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Burnham Apline with indirect DHW circulator and Taco Zone valves

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Cookhigheffhaus
Cookhigheffhaus Member Posts: 7
in Thermostats and Controls
I recently had an Alpine boiler installed and cannot seem to locate in the manual the proper wiring for a set up for indirect DHW in a system using zone valves instead of zone circulators. (Boiler has "system" and "boiler" circulators as stndard). My contractor has the DHW aquastat run to a Taco Zone valve controller -- Zone 4 priority on -- which operates the zone valve for the DHW zone but as far as I can tell, the boiler DHW circulator stays off. The control panel on the boiler also indicates Central Heat is on when there's a DHW call, which makes sense as the Taco zone controller cannot send a special signal to the boiler to differentiate between a heating zone call for heat and zone 4 call from the aquastat.

My question is whether the DHW indirect tank aquastat should be wired to both the DHW temp switch terminals on the Alpine boiler and to Zone 4 of the Taco zone controller. This should turn on both the boiler in DHW mode, boiler controls turn on the DHW circulator, and Taco controller opens the zone 4 zone valve. The Taco zone controller would also send a Central Heating signal to the boiler but if priority is set on the DHW by the boiler it should not matter that Central Heating is also on.

The only problem I foresee is that the DHW circulator may run before the DHW zone 4 valve is open since the Taco zone valves take about 30 seconds to fully open. The DHW circulator would be running briefly on a loop that is closed which might briefly overload the pump motor.

Any other setups with zone valves instead of zone circulators on the Alpine that have been field tested?

Comments

  • Cookhigheffhaus
    Cookhigheffhaus Member Posts: 7
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    Indeed I have both a DHW circulator and zone valve for DHW. An unusual design I believe but don;t think there's much harm.

    Problem I have tho is the Burnham Alpine boiler has separate inputs for boiler and DHW. But with the Taco zone valve controller there is only a single TT boiler output so even with DHW on priority zone, the Alpine doesn't know it's a DHW call. Since I have outdoor sensor, on warm days it takes forever to satisfy the DHW since the boiler temp stays about 140 (thinking it's a central heat call on a warm day).

    I found another thread here on point "DHW Priority Question" /discussion/151793/dhw-priority-question

    But I am wondering if there is an easier solution -- take a tap off terminals 2 and 3 on the DHW loop taco zone valve (end switch) and wire it to the input for the boiler DHW terminals. Then when the DHW thermostat calls for heat, the zone valve will open then trigger a DHW call to the boiler (again because the Zone Valve controller is getting a call the boiler will also think there is also a central heat call from the signal to TT but I don't think that will matter much).

    Anyone have an idea if this will work? Or should the DHW inputs be wired to to terminals 1 and 3 on the zone valve? Or would I need a relay on 1 and 3 then wire that to the DHW inputs on the boiler to isolate the zone valve switch from the boiler DHW inputs?
  • DNA
    DNA Member Posts: 3
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    Has anyone got an answer to this question? I have exactly the same configuration and same problem but am not sure if I can just connect the 24v signal going to Zone 1 (in my case for DHW T-stat off a 3-zone Taco controller) to the DHW T-stat contacts of the Alpine boiler? Is there an issue if the valve hooked up to the indirect water heater is managed by the Taco controller?
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,002
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    What makes the issue difficult is addition of a needless zone valve.

    The easiest off-the-shelf solution is to get a two or three zone valve control and wire the water heater aquastat to T-T, the end switch to "DHW Temp Switch" on the Burnham and the zone valve terminals to the zone valve.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    DNA
  • DNA
    DNA Member Posts: 3
    edited November 2022
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    Thanks for taking the time to look at my issue.

    When you say to get a valve control, do you mean a separate valve control from the currently configured three-zone switching relay (my SR503 TACO controller)? One that is only dedicated to a single zone valve and connected to the DHW terminal on the alpine?

    One more piece of data: when I attempted to manually call for DHW while the superstore zone valve was open, the boiler got an error that it was heating the supply too quickly and shut itself down, so now I'm concerned that my system is not plumbed correctly to use the DHW feature on the Alpine?


  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,002
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    When you say to get a valve control, do you mean a separate valve control from the currently configured three-zone switching relay (my SR503 TACO controller)? One that is only dedicated to a single zone valve and connected to the DHW terminal on the alpine?
    Yes

    One more piece of data: when I attempted to manually call for DHW while the superstore zone valve was open, the boiler got an error that it was heating the supply too quickly and shut itself down, so now I'm concerned that my system is not plumbed correctly to use the DHW feature on the Alpine?
    I'll bet the pump was off.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,002
    edited November 2022
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    I would even do something like this with a Taco SR501 transformer relay:



    Or, you could make it easy and replace the zone valve with a check valve. It could possibly be the intended us of the zone valve to act as a check valve, but more than anything, it complicates matters.

    With any of these examples, your boiler wants to be in control of the indirect; sensor and line voltage.


    https://api.ferguson.com/dar-step-service/Query?ASSET_ID=3249786&USE_TYPE=INSTALLATION&PRODUCT_ID=4154365
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • hot_rod
    hot_rod Member Posts: 22,139
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    For future reference, the Caleffi relay boxes have 3 end switches. Zone one has a dedicated end switch, it can be priority or not. We added this feature specifically for boilers that need separate DHW calls.
    The other two end switches activate by any of the zones. it is handy for cases where you have your situation.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • DNA
    DNA Member Posts: 3
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    Thanks everyone! This has given me some great ideas for how to fix my issue. 

    Too bad I can't simply take a second pair of wires from the same indirect water heater aquastat and hook it straight up to the DHW terminals on the alpine. I guess that could turn on the boiler without the zone valve opening if something went wrong with it.

    I'm still not sure why the boiler pump didn't come on when I simulated a call by shorting that DHW terminals on the boiler while zone 1 was on at the Taco. 

    I'll look into the second taco or the Caleffi relay option. 

    Many thanks again!

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