I've done some tests with a watt meter and my closed loop geo system. One third of the electricity use comes from running the flow center pump. This is maybe odd but not unexpected for the kind of system we had to do.

I have a 2 ton waterfurnace envision unit. Right now it is set to keep the temperature within half a degree (or close to that). It is very comfortable. I am wondering if I could program it so that it takes a larger temperature swing to turn it on. That way it would come on less often, the temperature would swing more and it would, perhaps, use less energy overall.

Using a honeywell visionPro programmable thermostat.

My theory could be wrong but at least I could test it with my watt meter.

First, look at the published pump curve for your flow center pump and at the pressures and flow rates of your system. If your volume and pressure numbers are not near the most efficient operating point of the pump you are expending energy needlessly. A too large pump is just as bad as a too small pump.

Once you know you have a right sized pump for the flow loop then look for other ways to save.

I do not have a pressure tester. If the pump is the wrong size I would have to get a new one. What I can do now is monitor the actual energy usage by tweaking the system.

Maybe it would be better to adjust the pump. However it is my suspicion that I could achieve energy savings now by bypassing the first stage and going directly to second stage heat because of my high Reynolds number. Any action I would take would be reversible and subject to testing. So how do bypass 1st stage heat on a waterfurnace envision unit with a honeywell vision pro thermostat?

If your thermostat has a Y1 and a Y2 terminal,  then take the wire from Y2 and hook it onto the Y1 terminal.

How long does it take for the heatpump to heat up the room after the thermostat calls for heat? 

Did you  figure out a way to increase the swing between calling for heat and shutting off? 

Start up on a heat pump compressor is the when the most wear occurs.  If yours is coming on and off frequently ( more than 3 times in a hour), I would definitely figure out a way to come on less times in an hour and run longer.   Your heat pump will last longer. 
What type of flow center do you have?  Does it have one pump or two?
Is it pumping more than 6 gallons per minute?   Your installer should be able to tell you how much it is pumping by measuring the pressure drop through the heat pump. Or you can do this with an inexpensive pressure gauge as long as the P/T ports were installed on the system.

What did you  mean when you said "This is maybe odd but not unexpected for the kind of system we had to do."  When talking about the energy use of the flow center.

We have 15 bore holes totaling 900 ft. for our closed loop system. We had to do it this way because of a boulder field about 80' down and some issues with running sand. (though I know if it was oil down there they could have gotten through it). The wells are attached at the header in a way to cause more turbulence and thus greater heat exchange. So I think it must be harder to pump the fluid through the system. The watt meter tells me that a third of our electrical costs are to run the flow center.

The building is a 4 unit condo building. The other units have single stage waterfurnace versatec units. We have the envision. On a 38 degree day it only takes a minute or two to go from 68 degrees to 69.

When the system was set up we did not think to put the flow center power on the public panel of the building. Now I have a wire run but do not want to hook it up until the flow center usage seems more equitable. The single stage versatecs do not seem to come on as often as our dual stage envision. I know the dual stage units put out a more constant comfortable heat but I do not think I would mind more temperature variability -> shorter cycles -> longer off times -> less energy used by the flow center. Instead of "less times in an hour and run longer", less times in an hour and run shorter.

The flow center has two pumps.

What do you think? Am I crazy?

So you have 15 bore holes 60' deep. Is each bore hole hooked up in parallel or are a few of them grouped in series, then those groups in parallel?

Or are all the bore holes in series? This is what would cause "more turbulence". The pumping costs of pushing all that flow down one path would far out weigh whatever small benefit the increase in turbulence might give you.

Does the one flow center supply all four heat pumps? If this is the case, then when only one heat pump is running, you have four times the capacity you need which would be why your pumping costs are so high.

It sounds like you are paying the pumping for all for units?

If one flow center supplies all four heat pumps, I don't see any way to reduce your pumping costs.

