Using 75% more electricity than expected
Last Post 25 Jan 2015 07:36 PM by docjenser. 54 Replies.
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docjenserUser is Offline
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01 Jan 2015 03:25 PM
It simply is the high load temp in combination with inefficient pumping, compared to the report which used artificially low load temps. That explains 75% higher than the predicted number.
www.buffalogeothermalheating.com
joe.amiUser is Offline
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02 Jan 2015 08:44 AM
"It simply is the high load temp in combination with inefficient pumping, compared to the report which used artificially low load temps. That explains 75% higher than the predicted number."
The upshot is that with a better pump and control strategy you could cut that usage down.
Joe Hardin
www.amicontracting.com
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05 Jan 2015 01:32 PM
I thought I would follow up with an update: I paid another local geothermal company come by to do an analysis of the system, and they had two people spent about 2 hours looking at the system and taking notes/measurements. They did make a number of comments on the system, but overall seemed to think that there was nothing obviously wrong with the system (e.g. no malfunctioning, and temperatures and amperages were within operating limits).

Their recommended solution was to use a larger buffer tank, and have the heat pump operate independently from the air handlers. They did not feel comfortable providing an estimated power savings, although they felt that if they had installed the system it would be using around 12,000kWh annually (versus the 18,000 or so I am seeing).

They noticed that the buffer tank was 30 gallons, and are recommending an 80 gallon buffer tank. They also noticed that the controller is powered down when the thermostats are not calling for heat, which causes the water in the buffer tank to slowly decrease in temperature until heat is called for again. And as a side-effect of that and the small buffer tank, when the thermostats call for heat, the temperature of the water in the tank is normally low enough that stage 2 is always used (in essence negating any benefit of having a 2-stage heat pump).
                                        -Scott

ChrisJUser is Offline
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05 Jan 2015 03:06 PM
Could they re-wire the controller to be on without a call for heat. Also have the heat pump operate independent without getting the larger tank for now.

At least then the tank would always be up to temp.

Chris
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05 Jan 2015 11:19 PM
Can someone answer WITH would a Geo go into stage 2 JUST to heat water when that function is supposed to be something additional when it's running??? The MAIN function of the Geo is to HEAT/COOL the house FIRST!! Heating water is a byproduct of that!!!
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05 Jan 2015 11:47 PM
Posted By robinnc on 05 Jan 2015 11:19 PM
Can someone answer WITH would a Geo go into stage 2 JUST to heat water when that function is supposed to be something additional when it's running??? The MAIN function of the Geo is to HEAT/COOL the house FIRST!! Heating water is a byproduct of that!!!

The original poster to this thread has a water-to-water geo heat pump, not a water-to-air heat pump with auxiliary hot water generator.  Heating and cooling water is all that his geo heat pump does.
jonrUser is Offline
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06 Jan 2015 08:27 AM
Perhaps you should get an actual COP measurement. It's the primary reason people pay more for geo and yet it is seldom measured, verified or guaranteed.
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06 Jan 2015 09:06 AM
Posted By ChrisJ on 05 Jan 2015 03:06 PM
Could they re-wire the controller to be on without a call for heat. Also have the heat pump operate independent without getting the larger tank for now.

At least then the tank would always be up to temp

That might be worth doing. It wouldn't be a simple undertaking (e.g. I think the electrical lines would need to be moved around, and extra parts might be needed), but still cheaper than replacing the 30g tank with an 80g tank (they were guessing around $6K-$8K to do the new tank and have the heat pump operate independently).
                             -Scott
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06 Jan 2015 09:09 AM
Posted By jonr on 06 Jan 2015 08:27 AM
Perhaps you should get an actual COP measurement. It's the primary reason people pay more for geo and yet it is seldom measured, verified or guaranteed.

