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PAnels /TRV/Constant Circ ?

Uni R_2
Uni R_2 Member Posts: 589
There's probably far bigger savings through more efficient pump motor designs than VS not to say that they are mutually exclusive of course.

Comments

  • Dave_4
    Dave_4 Member Posts: 1,405
    Panels / TRV's and constant Circ.

    I am a little confused with some of the newer control options for panel radiators.

    A TRV seems like the way to go, but I thought it would be used to supplement the control offered through each zones centrally located thermostat.

    Now I am hearing that the thermostat's should be eliminated and to use an outdoor reset and have the pumps constantly circulating. Somehow this does not seems all that efficient, having each zones pump constantly running. What is that going cost in electricity for 3 zones.

    I am still a little confused on outdoor reset, if it stays cold outside does the boiler fire constantly?

    Pete


  • if it is cold outside the zones should be requiring more btu's, thus if the boiler was firing constantly the heat would be being used. if your ODR curve is dialed in accurately the boiler and the TRV"s should be working in unison. if you were still worried about it you could employ an indoor sensor connected to your control: say a tekmar 076 or a 077 sensor with a 260 control.

    also, you can usually have a wider delta T with panel rads compared to say infloor. I don't know your exact scenario but as an example you could use a grundfos 15-10 in place of a 15-42, which would equate to 25 vs. 80 watts.
  • Big Ed
    Big Ed Member Posts: 1,117
    Keep in Mind

    If you install this system which works great by the way, you would need to also install a pressure by pass just incase all the trv's shut down.. The pbp will open as to not let the pump dead end......

    Just want to add needed info..
  • Big Ed
    Big Ed Member Posts: 1,117
    Keep in Mind

    If you install this system which works great by the way, you would need to also install a pressure by pass just incase all the trv's shut down.. The pbp will open as to not let the pump dead end......

    Just want to add needed info..
  • ALH_4
    ALH_4 Member Posts: 1,790
    Constant Circ

    The way a constant circulation system works is that the outdoor temperature sensor turns on the system circulator when the outdoor temperature drops below the desired indoor temperature. The boiler will probably fire a little, but it should be at a low temperature equal to the heat loss based on the heating curve. Ideally, this circulator would also vary its speed based on the pressure differential the system requires.

    It's a little complicated to describe because almost nothing is on/off, but the elegant synergistic simplicity of this type of system makes it an excellent choice for most homes with hydronic heat.
  • scott markle_2
    scott markle_2 Member Posts: 611
    pumping costs

    A grundfoss 15-58 uses 87 watts on high, or .089kw .089x 24=2.136 kw-hr/day 2.136x 200 heating days=427.2kw-hrs at 10 cents a kw-hr that is $42.72

    While this is hardly insignificant especially with multiple circulators,it is still not a huge percentage of over all fuel costs.

    Remember most systems are over pumped. A home run piped panel rad system should have very low power pumping requirements.You may not require three circs. Variable speed drive pumps such as the Wilo stratos or soon to be released eco will make possible much more efficient trv'd constant circ. systems.

    Even without these innovations(smart pumps)the combustion efficiency gains possible with low temperature condensing boilers and constant circulation will more than offset the higher pumping costs. Attention to actual flow and head requirements is crucial to preventing waste of electricity.
  • Dave_4
    Dave_4 Member Posts: 1,405
    thanks to all

    I have been reading John Sigenthal's (Siggy ?) Hydronics book and have just gotten into the controls section. I understand the ODR concept and it seems the way to go with Panels and TRV's.

    The amount of electric use for constant circ. is not as high as I was picturing. With variable speed pump electric use would be more efficient.

    Pete
  • ALH_4
    ALH_4 Member Posts: 1,790
    Savings

    Dollar-wise, I agree, but VS provides additional functionality to the system while also saving energy. It also may eliminate the need for the dP valve.

  • Tom Hopkins
    Tom Hopkins Member Posts: 545
    We're not there yet...

    Andrew, I was under the impression that with a boiler like a Prestige and TRV'd panel rads you only need the equiv of about a 15-58 on speed 1 which takes 60 watts, especially if the load is under 60 where many many houses are. Furthermore, if that pump was a high efficiency design it would only take around 10 watts or maybe even less. If it then requires a controller that needs a few watts to function (MCBA is 14 watts for example), there really isn't much savings to be had. I'm not sure how reliable dP vales are, not the cost of a VS pump and controller compared to a dP valve and single speed high efficiency pump.

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  • ALH_4
    ALH_4 Member Posts: 1,790
    I agree

    A Prestige with a 15-58 on speed 1 is already extremely energy efficient. That's one of the primary advantages TT has over its competition. I like the idea of VS pumps primarily for their function. They eliminate the need for a dP valve to make a single speed pump "behave". I'm not sure a VS circulator in that application would ever pay for itself.

  • scott markle_2
    scott markle_2 Member Posts: 611
    pump curves

    Although the curves are different and the grudfoss 26-99 performs above 20ft.hd , the smallest wilo stratos at it's highest output is fairly comparable to a 26-99. Yet the Stratos uses a maximum of 130 watts, the grundfos 196.

    So yes here efficiency improvements go beyond the VS aspect of design. Does anybody have an idea of what the actual efficiency of a circulator is? Is there a mathematical way to convert flow and head into a unit of energy such as kw.? If so how does the relationship between flow and head effect the energy in moving water?

    I think that perhaps variable speed pumps offer the possibility to bring higher efficiencies to condensing boilers in a way that may be more valuable than the electricity they save.

    I imagine a direct connect home run radiator setup sized for very high delt-t. and a vaiable speed circulator with logic that maintains that high delta across a broad range of operating conditions. Or perhaps just a linkage between boiler firing rate and circulator speed. Could this be as simple as spliting the 0-10 volts from a boiler control and the 0-10 input to a stratos? Probably not, they would not necessarily follow the same curve. Any one working with this sort of idea?

    While the actual logic used is a mystery to me, I believe a vitodens 200 is doing something along these lines with it's vario circ.

This discussion has been closed.