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Why is thermostat/zone valve wiring not done neater?

jmulla
jmulla Member Posts: 11
I have a 4-zone boiler system with 4 Taco 571-2 zone valves, 4 old-school 2-wire thermostats, one common circulator pump, and one common Taco SR501 controller.

I have been tracing through the wiring and labeling everything as I am planning to install Nest thermostats.

My question is: Why do the HVAC techs run all the wires in a configuration that used a whole bunch of intermediate wire nuts rather than making shorter parallel connections when they can.

For example, I have 2 transformers because of the 4 zone valves. Instead of connecting the two transformers (that are located side-by-side) in parallel and then connecting their R & W terminals to the appropriate thermostat and zone valve terminals, the two transformers are wired separately to thermostats and zone valve through a web of wirenut connections. See attached wiring diagrams.

Can someone explain why this is done? Is it just simpler from the installer's perspective? Is there a current limit for the 18 ga wire or a voltage drop problem if these connections are made using a daisy chain?

Am I missing something?





Comments

  • Big Ed_4
    Big Ed_4 Member Posts: 1,897
    edited July 3
    The Taco 571 would have 4 terminals Two for the motor and a dry contact end switch. In your diagram your showing a three terminal . Which is a power on and power off zone valve . You need a analog double contact thermostat . In the diagram you are trying to phase three transformers , the relay is the third .
    I have enough experience to know , that I dont know it all
    EdTheHeaterMan
  • Steamhead
    Steamhead Member Posts: 15,429
    edited July 3
    @Big Ed_4 , you're thinking of the Taco Zone Sentry which uses a ball valve. The 571 has the 3-terminal heat motor.

    @jmulla , I would not connect those two transformers together. I'd use one to power two of your ZVs and the other for the other two. Then use an isolation relay such as a Honeywell R8222 for each zone valve/transformer subset, since currently these ZVs output 24V to the SR501 which has its own transformer and expects to see just a switch turning on and off.

    The reason for all this is because transformers can fry if you get the wires reversed. Ask me how I know that................
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • jmulla
    jmulla Member Posts: 11
    Thanks, Alan. I would do what you suggest if I were doing it from scratch. But I'm dealing with an existing house. Also, I have only one circulator pump that drives all 4 zones, so the Taco SR501 with a single (combined) zone controller is sufficient.

    But back to my original question, even with a 1-zone Taco, why do HVAC guys wire like my first diagram and not the second? Are they just used to cutting both conductors of a cable, wiring one side up to a terminal on a zone valve or transformer, and then running the other leg to a wire nut with a jumper to wherever it has to go?

  • Big Ed_4
    Big Ed_4 Member Posts: 1,897
    edited July 3
    @Big Ed_4 , you're thinking of the Taco Zone Sentry which uses a ball valve. The 571 has the 3-terminal heat motor.

    Qne would be the hot for the motor , two would be a joint common and two and three would be the end switch to the relay ?

    I just checked out a wiring diagram ..
    I have enough experience to know , that I dont know it all
    rick in Alaska
  • Steamhead
    Steamhead Member Posts: 15,429
    Actually, 2 is the "hot", 1 goes to the thermostat (other side of thermostat goes to Common side of transformer) and 3 sends 24V to one side of the relay coil (other side goes to Common).

    All the zone valve 3 terminals on the same transformer can connect to the same relay coil.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,307
    edited July 3
    To answer your question, everyone wires their zones differently and since most hydronic installers don’t have the rigorous training that electricians have, it’s often messy and counterintuitive. 
    Also, I have only one circulator pump that drives all 4 zones, so the Taco SR501 with a single (combined) zone controller is sufficient.
    Yes, the SR501 is only a pump control and you have to freehand the zone valve wiring while the ZVC's combine zone valve wiring AND pump wiring all in one unit.

    The zone valve controls are ideal for retrofits.  

    @Steamhead said:
    Actually, 2 is the "hot", 1 goes to the thermostat (other side of thermostat goes to Common side of transformer) and 3 sends 24V to one side of the relay coil (other side goes to Common). 

    Normally, 3 is just a dry contact that joins 2 for end switch closure, no?

