Heating Zone Valve Wiring FAQs

Q&A on How to connect or wire a heating zone valve or zone controller

Taco ZVC403 Zone Controller Wiring & Troubleshooting.

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.)

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.

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.

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

I 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 ZVC403 ZONE VALVE CONTROL WIRING & MANUAL [PDF] (2013) # 102-391 retrieved 2017/12/10 original source: http://www.taco-hvac.com/uploads/FileLibrary/102-391.pdf
  The light codes and zone priority for this controller are excerpted below:
  
  Operation/External Diagnostics: When any thermostat calls for heat, the appropriate zone valve is energized and the yellow light goes on. When the zone valve is fully open, the red light goes on and energizes the end switch relay. The green light should always be on, indicating that power is connected.
  
  Priority Operation: When zone 3 is switched to the priority setting and is actuated, all other zones will stop operation until zone 3 is satisfied. When zone 3 is not switched to priority, all zones will operate independently.
  
  Note: When a circulator is used on the priority zone instead of a zone valve, jumper 3 and 4 of the priority zone.
• TACO ZVC403 ZONE VALVE CONTROL WIRING & MANUAL [PDF] (2006) # 102-089 retrieved 2017/12/10 original source: http://www.taco-hvac.com/uploads/FileLibrary/102-089.pdf|
  The light codes for this controller are given herein:
  
  Operation/External Diagnostics: When any thermostat calls for heat, the appropriate zone valve is energized and the yellow light goes on. When the zone valve is fully open, the red light goes on and energizes the end switch relay. The green light should always be on, indicating that power is connected.
• VIDEO of COSMOGAS BOILER OPERATION [85MB file: Cosmogas-Boiler-Overpressure.mp4 ] - OFFLINE, AVAILABLE on REQUEST - contact us - illustrates the sequencing of the TACO ZVC403 zone controller operation and LED light sequencing
  
  made during diagnosis of
  
  RELIEF VALVE LEAK DUE TO EXPANSION TANK

Taco's equipment manuals and contact information are

at TACO HVAC components & controls

Zone Valve Wire Identification FAQs

Which wires do what when hooking up zone valves & a low voltage transformer

Before I had tried to put the ground wire for the transformer with the ground wire for 110 volt ground that did not very well. But now that I have different for each .

I must be missing something here I have the wires from the thermostat to TH+TR and TH and TR zone valve which has 2 wires on for END Switch on zone valve .

Now The transformer has 24 volt blue wire to go to the to top of relay and the yellow wire from the transformer to a ground connection .

I have the the wire from the end switch on zone valve to lower 24 volt side and the other end switch wire also to the ground .

The other side of relay has 110 volts at top and pump wire at the lower side . On 2017-12-11 by Gene 12/11/17

Well I got tired of using those ventless heaters and trying to get this to run with zone valves and propped the zone open and connected the thermostat to relay and it is running good for now . Maybe I can try it another day tired of messing with it.

Some tell me that I should know the 24 volt transformer polarity and forget which I should use then someone says it does not matter which when you got AC going into the transformer you get ac current come out .How to check the current from what I have ?

How to connect wire for room thermostat and water pump prop open the zone valve and run just the pump

by (mod) -

Gene

I may be missing something too, but at https://inspectapedia.com/heat/Zone_Valve_Wiring.php (ZONE VALVE WIRING) where we note that on a typical Honeywell zone valve there are 4 wires, 2 red and 2 yellow, follow the instructions given by Honeywell and repeated at

HONEYWELL ZONE VALVE INSTRUCTIONS https://inspectapedia.com/heat/Zone_Valve_Wiring.php#Honeywell

this old sketch from heating school shows how we wired those connections

https://inspectapedia.com/heat/Honeywell_Zone_Valve_Wires_2.jpg

by Gene

First you say it does make a difference on the polarity how can I make sure it is right ? I got a blue and yellow wire out of the transformer I got it as blue hot and yellow as ground or neutral .

I have trouble making out the hand drawn article.

I did get to put out some heat with the zone valve manually opened if this is possible . Why can I not get with the zone valve ?
inspectapedia.com/heat/Honeywell_Zone_Valve_Wires_2.jpg

by (mod) - where to find details on zone valve and low voltage transformer for wiring

Take a look at a typical Honeywell zone valve. There are two identical red wires and 2 identical yellow wires. Those are not polarized.

See ZONE VALVE WIRING to read the complete details for all the wires, connections, functions.

For the low voltage 24VAC transformer by convention

A "C" or common terminal wire on the low voltage transformer is connected to the control relay that operates the heater or air conditioner, and

an "R" terminal on the transformer is connected first to the thermostat (which acts as an "on-off" switch) and from the thermostat onwards to a thermostat terminal found on the heater or air conditioner's primary control or circuit board.

