Honeywell V8043F 1036 Zone Valve for hydronic heating  at InspectApedia.comHeating Zone Valve Wiring FAQs
Q&A on How to connect or wire a heating zone valve or zone controller

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Hot water heating system zone valve installation wiring questions & answers:

Frequently-asked questions (and answers) about wiring heating zone control valves and zone controllers from all manufacturers.

This article series describes how to wire up heating zone valves. 

We include wiring diagrams and installation instructions for most zone valve model and multi-zone controllers, and we describe special wiring problems that can occur if you mix different types, brands, or models of heating zone valves on the same hydronic heating (hot water heating) system.

Page top photo: Honeywell V8043 Zone Valve showing a wiring connection terminal block.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Zone Valve Wiring Hookups for Hydronic (Hot Water) Heating Systems

Honeywell V8043 1000-series Zone Valve showing basic components & wire conections (C) InspectApedia.comThese Questions & answers about wiring up heating zone valves & zone controllers, were posted originally at ZONE VALVE WIRING

Annotated photo: Honeywell V8043-1000 series zone valve showing basic information about the red & yellow wire connections discussed on this page.

[Click to enlarge any image]

Taco ZVC403 Zone Controller Wiring & Troubleshooting.

Question: why does one of my zones shut off after just a few seconds?

... The other issue [besides the relief valve leak we discuss at RELIEF VALVE LEAK DUE TO EXPANSION TANK ] I'm having is with my 3 zone 1 pump radiant heat system.

Zones 2 and 3 work fine, but when zone 1 activates, the pump turns on for about 5 seconds, then shuts off

I'm using a Taco 3 valve control module and a Tekmar 360 mixing control.

This system is about 8 years old, and has mostly worked fine until lately. On the Taco, both the zone 1 thermostat and zone valve LED's illuminate.

Any suggestions or tips would be most welcome. - Karl Peterson by private email 2017/12/09

This discussion is indexed as ZONE CONTROLLER TACO ZVC403

More details about this system:

My boiler is an embassy industries Cosmogas BMS 15/29, and I have a manual. It is for both domestic hot water and heat in a radiant heat floor.

[The Cosmogas boiler manual for this heater/water heater gas fired combo boiler as well as company contact information is at COSMOGAS® boiler / water heater combo manuals - thanks to Karl for providing this document - Ed.]

Below is a photo of the front panel. It is supposed to have a minimum of 12 psi, and a max of 30psi according to the manual, but the relief valve is at 50psi (another photo below.)

Cosmogas BMS 15/29 Boiler control (C) Karl Peterson

At rest, the pressure is indeed about 12-15 psi generally, but after 2 or three cycles of the heater heating up water for the radiant heat, the pressure climbs to about 45psi, and the valve starts to bleed off pressure.

Its done this all last heating season, and possibly the previous season as well. it never does this in the summer time (or when the heat is off) and as I mentioned previously, it didn't do this at all for the first 6 or 7 years it was installed. There is no banging or hammer noises.

50 psi TP Relief valve (C) KP

[Click to enlarge any image] Above: Zurn Model P1000A temperature/pressure relief valve rated for 200,000 input BTUH and opening at 50 psi. This TPR is rated to handle thermal expansion of hot water and complies with ANSI Z21.22 / CSA 4.4 relief valve specifications.

The Taco [multiple heating zone controller ] is a ZVC403, and yes, the green LED is always on, and the zone 1 issue is after both the yellow/orange thermostat LED and red Zone Valve LED are illuminated. The pump starts for about 5 seconds, then shuts off.

Taco ZVC403 zone control LED lights (C) KP

Although, I did notice that at one point yesterday, zone 1 was the only zone calling for heat, and the circulation pump was running normally.

However, about 15 minutes ago, it was back up to it's new trick of only turning the pump on for 5ish seconds and then shutting off again.

At the time of this photo, the pump was not running, and there was no domestic hot water demand.

Reply: diagnosing a too-short zone-on cycle & the Taco ZVC403 control

Taco ZVC403 zone controller wiring illustration (C) KPI have not encountered the "just 5 seconds on" problem you describe so I can only speculate. The LED indicators you describe sound normal per the documentation I'll cite below. .

Since there's a common circulator pump and controls one might naturally suspect either the zone valve itself ( a bad connection, loose wire), or a bad control module in the Taco master zone control.

Take a look at the system temperatures and at whether or not you are using domestic hot water when this short-on-zone problem is occurring.

Watch out: also look for a leak into the hydronic system that could be pushing the pressure up abnormally, such as a leaky tankless coil (if you have one).

