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Garage unit heater open loop?

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arcticman
arcticman Member, Email Confirmation Posts: 24
We have Well McClain WTGO-5 oil boiler currently only running the basement zone baseboards to keep the basement at 66* and the on demand internal tankless domestic water heater in the boiler for hot water.

There is a small unit heater in my garage. I have always kept the loop open with the fan OFF unless I need more heat in the garage. Is it okay to close unit heater loop so that the boiler is not continuously circulating water through the unit heater even though the basement zone is seldom calling for heat?

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  • mattmia2
    mattmia2 Member Posts: 9,637
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    Does the circulator shut off when the basement zone isn't calling for heat? you don't want to dead head the circulator but as long as there is a zone open (assuming it is zoned by valves) you can close the garage loop. You may need some flow in the garage loop or to isolate and drain it in winter to keep it from freezing.
  • GroundUp
    GroundUp Member Posts: 1,907
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    I think you may be confused as to what "open loop" means. If it's connected to your boiler, it's a closed loop system. It sounds as thoiugh you may have a constant circ loop through the UH, but it's still a closed loop. If that is the case, the answer is yes- assuming there is no risk of freezing the piping or UH in the garage.
    mattmia2
  • PC7060
    PC7060 Member Posts: 1,159
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    Why not use a thermostatic radiator valve? You could set to the lowest level which is about 50° and turn up higher as required.  Response time to bring up temp would be bit slow I imagine with a big slab in the room but at least you would have some control. 
  • arcticman
    arcticman Member, Email Confirmation Posts: 24
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    mattmia2 said:

    Does the circulator shut off when the basement zone isn't calling for heat? you don't want to dead head the circulator but as long as there is a zone open (assuming it is zoned by valves) you can close the garage loop. You may need some flow in the garage loop or to isolate and drain it in winter to keep it from freezing.

    The circulator is a Taco 007-F5 cartridge circulator... it does not shut off if a zone is not calling for heat. It runs continuously. That's why I wasn't sure if I needed to keep the UH zone circulating or not. Would having all the zones off (not circulating) cause this circulator "dead head"? Also... What's a dead head?

  • arcticman
    arcticman Member, Email Confirmation Posts: 24
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    GroundUp said:

    I think you may be confused as to what "open loop" means. If it's connected to your boiler, it's a closed loop system. It sounds as thoiugh you may have a constant circ loop through the UH, but it's still a closed loop. If that is the case, the answer is yes- assuming there is no risk of freezing the piping or UH in the garage.


    Thank you for correcting... yes its a closed loop. As stated above its a Taco 007-F5 cartridge circulator... so in your experience its okay to shut off the UH zone and have no water circulating to any zones and it won't cause a problem with the circulator ?
  • mattmia2
    mattmia2 Member Posts: 9,637
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    Dead heading is pumping in to a closed pipe, someplace where there is no place for the water to flow. circulators aren't designed to run without circulation. It is possible that there is a bypass or something, some pictures of the boiler piping would help. You would need to set up the circulator to only run if there is an open zone if you shut off the loop to the garage, assuming there is no other bypass. It would save some electricity to set it up that way anyhow.

    I assume the system is zoned with zone valves?
  • arcticman
    arcticman Member, Email Confirmation Posts: 24
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    mattmia2 said:

    Dead heading is pumping in to a closed pipe, someplace where there is no place for the water to flow. circulators aren't designed to run without circulation. It is possible that there is a bypass or something, some pictures of the boiler piping would help. You would need to set up the circulator to only run if there is an open zone if you shut off the loop to the garage, assuming there is no other bypass. It would save some electricity to set it up that way anyhow.

    I assume the system is zoned with zone valves?

    There is no by pass.

    I have zone valves for the baseboards on each floor.

    The UH in the garage does not have a zone valve... it circulates constantly.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
    edited May 2022
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    This is not the "best practice", but someone designed the system so you must circulate water thru the unit heater always. Do not close the valve to the unit heater.

    You can redesign the piping with a zone valve to the unit heater, BUT you must also redesign the electrical controls in order to stop the circulator pump from constant operation. The Best Practice would be to use a relay that operates the burner and circulator by way of a thermostat to the zone valve with an isolated end switch to operate the combination circulator/burner relay. This design is very common and has been used for over 90 years.

    If you have a wiring diagram of your heating system "AS BUILT", we can assist you with a simple redesign and suggested control to accomplish it.

