Guide to the Honeywell (now Resideo) 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.

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 / Resideo 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]

This page describes the features of the L8148 and provides links to installation manuals for its various models.

For troubleshooting this control see our sister article

at AQUASTAT L8148 AQUASTAT INSTALLATION

Note: In 2018 Honeywell announced that Resideo would be the corporate name of the Honeywell Homes product portfolio and ADI global distribution businesses when they became a stand-alone, publicly traded company following completion of a spin that was expected by the end of 2018.

Honeywell L8148-series aquastat model differences

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.
  
  This control model has no adjustable DIFF or differential control. The control will turn on both burner and circulator on a call for heat at the thermostat, and will turn the burner OFF when the boiler temperature exceeds the HI or high limit.
• 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 references section.

[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.

See details

at OIL BURNER WONT RUN 

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

• Resideo L8148A,E,J AQUASTAT® RELAYS PRODUCT DATA [PDF] (2021) Resideo Technologies, Inc. 1985 Douglas Drive North, Golden Valley, MN 55422 1-800-468-1502 60-2278—10 M.S. Rev. 05-21 - retrieved 2022/11/25, original source: https://digitalassets.resideo.com/damroot/Original/10013/60-2278.pdf
  
  Note: "Resideo" is the current heating control product line name for controls previously sold under the product line name "Honeywell". Here we include both current Resideo manuals and older Honeywell manuals.
  
  Excerpts:
  
  The L8148 Aquastat® Relays are immersion type hydronic controllers that combine high limit protection with switching relay control of burner and circulator motors.
  
  All models are used with a 24 Vac thermostat.
  
  • Models include special terminals for adding remote, low limit temperature control.
  
  • L8148E,J have terminals for adding zone valve system wiring.
  
  • L8148E models are available with plug for connecting Aquastat Relay directly to D892/M892 Vent Dampers.
  
  • All devices include transformer to provide power for the low voltage control circuit. Different models provide switching of line, low, or millivoltage burner circuit.
  
  • Case available for horizontal or vertical mounting.
  
  • Combinations of two insulation and two insertion well lengths are available.
• RESIDEO L8148A,E,J AQUSTAT® RELAYS INSTALLATION INSTRUCTIONS [PDF] (2020) installation manual for the L8148 aquastat, current versions. 95-6933-12 M.S. Rev. 05-20
• HONEYWELL L8148A,E,J AQUASTAT RELAYS INSTALLATION INSTRUCTIONS [PDF] (2002) Honeywell Inc.
• 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.
• Honeywell L8148A,E,J AQUASTAT® RELAY SERIES MANUAL (Controllers) [PDF] (2001) product data & installation, operation manual including L8148 wiring diagrams

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).

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

What is the differential on a high limit honeywell L8148A aquastat

What is the differential on a high limit honeywell L8148A aquastat - On 2022-11-24 by phil

Reply by InspectApedia (Editor) - 15 degF. down to 5 degF for Aquastats that have Differential that is hard-wired, i.e. not adjustable

@phil,

Honeywell describes the L8148A control (without mentioning a differential):

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.

You would think that means that at ANY temperature more than just a few degrees below the HI (enough to avoid short cycling) the burner will start.

I've read through generations of L8148 documentation without finding a number. I think that's no accident as it may not be precise.

So the answer is: there is on single right answer as the company changed its fixed differential gap over the years, (oftenj ust 5 degF)

A reasonable guess is that depending on your aquastat's model and age if the model is using a fixed or hard-wired differential it will be 5 degF. to 15 degF - remember ythis is just for a control that has no adjustable differential and no standard LO limit control (though some models have provision for adding a LO limit).

The Standard Scale Range: 180°F to 240°F (82°C to 116°C).

