# Thermostat upgrade on 3 wire hydronic system



## Greenley77 (Nov 25, 2007)

Hey #1CarrierMan- seems like you're the man with the answers around here. I would like to upgrade an old 3 wire mercury manual thermostat with a programmable 5-1-1 but have found it very difficult to find a compatible thermostat to upgrade to- any advice

I have a 13 yr old hydronic system: 
The system consists of

Hydrotherm HCE2-1092 Gas Fired Water Cast Iron Boiler
Fields Controls SWG Sidewall Power Vent (with CK series control)
White Rodgers 1311 102 Zone A Flow Valves (5 zones)
White Rodgers 1E35-910 Mercury Switch Thermostats (1 per zone)
Weil-Mclain ThermaTrim Hydronic Baseboard
Looks something like this (all actual components from online tech manuals)


Here's how I know its a 3 wire system:


Its got Y6, R5, and a 4 (labeled in pic above)

Here's what one of the Zone valves look like at the distribution manifold: (each of the zone valves look like they're jumpered together somehow.


Is there actually a programmable digital thermostat on the market that I can just plug and play? I just bought a Honeywell FocusPro 6000 which says it can handle 3 wire hydronic but all the wiring diagrams show at least 4 wires coming into the unit... I've only got three to give! Also- do you know if my Zone Valves could be considered "Normally Open"? I don't think they are...

Any Help is appreciated

-J


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## Greenley77 (Nov 25, 2007)

I think we got it:
Here's the final config


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## kt633 (Jan 29, 2008)

*having the same problem...*

I am so happy to come across your post. I am having a similiar issue - but I know MUCH LESS about my system than you. It's old...it has Murcury Thermostats and White-Rogers zone-a-flow valves. I have 2 zones in the house. 
Your pictures look identical to what I've got to work with. I am just curious why you ended up with a wire in the Y slot of the new thermostat - I thought that was for cooling systems...and unless I'm completely misdirected by your post, your system is heat only. Please help me understand why/how that wiring worked!


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## Greenley77 (Nov 25, 2007)

*Its all in the schematic- real answer- "I had help"*

I was in the same boat as you were, so I researched the heck out of the problem. With enough searching you can find almost every manual online. It might mean summarizing your system the way I did, but its well worth the knowledge you gain.

My father knew about thermostats so he helped me out. The short answer is "hook it up like that" and it'll work, as to the explanation - it has to do with the picture in this document under Pinciples of Operation about the White Rodgers 1E35-910 and how the zone valves operate. I think the Y acts as relay voltage to close the valve at temp. Thats my guess (I'll challenge the professionals on this site to explain the real reason this config works)- but here's the real test- I'm warm and comfy, and it works... Thanks Dad. FYI- I didn't need to mess with any of the wiring on the zone valves in the basement. I replaced only 1 of 5 thermostats and the other 4 are all still working properly.

Good Luck

Here's a link to the Honeywell FocusPRO TH6110D pictured above in Final Config. Pretty reasonable price- some of the other 3 wire systems I priced were in the 130 - 150 price range. This was under $100 (retail) I think my Dad got it wholesale for $50... Let us know how you make out...


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## CFSPAWN (Jan 30, 2008)

*3 Wire Automag system*

I have searched all over due to a similar problem only I have Automag control valves and thermostats. I found this on their website and I think its the answer I have been looking for. Since I have seen this question all over the internet without many answers I am posting this even though the original poster found a different solution that worked with his system. Hopefully it will help someone else. Automag makes a CNV84 relay that adapts a 3wire system to a 2 wire thermostat. I haven't heard from them on price or where to purchase yet. Here is the link, I hope it helps. http://www.automagzonevalve.net/technical.php?section=technical


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## mbibus (Mar 31, 2008)

*Lonnox x4146*

After searching all over the place I finally got my Lennox x4146 working with White Rogers 1311-102 3 wire Valve.
Here how it needs to be connected. 
Red Wire (5) - R
White Wire (4) - W
Green Wire (6) - Y
Next step is to access the advance options on Lennox x4146 go to 0170 and set it to 5. 
Good Luck

THANK YOU!!!! THANK YOU!!!!!! THANK YOU!!!!!!!!!


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## bugmenot (Jul 26, 2008)

*Automag 3 wire zone water heater*

I recently changed old AUTOMAG 3 wire thermostats in my home. I used Ritetemp Model#6022 thermostats that I bought from HomeDepot. It is not that expensive and currently sells for $29.99. It is however very versatile and can be used for many type of heating/cooling systems including zone heating (that uses hot water).
There are 2 types of valves that are used in zoned (hot water based) heating systems namely Motor driven rotary valve and Solenoid valve. Motor driven valve is something that is OFF by default and is powered ON when heat is required, whereas Solenoid valve is always ON and is powered OFF when heat is NOT required. Ritetemp thermostats can handle both types with slightly different wiring.