A flow center with a single pump should be enough for your unit. You would have to decide if it makes sense to give each heat pump a flow center.

I am not familiar with the brand of thermostat you have. Can you set the spread on when it calls for heat and when it shuts off? Most thermostats allow you to set how long first stage runs before second stage kicks on.

If it only takes two minutes to raise the temp 1° then it sounds like your heat pump is too big for the job.

Is this a DIY job or did someone design this?

You don't have a lot of options here.


Good Luck !!!

 Just curious what is your Reynolds number? 

How did you determine it?

Another solution would be mathmatical: If I knew how long each unit was on per month then the power draw from the flow center could be divided equitably. I do have the capacity to put sensors on each of them, push that data out to the web and write a formula to divide it up. Fairness is a concern.

Then to lessen our draw on the flow center I could adjust our first stage/second stage timing. I don't think pumps on each unit would work.

Our heat pump is a little big because the smaller units did not have desuperheaters.

As far as the reynolds number, it comes from the designers at waterfurnace.

So are the heat pumps in series? Does the flow center push through one heat pump to get to the next and so on?

If your heat pump only runs for a minute and then is off for ten or fifteen the water in the loop is still for most of the time. In this case Reynolds number is meaningless.

If I was you, I would try and get the temp swing up around 2 or 3 °. Which is what you asked about in the first place. This is a function of the thermostat not the heat pump.

Please let us know what you try and how it works. It always good to hear the solutions.

Good Luck.

They are not in series.
Oh, and to answer a previous question, the ground loops are in groups of three. Within the set of three they are in series, the five groups of three are in parallel.

Over all the system works very well. We are warm in the winter and cool in the summer for a lot less than what other people are paying. But, as you may know, people that choose geothermal get intimate with their systems. Myself, when the heat pump kicks on, I think it's a failure of insulation, even with the poly-urethane SIPs.

yours does have the desup option??

I take it that any time any one of the 4 condo heat pumps kicks on the flow central pump turns on and you are running water through the entire ground loop system. Isn't this kind of like using a Mack truck to deliver a sand box full of sand? I think we need to do some creative thinking here to see if we can't come up an approach that more closely matches energy supply rate to energy demand rate. Right now you've got a situation, as I understand it, akin to keeping a bathtub full just above the overflow by adding water from a fire hose but draining it out through the overflow. Let's see if we can figure out how to cut down the size of the fire hose, not just turn it on and off less often.

4 smaller pumps? I wonder what would happen if they were all running at once.

The system would work just fine.   A two ton unit only needs 6 GPM.  Your operating costs would drop a bunch with 4 smaller pumps.  What the payback would be is the question.

' A two ton unit only needs 6 GPM' wow, my 3 ton is getting 16gpm right now, my loop is almost identical to Rsipgeo's cept i have 10 hole's. my pump is a grundfos SQ 1/2hp it draws about 5 amps @ 120v. is this to much pump? and if so, are there any other drawbacks other than excess power cunsumption? i will be adding a 2ton water to water system in the near future.

The main issue with over pumping is wasting energy. There is no advantage.

Depends on how they're connected to each other. If you put them in parallel they need to have as near the same discharge pressure for the required volume as possible. If one system needs 3 gpm and another needs 4 gpm, and the discharge is 50 psi, they can be in parallel as long as each puts out its required volume at 50 psi discharge pressure. Of course the discharge pressure will go up as more pumps are running and the flow rate increases because of the friction and back pressure of the loop.

The simplest would be to have four identical pumps in parallel and keep the flow through each system the same. If one system needs more heat than another, just let it cool the loop water more.

You can put them in series also but in this case every pump needs to have the capacity to handle the total flow. The pressure at the discharge of the last pump running would be the sum of all the pumps.

For your situation I think parallel would be easiest to configure and operate. You would need to have check valves in the discharge line of each pump so you don't get back flow whenever a pump is not running and or more of the others are.

I think this would go a long way toward improving your system overall.