    Often wrong, never in doubt.
  • Steamhead
    Steamhead Member Posts: 15,429
    edited July 3

     

    @Steamhead said:
    Actually, 2 is the "hot", 1 goes to the thermostat (other side of thermostat goes to Common side of transformer) and 3 sends 24V to one side of the relay coil (other side goes to Common).
    Normally, 3 is just a dry contact that joins 2 for end switch closure, no?

     



    Right. But it's technically not a "dry" contact since it has voltage on it when closed. A true dry contact gets whatever voltage it operates from some other unit.

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    Zmanmattmia2
  • GW
    GW Member Posts: 4,556
    1 is hot
    2 is common 
    2 and 3 are end switch 
    no??? 
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
    Alan (California Radiant) Forbes
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,307
    edited July 3
    Right. But it's technically not a "dry" contact since it has voltage on it when closed. A true dry contact gets whatever voltage it operates from some other unit.
    Two and 3 are the end switch to the boiler which has it's own transformer that picks up the closure.

    Often wrong, never in doubt.
  • Ironman
    Ironman Member Posts: 6,893
    No one knows for sure why it was done the way it was except the guy who did it.

    On another note: the Nest is not a good choice for a hydronic system.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    STEVEusaPA
  • jmulla
    jmulla Member Posts: 11
    @Steamhead & @Alan (California Radiant) Forbes : Great comments. Thanks for the advice.

    @Steamhead , you're right, I have the Taco ZV 571-2s that have 3 terminals and the functions and wiring should be as you describe above. Regarding the transformers, my current setup is a mess (not mine. :neutral: ) the previous guy has the hots of the two transformers tied together at one of the ZV terminal 2's, but the common from the first transformer goes to 3 thermostats and the common from the second transformer goes only to the 4th thermostat! I have tested the thermostats by connecting them in series so I know their polarities. I don't there will be any harm in connecting them in parallel.

    @Alan (California Radiant) Forbes Now that I've looked at my setup again (it's a mess but that's a story for later), I think I will take your advice and install a ZVC to clean up the wiring.

    Thanks all!

    MikeAmann
  • jmulla
    jmulla Member Posts: 11
    Ironman said:

    On another note: the Nest is not a good choice for a hydronic system.

    @Ironman, can you elaborate on why? Is it anything other than needing the C-wire? P.S. I only have a hydronic heating system, no integrated A/C. (I do have two stand-alone Mitsubishi splits.)

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,149
    If you go on Taco web site, they explain how the 3 wire valve works. It always confused me and I never liked the idea of two transformers "butting heads"

    But as Taco explains two transformers can be connected if only 1 wire of the second transformer is connected.

    See page 3 in the attached.

    Funny the information is in their brochure not in the install instructions
    Alan (California Radiant) ForbesZman
  • mattmia2
    mattmia2 Member Posts: 5,740
    If you want to save some money and do a little more work you could get some terminal strips and a piece of plywood and wire it up that way instead of getting the packaged zone control.
  • jmulla
    jmulla Member Posts: 11
    edited July 14

    @EBEBRATT-Ed ,

    If you go on Taco web site, they explain how the 3 wire valve works. It always confused me and I never liked the idea of two transformers "butting heads"

    But as Taco explains two transformers can be connected if only 1 wire of the second transformer is connected.

    See page 3 in the attached.

    Funny the information is in their brochure not in the install instructions

    That Taco brochure was very informative. But I think you're confusing my question about the two transformers with what the Taco brochure is talking about.

    My two transformers are the transformers that drive the thermostats & terminals 1/2 of the zone valves. (I need two thermostats because I have 4 zone valves that exceed the capacity of one transformer.)

    The two transformers that the brochure is talking about are
    (1) the transformer as above and
    (2) the transformer in the boiler controller.

    These two transformers are only connected at one leg as shown in the diagram in the brochure.

    Two separate issues.

  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 3,307
    edited July 14
    @jmulla: I think the conversation drifted off a bit from your initial topic of two driving transformers (driving meaning operating thermostats and transformers) to how the end switch closes the leg of the boiler transformer to turn the boiler on.

    These two transformers are only connected at one leg as shown in the diagram in the brochure.
    This is what my Taco diagram shows. However, both diagrams show two legs of the transformer.



