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Looking for a control that will take 120VAC input and output 24V to activate a zone valve

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I am trying to connect a boiler that has a DHW function but will only output 120VAC that would normally drive a circulator pump. I would like to have it activate a zone control valve (taco sentry) so ideally I need a relay box that will accept the 120V and activate 24V on the other side to make a zone valve open.
The goal is to use the existing hot water setup that is currently a zone on this system, but during economization it's not directing the boiler to run to 180, and at the lower temps its taking forever to satisfy the DHW call.

The boiler will handle the trigger of the DHW through it's own sensor the challenge is to convert the 120V output to 24V for the zone valve. Maybe I could just use the transformer alone, not sure if that makes sense. Thank you for any help with this
Chris

the boiler is an IBC VX150

Comments

  • The Steam Whisperer
    The Steam Whisperer Member Posts: 1,218
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    Just use a 120v to 24 transformer. As the 120 v is switched on and off so will the 24v signal to the zone valve. This is assumin power open/ spring closed zone valves.
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    mattmia2ratioSuperTechethicalpaul
  • HomerJSmith
    HomerJSmith Member Posts: 2,483
    edited November 2022
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    All you need a 24 Vac transformer and a 2 pole single throw 24 Vac relay. One pole would activate the pump and the other pole would activate the zone valve. Easy-peasy! But...wait, Homer, it may be more complicated.

    How does the DWH convert 120Vac to 24Vac? What kind of tank sensor are we talking about? What is the "existing hot water setup"you mentioned? A drawing would be helpful.
  • mattmia2
    mattmia2 Member Posts: 9,850
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    You could also use a 120v zone valve.
    HomerJSmith
  • ChrisWilliams2
    ChrisWilliams2 Member Posts: 29
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    mattmia2 said:

    You could also use a 120v zone valve.

    Wow I had no idea there was such a thing, I just found the multivotl sentry version. That may be exactly what i need to make it almost a straight swap. Its across the room so the wire might be an issue but this could be a very good option
  • ChrisWilliams2
    ChrisWilliams2 Member Posts: 29
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    All you need a 24 Vac transformer and a 2 pole single throw 24 Vac relay. One pole would activate the pump and the other pole would activate the zone valve. Easy-peasy! But...wait, Homer, it may be more complicated.

    How does the DWH convert 120Vac to 24Vac? What kind of tank sensor are we talking about? What is the "existing hot water setup"you mentioned? A drawing would be helpful.

    The IBC boiler handles DHW a little unique. It has a pump output for it to run the circulator, but then you no longer use the existing temperature probe/aquastat. You remove that and insert the IBC DHW sensor in there so it knows the temp and when it drops below the desire setting it will send 120v to the contacts on the IBC boiler that you would normally use to run the circulator pump but I currently have it as a zone valve, wired the same as the other zones. This would allow it to be seen as DHW and the boiler can go to full 180 but then get all the economizing when its a regular heating call using the outdoor reset.
  • ChrisWilliams2
    ChrisWilliams2 Member Posts: 29
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    Just use a 120v to 24 transformer. As the 120 v is switched on and off so will the 24v signal to the zone valve. This is assumin power open/ spring closed zone valves.

    This could be just what I need and this may be the simplest solution. Not sure if Taco Sentry valves need power to close or if they use a spring though
  • mattmia2
    mattmia2 Member Posts: 9,850
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    The standard 24vac taco zone sentry valves open with 24vac and close when you remove power. They have a capacitor that stores the energy to close them I think. Look at the opening time, it is about 20 to 30 seconds. Make sure you don't deadhead the circulator while it is opening.
  • HomerJSmith
    HomerJSmith Member Posts: 2,483
    edited November 2022
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    So you have a thermistor sensor that the IBC boiler uses to measure tank temperature. Do you have a boiler pump and an indirect pump (2 Pumps)? I'm kinda slow (long covid?). You want to add a pump and a zone valve to the indirect loop? Based upon the current 24V zone valve, you have only one pump, I think. If this is correct, you don't need another zone valve. It operates without one. It is how you plumb the sys that counts. The programing in the IBC boiler probably determines the boiler water temp going to the indirect, the tank differential temp, the space heating operational time while there is a call for Domestic Hot Water.

    All you should need is a pump and spring check valves. Your boiler rating should help you in pump sizing. I GPM for every 10,000 BTU. A 85,000 BTU output boiler would have a pump delivering 8.5 GPM. Pipe size from the boiler to the indirect matters as copper pipe has flow limitations. Companies usually give piping and pump recommendations.

    This doesn't mean you couldn't have a lower flow because of a smaller pipe size, It is just means that the recovery time would take longer especially so if space heating occurs at the same time. also, the pump would be sized to the flow rate. You would calculate the pressure loss (head loss) (drop) of the whole boiler-indirect circuit for your size pipe. Then go to a pump chart and match head pressure that has to make up the head loss in the circuit to the flow requirements.

    Things to consider: Look at the boiler programing for connecting a tank sensor, and pump to the control board and how to program. Recommended piping size. Recommended flow rate. You can then choose a pump, which the company may suggest based upon their recommended pipe size.

  • Zman
    Zman Member Posts: 7,589
    edited November 2022
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    Just use a 120v to 24 transformer. As the 120 v is switched on and off so will the 24v signal to the zone valve. This is assumin power open/ spring closed zone valves.

    This could be just what I need and this may be the simplest solution. Not sure if Taco Sentry valves need power to close or if they use a spring though
    Have you considered how you will disable the heating zone when you have a DHW call? A double pole/double-throw relay with a 120-volt coil might be the answer. It will open the heating circuit on one side any time you energize the coil to close the DWH on the other side. If you post a picture and some more details of your zone valve wiring, someone will surely walk you through it.

    https://www.supplyhouse.com/Tekmar-004-Relay-120-V-ac-coil-7924000-p

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • GGross
    GGross Member Posts: 1,076
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    @ChrisWilliams2

    If powering the device from the pump output on your boiler just keep in mind that the device will only be powered when your boiler thinks it needs to power the pump. So in order for it to work you will need to make sure that the boiler is sending power to "the pump" constantly. I go through this pretty regularly where people try to power a zone valve relay from a boiler pump output, and they wonder why the relay will not turn on, well it is because the only time the pump is powered is when there is a call for heat... since the relay is what is sending the call for heat and it can't be powered until the call for heat is active.. well you see the issue hopefully. Just make sure that where you are stealing power from the boiler will always be powered
  • pedmec
    pedmec Member Posts: 994
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    All you need to do is add the transformer so the 120 that's for a DHW circulator gets stepped down when there is a DHW call.
  • ChrisWilliams2
    ChrisWilliams2 Member Posts: 29
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    It ended up being a very different solution but it seems to work perfect. The IBC VX150 can take a dry contact input to a second thermostat input. This can be programmed for DHW with non-eocnomiozed settings. Fortunately the Taco zone valve control relay board allows a dry contact either NO or NC when the valve opens. I tied this into my boiler an it worked great. Kudos to the IBC support guys I cant believe how flexible this boiler is.
    MikeAmannmattmia2