    Since you have a tankless coil for DHW and your boiler maintains a minimum boiler temperature for DHW, Your savings in fuel cost will be substantial if you do the repipe and electrical control redesign.

    Here is a possible solution to the electric redesign using one Taco ZVC 403 zone valve control and adding a zone valve to the Garage unit heater.

    If you have more than 2 zones of baseboard, then purchase a ZVC 404 or a ZVC 406 as needed.

    The thermostat from the room or garage will operate the zone valve motor, when the end switch on the zone valve closes the burner circuit and the circulator will start. When there is no call for heat, the burner circuit and the circulator will stop. This is how I would do it in your situation.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    Zman
  • arcticman
    arcticman Member, Email Confirmation Posts: 24
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    This is not the "best practice", but someone designed the system so you must circulate water thru the unit heater always. Do not close the valve to the unit heater.

    You can redesign the piping with a zone valve to the unit heater, BUT you must also redesign the electrical controls in order to stop the circulator pump from constant operation. The Best Practice would be to use a relay that operates the burner and circulator by way of a thermostat to the zone valve with an isolated end switch to operate the combination circulator/burner relay. This design is very common and has been used for over 90 years.

    If you have a wiring diagram of your heating system "AS BUILT", we can assist you with a simple redesign and suggested control to accomplish it.

    Since you have a tankless coil for DHW and your boiler maintains a minimum boiler temperature for DHW, Your savings in fuel cost will be substantial if you do the repipe and electrical control redesign.

    Thank you... I have a wiring diagram from the original Well McClain installation manual but I'm not sure if the installer followed it exactly. I can post a picture of the wiring diagram from the manual along with pictures of the actual wiring if you think it would be of use.

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
    edited May 2022
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    arcticman said:



    Thank you... I have a wiring diagram from the original Well McClain installation manual but I'm not sure if the installer followed it exactly. I can post a picture of the wiring diagram from the manual along with pictures of the actual wiring if you think it would be of use.

    Yes... take the pictures and post them. You are probably correct with the wiring diagram being different if your circulator operates constantly. How the zone valves are wired will help and where the circulator is wired will help. Also a picture of the wires inside the Aquastat relay with the cover off.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • arcticman
    arcticman Member, Email Confirmation Posts: 24
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    arcticman said:



    Thank you... I have a wiring diagram from the original Well McClain installation manual but I'm not sure if the installer followed it exactly. I can post a picture of the wiring diagram from the manual along with pictures of the actual wiring if you think it would be of use.

    Yes... take the pictures and post them. You are probably correct with the wiring diagram being different if your circulator operates constantly. How the zone valves are wired will help and where the circulator is wired will help. Also a picture of the wires inside the Aquastat relay with the cover off.
    Here are the pics of the wiring diagram and the boiler components. I traced my wiring and it matches the diagram. A low water cutoff and additional temperature limit control are not used from L1 and B1 on the relay. I really appreciate you taking the time to help out.





    The pipe on the right side of the manifold is the UH zone... it has no zone valve.
    The zone valve in the center is disconnected and no longer in use.




  • Zman
    Zman Member Posts: 7,569
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    As Ed suggested, install another zone valve and a zone controller and wire it per his drawing. If you can get a wire to the garage, a t-stat there would be nice. If not, a simple switch in its place (in a location you can get to) would do the trick. Is there any chance the garage could go below freezing when the heat is switched off? If so, a t-stat or glycol to prevent freezing the heat pipe would be a good idea. https://www.supplyhouse.com/Taco-ZVC404-4-4-Zone-Valve-Control-Module-with-Priority
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    From what I see here in your pictures, the Taco 007 F5 circulator does not operate constantly. That circulator only operates when there is a call for heat from the C1 terminal of the L8124 aquastat relay. There is one problem I see, There is no low voltage "thermostat" wire from the end switch wires of the zone valve end switch wires. (red wires). Those red wires should be connected to the T T terminals of the L8124 aquastat relay.

    The original installer who designed that wiring logic should be banned form working on HVAC equipment of any kind or anything that uses any form of energy. Unless that person agrees to pay for the energy used by their unique electrical control design. I Wonder if they drive a car with no accelerator peddle. just wire the gas peddle to the floor and use the breaks to control the vehicle speed. Shouldn't be to difficult to drive that way

    This is not too difficult to fix, here is the diagram you need. This can be a DIY if you don't want to pay for a service call. You won't need to buy any controls. Then you can close the valve to the garage unit heater. CAUTION... you may have a pipe freezing problem to the garage pipes in the very cold winter months.

