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Hot water heating system zone valve installation:
This article describes how to wire up heating zone valves. We include wiring diagrams for most zone valve models 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.
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Question: Having trouble wiring up different zone valve controller brands together
Hi, I have a HE II Weill McClain nat gas boiler. A few years back I converted about 1/4-1/3 or my house into hydronic radiant floor heat running off same zone as the baseboard. The guy who sweated the tubes and zoned it out has never come back to hook up the zone controller.
Schematic at left: wiring hookups for a mixed-brand zone valve installation: Honeywell & White Rogers. Click to enlarge any image or schematic.
Someone else came out the other day to hook it up. I have a TACO SR502 2-zone controller and this person purchased a Honeywell L6006C 1018 aquastat controller.
I am thinking he purchased the wrong aqua stat. He said the whole system will never allow for 2 zones. I spoke w/techs @both TACO and WeilMcClain who, both said, I can have my floor heat operate separately from the BB units. (I do have 2 thermostats). Can you shed a little light on this, please? Thanks, - T.B. 10/27/2013
Reply: known problem; check with the manufacturer, the wiring diagram, or send us more details
Properly wired, the individual thermostat calls for heat, the zone valve opens, when the valve is fully open an end switch in the valve connects a second pair of wires that turn on the circulator pump back at the boiler.
Photo at left (reader contributed) illustrates typical wiring connection at two zone valves. Click to enlarge any image.
On most U.S. systems the circulator runs sending water through the open zone loops and a primary control at the boiler, monitoring water temperature, actually turns the boiler on or off as needed to re-heat the water.
When I got into that trouble years ago I was wiring up a Honeywell zone valve to a system already using Flair zone valves. I called my heating supplier who had Dave Ferris (now retired) on deck to answer wiring questions. The solution was trivial once Dave said - Just hook the red wire to terminal "x" and the yellow to "y" and so on.
My ugly rough sketch above needs to be re-drawn neatly, but there I show how we successfully wired-up a mixed brand zone valve installation. I had two Honeywell zone valves and one White Rogers zone valve.
Watch out: in wiring the mixed-brand zone valves shown in my sketch above, it is important that
The correct wiring depends on the zone valve models. Without Dave the next-best is to look with care at the instructions that came with the zone valves, and at the wiring diagrams for hook-up instructions; if you are left still confused, the manufacturer will know how to hook-up.
More about wiring Taco zone valves - see TACO ZONE SENTRY VALVES [PDF] installation instructions
Zone Valve Compatibility Notes
Watch out: The Honeywell zone valves are NOT compatible with Flair and White Rogers unless you follow careful wiring details.
I give an example above, but you may need to review wiring with the manufacturers of your zone valves.
In fact Zone-A-Trol zone valve installation instructions carried this warning:
Master Control & Zone Valve & Thermostat Wiring Connection Tips
The thermostat wires on the master (primary) control will show about 20-volts from the on-board thermostat relay transformer inside the primary control.
No voltage should be presented by the zone valves, thermostat, or transformer circuit TO the primary Controller.
We see 24-volts through the zone controllers and transformer but Zero voltage on the zone valve end switch wires that go to the thermostat TT terminals on the master or primary control.
Reader Question: how many zone valves can be connected to a single thermostat?
3/5/2014 tej said: how many zonal valves for floor heating can be connected to one room thermostat
This question originally was posted at ZONE VALVES, HEATING
Reply: use of a switching relay to control multiple devices from a single thermostat
Normally one thermostat controls one heating zone and is connected to one zone valve. But as the thermostat is basically an on-off switch, indeed we've discussed with readers the successful combining of more than one zone valve switched by the same thermostat.
WATCH OUT: to avoid overloading the tt or its power or circuit, check the zone valve wiring instructions. For switching multiple zone valves with one thermostat you may need to have the thermostat control a switching relay that in turn switches the gang of multiple zones. A typical switching relay such as the Taco SR502 - 506 can swit3ch 4 zone valves or more.