AUTOMAG is a Solenoid valve system. AUTOMAG zone heating thermostats have 3 wires, colored Red, Blue and White. Here is what I gleaned from AUTOMAG's site about how their thermostats work. 

http://www.automagzonevalve.net/technical.php?section=technical

========From above Automag link===
With thermostat turned up (calling for heat) there
should be continuity only between "Red & Blue" terminals. With thermostat turned down (satisfied) there should be continuity between only "Red & White".
================

Here is how I connected the existing AUTOMAG wires to the new Ritetemp thermostat to get it working. 

Red Wire ==> (RH) Terminal
Blue/Yellow Wire ==> (W) Terminal
White Wire ==> (A) Terminal

I arrived at this based on the following information from Ritetemp thermostat help I have linked below.

http://www.ritetemp-thermostats.com/zoned.html 

=============From RiteTemp Link
ZONE HOT WATER HEATING SYSTEMS (3 wires to thermostat)
SOLENOID VALVES
When heat is not requested, RH is connected to A and
holds the solenoid valve in the OFF position. When heat is requested,
RH disconnects from A which lets the solenoid go and
its spring opens the valve. At the same time, RH connects to W
and turns on the boiler. Any zone's thermostat can turn on the
boiler.
=============

Hope this helps.


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## bill907 (Dec 3, 2009)

*Help?*

Hi, thank you for taking time to post your information. It appears that some of the information you took time to post is no longer available. Please re-post the information. I am desperate for assistance and I am in a similar situation.

Thanks!

Bill


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## bill907 (Dec 3, 2009)

Hi Greenley77,

I need your assistance. It has been nearly a year since you posted your messages, however, I don't see the attachments you referenced. I have a honeywell RTH 6300B programmable thermostat that I'm trying to connect to a three wire heating system (White Rogers Three Way Zone Valve). I called honeywells tech support and I'm not getting very far. Please re-post your documents. thank you!


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## beenthere (Oct 11, 2008)

Last I knew. The RTH6300 isn't compatible with that zone valve.


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## bill907 (Dec 3, 2009)

*three wire zone valve : White Rogers 1311 102*

Thank you for responding - I returned to Lowes and bought the RTH 6300B because honeywell's tech support told me the RTH 230B was not compatible but that the RTB 6300B was compatible.

Do you know which programmable thermostats work with a three wire zone valve? It would be best for me if you knew of one compatible with the White Rogers 1311 - 102 available through Home Depot or Lowes. I need to fix it ASAP.

I appreciate any assistance you can offer. THank you!


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## beenthere (Oct 11, 2008)

I'm not aware of Lowes or HD carring any that are compatible.

You may want to see about ordering a thermostat on line.

See if you can find a site that sells the White Rodgers
1F80-0471
It can be set up as programmable, or non programmable. And is capable of 3 wire control.


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## bill907 (Dec 3, 2009)

*Three Wire Zone Valve & Programmable Thermostat Mystery Solved*

"Beenthere", thank you for your assistance. Yes, your response was helpful and accurate. I bought the White Rodgers 1f80-0471 programmable thermostat and it works just as it should. 

In hope of this information being used by someone else, I will add a few more notes.

I sought out to install a programmable thermostat for the obvious reason: to conserve energy by lowering room temperature while I'm away from the house and/or sleeping.

Before hearing from a contributor to this forum ("beenthere"), I had purchased three different programmable thermostats all of which purportedly work with a "three-wire" heat system. I'm sure they do, though not with systems using heat-only, single stage, and three-wire zone valves, which is what I have.

I have three wires coming out of the wall: Red, White, and Green. The red is from the transformer (I believe), and the white and green are both from the zone valve. White calls for heat subsequently _*opening*_ the zone valve, while green tells the zone valve the desired room temperature (set at the programmable thermostat) has been met, subsequently _*closing*_ the zone valve. The White Rodgers IF80-0471 is fully compatible with three-wire zone valves in addition to other wire configurations. Since I am talking about the three-wire zone valve, I'll include a link to a PDF showing the schematic for the IF80-0471: click to download.

Let me tell you which programmable thermostats _*DO NOT *_work:
Honeywell RTH 230B
Honeywell RTH 6300B
Hunter 44260

It's worth noting that Home Depot and Lowes do not sell a programmable thermostat that is compatible with a three-wire zone valve. Well, they may in some states but not here in Alaska. It is also worth noting that after my initial purchase of the RTH 230B I called Honeywell's tech support and they instructed me to buy the RTH 6300B, stating it would work; nope, strike two! I tried a local hardware store where a representative told me the "Hunter 44260" would work; nope, strike three! Luckily I wasn't playing baseball, because after using google and landing here (on this forum), I had a fourth chance to connect and knock it out of the park by following "beenthere's" suggestion, buying the White Rodgers IF80-0471 at a local plumbing store.

