We purchased a cottage in early December with a geothermal heating and cooling system. The place has been generally empty most of the time and we have turned down the heat to between 50 & 55F when we are not up there, all lights are off, and there is for the time being no electronics or anything of the sort brought up. So besides the furnace, only things plugged in or running are the refrigerator, oven (clock timer only!), a dehumidifier in a cool crawl space (with sump pump which I don’t think has tripped on at all), an HRV, and the hot water tank (which is also tied in to the geothermal furnace).

We were dismayed to see our December Electrical bill which totaled some CDN$354, for an unused cottage with the heat down (we went up 1 day only in that first month) and wonder if our system is functioning correctly. Here are details as I know them:

1) Cottage – Haliburton, Ontario (purchased December 2015) – House is a Viceroy cottage, 1911 sq.ft. main level (lots of panoramic windows), basement (walkout) is 1568 sq. ft – about 2/3 of that is finished plus a 320 sq.ft. unheated crawlspace
2) Heat loss/gains – No idea at the moment
3) Waterfurnace Premier (circa 2004), Model No. P070TL111NBD – understand this to be a 2 stage, 70,000 BTU unit, no idea of tonnage for cooling
4) Closed loop, goes out into the lake, about 400 or 500 feet out into the lake or so I was told
5) Average cost = CDN$0.22/Kwh (includes electricity, delivery and other add-on charges and 13% taxes), Monthly Electrical Consumption:
    a. Dec 5 – Jan 6 = 1672 kWh (avg = 49.2 kWh/d when we are not there), 611.6 deg. Days (deg. Celsius) – CDN$354
    b. Jan 7 – Feb 4 =1824 kWh (avg = 56.6 kWh/d when we are not there), 717.6 deg. Days (deg. Celsius) – CDN$407
    c. Feb 5 - 17 = 986 kWh (avg = 51.2 kWh/d when we are not there), 717.6 deg. Days (deg. Celsius) – not yet billed, currently estimated at CDN$217 for 13 days
6) EAT, LAT measured immediately upstream and downstream of the heat-pump – will attempt measurement this weekend
7) EWT, LWT measured at the geo system – will attempt measurement this weekend
8) Percent of load to be covered and balance point – No idea at the moment 
9) Installers assessment of the system - To be determined when a technician is on site during March Break - fellow turns out to be the original installer, so hopefully I can get answers to some of the other questions
10) Projected operating costs, actual operating cost and previous heating and cooling costs
   a. Projected costs no good idea yet as we have no history of usage
   b. Actual costs – I have my costs above for ~ 2.5 months (winter) and previous owner left me with spreadsheet with about 11 years data (2004-2015) on kWH usage (they lived at place full time)
      i. Dec-Jan ranged between 72.5 and 145.6 kW/d (average = 118.2 kWh/d) (all 3 numbers are daily monthly averages over these months)
      ii. June – Sept ranged between 17.1 and 54.9 kW/d (average = 35.2 kWh/d
      iii. Average cost of electricity in 2008 was CDN$0.12/kWh, currently CDN$0.22/kWh

We find our daily use when we are there increases substantially when we are there because my wife wants the place at 70F so we kick in the auxiliary heat to get up there (heats up fairly quickly).  Two weekends ago when we went up temperatures were in the -25 to -38 C range so our daily use was 151, 203 and 136 kWh over each of the 3 days we were up there.

Through reading this site I realize that lowering the temperature in the house like I do at home with my gas furnace is not a great idea, and I will be leaving it at 68F next time we leave the cottage to see how that affects daily electrical demand while we are away. I do know that when furnace is not running (such as after we leave the cottage and the cottage is warmer than the set temperature, or often around noontime on sunny days, our electrical loads are consistently in the 0.33 kWh/h range, so that is only the fridge, water heater, dehumidifier, etc. running. 

My basic question is: Does the system appear to be functioning normally? If not what are some things I should be looking for? (Air filter was clean by the way, and I gave it a wash last time I was up (it’s a reusable type))

Second question, when measuring the temperatures of incoming/outgoing air and water this weekend, how should furnace be running, with or without auxiliary heat running for example?

Thanks,

Andrew Kulin

This is a manual on Premier's. The largest listed is 066 and I believe that is 6 tons.

http://secure.waterfurnace.com/docs/FB507406666/manuals/premier/SP1555.pdf

Your unit is a large one. Is the whole house one zone?

What is the Aux heat? electric element inside unit?

There are probably a couple of large pumps that run to circulate the brine out to the lake and back. They use quite a bit of electric.

I have heard that running at low indoor temps can cause the units to shut down the compressor and run on Aux only. If you haven't seen any fault lights flashing it may be running fine.

I am just a homeowner not a pro.

ChrisJ

I would spend my effort making the house able to easily and safely freeze. Ie, an air compressor all set to blow out the water lines, etc. Then add something to turn on the heat the day before you get there.

Remember - sooner or later the heating system or power will fail. Until then it's costing money to heat an empty house.

Hi Chris:

House is a single zone as far as I know (only one thermostat in the place).  And auxiliary heat is electric.  I have seen no fault lights on the unit, as anytime I have looked, they all are fine.