You might want to give Taco a call directly to ask about this situation as I'd bet a beer that their engineers have encountered it before.

Or we can wait a few days: I have posted this question with Taco's customer technical support and asked for an opinion, the support rep responded immediately, and has said that he is not familiar with the problem you describe but he also asked for wiring photos - now sent from those you provided.

In the U.S. contact Taco at Taco Comfort Solutions, Inc. 1160 Cranston St. Cranston, RI 02920 Phone: (401) 942-8000 FAX: (401) 942-2360 International readers should also use this contact address.

In Canada contact Taco at Taco (Canada) Ltd. 8450 Lawson Road Unit # 3 Milton, Ontario L9T 0J8 CANADA Phone: (905) 564-9422 FAX: (905) 564-9436

Watch out: some multiple zone controllers like your Taco permit assigning one of the zones as a "priority" zone - typically used to assure that an indirect fired water heater for domestic hot water supply will get priority over heating zones. That controller will turn off zones 1 and 2 when zone 3 is calling for heat if zone 3 is set up as "priority zone".

Watch out: also some digital thermostats can fail to work properly when connected to this zone controller.

The instruction manual and wiring diagram for your Taco ZV403 Zone Valve Controller will be one of these two documents

Taco's equipment manuals and contact information are at TACO HVAC components & controls

On 2017-12-09 by (mod) - mercury bulb thermostats wanted for research - limited exchange offer

Email is at the page top or bottom CONTACT link


Also see HONEYWELL V8043 ZONE VALVE - [PDF] complete installation and wiring instructions.

Watch out: some multiple zone controllers permit assigning one of the zones as a "priority" zone - typically used to assure that an indirect fired water heater for domestic hot water supply will get priority over heating zones.

A typical design will permit the priority zone to run while shutting down the other zones for an hour, the controller figures if you're still in the shower you ought to get out - so it turns the other zones back on.

On 2017-12-09 by Gene 12/8/17

@Dec. 8 2017 Gene, Yes I will exchange one with you. what is your email

On 2017-12-09 by (mod) - trouble hooking up wiring for Taco zone valves and controller


I'm pretty sure that when two of your zone valves are wired normally closed and two are wired normally open you need to take care not to run into both wiring incompatabilites and also low voltage transformer overloads and burnout.

But we can confirm that your zone controls are wired properly by finding the installation wiring guide for your particular Taco zone valve model.

We give Taco zone valve wiring instructions and links to PDF copies of installation guides at ZONE VALVE WIRING and also at .

The thermostat is wired to the zone valve and on a call for heat opens the valve (in a normally-closed zone valve design). Once a zone valve is open it makes an end switch witch turns on your circulator relay.

On a normally-open zone valve the thermostat closes the valve and turns off the circulator.

We describe that wiring in the ZONE VALVE WIRING article.

If you previously had all these working and you haven't change the wires I would start by asking if it's possible that the low voltage Transformer has failed from being asked to run too many zone valves.

An overloaded Transformer can work for years until by coincidence all of the Zone Motors are asked to run at exactly the same time.

Also I'm interested in obtaining a Mercury bulb type thermostat for research purposes. If you're willing to exchange I'll be glad to mail you a newer non Mercury thermostat by Honeywell. Use a page bottom contact link and I can give you the details.

Shown below: the Omron G2R 24VAC - 120/240V switching relay discussed by the reader Gene.

On 2017-12-09 by Dec. 8 2017 Gene

Omron 24VAC - 120/240V Switching Relay at InspectApedia.comI forgot to add my name to the to the problem below.

I have 3 small pumps and and 6 zone valves which as near as I can tell they are V8043F by Honeywell and 6 thermostats - can you tell me how to get these to all connect and work properly .

The 4 thermostats are Honeywell round with mercury for connection and 2 Honeywell digital cheap programable type.

and I am using 6 Omron G2R-2-S 24 volt VAC relays for 110 or 220 volt .they have 2 normally open and 2 normally closed .

I have had 4 zone valves working great for 2 or 3 winters and I had 2 more zone valves to connect with wire they were already in the pipe system this is for under floor added heat.

And if you can help me with I had also I had indicater light that would light up each time a relay connected . I seamed to have lost how of this this was be for but it worked well last winter . Can you help me ?

On 2017-10-16 by Barry

Is it possible to control 1 Honeywell V4043 valve from 2 seperate thermostats (one wired with its own clock and one from a programmable clock and thermostat) so that whichever stat is asking for heat (even both) then the valve will be opened.

The valve will only close when neither stat is demanding heat?