To find out more about the Taco switching relays I cited contact
Taco Inc., 1160 Cranston Street, Cranston, RI 02920 Telephone: (401) 942-8000 FAX: (401) 942-2360 - USA
The company's website is at www.taco-hvac.com and their wiring guide is at www.taco-hvac.com/uploads/FileLibrary/100-9.0.pdf
Individual Hydronic Heating Zone Valve Wiring Notes
Honeywell Zone Valve Wiring Wire Colors
[Click to enlarge any image]
See this image for Detailed wiring diagrams for Honeywell Zone Valves V8043E & T822 & T822
Above Honeywell zone valve wiring diagrams are from Honeywell's motorized [zone] valve installation instructions 
Watch out: when installing zone valves not to overheat the valve or its parts. We were taught to completely remove the zone valve motor and electrical parts while sweating the zone valve to the heating system piping, but even so, overheating can damage the zone valve moving parts or o-ring seals. Honeywell warns not to use silver solder when sweating zone valves because of the higher temperatures required with silver solder.
Honeywell Zone Valve Instructions
From Flair Manufacturing's original installation instructions for the Flair Zone-A-Trol we include these wiring details. The Flair Zone-A-Trol valves in the company's wiring diagrams are typically shown wired in parallel.
How Are Multiple Zone Valves Wired?
On installations where it is not convenient to wire from valve to valve as in the diagram, a separate 3-color wire conductor can be run from terminals 1, 2, 3 of each zone valve to a convenient junction point.
By observing and respecting the color codes, conductors from corresponding-numberd terminals of each zone valve may be joined or spliced together and a single conductor may be conducted from that splice to the appropriate power and control terminals shown in the wiring diagram.
Wiring the Zone Valve:
Wiring the Thermostat with this zone valve
Watch out: when connecting wires to terminals at the zone valve and at the thermostat or any other control, do not let the stripped end of the wire touch or short out against any other wire or terminal.
Multiple zone valve wiring
Below we illustrate how a "gang" of Flair zone control valves would be wired-up.
See this image for Complete and detailed wiring diagrams for FLAIR 2-WIRE ZONE-A-TROL VALVES. [image] An example from that page is shown just below.
See this image for Complete and detailed wiring diagrams for FLAIR 3-WIRE ZONE-A-TROL VALVES [image]
The Flair control wiring diagrams below are excerpted from THERMOSTAT WIRING DIAGRAMS
In this application the thermostat is acting as an spst (single pole single throw) switch to turn heat on or off, often by operating a zone valve.
When used to operate a zone valve the thermostat wires are connected to the zone valve terminals, not to a primary control on the heating boiler.
[Click any image to see an enlarged, detailed version]
At left the thermostat wiring diagram illustrates typical use of a Flair APOV2 wall thermostat in a 3-wire application controlling a heating appliance.
In this application the thermostat is acting as a single pole double throw (spdt) switch to control heating & cooling or in some zone valve applications.
Also see our table of Flair thermostat wiring connections found above at
The table below is an excerpt from THERMOSTAT WIRE CONNECTIONS
Reader Question: Adding a third heating zone with its own zone valve
I am adding a third zone (basement) to my oil fired hot water baseboard heating and have it all planned as far as the plumbing is concerned.
The add-on heating zone will have it's own 24V zone valve so will require a wall mounted thermostat. I'm only looking for heat so I believe a 2 wire thermostat is sufficient. My other two zones have their own valves and thermostats and the wiring at the valves is all connected with wire nuts and doesn't make any sense to me.
I guess my question is, can I just connect my new valve and thermostat directly to the aquastat terminals that "appear" to power the other valves and thermostats ?
If so, is there anything I need to be aware of, like possibly wiring it backwards and frying something ?
If you need me to provide more detail on the types of thermostat, aquastat and zone valve I am using I can. My zone valve has two red wires and two yellow wires. The instructions seem to indicate that I only use the yellow wires and the red wires were for auxiliary, whatever that is. Would much appreciate your input. Thanks. - Will 11/10/11
Will I think this will help clear things up a little for wiring a 3rd heating zone using a zone valve approach:
Dan, thanks for the information. So I effectively have two circuits to connect. One 24v circuit runs in series as follows - transformer, zone valve, thermostat, transformer. Please can you confirm this.
The other circuit is simply connecting the other two wires on the zone valve to the connections on the circulator relay.
For the first circuit, do you know where my transformer is likely to be located ? I have the box on the front of my furnace which contains controls for how hot the water gets and when it needs to be heated. Would it be in there ?
For the second circuit to the relay, I'm assuming the relay is attached to the circulator pump itself.
Zone Valve Installation Instructions & Product Specs
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