The optional operating range is 140°F to 240°F (60°C to 116°C)

If you don't have it, you can download the manual for your L8148 aquastat

at

HONEYWELL L8148A,E,J AQUASTAT® RELAYS (Controllers), product data & installation, operation manual including L8148 wiring diagrams [PDF]

How to add a line voltage relay if using a 24VAC controller to turn on 120V equipment

I have a L8148E 1265 that i want to put on my boiler. The problem is i have a blower that needs to be 120v.

On the old control board L8148A the blower was wired to the B1 and B2 terminals witch on the L8148A is 120v but on the new control the B1 and B2 terminals are only 24v. How can i use this board to work and power my blower on?

I'll pay someone to help me figure out how to make this work On 2022-11-24 by corey

Reply by InspectApedia (Editor) -

@corey,

I think that if you want to use that new 24VAC version of the control you would need to add a line-voltage relay - as an additional control.

Then the Blower is run at 120VAC connected to the 120V side of the line voltage relay

and the relay is operated by the 24VAC circuit that is connected to the L8148E

An example would be to use the

Switching Relay w/ Internal Transformer DPST Line Voltage Relays
Brand:
Resideo
SKU:
R845A1030

Let us know if you need more help.

Of course you can always call your heating service company and ask for an experienced technician to install the relay for you.

Why is the B1 terminal different from the other screw terminals on the L8148 Aquastat?

Why is the B1 terminal different from the other screw terminals? On 2022-10-07 by Anonymous

Reply by InspectApedia-911 (mod) - B2 is a terminal intended to be connected to by a copper wire looped end, while B1 is intended to be connected to by a tab type connector that is in turn crimp-connected to the control wire.

@Anonymous,

Thank you that's a great question.

The difference between those two burner control terminals on the aquastat is that the B2 is a terminal intended to be connected to by a copper wire looped end, while B1 is intended to be connected to by a tab type connector that is in turn crimp-connected to the control wire.

Also take a look at the wiring diagrams in the instruction PDFs that we provide on this page and you will see how B1 and B2 terminals are used differently.

 

Can I test a Honeywell 8148 Aquastate before installing it?

Is it possible to test a honeywell l8148a1017 aquastat ,to be sure it is in working condition, before you install it? - On 2022-04-18 by Rick Lambos

Reply by Inspectapedia Com Moderator - how can I test Honeywell Aquastat before installation? - No, bench testing is impractical: need the temp sensor working

@Rick Lambos,

That's a great question, thanks.

At AQUASTAT TROUBLESHOOTING

We list the standard aquastat test procedure steps,

but

I don't know of a complete BENCH-TEST procedure for a brand new aquastat - not one that could be completed on a typical test bench; you'd need to be able to expose the temperature sensing bulb to the range of temps expected at the boiler for a complete test.

Keep in mind that the aquastsat is designed to respond to the temperature sensed by its sensor bulb that's mounted in a sensor well on the heating boiler.

So in theory you could immerse your sensor in water of a known temperature and then use a VOM or DMM to see that the aquastat turns on the circulator as expected.

But in my opinion it's both impractical and unnecessary.

I think the failure rate of brand new aquastats due to factory defects must be extremely small.

Buying a used control is always a pig in a poke, but there I would inspect the device for evidence of water leaks into the control, for corrosion, and for signs of overheating on the circuit board - visual inspection only.

 

How do I keep the circulator pump on all the time on my heating boiler?

If I want to have the boiler pump on 24/7 while the L8148A is powered. Can the high/low limiter controler do that? - On 2022-03-03 by Paul Tesolin

Reply by Inspectapedia Com Moderator

@Paul Tesolin,

In Canada it's common practice for the circulator to run 24/7 all during the heating season.

In that set-up the circulator is wired-direct from an on-off switch, not from the aquastat, and ALL the aquastat does is turn on the boiler when the boiler temperature drops.