    Often wrong, never in doubt.
  • JimP
    JimP Member Posts: 47
    The original install has the two transformers wired in parallel. One is wired to three zones and the other to one. They share the load. The suggestion to install a wiring block is a good one. That way you can more easily trace and diagnose any problems. You could split the load between two zones or install a larger transformer.
  • 109A_5
    109A_5 Member Posts: 160
    edited July 16
    @jmulla,

    When it come to wiring it seems neatness and aesthetics is an Art, not all Installers, Technicians, Electricians, etc. possess that talent or if they do they don't have the time and / or other resources to bother, bottom line, it just needs to work.

    A nice neat job does benefit the next guy (who may be the original installer) that needs to figure it out and make a repair.

    As far a paralleling transformers in your case, I would not. Yes, it would work if done correctly, but consider this.

    40 VA transformers are almost as common as dirt and they match up with the load of a 3 zone valve system for a nice 'Modular' cost effective package. When installing larger systems, say 7 zones or greater you want to stay within the Class 2 wiring criteria (100 VA or less I believe). So go modular, it's easy.

    Also consider the other picture on page 3 of the attached PDF above, your "Current System" is wired the same (electrically speaking), just cover up the Left two optional zones. However your system may have more wire nuts and yet it still works.



    Additionally if you parallel the transformers, if TRANS 1 fails (for any reason) it may take out TRANS 2 also, leaving you with no heat. Also if there is an over-current type defect out in the system it will probably burn up both transformers instead of just one transformer.

    If you stick with the modular approach and TRANS 1 fails your Master Bedroom will stay toasty warm. Also you could swap transformers to warm the rest of the house if you know the transformer's failure was not caused by a defect out in the rest of that part of the system (you would have one good transformer for troubleshooting purposes too).

    Also to minimize confusion the boiler probably has its own transformer (or a third transformer).

    If you want to neaten up your system and make it more aesthetically pleasing and probably easier to troubleshoot by all means go for it, however I would not parallel the transformers.

    If it was my system I probably would have 2 zones on each transformer, to heat the house more evenly in the event of a single transformer failure.
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    ratioMikeAmannEdTheHeaterMan
  • HVACNUT
    HVACNUT Member Posts: 4,624
    @jmulla, why not just use one 75 va transformer with a circuit breaker?
    And the Honeywell brochure diagram doesn't seem right to me. Terminal 1 is common (ground). Terminal 2 is 24 volts. Terminals 2 and 3 are the end switch. The diagram shows Common switching through the thermostat to Terminal 1. There's constant 24 volts at Terminal 2. When 2 and 3 close, it looks like a direct short to the Independent transformer. Or am I not looking at it right?

  • 109A_5
    109A_5 Member Posts: 160
    HVACNUT said:

    @jmulla, why not just use one 75 va transformer with a circuit breaker?

    You could, and it would probably work (since there are presently only 4 zones in this case). And a properly rated and placed circuit breaker is a good idea.
    However 40VA + 40VA is not 75VA and 40VA with three zones is already pushing it (0.9 A for each zone valve). If I had to use one transformer, I would use a 92 VA or a 96 VA (for 6 zone compatibility), BUT the cost !!! Two 40 VA units is much cheaper. And I believe @jmulla already has the two 40 VA transformers and wants to add a power hungry thermostat. So, if needed, he could add another 40 VA transformer for little cost to power the power hungry thermostat.
    HVACNUT said:

    And the Honeywell brochure diagram.

    "Honeywell" I'm assuming that is a typo.
    HVACNUT said:

    And the Honeywell brochure diagram doesn't seem right to me. Terminal 1 is common (ground).

    Terminal 1 on the Zone Valve internally goes only to one side of the heater that is around the wax filled element (not 'common' and no 'ground'). So Terminal 1 is only connected the the Independent transformer through the thermostat switch(s) and that side of the transformer is floating (not connected to anything except the thermostat(s)).

    Again, in this case, for multiple reasons mentioned above by @Steamhead and myself I would have two zones per transformer which may leave enough transformer capacity for the power hungry thermostat.
    A six zone controller would also work if you want to pay for it.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • jmulla
    jmulla Member Posts: 11
    @109A_5 , @Alan (California Radiant) Forbes , @Steamhead
    Thank you, thank you, thank you! Your comments have been most helpful and illustrative.

    I now understand why paralleling the two transformers, or going up to a greater VA transformer would not be a good idea. I will split the 4 zones evenly across the two transformers.

