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Taco's zone lights not coming on

mseifert9mseifert9 Member Posts: 13
edited October 2019 in Radiant Heating
I've got 3 zone radiant heat with two wired and one wireless thermostats. The Taco SR503 has the green power light but none of the red zone lights are coming on. The end result is that the Hydronic Recirculating Pump is not running, I can 't tell if the Honeywell valves are open or not. The system was working this past spring, so trying to figure out what has gone wrong.

I presume I have 24v because I have my water thermostats wired to the Taco and they are showing power. But when I tried to test the 24v with one multi-meter end to the 24v screw and other end to ground I got nothing . Not sure how to test - besides the front facing 24v screw (there are two), what should the other multi-meter end touch? I am also not getting any power to the valves as far as I can tell. The Honeywell THM5320R wireless thermostat base is showing a call for heat (power, heat, and fan lights are on) as are all 3 zone thermostats inside the house.

I have a HVAC service set for Tuesday, but I want to understand and be able to troubleshoot myself anyway. Any suggestions what my next steps can be? Here is a DIY rough schematic of my wiring. It leaves out most of the heating end of the wiring which involves the Water Thermostats (in the buffer tank) which call for heat and the Geothermal unit.

A slightly different question - One of the Honeywell zone valves had the lever on top set to manual and the other two to Auto. My understanding is that they should all be on Auto. Any insight on this would also be appreciated.

Thanks in advance for your help.

Updated to show all wiring
Current System


Proposed System

Comments

  • STEVEusaPASTEVEusaPA Member Posts: 4,142
    You're diagram makes no sense to me. Seems wrong or incomplete. You're saying 'SR503' and 'zone valves'. One of those things is wrong
    steve
  • mseifert9mseifert9 Member Posts: 13
    edited October 2019
    Confusion is probably caused because "Zone" means two different things on the Taco SR503 Zone Switching Relay .
    1) The "Thermostats" section on the top of the Taco board (see below) shows 3 zones. I would have expected these 3 sections to each be tied to one of the house thermostats, but they are not. Zone 1 is a call for the Geo Loop Pump (based on a complicated group of inputs). Zone 2 is a call for the Hydronic Loop Pump - whenever any Hydronic Zone Valves are open due to house thermostat calling for heat.

    2) The 120v Circulators section on the bottom of the Taco board also shows 3 zones. Zone 1 is connected to the Geothermal Loop Pump and Zone 2 is attached to the Hydronic Loop Pump. I've updated the drawing to include the Geo Loop Pump for Zone 1.

    The broken functionality is around calling the Recirc Pump and I believe this is reflected in the Zone 1 Light on the side of the Taco SR503 not illuminating.

    The house thermostats are supposed to open the "zone valves" when calling for heat. I believe the way it is supposed to work is that when the zone valve is open, the "End Switch" side of the zone valve send the signal to the Taco which then energizes the Zone 2 Hydronic Loop Pump (and Lights Zone 2 indicator).

    The rest of the incomplete part of the drawing is related to the Geothermal unit. The call for heat to the boiler is made only when the temperature of the hydronic water drops below set point which is determined by 3 water thermostats and an Outdoor Reset (ODR) along with a Tekmar Boiler Control 256. These have connections to the Taco SR503 which I've left out due to the complexity (see the image) and I don't believe are part of the problem.

    Thanks for taking the time to read this.



    HVACNUT
  • mseifert9mseifert9 Member Posts: 13
    After explaining how this all works, I believe the issue is around the cut green wire on the Taco's Thermostats Zone 2 terminal. One Zone 2 terminal is connected to one side of the Zone Valves' End Switch (they are all joined by a white wire). What should the other Zone 2 terminal be connected to?
  • ZmanZman Member Posts: 5,830
    The controller is supposed to clean up the wiring and make diagnosing easier. What you have there is a wiring mess. The transformers in the controller were not designed for the additional load of the zone valves and are likely maxed out.
    I would add a taco zone valve controller to manage the t-stats and zone valves. You could then tie the end switches from the zone valves to the thermostat terminals on this controller so it can control the circulators. As you are experiencing first hand, trying to troubleshoot spaghetti wiring is very frustrating.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    STEVEusaPAkcoppCanucker
  • mseifert9mseifert9 Member Posts: 13
    @Zman Thanks for taking the time to look through my post. Your advice makes sense. It'll be interesting for me to see what the solution is when my repair tech visits - whether it is a wiring issue or a hardware failure.

