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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 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.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Zone Valve Wiring Hookups for Hydronic (Hot Water) Heating Systems
Individual Hydronic Heating Zone Valve & Control Wiring Notes by Brand
Illustration: the wiring diagram for the Taco ZVC 403 Multiple-Zone-Valve Controller. [Click to enlarge any image] - be sure to check the exact wiring diagram for your particular control and application.
Watch out: take care about which zone is connected to which zone terminal in this control and to how you specify the priority setting switch for that zone. That feature is intended to permit giving heating priority to a domestic hot water source.
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.
TACO ZVC403 ZONE VALVE CONTROL [PDF] (2010) & ZVC403-ZVC406 Zone Control Wiring conected with system pump, wiring & installation instructions. This controller permits setting zone 3 to a priority setting that stops other zones for up to one hour (such as to assure providing domestic hot water in an indirect-fired water heater). Excerpt explains the LED light codes for this zone controller:
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.
How to Wire Multiple Taco SR502-SR506 Switching Relays
To control up to eight heating zones you might wire multiple standard switching relays together as shown in this TACO wiring diagram. This illustration is from the TACO SR503-4 Switching Relay Instruction Sheet whose link is given above. [Click to enlarge any image]
Watch out: Be sure to see important instructions and safety notes in that document.
Question: Having trouble wiring up different zone valve controller brands together
Hi, I have a HE II Weill McClain natural 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 above-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. [Click to enlarge any image]
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; Example of Wiring Different Brands of Zone Control in Same System
Absolutely, if properly wired, you can take a single loop of hot water baseboard heat and subdivide it, giving each sub-loop its own thermostat and zone control valve.
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 below, (reader contributed) illustrates typical wiring connection at two zone valves.
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.
In addition to your control, the Honeywell L6006C 1010, Honeywell's L8124A,C and 8151A are triple aquastats similar in function, often used to control zone valves. Where you can run into trouble is with an installation that has a mix of different brands of zone valves. In that case, the wiring instructions for one company may be different from the other.
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 on thi spage 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. [Click to enlarge any image].
Watch out: in wiring the mixed-brand zone valves shown in my sketch above, it is important that
The Common wire, NOT the Load side of the low-voltage transformer is taken to Terminal #2 on the White Rogers and
The Load wire is taken to Terminal #1 on the White Rogers zone valve so that when it makes aux switch #2 there is no voltage across the switch,
and the load is taken TO the thermostats directly for the Honeywell zone valves, and
The Common is taken to the Yellow Honeywell zone valve wire.
The other yellow wire is common to the thermostat.
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.
The Flair and White Rogers are compatible with one another with no special tricks
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:
Zone-A-Trol Valves should not be wired in the same circuit with zone valves of a different make or manufacturer without first consulting your local Zone-A-Trol representative or our factory engineering department for special wiring information. 
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
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
or if you are in Canada contact TACO (Canada), Ltd., 8450 Lawson Road, Unit #3, Milton, Ontario L9T 0J8. Telephone: 905/564-9422. FAX: 905/564-9436.
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
Honeywell Zone Valve Wiring Wire Colors
General Honeywell Zone Valve Wiring instructions (just below) are followed by links to Honeywell Zone Valve Instruction Sheets
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 thermosatat 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 conects to one side of the external DPDT relay that operates the circulator pump. (DPDT = "double pole, double throw" switch)
How does this little zone valve red-wire circuit work?
When the pair of yellow wires have told the (normally closed) zone valve motor to "open" that motor rotates to actually open the valve to let hot water flow.
When the zone valve has rotated to its fully-open position, inside the zone control head the two red wires are connected to turn ON the circulator pump by in turn operating a relay switch that handles the 120VAC power required to actually switch on the circulator.
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.
Flair Zone Valve Wiring Connections at the Thermostat & at the Zone Valve
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:
Black wire goes to terminal 1
Red wire goes to terminal 2
White wire goes to terminal 3
Wiring the Thermostat with this zone valve
Black goes to terminal 4
Red wire goes to terminal 5
White wire goes to terminal 6
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.
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 I can just add the new "loop" directly to the aquastat, in what order are the connections made ? Example, aquastat to one connection at valve, 2nd connection at valve to one connection at thermostat, other connection at thermostat back to aquastat ?
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:
When the TT calls for heat (yes 2 wire is fine) it tells the zone valve for its zone to OPEN. When the zone valve is fully open it in turn tells the circulator pump to start pumping. (There is an "end switch" in the zone valve that performs this second function).
So you'll find a pair of wires from TT to the zone valve and a pair of wires from the zone valve to the circulator relay.
Watch out though: the wiring connections can vary a bit among zone valve brands - if all of yours are the same brand you can look at the existing valve, follow the wires, and you'll see how the zone valve is hooked up. If there are different brands you'll need to ask for a clue from your HVAC supplier or the manufacturer.
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.