On 2017-10-11 by Mike

Im replacing a zone valve in a 2 zone system. Old zone valve has 5 wires but new zone valve has 4

I followed all wires took apart 1 for 1 and matched them up.

2 wires to zone motor and

two wires to end switch i believe.

I dont know what to do with the fifth wire

On 2017-03-26 by (mod) - two zone hot water system that was wired wrong

I'm not sure what the other wires and devices are in your description so I'm chicken to give too specific advice but I'll include some general advice here and also refer you to our ZONE VALVE WIRING article.

I would follow the thermostat wires to see where each thermostat is connected.

I'd expect to find each thermostat going to one circulator control relay, or on some systems, one circulator relay is in the main boiler aquastat and the second relay is a separate wall-mounted device.

At HONEYWELL ZONE VALVE INSTRUCTIONS we describe how the red and yellow wires for a zone valve are usually connected:

One yellow wire connects to the C terminal on the low voltage transformer.

The second yellow wire connects to a "heat on" wire from the room thermostat.

One red wire connects to the R-side of the transformer (Think "R" = "Red")

The other red wire conects to one side of the external DPDT relay that operates the circulator pump. (DPDT = "double pole, double throw" switch)

On 2017-03-26 by joe - my two zone hot water system is wired wrong

hi my name is joe,

i have a two zone hot water system that was wired wrong ,

when the first floor call for heat both of the zones turns on and when it goes off turns both them off .looks like that the wire from the therm and the tranf and the motor are connected right ,

but there are 2 red wire that coming from the a device on the chimny that are also connected by the valves and motor i m assuming that is a cut off safety ,

i have been looking on the web and i haven't find one boiler wired up that way . can anybody tell me how to wire up the right way .thank in advance

On 2017-01-29 by Ron Walker

I put a new thermostat onto a 4 zone system. as soon as I did now I have no power to any of my thermostats.

On 2016-12-31 by (mod) - honeywell minizone system with heat pump wiring & actuators

Mixed brand zone valve wiring schematic (C) Daniel FriedmanThanks for the feedback, Randy, that will help others.

For other readers, the "ARD" that Randy describes is perhaps a Honeywell Automatic Round Damper used on a forced-air system not a hot water zone valve system such as those on the page ZONE VALVE WIRING

The company provides models described as power-close, spring-open models ensure low leakage while controlling circulating air in heating, cooling and ventilation systems.

On 2016-12-31 by Randy

I had 3 bad actuators they have been replaced with new ARDs

With the honeywell minizone system with heat pump does it matter on thermostats or do you need a master and 2 slaves I have 3 zones right now my zones aren't closing like they are supposed to

On 2016-11-29 by Ruben

I am trying to wire a Honeywell zone valve and have a red and white wire coming from my thermostat and I need the correct wiring as I see no 24v transformer I think it is in the broiler room in a condo building. Central broiler for all units.

On 2016-10-12 0 by Anonymous

Hi my cir pump is running all the time in my heating system

On 2016-09-07 by Andy P.

I have been looking into getting an Ecobee3 thermostat but I have an older Burnham boiler with no "c" wire.

My wiring is currently all 2 wire since its only for heating. I was thinking about just running a C wire from the transformer that powers my 4 Taco zone valves.

Looking into it I realize I have a 40VA transformer for 4 0.9amp valves. All my reading says I should only have 3 valves on a 40VA transformer.

Should I put in another 40VA transformer and run one valve off it and the "C" wire to the thermostat?

If I do this and run the "c" wire to the c on the thermostat, what would I connect the other terminal wire to, Rc on the Thermostat?

On 2016-08-22 by Walter Hawn

Thanks you for this site. Been fussing how to wire a Honeywell L8124E with two V8043E zone valves and one circulator. Your site verified that I'd gotten it worked out correctly, so now I can go ahead!

Moderator reply: how to wire thermostat to honeywell zone valves

Anon: see

On 2016-06-01 by Anonymous

I need to know how to wire thermostat to honeywell zone valves and then to a Weil-McLain noiler

On 2016-02-01 by John

I am seeking to verify that the V8043E Zone Valves I bought are compatible with our L8124A Aquastat on my oil boiler.

Figure 13 of the manual that came with the zone valves would seem to indicate they are compatible as Honeywell shows them together. But I remain concerned because the Aquastat boiler control unit is noted at 120 volts and the V8043E Zone Control is 24 Volts.

On 2015-12-18 by (mod) -

The existing 24VAC transformer used by your boiler for the existing thermostat may be sufficient.