    @Alan (California Radiant) Forbes , I am not thinking of reversing my thoughts on replacing the SR501 with an SR504 4-zone controller. It will also help make for neater (structured) wiring.

    Any last suggestions?
    MikeAmann
  • HVACNUT
    HVACNUT Member Posts: 4,624
    jmulla said: Any last suggestions?
    Yes, this.
  • jmulla
    jmulla Member Posts: 11
    @Alan (California Radiant) Forbes
    Oops, type above. Sorry. 
    “I am not …” should be “I am now…” 

  • 109A_5
    109A_5 Member Posts: 160
    HVACNUT said:

    @jmulla, When 2 and 3 close, it looks like a direct short to the Independent transformer. Or am I not looking at it right?

    @HVACNUT I now see what you mean, and I agree, I was looking at the other drawing. See the Red circle below, I think it should be the coil of the "Boiler Control (Circulator Relay)" not the N/O contact shown as closed.




    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    jmullaEdTheHeaterMan
  • 109A_5
    109A_5 Member Posts: 160
    @jmulla, One possible wiring method (least expensive). 4 NEST units, loads appropriately distributed with 40VA transformers.



    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    jmullaMikeAmann
  • jmulla
    jmulla Member Posts: 11
    @109A_5 : BEAUTIFUL!! Thanks!

    [Two last] questions:

    (1) Since these 40 VA transformers (TRANS 1 & 2) are not bonded to ground (i.e. floating on the load side) I assume that which terminal is called W and which is R is irrelevant as long as I stay consistent for each transformer. Correct?

    (2) I am only planning on replacing ONE of the old thermostats with a Nest. In that case, couldn't I drive 2 zone valves and one Nest from TRANS 1 without a need for the additional TRANS NEST 1? That should work if I use the W terminal of TRANS 1 for the C wire. Correct?
  • 109A_5
    109A_5 Member Posts: 160
    Hello @jmulla,

    (1) Yes if the wiring is consistent, I don't think you will have any problems there. By not paralleling the transformers you don't run the risk of that issue being wrong (for any reason). Also not that it matters here, there may be a equipment ground bond inside the TACO Relay unit (just so you know). As long as that is the only bonding point as far as the zone valves / NEST / transformers are concerned there should not be any problems in that sense.

    (2) You suggest this (I think);

    Or this

    Either may work for you. However in either case 40VA transformers could be mildly overloaded for a time.
    (0.9 + 0.9 + 0.2) = 2.0 A x 24 V = 48 VA for TRANS 1 in the first example. 0.9 Amps of the duty cycled load of the two TACO zone valves and the 0.2 Amps worst case (?) current draw of a NEST (that I found and that may depend on the NEST model).

    To be conservative with the loading of the transformers and utilizing a configuration often found on the net to resolve NEST issues, I would recommend this configuration.


    I believe heat and heat cycling is the enemy of most electrical / electronic devices. A 40VA transformer probably should run 24/7 with a 40VA load. Mild overloads of 8VA with duty cycled load reduction of at least 22VA less may keep a 40VA transformer relatively safe and not overheated to the point of failure. As compared the the apparently acceptable maximum load (duty cycled) of (0.9 + 0.9 + 0.9) = 2.7 A x 24 V = 65 VA to run three zones on one 40VA transformer.

    The TACO zone valve has two duty cycles as I see it. One is the call for heat and it varies a lot between mild weather and design days. The other duty cycle is the cycling rate of the Wax Filled Element Heat Motor (see that Heater Switch modulated by the piston position in the zone valve drawing). No clue to what that duty cycle is, maybe 50% after the Heat Motor warms up.


    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • jmulla
    jmulla Member Posts: 11
    Hi @109A_5:

    Thanks again. Excellent explanation. I think I will go with the last diagram and add the TRANS NEST 1.

    I never gave much thought to overloading the transformers, but your reply got me thinking. This is a vacation home and the worst-case scenarios could easily arise (e.g. we walk in during the winter and we simultaneously turn up all thermostats from their winter setting of 50° to 72°.)

    Now this brings up another question. Although TRANS 1 and TRANS NEST 1 are only connected on one leg (so not strictly in parallel), is it necessary that the two transformers should be on the same primary phase?

