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Zone controls...

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Piker, Nov 9, 2008.

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  1. Piker

    Piker Minister of Fire

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    Oct 6, 2008
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    Hi folks,

    I was thinking about using a zone control module to run the 6 zone valves on our new gasifier system. Seems like a control module would make the wiring easy and trouble free on most of my zones, but I have 2 zones with special circumstances that I could use some help with.

    So here goes...

    1) One zone requires a mixing valve... and thus requires an additional circulator after the valve that will need turned on and off with the opening and closing of the zone valve. What is the best way to achieve this?


    2) Another zone is circulating water through an air handler, and is basically the same situation as the first zone... I need to be able to turn the blower on in the air handler when the zone valve opens... again... what is the best way to achieve this?

    I had thought I could just use switching relays connected to the "end switches" of the zone valves, as long as the end switches are dry contacts... and I think they are? They are Honeywell zone valves... Since I am using the zone control module, I shouldn't need the end switches on the zone valves to run the load circ right? That means I could use them to run the switching relays, right?

    thanks in advance for you help.

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  2. Chris S

    Chris S New Member

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    Orange County NY
    For air handler applications, we often have the thermostat control the circulator (in your case zone valve), then install an aquastat in the return line form the coil. The aquastat turns on the blower. In this manner, your blower won't come on unless there's hot water available- you won't be blowing cold air around.
    My question is this.. hydonic coils in air handlers generally have high head losses, and require specific pump sizing. Have you taken this into account.
    As for the mixing valve I would use a seperate circulator with a relay, and keep it seperate from the zone manifold.

    Chris
  3. Nofossil

    Nofossil Moderator Emeritus

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    Chris has it right. Relays are your friends in these applications, and zone end switches are just mechanical switches. Using the end switch is good, since the circ won't start until the zone valve is open.
  4. RJP Electric

    RJP Electric Member

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    Loc:
    N. New Hampshire
    If I am not mistaken all 4 wires from the Honeywell zone valves need to go back to the controller. This is what I would do.

    Question 1
    Instead of bringing back the 2 dry contact wires from the zone valve back to the controller, bring them to the TT of a taco SR-501 relay, feed your new circulator pump and then use the dry contacts from the SR-501 back to the Honeywell controller.

    Question 2
    I would use a Honeywell strap on aquastat and connect to pipe near blower and connect it to R and G in fan center of furnace. It will turn on and off fan on temp rise respectively.
  5. brad068

    brad068 Feeling the Heat

    Joined:
    Nov 20, 2007
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    445
    Loc:
    Central Wisconsin
    Hey guys, I have a problem with a fan coil placed in my furnace. The coil is placed horizontal and it is plumbed in with the main loop. The problem is is that when my water is up to 180-200 the convection is so great that the thermal disc switch keep tripping out and starts the fan like every 10 minutes. I know I need a zone valve and I purchased a 3-way which should do the job but I am concerned about how small the ports are. Its a caleffi 1" 3-way and I'm wondering if I shouldn't go with two, 2 way ball valve zone valves. The Cv factor is much higher and I could go with one normally open and one normally closed. What ya think?
  6. Piker

    Piker Minister of Fire

    Joined:
    Oct 6, 2008
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    618
    *sigh*
    apparently the controls of these hot water systems are a little over my head... along with the plumbing and everything else.

    I didn't plumb a secondary loop for the zone that requires mixing... and I would prefer not to hack into any of the plumbing that I have finished... I used nofossil's "simplest" storage solution, and wasn't able to figure out how to run a secondary loop without water going where I didn't want it to go... not saying there isn't a way... I just couldn't figure it out... so it looks like I am going to have to plumb a circulator AND a zone valve for that particular zone.

    And no... I did not take into account head loss of the heat exchanger when I sized my pump. The heat exchanger setup will be used temporarily this winter until I can afford to install the rest of the radiant floor heat in the downstairs. I guess I will find out sooner or later whether the pump is big enough. Its just a ups15-58 grundfos that I will be using for a load circ. On the coldest day, it needs to move 10 gpm... (about 100,000 btu/hr load) with all zones open at once. The curve chart for that pump looks like it will pump 10 gpm at 10' of headloss... I couldn't find reliable data on head loss for pex tubing, but decided most of my zones only need at most 2 gpm per zone. Basically I took a chance with a less expensive pump. Well see...

    So... I guess it's back to the drawing board for some more research on the wiring... but it's really starting to get get cold around here... and without a backup at this point to the gasifier... it's getting a bit nippy in the house. I may forego the zone valve controller and just hook up the heat exchanger for now until I get it square in my head exactly how the wiring has to be.

    thanks again... and if you have any additional insight, I would be more than happy to hear it.
  7. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Northwood, NH
    Use two control panels. One is a circulator switching panel (SR503 or SR504 - 4 would give you future expansion). That controls your two circulator zones, and a third circulator which feeds a header with zone valves attached. Those zone valves are controlled by a zone valve panel (ZVC404 or ZVC406) - the "end switch" contacts from that panel, which would normally connect to the boiler, instead connect to the "thermostat" contacts on the circulator panel, for the "zone" that is the circulator feeding all of those zone valves.

    I'd also note that there is no need for the zone valve header to be near the circulator feeding them. We often use this strategy on larger houses, where we have circulators at the boiler which feed remote zone-valve panels (running a pair of large pipes and one control wire from the boiler to a remote panel is a lot easier than running a nest of small pipes and a separate control wire for each zone).

    How close are you on head loss?

    Calculate the head loss of the valve, and then figure out if it will work.

    head loss = (flow/Cv)^2 * 2.31

    So, for a typical zone valve with a flow of 5 gpm and a Cv of 7.5, the head loss would be 1 foot. For the same valve, at 10 gpm, the head loss would be over 4 feet.

    Joe
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