On 2015-12-18 by Howard

I am trying to wire 2 white Rodgers zone valves ( 1361-104) that are currently not wired. The thermostat is wired directly to the boiler ( mini therm 2 jvt125n) not sure if I need an external transformer to power them... Any help will be highly appreciated

On 2015-12-15 by Shawn

Any idea how to hook up a 3 zone system with circulating pump to the boiler?

On 2015-11-21 by (mod) -

Thanks for helping-out Radiant.

On 2015-11-21 by RadiantGuy

@Marie, I am not sure what a elecdiccircuit is. In a hydronic radiant install with two zones, if one works and the other doesn't then the issue is most likely the zone valve controller for the zone that isn't working. It could also be the thermostat for the zone that isn't working.

On 2015-11-20 by Marie

I have one floor house with two zones one side heat goes on the other does not,.

Do I have two electdiccircuits? Could one circuit not be working

On 2015-11-09 by (mod) - install a bell and Gossett model SZV-075N-4WE snap zone valve for an upstairs hot water heat system.


As Bob Dylan said many times, I believe that can be easily done - and [without having to hitchhike] out on Hwy 61: you need a thermostat for the upstairs heating zone, wire from the thermostat down to the location where you're installing the B&G circulator, maybe a 24VAC transformer to power the thermostat if you don't already have one installed nearby, and a separate zone control relay to turn the circulator on and off under thermostat control.

When the TT calls for heat the circ will run and send hot water around the system on the zone to which it's connected (provided it's not shut off from water by a valve somewhere).

The drop in temp at the boiler will turn the boiler on as needed.

Perhaps I misunderstood something?

On 2015-11-08 by farmerdave

I would like to install a bell and Gossett model SZV-075N-4WE snap zone valve for an upstairs hot water heat system. It’s not clear to me how it should be wired into your Azel SZ-V6 zone controller.

I need to wire the zone valve separate from the 6 zones I already have setup.

On 2015-10-01 by Anonymous

And why do you not want zone control (thermostats ) on each zone?

thats the point of zoning! Anyways - sounds like you have multiple issues that would be better served by having a professional look at.

Do you have a mixing valve installed for the radiant floor? or are you just running high temp water there? Lots to know about doing this properly.

On 2015-10-01 by Anonymous

Hey Guys - transformers are rated for Va, Zone valves are also rated at specific Va,

you cant say 1 transformer will power 5 zone valves, what if its a 25 Va transformer? or a 40Va? both sizes are quite normal...

On 2015-07-25 by (mod) -

Typically Sam one transformer can power up to a maximum 5 zone valves. Check the total VAC provided by your transformer against the total VAC draw should all four of your zone valves try to open at the same moment.

Normally one thermostat ought to be able to switch two zone valves on by using common connections - power is coming from the transformer.

The thermostat is basically operating as a low voltage switch. But it might be significant that I have not seen this example in any of the wiring diagrams for zone valves.

Click on the PDF files given at ZONE VALVE WIRING to see zone valve and thermostat wiring diagrams in more details. You'll also find our contact information for Honeywell to ask further.

On 2015-07-25 by sam

I have 4 Honeywell zone valves and 2 thermostats I want to wire 1 tstat to 2 zonevalves not sure how to do

On 2014-11-27 by (mod) - zone valve wiring error - both zones open when just one thermostat calls for heat


I agree that
it sounds as if there is indeed a wiring error.

Check that each thermostat only talks to one zone valve. That's where I'd start.

The thermostat wires open the zone valve.
When the zone valve is open an end switch turns on the circulator.

Also check that neither zone valve is manually latched "open"

On 2014-11-27 by Mark

I have a Navian combination boiler/hot water heater and I'm trying to wire it to a Honeywell switching relay and Honeywell zone valves. There is an upstairs zone and a downstairs zone. When I turn it on, both zones open, but the upstairs zone is only calling for heat.

On 2014-10-22 by (mod) - room gets too hot, heat doesn't turn off

Anon and Scott:

Check for thermostat wires that are shorted together - always calling for heat.

A zone valve stuck open or opened manually can give the same overheating trouble.

A thermostat improperly located on a cold wall or in a draft could also be a problem.

See these diagnostic articles

On 2014-10-21 by Anonymous

I have the exact same problem, did you a answer to your dilemma?

On 2014-10-14 by scott furey

I just put a new thermostat in hoping to solve this problem. It has not helped.

No matter what temperature I set my thermostat to, the room gets oppressively hot. Can the zone valve be wired incorrectly?

Or can you wire it to remain on full time? I'm at my wits end and don't want massive bills as a result. Thanks in advance.


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