That would be nice. The problem is that to get the COP, you need to get the flow rate. But there are no P/T ports, which I understand makes measuring the flow rate extremely difficult.
                      -Scott
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06 Jan 2015 09:21 AM
Ok, I like the idea of sticking with the 30 gal tank for now. something as simple as a Ranco Aquastat could operate the geo, but I don't know how your pumps are set up. http://www.supplyhouse.com/Ranco-ETC-112100-000-Single-Stage-Temperature-Control-w-Sensor-24V-Input-0-10V-Ouput?gclid=CN-mjYTI_8ICFcFzMgodsRwAAw

What pipe diameter runs between geo and buffer tank?
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort!
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06 Jan 2015 01:20 PM
Posted By joe.ami on 06 Jan 2015 09:21 AM
Ok, I like the idea of sticking with the 30 gal tank for now. something as simple as a Ranco Aquastat could operate the geo, but I don't know how your pumps are set up. http://www.supplyhouse.com/Ranco-ETC-112100-000-Single-Stage-Temperature-Control-w-Sensor-24V-Input-0-10V-Ouput?gclid=CN-mjYTI_8ICFcFzMgodsRwAAw

What pipe diameter runs between geo and buffer tank?

Ah, there is a controller just like that one. The catch is that it doesn't do much -- the temperature in the buffer tank is almost always below the setpoint, so it (almost) always has the geothermal unit running on stage 2. Once the thermostats stop calling for heat, the controller is powered off.

The pipe between the geo and buffer tank is 1 1/4".
                             -Scott
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07 Jan 2015 08:30 AM
OK good news on the pipe size. The reason the control doesn't do anything is the geo only runs when the air handlers are on. That means the air handlers are woking at lowest posible efficiency because the water isn't to temp when they come on. We might be able to change the control strategy if you have enough pics. to identify whether geo pumps into tank independent of circulators to air handlers.
getting this part right may cut your energy use 10-20%
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort!
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07 Jan 2015 02:18 PM
Looks like you are getting some good advice here Scott.  

One thing to consider if you do go with a separate control for the water-water geo unit is the addition of warm weather (WWSD) and cold weather shut down (CWSD) controls.  That way your geo unit won't run unless it's cold enough or hot enough outside such that your room thermostats might start calling for hot or cold water.   This minimizes inefficiency concerns about keeping a tank of water hot or cold that you don't need. 

I have WWSD for my system set for a 60 degree outside temperature, the geo unit will start heating the buffer tank once the temp outside goes below 60 degrees.  (Just installed CWSD this past fall, probably will use 70 degree outdoor temp for it.)

Tekmar has controls that will do warm and cold weather shut down (along with outdoor reset).    Sure there are others that do the same.

Andy
Bill NeukranzUser is Offline
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23 Jan 2015 10:15 PM
Posted By jonr on 06 Jan 2015 08:27 AM
Perhaps you should get an actual COP measurement. It's the primary reason people pay more for geo and yet it is seldom measured, verified or guaranteed.

And with a WEL unit, measurement of COP is straight forward and inexpensive and accurate.

You do need P/T ports though.

Best regards,

Bill
Energy reduction & monitoring</br>
American Energy Efficiencies, Inc - Dallas, TX <A
href="http://www.americaneei.com">
(www.americaneei.com)</A></br>
Example monitoring system: <A href="http://www.welserver.com/WEL0043"> www.welserver.com/WEL0043</A>
docjenserUser is Offline
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25 Jan 2015 07:36 PM
Posted By jonr on 06 Jan 2015 08:27 AM
Perhaps you should get an actual COP measurement. It's the primary reason people pay more for geo and yet it is seldom measured, verified or guaranteed.


People often don't understand that it is up to the designer to have a nameplate COP of 4.0 run actually at 4.0 or 2.0. The OPs system is the best example. I don't focus on monitoring COP, I focus on 1) low pressure drop, (2) low circulation pumping power, (3) and lesser lift between source and load. Nothing else influences the COP of a geo heat pump system.
www.buffalogeothermalheating.com
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