    The only expense is some thermostat wire and a few wire nuts. With your expected savings, it's worth a $200 service call but a DIY cost is less than $10.00

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    One more question....

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • arcticman
    arcticman Member, Email Confirmation Posts: 24
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    One more question....

    That wire is goes to a junction box hard wired to the boilers dedicated 120v circuit.

    I'm pretty sure the Taco circulator is running continuously. I tested by disconnecting the white neutral wire at the circulator. With no zones calling for heat... when I touch the wires back together I can clearly hear the circulator activating. Could this be caused by the T T jumper wire the installer put on?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
    edited May 2022
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    arcticman said:



    That wire is goes to a junction box hard wired to the boilers dedicated 120v circuit.

    I'm pretty sure the Taco circulator is running continuously. I tested by disconnecting the white neutral wire at the circulator. With no zones calling for heat... when I touch the wires back together I can clearly hear the circulator activating. Could this be caused by the T T jumper wire the installer put on?

    Exactly right. remove that jumper from T T. the circulator will stop but the burner will maintain boiler temperature for DHW.

    Then take the unused red wires from each zone valve and connect one from each zone valve to a thermostat wire. (let's say the white conductor). place that white conductor on one of the T terminals on the L8124 aquastat relay. Now take the other red wire from each zone valve and wire nut them together with another conductor in the thermostat wire. (lets say the red wire). Now connect that wire to the other T terminal on the aquastat relay. When ever there is a call for heat from a thermostat, the corresponding zone valve will open. The end switch on that zone valve actuator will close and complete the T T circuit in place of the removed jumper.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    mattmia2
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    You may find that you experience insufficient hot water (and you may not). If you do experience insufficient hot water, then you can adjust the aquastat settings to accommodate for the new operating logic. My starting settings for this type control is 160°Low. 180° Hi and 10° Diff.

    Currently your are set at 170° Hi and 12° Diff. With the jumper on TT your Low at 140° has no function since there is always a call for heat by the jumper wire.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • arcticman
    arcticman Member, Email Confirmation Posts: 24
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    arcticman said:



    That wire is goes to a junction box hard wired to the boilers dedicated 120v circuit.

    I'm pretty sure the Taco circulator is running continuously. I tested by disconnecting the white neutral wire at the circulator. With no zones calling for heat... when I touch the wires back together I can clearly hear the circulator activating. Could this be caused by the T T jumper wire the installer put on?

    Exactly right. remove that jumper from T T. the circulator will stop but the burner will maintain boiler temperature for DHW.

    Then take the unused red wires from each zone valve and connect one from each zone valve to a thermostat wire. (let's say the white conductor). place that white conductor on one of the T terminals on the L8124 aquastat relay. Now take the other red wire from each zone valve and wire nut them together with another conductor in the thermostat wire. (lets say the red wire). Now connect that wire to the other T terminal on the aquastat relay. When ever there is a call for heat from a thermostat, the corresponding zone valve will open. The end switch on that zone valve actuator will close and complete the T T circuit in place of the removed jumper.
    Thank you Ed!

    I followed your instructions and the systems is now operating correctly. The Taco circulator stays off until there is a call for heat then turns off when the zone reaches the set temperature.

    I closed the valves on the UH zone... hopefully I'll save a little in fuel costs without the UH zone constantly circulating.

    Thanks again... really appreciate your help!
    Dave CarpentierEdTheHeaterMan
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,834
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    arcticman said:


    Thank you Ed!

    I followed your instructions and the systems is now operating correctly. The Taco circulator stays off until there is a call for heat then turns off when the zone reaches the set temperature.

    I closed the valves on the UH zone... hopefully I'll save a little in fuel costs without the UH zone constantly circulating.

    Thanks again... really appreciate your help!

    That was easy! Now remember about that zone during a deep freeze. It those pipes get exposed to the cold, they may freeze and burst. The entire system will loose water upon thaw of that burst pipe.

    To be safe... Think about adding a zone valve to that UH loop. then set a thermostat to a very low minimum temperature.
    ...........OR..........
    Cap off that loop and drain that piping, You don't want to get a surprise next winter..
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    mattmia2