    I'll mention your advice. However, adding another controller and having to rewire the whole thing looks expensive based on the number of connections.
  • ZmanZman Member Posts: 5,830
    The honeywell zone valves are probably not proving the end switches. Those valves are know for that, especially when not adequately powered.
    If you pick up 3 of these https://www.supplyhouse.com/Honeywell-40003916-026-Replacement-Head-for-V8043E-Zone-Valves-8632000-p
    and 1 of these https://www.supplyhouse.com/Taco-ZVC403-4-3-Zone-Valve-Control-Module-with-Priority

    A good tech should be able to install it in a few hours
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mseifert9mseifert9 Member Posts: 13
    edited October 2019
    @Zman I understand the need for the Taco Control Module to help fully power the valves. And it makes sense that the valves might not be opening completely, causing the lack of the signal making it to the Taco (I presume this is what you mean by 'proving').

    If the new Taco Control Module handles the power issue for the valves, I don't see a need for the replacement heads as the valves were installed less than a year ago.

    Thanks for the suggestions.
    Zman
  • Joe MattielloJoe Mattiello Member Posts: 589
    I was reading tread on the power robbing thermostats when used with Taco control. The thermostats need power to energize closure of switch on demand. As you’ve witnessed with diagnostic tests, no power is available at RW unless there is a demand. I believe a resistor ohms depends on stat requirements should remedy the issue.
    I suggest you contact Taco tech support for more information at 401-942-8000, ask for tech support.
    If you’re not successful, please reach out to me at 401-261-4890, and I’ll make sure you get the help you need. Thanks for using Taco products.
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
    Rich_49Erin Holohan HaskellZman
  • mseifert9mseifert9 Member Posts: 13
    edited October 2019
    @Zman - Local tech came out and refused to work on it, saying it's all wired incorrectly. Company is not able to do the work this year - and honestly, I wouldn't trust them to do a complete rewire based on his comments. We're in a small town and to find a company with qualified trained techs, I had to call a company 2 hours a way. Including $/hr travel time), they guessed $-$ to rewire. They'd rip it all out and start over - and couldn't do it before December.

    I'm thinking of taking on the rewiring myself and started looking for wiring diagrams which show my Taco SR503 Switching Relay wired to the Taco Zone Valve Control ZVC403 that you recommended. I found a Taco Zone Controls Wiring Guide at: http://www.taco-hvac.com/uploads/FileLibrary/100-9.0.pdf with lots of Taco combinations but not these together.

    Is it just a matter of wiring the thermostats to the ZVC403 and then wiring from its End Switch back to one of the Thermostat Zone Inputs on the SR503?

    I would appreciate any wiring guidance on how these two would be wired together.
  • HVACNUTHVACNUT Member Posts: 3,366
    If all control wiring is clearly labeled, and we know exactly what each serves, come back in the spring and we'll help.
  • WellnessWellness Member Posts: 100
    edited October 2019
    I don't understand the reason for all the wire nuts in your Taco control box. The thermostat wires look like they are home runs, so you should be able to terminate them neatly, and individually to the thermostat terminals in the upper right hand corner of your picture. First shut off the breaker in your main panel that supplies power to the Taco Control box. If you don't know which thermostat is which, borrow or buy a voltmeter or a network toner to trace the wire from the thermostat to the control box. Get that fixed, then you can address the faulty LED and all the other issues going on in your control box.
  • ZmanZman Member Posts: 5,830
    Wellness said:

    I don't understand the reason for all the wire nuts in your Taco control box. The thermostat wires look like they are home runs, so you should be able to terminate them neatly, and individually to the thermostat terminals in the upper right hand corner of your picture. First shut off the breaker in your main panel that supplies power to the Taco Control box. If you don't know which thermostat is which, borrow or buy a voltmeter or a network toner to trace the wire from the thermostat to the control box. Get that fixed, then you can address the faulty LED and all the other issues going on in your control box.