How to connect a WYZE C-wire for a thermostat connection to a honewell aquastat L8148E box

how do i connect a wyze C-wire for a thermostat connection to a honewell aquastat L8148E box? - On 2022-02-18 by jp -

Reply by Inspectapedia Com Moderator - how do i connect a wyze C-wire for a thermostat connection to a honewell aquastat L8148E box?

@jp,

The C wire is Common or a voltage supply to the thermostat.

The aquastat terminals don't provide that wire. You'd need to obtain C from the thermostat's 24VAC power transformer.

Or you can plug in a local transformer and run a wire up to the thermostat directly - that's the simplest solution.

See details

at COMMON WIRE at THERMOSTATS

Why did Honeywell discontinue the L8148A1090 aquastat ?

why did Honeywell discontinue the L8148A1090 aquastat ? the cross reference is the L8148A1017 which is a "cold start" stat. On 2022-02-10 by Bruce -

Reply by Inspectapedia Com Moderator

@Bruce,

Fair question and I don't have an authoritative answer other than to trust the Honeywell engineers.

But I think that the company wanted to simplify the product line by making a more universal aquastat; that makes repair parts stocking at the local vendor easier too.

Check the L8148A1017 IO manual for wiring and switch opinions.

See AQUASTAT L7224U UNIVERSAL

 

Which model number L8148 Do I neeed?

@Inspectapedia Com Moderator,

I am looking for an Aquastat relay with 24 volt on the burner circuit I don't need any damper control just straight-up 24 volt and 110 for the circulator does anyone know the model number for this - On 2022-01-20 by Anonymous

On 2022-01-20 by Inspectapedia Com Moderator -

@Anonymous,

Take a look in the L8148 manuals / instructions [PDF files] given on this page and you'll see the 24VAC rating for some models of the control - eg. in the table below excerpted from the L9148 instructions.

8148J Aquastat relay differential went from 20 degrees to 5 degrees over the years.

On my SB Smith boiler, my L8148J Aquastat relay differential went from 20 degrees to 5 degrees over the years. I read the low limit is not adjustable. Does that mean my probe or my relay is bad? High limit works fine at 180 degrees. Shuts off fine with temp. satisfied. Drops down with circ pumps running to 175 degrees and fires up the boiler again. Not 160 degrees.

Also after looking at the literature on your site for my Aquastat relay, how do I know what my factory differential setting is? I'll try to keep searching. Thanks - On 2021-10-19 by Chuck S L

Reply by inspectapedia.com.moderator -Factory differential settings on Aquastats

@Chuck S,

Factory setting is typically 180 for the HI and the LO will be set to at least 20 degrees below that, so 160 or less, and the DIF may be anywhere in this range.

You'll see those details in a thorough explanation in the article above on this page

It's true that there are some controls in which the low is fixed at 20 degrees below the high setting.

Keep in mind that this is not lab grade equipment and that the actual measured temperature may vary a bit from the setting on the control. It's also the case that the boiler gauge itself is not lab grade and it may not be precise either.

How to add a Honeywell HPZC105 to a boiler

Hi. I'm trying to add a Honeywell HPZC105 to my boiler. But I can't find anything anywhere that discusses the connections between the controller and aquastat.

Can you point me in the right direction. My aquastat is an L8148e and the valves are 4 wire 8043e's. Thanks. On 2021-09-20 by Mark

Reply by Inspectapedia Com Moderator - connections between boiler and aquastat

@Mark,

and other readers; if you don't already have the IO instructions in-hand, see

HONEYWELL HPZC105 ZONE CONTROLLER INSTALLATION MANUAL [PDF]

that has some simple wiring examples like one I'll show below.

If that's not enough, see the more-detailed help given in

HONEYWELL HPZ & HSR HYDRONIC PANEL WIRING DIAGRAMS [PDF]

from Residio Resideo Technologies, Inc.
1985 Douglas Drive North, Golden Valley, MN 55422
1-800-468-1502
33-00476—02 M.S. Rev. 02-20

Where do I get a C wire for my new Smart Thermostat if none came through the wall from the heater?