Details about thermostat wiring and low voltage control wiring are found

at THERMOSTAT WIRE CONNECTIONS

by Gene

Well I This is how I have it here I got a whole roll 6 inch diameter of 4 wire sheath covered 1 red,1 white, 1 blue 1 yellow it is right size all for $ 2 .

So I am at the zone valve vertical screws on top TH+TR yellow+white wires.. Then TH in the middle gets the Red wire from thermostat then Blue wire on TR transformer wire...

Then the End Switch wire I have a Red and a White wire then I take the red wire to the relay and the white wire to the ground . Do you see any reason why this would not work ? Is there a hot wire as well as a ground wire on end switch ?

by (mod) - Typical zone valve yellow & red wire connections:

Yellow wire connections at the zone valve: the pair of yellow wires on a zone valve are the zone valve motor actuator control.

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.

How does this little zone valvce yellow wire circuit work?

On a traditional two-wire room thermostat one wire, usually the red one, connects to the R terminal (24VAC live) on the low voltage transformer. The second thermostat wire, usually white, connects to the yellow zone valve motor actuator wire.

The second yellow zone valve wire normally connects to the C terminal (Common) on the low voltage transformer.

When the thermostat calls for heat it's acting as a low-voltage (24VAC) "on" switch that takes voltage from the low voltage transformer, through the thermostat, to the zone valve actuator motor. The second wire from the zone valve back to the low voltage transformer completes the circvuit.

Red wire connections at the zone valve: the pair of red wires are "end switch" wires used to energise an external relay that turns on the circulator.

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

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

At the thermostat

The red wire from the heater or air conditioner control is mounted to the "R" terminal on the backing plate. Typically the red wire is originating at the heating or air conditioning low voltage transformer and brings power to the thermostat..

The white wire from the heater or air conditioner control is mounted to the "W" terminal on the thermostat mounting plate. Typically the white wire is taking power from the thermostat to the operating control circuit board in the heater or air conditioner.

by Gene

Ok I was going to try it again I am at the end switch there are 2 wires one goes to the relay to turn on the circulator pump which one and do what with the other wire ? Ground to the yellow from the transformer . I think it will work Hope so.

by (mod) - The 2 red wires are the zone valve end switch wires.

RIght Gene
The 2 red wires are the zone valve end switch wires.

One red wire connects to the R-side of the transformer (Think "R" = "Red" and look for a little "R" that may be stamped on low voltage transformer by its wire connector screws)

The other red wire connects to one side of the external DPDT circulator relay that operates the circulator pump. (

DPDT = "double pole, double throw" switch)

It's that relay that actually is going to send 120V to run the circulator pump

Wiring for Honeywell L8124E with V8043E zone valves FAQs

Tip: See

• HONEYWELL V8043A,E,F 5000 SERIES ZONE VALVES [PDF]
• Honeywell V8043D ZONE VALVE INSTALLATION GUIDE [PDF]
• HONEYWELL_ZONE_VALVES_V8043_SERIES_U [PDF]

Honeywell L8124E + V8043E Wiring Worked For Me

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! On 2016-08-22 by Walter Hawn

by (mod) - honeywell minizone system with heat pump wiring & actuators

Thanks 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 MANUALS & WIRING INDEX

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

Other Readers:

see

• HONEYWELL ZONE VALVE INSTRUCTIONS - wiring connections
  
  And also
• HONEYWELL CONTROLS On HVAC Equipment, thermostats, primary controls, zone valves

24-volt V8043E Zone Valve Wiring

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 2016-02-01 by John

Reply by (mod)

Take a closer look at the instructions for your zone valve HONEYWELL V8043A,E,F 5000 SERIES ZONE VALVES [PDF] and you'll see that line voltage (120VAC) is used to power the actual circulator pump by the "end switch" that closes when the zone valve opens, but the zone valve itself is connected through the thermostat using the 24VAC low voltage transformer wires.

Figure 14 (below) from those instructions adds details that I've annotated by using colored lines for a bit more clarity - Daniel F.

Bell and Gossett model SZV-075N-4WE snap zone valve wired to Azel SZ-V6 Zone Controller

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 2015-11-08 by farmerdave

Reply by (mod) -

Farm

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?

How many zone valves can one thermostat control?

I have 4 Honeywell zone valves and 2 thermostats I want to wire 1 tstat to 2 zonevalves not sure how to do On 2015-07-25 by sam

Reply 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 MANUALS & WIRING INDEX to see zone valve and thermostat wiring diagrams in more details. You'll also find our contact information for Honeywell to ask further.

Diagnose Honeywell Zone Valves with Honeywell Switching Relay

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 2014-11-27 by Mark Navien

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

Mark

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"