    It is a pump relay that is being hijacked to also power the zone valves.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ZmanZman Member Posts: 5,830
    mseifert9 said:

    @Zman - Local tech came out and refused to work on it, saying it's all wired incorrectly. Company is not able to do the work this year - and honestly, I wouldn't trust them to do a complete rewire based on his comments. We're in a small town and to find a company with qualified trained techs, I had to call a company 2 hours a way. Including $/hr travel time), they guessed $-$ to rewire. They'd rip it all out and start over - and couldn't do it before December.

    I'm thinking of taking on the rewiring myself and started looking for wiring diagrams which show my Taco SR503 Switching Relay wired to the Taco Zone Valve Control ZVC403 that you recommended. I found a Taco Zone Controls Wiring Guide at: http://www.taco-hvac.com/uploads/FileLibrary/100-9.0.pdf with lots of Taco combinations but not these together.

    Is it just a matter of wiring the thermostats to the ZVC403 and then wiring from its End Switch back to one of the Thermostat Zone Inputs on the SR503?

    I would appreciate any wiring guidance on how these two would be wired together.

    That is pretty much all there is to it. If you are comfortable with the line voltage side of it you should be good to go.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mseifert9mseifert9 Member Posts: 13
    edited October 2019
    @Zman - I have ordered the Taco ZVC403 as you suggested. I also dug deeper into the wiring to understand it as best I can. The revised drawing is uploaded to the original post.

    I've also added a Proposed drawing to the original post at the bottom which is my understanding of how the new ZVC403 should be wired.

    My Questions:
    1) It appears to me that the old wiring provided 24v (via the blue 24v terminal) to the Zone Valves and the Wired Thermostats. With the new Taco ZVC403, do I need to wire 24v from the Taco to any of these or is the 24v supplied via the terminals?

    2) The Honeywell Wireless Thermostat doesn't have a second wire coming from the Relay to Zone 2. What goes to the other Zone 2 terminal - a wire to the Blue 24v as shown?

    3) I'd like to understand the difference between the two Taco 24v terminals - Blue and Red. The blue appears to supply the power and the red appear to be the common to complete the circuit for those external devices which the Taco powers. Am I correct - can someone explain?

    4) Anything I'm missing?

    Some Notes:
    1) The immense amount of wiring in the existing Taco has a lot to due with the 3 Aquastats. I believe the main aquastat is actually superfluous as the Teckmar was installed afterwards and supersedes it. I feel I have a pretty good handle on how the system works now including the Relay and the Aquastats. If something doesn't make sense, I can explain why it is wired this way.

    2) I have not cracked the Tekmar to verify 100% the wire assignments - but am taking a reasonable guess based on position of wires and the wiring diagrams. I also haven't cracked the Johnson Aquastats to see what terminals the wires go to, but I bet they are obvious to all of you. If not, I'm happy to do this.

    3) I included both the Supply Wiring and the Switching Circuits on the same drawing. I discovered two hand drawings from my original installer which separate these two as documentation. If these would help, I would be happy to upload them. The original installer passed away many years ago.
  • ZmanZman Member Posts: 5,830
    1. The ZVR will handle power to the t-stats and zone valve motor.
    2. It looks like they are activating the relay by powering the load side. I don't love it but it likely works. G would need to be on the right. I would not run the new wire as drawn.
    3. You are correct about the red and blue.

    Your drawing is very clear but it is impossible to follow without some more detail.
    https://heatinghelp.com/store/detail/quick-and-basic-electricity-a-contractors-easy-guide-to-hvac-circuits-controls-and-wiring-diagrams-practical-is-good-p-i-g-technical-training-series

    The very wise Carol Fey would say that everything in an electrical circuit is either a power supply, a switch or a load.
    If you label everything that way it is very easy to follow. Keep in mind that a relay is a load that activates the switch(s)
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mseifert9mseifert9 Member Posts: 13
    edited October 2019
    Zman said:


    2. It looks like they are activating the relay by powering the load side. I don't love it but it likely works.

    When the main (Wireless) thermostat is put into "Cool" mode, this activates the relay, and opens terminals 4 & 5, shutting off the Tekmar. It also opens terminals 1 & 2, shutting off any possibility of opening Zone Valve 2.