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? - On 2020-11-07 by grnnatmu

Reply by (mod) -

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 thermostat 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 new thermostat where none is found at your old wall thermostat, see the procedures we describe

at COMMON WIRE at THERMOSTATS

For a Gas boiler do I use the r,w terminal? or r,b terminal?

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) On 2020-03-10 by Angelina

Reply by (mod) -

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 connections

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.

Details needed for re-wiring my Honeywell zone valves/Honeywell Aquastat/and thermostat wiring

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.

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. - On 2020-01-10 by Jim Davis

Reply by (mod) -

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.

Reply by (mod) - zone valve wiring connections to the L8148

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.

 

What does the DIFF or "Differential" mean in a high-limit-only Aquastat?

What does the differential mean in this high-limit-only Aquastat? For example, how would the operation differ for the 8-degree differential version vs the 15-degree differential version? - On 2019-12-11 by Fred -

Reply by danjoefriedman (mod) - Honeywell Aquastat differential explained

Thank you for the question on clarifying the DIFF on the Honeywell R8148, Fred.

Over at the home page for this topic - AQUASTAT L8148 DIAGNOSIS & REPAIR

we give a link to two manuals for the R8148

HONEYWELL L8148A,E,J AQUASTAT® RELAY SERIES MANUAL (Controllers) [PDF] (2001) product data & installation, operation manual including L8148 wiring diagrams

On this model the Differential is hard-wired in the control, it's "Nonadjustable."

Only the high limit is adjustable.

So if the HIGH is set, for example, to 200F, then when the boiler temperature drops to 192 degF (on the 8-degree model) or drops to 185 degF (on the 15-degree differential model) the switch will allow the boiler to turn on.

HONEYWELL L8148A E J AQUASTAT RELAYS MANUAL [PDF] (2002)

 

Where do the thermostat wires connect to this control GuardDog RB-24 low water cut-off.

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. - On 2019-11-28 by tightwoods -

Reply by (mod) - wiring 24VAC controls

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

Followup by tightwoods - I'm trying to use this as a power source for a GuardDog RB-24 low water cut-off.

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.

Followup by tightwoods

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.

Reply by (mod) - wiring details: connecting the thermostat to the L8148

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

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.

Reply by (mod) - low-voltage 24VAC wiring - no polarity on AC Low voltage transformers

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.

 

Need a Manual for Honeytwell L8148G Aquastat

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. - On 2018-10-09 by Mal

Reply by (mod) - provided here

A HONEYWELL R8148G MANUAL [PDF] is here:

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.

Followup by Mal

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.

Reply by (mod) -

Well that's certainly a HONEYWELL L8148G AQUASTAT MANUAL [PDF]

Indeed relay and control numbers form a sea of characters upon which anyone 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

L8148B, L8148E, and L8148G

this link provides a control cross reference chart:

HONEYWELL CONTROLS CROSS REFERENCE CHART [PDF]

And this link

HONEYWELL TRADELINE PARTS CROSS REFERENCE GUIDE [PDF]

provides a huge 992 page list of Honeywell Tradeline controls cross-referenced with their replacements.

 

 

On 2016-11-26 by Marquette

replacement aquastat for honeywell (L8148E1266) that's obsolete

 

Thank you to our readers for their generous comments

On 2021-09-22 by Mark - link you sent I think fits my situation exactly.

@inspectapedia.com.moderator,

Thank you. I just finished up wiring the zones and valves. And the second link you sent I think fits my situation exactly.

Much appreciated. It's a drawing that comes from an addendum that I haven't seen.

On 2021-09-22 by Inspectapedia Com Moderator

@Mark, Thank you.

We've worked hard on this material for decades, so I'm really grateful when a reader finds it useful and trustworthy.

We also welcome your photos, questions, criticism or suggestions.

...

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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Suggested citation for this web page

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

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING BOILERS

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