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viessman on constant ciruclation

Steve W.
Steve W. Member Posts: 4
Thanks for the info on the A terminal in the pump module. Yes to the last question. I curently am running the entire first floor radiant off one large circulator that runs constantly, pushing water to the manifolds. It is fed by the output of the 4 way mixing valve. The 4 way is controled by a motorized actuator that is controlled vy the vitotronic. I piped the system with additional areas to tap off of for two more circ pumps. One will feed the second floor manifold for the two tile bath floors, the other will feed the manifold for the basement slab floor. I'll control these two circs with the other zones on the Argo, and have a tstat in the basement, and a tstat with a floor sensor in the bathrooms. What did you think about my question regarding shift on the high temp circuit, or setting a minimum temp on that circuit?

Comments

  • Steve W.
    Steve W. Member Posts: 4
    Viessman constant circulation

    VB2-40 with vitotronic controller. Zone one (high temp circuit) has one circ pump on it for DHW tank, and another for hyrdonic air handler located on third floor, that heats second and third floors. Second (low temp) circuit feeds 4 way mixing valve (controlled by vitoronic), supplies low temp water for underfloor heating for the entire first floor, basement in slab, and two tile floors in bathrooms of second floor. System works very well on first floor. After some tweaking of the slope, and shift for circuit 2. Issue I have is with the air handler. When we have a warm spell in late fall, the outdoor temp sensor makes the boiler temp drop too low to satisfy the needs of the air handler. Obvious fix would be to program the controller to not allow the temp to drop below a certain minimum temp during the heating season. The reason I have not done this is that the controller keeps the circ pump on all the time. This seems like a waste of energy to me. If the handler blower is off, hot water is being pumped up to the third floor and back again for no reason, and the circ pump is using electricity 24/7, even though the programmable tstat on the second floor is only set for a few hours a day. I am thinking of installing a zone controller for the air handlers circulator, Does this make sense?? Also, what should be the minimum temp for the air handler? Is it specific to make/model?? Should the slope be set to 0 ? Input is appreciated, and I can provide more info if needed.
  • Paul Pollets
    Paul Pollets Member Posts: 3,427
    Vitotronic 200 control

    The Vitotronic 200 control has 3 pump circuits available. The Power Pump Module is labled for wiring the pumps to the correct circuit. The DHW tank is one circuit, and no other pump should be attached (not the air handler)!
    Circuit "A" is for high temp zones (air handler coils or radiators) Circuit "B" is the mixing valve circuit. When connecting the HW coil for the air handler on Circuit "A", I usually set the slope between 2.0 and 2.5, depending on coil size. I also set the max temp for the circuit at 180. On circuit "B" set the max temp at the highest temp required for the RFH. The boiler and mixing valve will do the rest.

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  • Steve W.
    Steve W. Member Posts: 4


    Thanks for the reply. Just to clarify, I do not have the DHW circ pump and air handler circ pump running off the same electrical circuit, I used "circuit" in this case to describe the plumbing setup, my apologies for the mixup, I think I read the term used this way in the installation manual. Anyhow, I do have the pump power module wired as you described, but my question still stands, The module sends power to the air handler circ pump all the time during the heating season, isn't this a waste of BTU's to have hot water pumped out of the boiler, sent up to a coil in an air handler that may not even be running, and then back to the boiler?? Seems to me, if I add a zone control I could get the circ pump to only run when the 2nd floor tstat calls for heat, thereby keeping the btus in the boiler untill actually needed. I also plan on adding a stap on aquastat at the air handler so the air handler will not run until the coil is hot enough. Just to avoid an initial cold air blowing situation when the circ pump first turns on. I figure the aquastat should be on the return line of the air handler. This can also stop the blower from activating when the boiler is off, like last spring, I shut off the boiler heating circuits (DHW only), but forgot to shut off the tstat. Came home to an air handler that had been blowing cold air all day.
  • Paul Pollets
    Paul Pollets Member Posts: 3,427
    AHU wiring

    When we install an air handler HW coil, we use a single zone relay (Taco 501) and wire the relay power terminal from the "A" circuit terminal on the Vitotronic PPM,then run the circ pump power from the zone relay. This allows the HW coil to run whenever the AHU thermostat calls for heat, rather than running the coil constantly. Adding an aquastat delay to avoid blowing cold air is also advisable. Certain integral AHU controls have built-in circuitry that negates having to add the air sensing aquastat that makes on rise.

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  • Steve W.
    Steve W. Member Posts: 4


    Thanks Paul, What you describe is exactly what I want to do. But I am using a 4 zone control because A) it was cheap on Ebay (Argo ARM842 $60) B) I can use the other zones to hook up my cellar floor, and tile bathroom floors. I also picked up a new Johnson A19DAC-1C for $10 to handle the delayed start of the air handler. The only thing I was going to do differnt was run the ac power coming from the PPM to the blowers circ pump, into the Argo zone control. What is the "A" terminal in the PPM?? Is it always energized? Just curious. You mention setting the slope to 2 to 2.5, and max temp to 160.......what about min temp? Do you employ any positive shift to ensure the water is always at least around 140 degrees. Thanks again for taking the time Paul.
  • GW
    GW Member Posts: 4,302
    A

    Paul has stepped out for a moment. A is the high temp circuit. If it's below WWSD, it's hot, unless DHW priority kicks it off. Does your Argo has a ZC (I'm only familiar with the Taco) terminal? I think I understand your confussion. Are you into relays? In any case, if you only have one or two circs (look at the max amp rating on the A, is it 3 amps???), just power up your Argo off of the A terminal.

    As for radiant: are you gonna go constant circ with modulating mixing? That's how it 'should' be done.

    gary

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    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
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