    In Heat Mode, terminal 4 & 5 are Normally Closed and signals Boiler Demand on the Tekmar. Also, 1 & 2 are Normally Closed and allows Zone Valve 2 (main floor) to open when (Wireless) Thermostat calls for heat (on terminal Y).

    This may be the same as what you said, but I wasn't sure.
    Zman said:


    G would need to be on the right. I would not run the new wire as drawn.

    Thanks for the heads up on switching the G to the right. I can almost see why. If I were to wire it to the wrong side, is there any danger to the components?

    I understand about not adding the new wire, but how will the "G" wire which is powered through terminal "Y" (via the relay) on the Wireless Thermostat be closed? Are the common wires connected between the two Tacos? Currently, the common "R" terminal on the Thermostat is wired to the existing Taco SR503. Would I need to run another wire from "R" on the Thermostat to the new Taco or in some other way connect them?
    Zman said:


    4. You are correct about the red and blue.

    Thank you. No amount of Googling helped me confirm this. It is starting to make more sense.
    Zman said:


    The very wise Carol Fey would say that everything in an electrical circuit is either a power supply, a switch or a load.
    If you label everything that way it is very easy to follow. Keep in mind that a relay is a load that activates the switch(s)

    Makes sense and I'll try to make more sense in my drawings for the future home owners and techs to help out.
  • ZmanZman Member Posts: 5,830
    There is probably a simpler way to wire the whole thing. If you draw in your supplies, switches, loads and an control narrative, we can probably help you get there. It is hard to get there with just components and wire colors.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ZmanZman Member Posts: 5,830
    You absolutely could let the smoke out of something if you get it wired incorrectly. May sure all the power sources are wired to the same 120 volt breaker so you don't go to 48 volts. If you pick up some in line automotive fuses you will reduce the risk of smoking a transformer.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • WellnessWellness Member Posts: 100
    @Zman. Good catch on the relays. So he should get a separate junction box for them instead of crowding the Taco switching relay.
  • mseifert9mseifert9 Member Posts: 13
    edited October 2019
    I installed the new ZVC403 and both hard wired thermostats are correctly opening the corresponding zone valves. However the Honeywell wireless thermostat which goes through the relay does not. I've tried connecting the wire from the relay (terminal 1) to both the ZVC's right (as suggested) and left zone 2 thermostat terminals without success.

    I've simplified the drawing (below) to the essentials for the zone 2 circuit (my apologies if it is still not a "standard" electrical drawing). I am trying to wrap my head around how the circuit should be made when there are 2 Taco boxes involved. I've colored in green what I think is the path involved. What appears to be missing is a link between the two Taco boxes. It looks like a wire should go between the ZVC403 left zone 2 terminal and the common (blue) of the SR503 (the red dotted line). Is this safe to try? I don't know what else to do or try.

    I am also trying to figure out how to test with my multimeter. I can measure 24v across the TVC's zone valve terminals. But when I measure against the two corresponding zone's thermostat terminals, I don't show 24v and presumed I would. I was trying to figure out how to test what would close the zone circuit in question but if I can't detect voltage in a known working zone calling for heat, I don't have a clue. Any help would be appreciated.


  • ZmanZman Member Posts: 5,830
    When you get no voltage across the switch, it is because the switch is closed. An open switch will show voltage across.
    You if you are trying to figure out what is powered, test from the wire to common or ground.

    I think this is your answer. Pull the jumper and keep the transformers separate.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ZmanZman Member Posts: 5,830
    No that only works if you pull the common off the relay coil like this.
    I have never worked on that honeywell but I think I understand it. If anyone sees an easier way chime in
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mseifert9mseifert9 Member Posts: 13
    I still need cooling mode to energize the relay. Would this still work? Will not having a wire to Rc prevent cooling mode power?

