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Multiple Circulator & Zone Valve Relays with Post-Purge?

SteamheadSteamhead Member Posts: 11,322
Looked at a HW job yesterday with six circs and four zone valves. The control system for this looks like someone threw a whole bunch of spaghetti onto the wall and it stuck. Since we'll probably be re-wiring this, does anyone know of a mutiple circulator or zone valve relay that will allow the circs to purge some of the heat out into the zones after shutting off the burner?

All Steamed Up, Inc.
"Reducing our country's energy consumption, one system at a time"
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Baltimore, MD (USA) and consulting anywhere.


  • hot rodhot rod Member Posts: 7,003
    does it have an indirect?

    if not the priority relay output on most pump relays has a post purge. I know the Caleffi ZSR has a non-adjustable 2 minute post purge on relay 1
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • STEVEusaPASTEVEusaPA Member Posts: 1,448
    Make your own

    Unless someone has some commercial controls experience, you may be better off getting your own relays/contactors (Grainger's) and making it yourself.  I know a real wizard up here in the Philly Suburbs who used to build/service elevators before he started his HVAC career. I've seen him do some interesting things with relays and contactors.  Send me a message if you want his info.

    Tekmar boiler controls (I know the 374 does) also post purge on the DHW contacts ( think until 10 or 20 degree drop).
  • Mad DogMad Dog Member Posts: 3,169
    Wow that's cool stuff , steve. Mad Dog
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  • wogpa67wogpa67 Member Posts: 238
    Th e Honeywell AQ2000 series does, also the Exp Taco has available plug in cards to do that.
  • Robert O'BrienRobert O'Brien Member Posts: 2,930
    AQ2000 is the way to go,does that and a whole lot more. Why reinvent the wheel!
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  • Ron Jr.Ron Jr. Member Posts: 527
    Does,the AQ have the capability of being used for circs or zone valves with the same control ?
  • MikeMike Member Posts: 36
    installing in floor heat for all floors for a new house, used gypsum over pex for the main level and 2nd floor. I will have 5 pumps for the floors, one pump for air handler, one for indirect tank.
    counting on not using air handler much,
    any ideas for switching relays?
    they have a huge shower 5-6 heads, not sure if I want to stop making hot water and switch to floor, 80 gallon tank.
  • Joe MattielloJoe Mattiello Member Posts: 545
    Taco offers several controls to facilitate wiring similar to yours, including the SR506-4 EXP with 120 volt output for up to 6 circulators. It has a post purge feature built into the control, which is unique to the priority zone 6, normally used for DHW. If you prefer, you can use zone 6 for another heat zone, and use the post purge feature for that zone. However, it will not work on all the zones, as you mentioned. Frankly, I don't think anyone makes a control that enables you to purge residual heat, and dump into all the zones. Usually, the purge is synonymous with DHW.

    For your reference, I attached the Taco zone control wiring guide which is a great resource when challenged with a wiring issue. Please advise if you have any questions or concerns.
    Joe Mattiello
    Application Field Service Engineer
    Taco, Inc.
  • HatterasguyHatterasguy Member Posts: 6,058
    The fundamental problem with the post purge feature on the SR506-4 EXP is the fixed time of two minutes, This is, effectively, useless to extract any significant amount of heat from the boiler.

    A time of 10 minutes would be more suitable to bring the boiler temperature back to the 135°F level of the indirect.

    The heat transfer between the boiler and the indirect becomes quite small as the temperature of the boiler approaches the temperature of the indirect so quite a bit of time is required.

    One could make a good argument for a 15 minute time to fully extract as much energy as possible. Of course, the time is dependent on the volume in the boiler. New boilers with minimal water content would obviously need less time.
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