Continue reading at ZONE VALVES, HEATING - home, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Taco, Inc., "Taco Zone Controls and Wiring Diagrams", Taco Inc., 1160 Cranston Street, Cranston, RI 02920 Telephone: (401) 942-8000 FAX: (401) 942-2360 - USA
TACO (Canada), Ltd., 8450 Lawson Road, Unit #3, Milton, Ontario L9T 0J8. Telephone: 905/564-9422. FAX: 905/564-9436. Retrieved 3/4/2014, original source: http://www.taco-hvac.com/uploads/FileLibrary/100-9.0.pdf
 "Installation Instructions, Flair Zone-A-Trol Models"
3-wire sweat type zone valves: VJ1B0, VJ1C0, VJ1D0, VJ1E0 (models represent pipe diameters 1/2" to 1 3/4"
2-wire sweat type zone valves: VJ5C0, VJ5C2, VJ5D0, VJ5B2
Flair Manufacturing, 600 Calebs Path, Hauppage, LI* NY 11787
 "Motorized [Zone] Valves [Installation Instructions]", Honeywell Corporation, 1957, Honeywell, Minneapolis MN 55408, International sales offices in principal cities of the world, Manufacturing in Australia, Canada, Finland, France, Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, USA.
Thank-you to Mr. Scott Meenen , G&S Mechanical Services , for providing some common thermostat wiring codes also found at Mr. Meenen's web page Malware Deleted 12/9/2014 . Mr. Meenan provides heating, heat pump, and air conditioning repair services in Maryland, Washington D.C., and northern Virginia. He can be contacted at 301-591-1646 or by Email to Malware Deleted 12/9/2014 - 10/2010. Quoting:
We service American Standard, Amana, Arco, Arco-Air, Bryant, Carrier, Coleman Evcon, Comfortmaker, Day/Night/Payne, Dunham-Bush, Fedders, Fredrich, Goodman, General Electric, Heil, Intertherm, ICP, Janitrol, Lennox (Armstrong, Johnson Air-Ease), Miller, Modine, Nordyne, Rheem/Ruud/Weatherking, Sears, Stewart Warner, Trane, Weather King, Williams, White-Westinghouse, Whirlpool, Weil Mclain, York, (Frasier Johnson/Borg Warner) and others.
 Honeywell Controls, the company wants you to use their contact form at this web page: http://www51.honeywell.com/honeywell/contact-support/contact-us.html
Honeywell Consumer Products,
39 Old Ridgebury Road Danbury, CT 06810-5110 - (203) 830-7800
World Headquarters, Honeywell International Inc.,
101 Columbia Road,
Morristown, NJ 07962,
Phone: (973) 455-2000,
Fax: (973) 455-4807 1-800-328-5111
Honeywell product model numbers & instruction Manuals: see http://yourhome.honeywell.com/home/Applications/FindYourModelNumber.aspx
 White Rodgers Thermostats and HVAC controls,
Homeowner information: http://www.emersonclimate.com/en-US/brands/white_rodgers/Pages/wr-homeowner-info.aspx
Contractor information: http://www.emersonclimate.com/en-US/brands/white_rodgers/wr_contractor_info/Pages/white-rodgers-contractor-info.aspx
White Rodgers Product Catalog (don't misspell the company's name as White Rogers Thermostats) -
http://www.emersonclimate.com/Documents/thermostats.pdf - Thermostat Catalog
 White Rodgers 1F90 Low Voltage Digital Comfort-Set thermostat Installation Instructions, PN 37-3654, White-Rodgers Division, Emerson Electric Co., 9797 Reavis Rd., St. Louis MO 63123
 Thermostat wiring color codes & conventions,
Thanks to reader "
Helpful Pointers" Regarding 24V T, 10/7/2012
 Domestic Central Heating Wiring Systems and Controls, 2d Ed., Raymond Ward, Newnes, ISBN-10: 0750664363, ISBN-13: 978-0750664363, Quoting from Amazon.com:
This unique A-Z guide to central heating wiring systems provides a comprehensive reference manual for hundreds of items of heating and control equipment, making it an indispensable handbook for electricians and installers across the country. The book provides comprehensive coverage of wiring and technical specifications, and now includes increased coverage of combination boilers, recently developed control features and SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) boilers ratings, where known.
In addition to providing concise details of nearly 500 different boilers fuelled by electric, gas, oil and solid fuel, and over 400 programmers and time switches, this invaluable resource also features numerous easy-to-understand wiring diagrams with notes on all definitive systems. Brief component descriptions are provided, along with updated contact and website details for most major manufacturers.
 "Heating Control Handbook for the Installer and Service Man,Oil Burner, Gas Burner and Stoker Controls", Honeywell Corporation, March 1949 [copy on file as HoneywellControlsHandbookSA1399-2-1949.pdf] . Some of the controls discussed in detail here include the
Honeywell T1 and T11A = Series 10
Honeywell T21A (T2) = Series 20
Honeywell T847A = Series 80
Honeywell RA117A (RA1) = Series 10
Honeywell LA101A = Series 10,
Honeywell LA419A (LA4) = Series 40
V155A = Series 10, V435A = Series 40, V575A = Series 50, V835A = Series 80
 Trane TCONT800 Series Touch Screen Programmable Comfort Control Ownes Guide, American Standard, Inc., Troup Highway, Tyler TX 75711, January 2005, Telephone: Customer Service: 1-877-3381, website: www.trane.com
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