Andrew

Jon:

Thanks for the suggestion.  I believe the geothermal lines have anti-freeze of some sort in them and if we are going to be away for a long time, and too far to get back to the place, we drain the house plumbing, put anti-freeze into the toilets and shut off the well pump and main line into the cottage.  Otherwise if we are not going up for a week or two we just shut off the well pump and the water main into the house.  The cottage has an emergency generator (12kW) , and the guy who plows the road and our driveway in the winter has a key to the place and will look after the generator and emergency heating if there is a power failure.  Unfortunately the generator cannot run the furnace, previous owner explained that the furnace was 60 kW, so we have brought up some space heaters to be used if needed.

Andrew

Does anyone else have any ideas or suggestions to give me some ideas if anything is going wrong with our system?  (i.e., is the electrical usage out of whack, or is within the expected range?)

And we are going up this weekend, and I'd like to measure the incoming and outgoing temperatures of the loop lines and air but I don't know what is the best way to do this as far as how the system should be running for the numbers to be meaningful.  I assume it would be better to do this without aux. heat going, but how long should system be running before I do so, and is there an ideal indoor air temperature for the house to be at when I do this.  For example the temperature will be around 55F when we get there.  Is that the time to do the temperature measurements, or do we wait until the house stabilizes around 70F to do so?

Thanks,

Andrew

Aux heat is inefficient - I'd try disconnecting it. Or put a separate meter on it.

You should measure COP, which requires accurately measuring the flow rate and temperature change of the lake water. And the HP power draw at that same time. I'd do it under normal, steady state load conditions (1st stage).

If COP is OK and aux heat isn't running much, then any problem is on the load side (ie you need better air sealing and insulation).

If you can't measure COP, then there are other techniques - like run on aux heat only for 24 hours and then run on HP only for a similar 24 hours and compare the furnace kwh.

You could also take some specific measurements of the structure(Floor, wall ceiling surface areas), windows(also surface areas) and insuilation thickness and window specifications(number of panes, any spec info like U factor if available), to try and determine your overall insulation value. With that you can get an idea of how much energy you need to maintain a given inside temp at a given outside temp. That might help confirm if the system is operating in a reasonable fashion given the circumstances.

Does this system use ductwork? Are you sure it is all sealed, and there isn't a pipe leak or unused run dumping a bunch of heat into a cralwspace or attic somewhere?

Is it possible to shut off the DHW heater while you are away?

Sounds like you have a hot water generator (desuperheater) in use. With a single tank setup vs a two tank setup, 1 un-powered storage and a powered finishing tank, the hot water generator can actually steal heat from the DHW tank. Causing the electric elements to run more then necessary.

ChrisJ

I measured temperatures of the geothermal today once the cottage temperatures had stabilized at 71F.  I used two devices:

1. An indoor-outdoor air temperature device that I have had for years at the house.  I am reasonably confident about its accuracy for air temperature, but with the way the temperature sensor is set-up, not so sure about the accuracy of readings regarding the coolant temperatures
2. A temperature probe on a current clamp gauge that I have, that responds to temperature differential very rapidly (way faster than my other device) but I am not certain about its accuracy.  There was a notable temperature difference reading air temperatures from a heating register.

I noticed the geothermal unit ran continuously with fan on low speed most of time (say 60-70%) and on high speed the rest of the time (Am I correct assuming low fan speed = Stage 1, High fan speed = Stage 2?).  I did not see the thermostat indicating Aux. Heat today.  Occasionally, the DHW Hi limit light on the Waterfurnace flashed amber during the day.  Outdoor temperatures during the day ~ 27F

Temperature readings: 

Using device #1:

EAT = 65F

LAT = 89F

EWT = 39F

LWT = 35F

Using Device #2

- Low fan Speed

EAT = 62F

LAT = 82-83F

EWT = 27F

LWT = 24F

- High fan speed

EAT = 68F

LAT = 87F

EWT = 31F

LWT = 26-27F

Does this data provide any insights?

Thanks,

If you are sure Stage 2 did not engage then it may be setup like mine. Fan is on very low at all times to circulate air then when Stage 1 kicks in --fan ramps up. Then if Stage 2 would kick in Fan would go even higher CFM. ClimateMaster also. My LAT is never that high in Stage 1. I think air temps. are good.

Marmar:

My fan is set to Auto so it should only be running when heating or cooling is engaged.  I don't know much about the system itself, I am only assuming that lower fan speed indicates Stage 1, higher fan speed indicates Stage 2.

JonR:


I don't have a pressure gauge I could use, nor do I have any idea where I would insert it onto my geothermal system, so I cannot do the flow calculations.

My electrical panel has two furnace breakers.  One labeled as Furnace Compressor, the other labeled as Furnace Elements.  When I shut off the second breaker (furnace elements) the fan in the furnace shut down too, so I left it turned on as I figured this breaker also controlled my blower and that is needed to get the heated air moving to the rooms.  So I don't think I can also do the technique you mentioned at the very end either.  (plus to run Aux heat only, I guess I would have to turn off the furnace compressor only?  And that would not cause any damage to the system, right?)

Andrew

Chris:

Not sure I understood you. The furnace is connected to a single hot water tank.  But it is not clear from how you worded this if it is the 1 tank, or 2-tank system, that you think could be stealing heat from the DHW tank.

The single tank setup can allow the heat pump to steal heat from the DHW tank.

Having a second unpowered tank is more efficient.

Chris

We have a technician coming out to our cottage next week to look at the system. What things should we be aware of as possible reasons for the high electrical usage we are seeing from our system? What should he be looking for when checking the system so we are aware in advance? What questions should we be asking?

We are also getting a blower test and energy audit done next week as well to confirm if we have an insulation/heat loss problem or not.

Thanks