    I presume the yellow line you drew going to common is the "C" terminal on the ZVC thermostat screws (zone 2)?
  • ZmanZman Member Posts: 5,830
    Jumper to RC then using the same transformer as the common for cooling. You want to land the yellow wire on the ZVC common.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mseifert9mseifert9 Member Posts: 13
    edited October 2019
    UPDATE
    I am beginning to suspect I need to change settings from "O/B terminal controls valve in cooling mode" to "controls valve in heating mode". Then I might be able to use W for heating and Y for the cooling mode. Needs more testing...
    ****************

    I took off all the thermostat R jumpers and added one from R to Rc.
    I connected Rh from the left zone 2 terminal to the Thermostat which now powers Rh.

    I did not yet pull the common off the relay coil because there is no common terminal on the ZVC except on each individual zone thermostat (see picture).

    Now that the Rh has power it should complete the circuit IF the thermostat closes the connection to Y under call for heat, which it does not. When I tested with a multi-meter, a demand for heat does not produce continuity with ANY terminal on the Equipment side. I am not sure how this ever worked using the Y terminal.

    Some important thermostat settings:
    • "2 heat/1 cool" mode. (Y = Compressor contactor)
    • O/B terminal controls valve in cooling mode
    The ONLY change I found in heat mode was that Y and G show continuity. So I jumped Rh and G so that Y is then energized when there is a call for heat. IT WORKS but this seems a ridiculous solution.

    I put the unit into cool mode to see what might happen and did not have the best results (sounded like the two transformers were at odds somewhere). It might have to do with the common wire you suggested moving since I discovered that it is Rh which powers W and W2 in cooling mode (seems odd to me) and so the wrong common is being used.

    *************
    Also, I did some more multi-meter testing on the Honeywell

    I disconnected Rh so that I only had power to R and had it jumped to Rc. I presumed there would be no power to Rh.
    • However, when in cool mode, I am able to get 24v from Rh to G and Y terminals. How is this possible?
    When I tested continuity, I found only these scenarios where there was continuity:
    In Heat Mode
    • Between (Rc and G) and (Rc and Y) when there was a call for heat
    In Cool Mode
    • Between (Rh and W) and (Rh and W2)
    • Between (Rc and G) and (Rc and Y)
    Questions:
    • Why does Rh have continuity with W and W2 when calling for Cool (shouldn't it be Rc powering W and W2 with the setting: O/B terminal controls valve in cooling mode?)
    • Why does Rc have continuity with G and Y when calling for heat?
    @ZMan I appreciate so much the time you've taken to help me get through this - and educate me along the way. What should I try next? It seems that I am so close.


  • mseifert9mseifert9 Member Posts: 13
    edited October 2019
    ** Combined with previous post for succinctness **
  • mseifert9mseifert9 Member Posts: 13
    edited October 2019
    I was able to get the system working by switching the thermostat from 2h/1c Heat Pump mode to 2h/2c Conventional Heat mode. The Honeywell's 2h/1c heat pump mode didn't support 2 transformers (and there wasn't a 2h/1c mode of any sort that did).

    I had to swap the Y and the W wires on the thermostat (since it was set up that cool controls O/B which is opposite from conventional heat mode).

    My biggest concern now is that the Em-Heat function is not available with this mode but is replaced by Stage 2 Heat and it looks like I can't control when Stage 2 Heat comes on.

    With Em-Heat, I had Droop Control and set it to 5 degrees, but this is not an option with Stage 2. I've read that Stage 2 automatically comes on when there is a 2 degree drop, which isn't going to work. So I think I need to spring for a new thermostat. The Honeywell THM5421R1021 EIM (with thermostat THX9421 or THM5421R1021 ) seems to have a heat pump mode supported with two transformers. Anyone have suggestions of a better thermostat solution?
  • ZmanZman Member Posts: 5,830
    When you are testing the Honeywell and Tekmar, are all the wires off it. I suspect you are being tricked by the circuits attached. It sounds like most of your questions now are about the logic of the controllers. You can try to figure it out by messing with the settings but tech support might be an easier path.
    BTW, always tell tech support you are a tech, so they don't play the "we can't talk to a homeowner" card. Keep in mind that at least 1/2 of the residential techs out there cannot even find there multimeter, you at least have one and are trying to use it.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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