I hope all of this information is useful. I appreciate the amount of time so many people invest into sharing information on user forums which inevitably save hundreds of dollars. Although I probably lost any possible savings last night while both zone valves were wide open all night. Yeah, it was hot! Even here in Alaska.

Thanks all.


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## beenthere (Oct 11, 2008)

Glad to been of help.

Yeah. Honeywells tech support, leaves a lot to be desired.


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## geekwisdom (Jan 18, 2010)

Here's my documentation for using a 24vac SPDT relay to control a 3-wire zone valve with a 2-wire thermostat
http://www.geekwisdom.com/dyn/node/234


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## lazysummer (Oct 9, 2011)

*Using the Y terminal for a 3 wire hookup*



mbibus said:


> After searching all over the place I finally got my Lennox x4146 working with White Rogers 1311-102 3 wire Valve.
> Here how it needs to be connected.
> Red Wire (5) - R
> White Wire (4) - W
> ...


Hi mbibus and Greenley77 (or others),

We have a 3-wire hydronic system (3 zones) and are trying to replace the old mercury thermostats. We bought new thermostats without realizing that not all thermostats that are compatible with hot water systems are compatible with 3 wire valve systems. Our 3 wires are red, white, and black. If we hook up the black wire to the Y terminal, the red to the R, and the white to the W, will our system work?

Thanks for any feedback!


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## Houston204 (Oct 18, 2009)

Probably not without adding a relay. Post the make and model number of your new stat.

The VisionPro 8000 series will control your 3 wire, power open, power closed valves. (option 170 = 5)


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## lazysummer (Oct 9, 2011)

Thanks, Houston204. The thermostat(s) we bought was a Honeywell Pro 2000 (TH21101009). We bought it in part because it has a vertical orientation and one of the existing thermostats was flush against door trim. We also thought it was good for a hydronic system (not understanding the 2 vs. 3 wire distinction).

How hard are relays to install?

Thanks again.


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## Houston204 (Oct 18, 2009)

Have you verified that you are using 3 wires at the stat?
Some zone control boards supply power to close when no heating demand is present...











Relays are not hard to install but this may approach the cost of a better stat.


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## lazysummer (Oct 9, 2011)

It definitely has 3 wires - red, black, and white. 

I hooked a thermostat up the way I'd mentioned in my first post (red - R; white - W; black - Y) and found it was a 'close, but no cigar' configuration. When hooked up this way the heat came on when the actual temperature was above the set point (i.e., actual temp = 72; set point = 68) and went off when the actual temperature was below the set point (i.e., actual temp = 72; set point = 75). 

Can I reverse 2 wires and get this working correctly? If so, would this cause any problems such as damaging the thermostat or the heating system?


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## Houston204 (Oct 18, 2009)

http://customer.honeywell.com/techlit/pdf/PackedLit/69-1968EFS.pdf

I see nothing to indicate that 24VAC is supplied to the Y terminal when a heating demand is not present. If your hot water valve requires power to open and power to close you will probably require a relay.










Do you have a meter to measure for 24 volt power to close when demand is not present?


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## gegesns (Oct 17, 2011)

*problem with 3 wire zone valve*

I have Edwards Zone-A-Matic valve on my hot water baseboard heating and I want to switch thermostat. I already bought one at Lowes Honeywell nonprogramable one RHTL111B and have problem with closing the valve. Is this 24vac SPDT relay will help to work it porperly? 
The thermostat works when I when I want more heat but when I lower the themperature it wont close the valve so thats my problem. 
Thank for answer.


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## rmitch800 (Nov 8, 2011)

*3 wire hydronic thermostat WR 1F80-0471*

After much research and reading posts here, I purchased a White Rodgers 1F80-0471 programmable thermostat (purchased on E-Bay) to replace a very old White Rodgers mercury thermostat to control one zone on an old Hydrotherm hot water system with 3 zone valves and 3 wires (red, white and green). 

The White Rogers wiring instructions for this thermostat leave something to be desired (the instructions only show 2 of the three wires - the red and white ones coming from the transformer. I connected the red wire to the RH thermostat terminal, the white wire to the W thermostat terminal and the green wire to the o/b termial. The thermostat would turn the zone on, but would not turn it off when the desired temp was reached.

In short - after help from my PHD engineer neighbor and time with a multimeter today- we connected the white wire to the RH terminal, the red wire to the W terminal and the green wire to the O/B terminal and now (fingers crossed) it appears to be working correctly. This appears to be a really nice thermostat - so I hope it keeps working!


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## Machoman22! (Oct 15, 2017)

rmitch800 - Thanks for the info! I was pulling my hair out today, getting NOTHING to work, until I found your comments. Sadly though, mine still isn't working 100% correctly. I hooked it up as you said (white - RH, red - W, green - O/B), but now the valve does open, so I get heat, but it won't shut off once the desired temperature is met. That said, am I also supposed to leave the jumper wire in/connecting between RH and RC, or...? Any comments would be MUCH appreciated.


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