Geo thermal HP dual fuel

mikea23

I have done it before, it gets tricky with controls and or staging if you have multiple heat pumps and backup boiler. the best way that I found was injecting the boiler into prim loop to get temps above 120.Works best with MODCON boiler. I will take a few pics and post them

MIKE A

Wayco Wayne_2

I've run into several jobs lately that

want to use a geothermal heat pump but have nice big cast iron radiators. I did a heat load of a beautiful old farm house where the Parlor had a heat loss of 10000 btuh, and had two big radiators with a sq ft of 80 each. (That's 10000 btuh divied by 160 sq ft = 63 btu per sq ft. of available radiator surface.:o ) Looked it up in my EDR book. None of my EDR charts even go that low in temperature. The lowest they have is an EDR of 110 btu/sq.ft. @ 150 F. The short of it is if a water to water heat pump can generate up to 120 F. we are not that far from design temps. Can you do a dual fuel set up with a back up boiler? Has anyone done it? Inquiring minds want to know. Thanks for any responses. WW

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Wayco Wayne_2

Thank you Mike

I was thinking of just having a switch over point based on outdoor temps. WW

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GW

WW

I'm new to the geo stuff as well but energy is energy. Unless I'm missing, i can't see how using both methods at the same time would work....if the return temps from the system are greater than the supply temps from the hp, not gonna work, unless your cust doesn't mind wasting electricity.

Because every house is different, you likely don't know what temps are required at design conditions. If this house is old, with jumbo rads, and the house has been tightened/insulated, you may have a perfect environment for dual fuel. What I'm saying is you likely don't know at what outdoor temp 120 will fall short. If the house is an energy hog I'd be very careful going forward.

I would say to the ho "this system will save you money. It will require some experimentation to maximize the efficiency of the new hp; we need to learn at what outdoor temperature the oil system should take over".

gw

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GLENN_14

mike is right

setup can get tricky but you may want to also look at a stat that can pick the point of swich over. The point is determined by knowing the cost of each of the fuels and the efficiency of the equipment. Then you crank the numbers and you find the balance point. Once that is determined you end up with a system in which the stat determines which soucre to run. works great... we have several systems running in this fashion...

don_192

Well said Glenn

Balance point is the key.And if I were doing it instead of getting fancy I would just take out the geo system once I was at my balance point.

Then again that does depend on where one lives and if he was at balance point or below most of the winter.

Personally I feel in my area that I lose any benerfit out of the geo system when now I;m running well pump,refrigeration equipment and now a boiler along with circs.You start to think where the savings.

I'm lucky, I have milder winter then most of yous guys so,I
can take advantage of a more simplier system.