    I'm still cogitating whether I should replace the SR501 with an SR504. Spoke to a local HVAC person and he said that the Taco relays are notorious for failing and having 4 zones would just increase the probability of a relay failure. He claimed that the relays are not replaceable (although I see them for sale on the Internet). However, losing a relay in an SR504 would only mean the loss of one zone, which would be better than losing all zones with a relay failure on the SR501. Right? Or am I missing something?

    Thanks
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,336
    edited July 25
    The Taco 571 power head is not compatible with the Nest thermostat. This is because the valve actuator is not always powered. As the wax in the hydraulic piston heats up and expands three things happen in this order.
    1. The valve opens to allow flow thru the valve... as the wax increases in volume there is a cam that (see #2)
    2. The cam actuates the end switch contacts in order top operate the boiler or circulator relay... As the wax increases in volume and pushes the piston further that same cam (see #3)
    3. The normally closed Heater Switch contacts open to stop the wax expansion and over heat causing a piston leak failure ... the wax cools and decreases in volume closing allowing the piston to move towards closing. the cam allows the heat switch to close and the wax heats up. this causes the cam to open the heat switch that opens the circuit. and on and on and on.

    This opening of the heat element circuit is interpreted by the Nest as the open circuit or NO PPOWER fault and the thermostat goes thru a lockout and reboot procedure. Since this is normal for the valve actuator and may happen 6 or more times a minute, and not normal for the Nest, you will experience a no heat condition. The fix for Taco 3 terminal zone valves is to use an isolation relay like this one. by DiversiTech part number D90-290Q. it is also made by White Rogers and Supco. It is a pretty standard HVAC relay.

    Here is how I would wire it:


    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    MikeAmann
  • @EdTheHeaterMan said:
    This opening of the heat element circuit is interpreted by the Nest as the open circuit or NO PPOWER fault and the thermostat goes thru a lockout and reboot procedure.
    Does the Nest thermostat really know what the zone valve is doing, i.e. on-off-on-off.......I don't think so.
    Often wrong, never in doubt.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,336
    edited August 2

    @EdTheHeaterMan said:

    This opening of the heat element circuit is interpreted by the Nest as the open circuit or NO PPOWER fault and the thermostat goes thru a lockout and reboot procedure.
    Does the Nest thermostat really know what the zone valve is doing, i.e. on-off-on-off.......I don't think so.
    Perhaps the AI of the thermostat is not as smart as I may have made it sound. However when the nest thermostat has a wire inserted into the W1 terminal and there is a call for heat then the W1 has power to the Taco #1 terminal to the heating element. There is a return path from that heating element thru the heater cam switch back to the #2 terminal that continues to the transformer common. The thermostat measures that current movement thru the thermostat as a normal operation. Once the heating element activates the cam to open the heating switch the current flow thru the thermostat is interrupted. This (although normal for the zone valve actuator) is identified by the Nest internal circuitry as a Fault. I believe it is the E 82 code which says in the troubleshooting guide "No Power to the W1 terminal. This is actually an incorrect statement because there is power to W1 terminal but the circuit is broken so it does not have complete path to the source. Since most repair personal are not so exacting in their use of electrical terminology, it is easier to understand "No Power to W1 wire detected" as opposed to "there is an open circuit in the path from W1 on the thermostat to the heating control device, relay, valve, or actuator back to the source that we believe should trigger this error code"




    So me using the phrase "The thermostat knows this as a problem" is really me saying in less technical terms "there is an open circuit in the path from W1 on the thermostat to the heating control device, relay, valve, or actuator back to the source that we believe should trigger this error code"

    I will try to be more clear in my future discussions

    So YES the thermostat knows On - Off - On - Off is happening and the E82 error code is generated.

    BTW, you can fix this problem with an isolation relay

    EDIT:
    Really Alan, Don't you know that the computer or tablet screen you are viewing this reply on, is actually recording every keystroke and saving it so that your response can be viewed by everyone with an internet connection. Think about it. They don't even need to sign up. They can look at this as a guest. And you think thermostats don't know any better. Be careful what you say. You never know who is monitoring!?!?! >:)
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • Labenaqui
    Labenaqui Member Posts: 50
    Our modular, patented appliance is by definition virtually pre-built. The Supply Assembly Zone Sentries are pre-harnessed into 4-wire cable drop that attach to the E-Switch Control Box. Just drop the T-Stat Wires and 3-Wire Power to complete an install.
    Note that by compacting & orienting the Zone Sentry LEDs negates the need for a Switching Relay entirely. The LED Status Indicators are "smarter" than a Relay, so haven't used one in well over a decade .....
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,336
    Labenaqui said:

    Our modular, patented appliance is by definition virtually pre-built. The Supply Assembly Zone Sentries are pre-harnessed into 4-wire cable drop that attach to the E-Switch Control Box. Just drop the T-Stat Wires and 3-Wire Power to complete an install.
    Note that by compacting & orienting the Zone Sentry LEDs negates the need for a Switching Relay entirely. The LED Status Indicators are "smarter" than a Relay, so haven't used one in well over a decade .....

    Great concept for using Zone Sentry to eliminate the need for an iso relay. However in this case, it is a little overkill, don't you think? Adding an isolation relay to an existing 571 actuator is less costly than re-plumbing a bunch of new zone valves (whether or not they are patented or not).

    Remember we started with
    @jmulla Member
    Posts: 10
    July 2

    I have a 4-zone boiler system with 4 Taco 571-2 zone valves, 4 old-school 2-wire thermostats, one common circulator pump, and one common Taco SR501 controller.
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
  • SteveSan
    SteveSan Member Posts: 122
    @EdTheHeaterMan The Nest t-stats are compatible with our 570 series, ZVC & SR controls. Attach is a wiring diagram showing how to wire Nest to our controls and to 570 series zone valve. The only issue you will have is with more than 2 Nest to our SR controls. More than two Nest you will need to wire in an external transformer because of the VA draw on the Nest. Our 1000ohm 1/2watt resistor will not work with Nest T-stats. Nest suggests you use a 220ohm, up to 5watt resistor if needed. Any questions please contact Taco Tech Support during normal business hours Mon-Fri 8am-5pm EST. Hope this helps.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,336
    edited August 3
    SteveSan said:

    @EdTheHeaterMan The Nest t-stats are compatible with our 570 series, ZVC & SR controls. Attach is a wiring diagram showing how to wire Nest to our controls and to 570 series zone valve. The only issue you will have is with more than 2 Nest to our SR controls. More than two Nest you will need to wire in an external transformer because of the VA draw on the Nest. Our 1000ohm 1/2watt resistor will not work with Nest T-stats. Nest suggests you use a 220ohm, up to 5watt resistor if needed. Any questions please contact Taco Tech Support during normal business hours Mon-Fri 8am-5pm EST. Hope this helps.

    Thanks for your reply Steve. I looked at that last diagram and did just that many many years ago when Nest first came out. I got the E82 error as soon as the heat switch opened. I fixed it with the relay. Ever since that I have always used the isolation relay. (fool me once...). So I guess there have been changers in the programing since those early Nest thermostats. Being connected to the internet you never know what that darn thermostat is going to learn next.

    Retired now so I will probably only work on my own stuff. But good to know.

    I was a Taco fan long before you worked there. I won a Color TV from Taco by being one of the 4 fastest people to swap out a Taco 007 cartridge at the Lancaster PA Service Manager's convention in 1980. I came in 3rd. My brother came in 5th. I have preferred Taco because of that promo my entire professional career. Keep up on those promotions! They work!

    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    SteveSan
  • Tim McElwain
    Tim McElwain Member Posts: 4,517
    If you are going to all this trouble why not purchases some terminal strips from your local electrical supply and rewire to those strips makes for a much neater job and also easier to troubleshoot when problems arise. We need to hear from Alex the wiring nut!!!
    jmulla
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 3,336
    edited August 4
    After reading @Tim McElwain comment I had to add this again.

    The large lines are the pipes, the smaller ones are the wires. But all you already knew that just by looking at it!

    Mr. Ed
    Edward Young
    Retired HVAC Contractor from So. Jersey.
    Services first oil burner at age 16
    P/T trainer for EH-CC.org
    jmullaGGross
  • jmulla
    jmulla Member Posts: 11
    edited August 8
    If you are going to all this trouble why not purchases some terminal strips from your local electrical supply and rewire to those strips makes for a much neater job and also easier to troubleshoot when problems arise. We need to hear from Alex the wiring nut!!!
    After much thought and advice from commenters, I’m going with terminal strips. Will post pics after completion.
    GGrossCanucker