooked up the new circulator pump and it did not work but it works when i plug it into an extension cord so I believe it is something wrong with my aquastat relay differential. can you help me mine is an oil boiler

Louis

If a gas burner won't ignite

- confirm that there's fuel

- check for a tripped flue gas spill switch sensor - some have to be manually re-set

- With electronic ignition there's no standing pilot but you could have a bad igniter or bad igniter wiring. If the igniter doesn't spark on a call for heat that's what I suspect.

- if those are not the issue the eliminate the thermostat from the circuit by disconnecting it at the aquastat and try jumping the two

Thermostat terminals - If the valve opens and burners ignite we have isolated the issue to the thermostat wiring or thermostat itself

Heater will not fireup has electric startcan you helpgot new sensor and pilot

Well that's certainly a Honeywell L8148G Aquastat

for which the manual is at

inspectapedia.com/heat/Honeywell-R8184G-N-4184D-Manual.pdf

Indeed relay and control numbers form a sea of characters upon which anyone asail can easily lose one's bearing.

Clarifying, the L8148-series is a aquastat control, monitoring boiler temperature and controlling the burner. Hence the word "Aqua" (water) in the name.

Honeywell does produce zone switching relays such as the

Honeywell R8146 series such as the L8148J1009/U

The "U" in the name stands for "Universal" as this relay was designed to replace a long list of older 8148 models such as the

Apologies for my ignorance. I believe I have a L8148E Aquistat. The added zone relay is labeled Aguistat relay type L8148G. The covers were switched. Reading glasses and a good light helped.

I did find this schematic inside the cover.

IMAGE LOST by older version of Clark Van Oyen's useful Comments code - now fixed. Please re-post the image if you can. Sorry. Mod.

A honeywell R8148G manual is here:

www.inspectapedia.com/heat/Honeywell-R8184G-N-4184D-Manual.pdf

or use the CONTACT link at page top or bottom and I can email you that PDF

It's a big 5MB file so give it a moment to load before you try downloading it.

If your control is in fact an "L" 8184G please post here a photo of the control cover, label, and interior as photos that you can include using the "Add Image" button (one per comment) and I'll check further.

I have a Honeywell L8148G Aquastat Relay. This is a model "G". Is there a manual or any diagrams for this model? I can't find one.

...

Continue reading at AQUASTAT L8148 HONEYWELL DIAGNOSIS, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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AQUASTAT L8148 CONTROL at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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