KimKong
New Member
Posts:17
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| 16 Jan 2011 02:57 PM |
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I am having high electricity consumption problems with my unit and so is my neighbour who had his installed by the same installer and at the same time (August 2008) during the construcion of our new homes.
I am currently using about 175 Kwh/day for a 2500sq/ft home.
Let's start with the required information;
1) We live in Ottawa, Ontario, Canada... I know it's cold but not as cold as you think! :)
2) Heat loss/gain calculations? I will have to look into this and get back to you.
3) Brand, size (model), age and type of heat pump
Maritime Geo Thermal Unit
Nordic DX Series (Direct Expansion)
5 ton
2 years old
HACW (Heating, Active Cooling, Hot Water)
Voltage 230-115
1 stage
4) Type of loop field (open/closed/vertical/horizontal) size and design parameters
Vertical 5 loops 100 feet (down to 4 loops as a result of a leak in one of the loops... see aditional notes later)
5) Average cost/Kwh of electricity and consumption
We have a smart meter and costs are based on time of day usage as follows;
5.1 cents/kWh (9pm-7am)
8.1 cents/kWh (11am-5pm)
9.9 cents/kWh (7am-11am, 5pm-9pm)
Daily usage 172 kW
6) Entering and leaving air temperatures (EAT, LAT) measured immediately upstream and downstream of the heatpump
Note: I don't really know what I'm doing here but I have a heat detector and put it on the cold air return and the heat vent directly before and after the unit and this is what I got...
EAT - 70 F (measure at cold air return)
LAT - 84 F (measured at heater vent)
7) Entering and leaving water temperatures (EWT, LWT) measured at the geo system
Note: Same as previosu comment... in thgis case have not wau of measuring the water temperature so i used the heat detector and put it on the copper pipes before and after the unit and this is what I got...
EWT - 60 F
LWT - 69 F
8) Percent of load to be covered by geo and balance point
Sorry... don't know how to answer or calculate this.
9) Installer's assessment of your systems operation.
Installer was originally perplexed with the high electricity consumption. In 2008/2009 he suggested that our auxiliary heater was coming on to heat the house because we were adjusting the thermostate too drastically (65 F at night and 72 F during the day) He said that we should keep it at 72 F all the time because the unit could not catch up quick enough thereby kicking in the auxiliary heat.
This helped reduce the use of the auxialry heat during the winter of 2009/2010 (was at about 225kW) and so far this year (2010/2011) the auxiliary heat has not kicked on. However, our electricity consuption is still very high (175kW) for the size of our house compared to others in our area.
This past summer, we had a problem with the unit and it would stay on 100% of the time and was not cooling the house. With the assistance of our house builder (they have been great) they called in another company to assess the system. It took them several days but they found a leak in one of the loops. They advised our builder that our system was oversized anyways and could run on 4 loops. They disconnected the leaking loop and we have been running on 4 ever since (August 2010).
10) Projected operating costs, actual operating cost and previous heating and cooling costs
2009 electricty bill $5456.13
2010 electricity bill $4788.16
Please note that in 2010 I added a propane fireplace and the propane cost me $800/year and I burned 4 cords of wood in my wood burning fireplace.
Based on my previous 3400 sq/ft home with natural gas heat in the same area, I was paying about $1200 for electricity.
I have contacted the builder once again but thought I would do my own research because neither the original installer or the second company have been able to figure out the problem.
Thanks for your help in advance.
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ICFHybrid
Veteran Member
Posts:3039
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| 16 Jan 2011 03:18 PM |
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Short of heat loss information, can you describe your home layout and construction type? One story? Two story? Foundation type? Basement? Crawlspace? Attached garage?
Are there any areas in the home that seem colder than others? Around windows or doors? Near electrical outlets? First floor? Second Floor?
Have you stuck a ruler in the ceiling insulation to see how thick it is? Looked at how much insulation is under the floor? |
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KimKong
New Member
Posts:17
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| 16 Jan 2011 03:29 PM |
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Thanks for your reply...
The home was constructed in 2008 and is a 1 1/2 storey 4 bedroom home with attached 2 car garage. I can attach a picture if it helps.
My daughters room is colder than others and we recently added a vent fan to provide her with more heat. I have checked for heat loss in some areas and have found some colder areas in the basement and kitchen exhaust fan area.
I have also looked at the installation manual for the Gethermal unit and it states that I shouild have a 5 ton unit for a house that is 2600 sq/ft (mine is 2530 sq/ft not including the fully finished basement). It also provides a chart that shows that I should have 21 heater vents but my house has 27. |
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KimKong
New Member
Posts:17
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| 16 Jan 2011 03:29 PM |
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Photo of my home... |
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ICFHybrid
Veteran Member
Posts:3039
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| 16 Jan 2011 04:34 PM |
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They advised our builder that our system was oversized anyways and could run on 4 loops. Maybe that is the case and maybe it isn't. As a homeowner, this is what I would advise; 1) Talk to the manufacturer about whether 4 loops is a workable situation with this model 2) Get a third-party HVAC expert who has experience with this make to come in and take a look at the function, (i.e. NOT one brought in by the builder or original installer) 3) Get a whole-house energy audit. Why? Look at the manual that came with that unit and see how many feet of borehole they recommend per ton of capacity. It may have been 100', but they are now saying 120'. In either case, taking out one of the loops reduces your capability about 20% more. If they have now decided that you really need 120' per ton, then it is even more likely you don't have enough. The outside HVAC specialist should be able to take a look at the loop function and the rate at which they are utilized to figure out where you are. BTW, you have a DX (Direct Exchange) unit which means that copper loops with refrigerant go directly into the ground without using water as a cooling fluid. There is no "Entering Water Temperature" per se. It would be a big hassle to have to bring out all the equipment to repair the one loop or drill another. That's why they don't want to do it. Between the builder and the installer, you need to consider what your warranty rights are with respect to the DX ground system. You might consider whether or not the evidence suggests that one loop leaked from the beginning and if they should have caught it before the system was put into service. 3) You might want to get up to speed on the things that you can do to save energy in your house and an audit by a qualified person would be a good place to start. A hurting heat pump and a leaky or inadequately insulated home could team up to create the situation you see now. |
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KimKong
New Member
Posts:17
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| 16 Jan 2011 05:13 PM |
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Thanks for the reply...
I will start looking into a qualitfied 3rd party HVAC specialist this week and will report back. |
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engineer
Veteran Member
Posts:2749
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| 16 Jan 2011 06:36 PM |
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The 14*F air side delta T (84 - 70) is quite low.
I don't know what to make of the copper line temps.
Electricity consumption seems very high for a new home of its size. |
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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KimKong
New Member
Posts:17
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| 16 Jan 2011 07:28 PM |
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Hi Curt... thanks for the comments.
Please disregard the copper line temps... these lines are for the hot water heater. As identified by ICFHybrid " I have a DX (Direct Exchange) unit which means that copper loops with refrigerant go directly into the ground without using water as a cooling fluid. There is no "Entering Water Temperature" per se."... my rookie mistake.
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KimKong
New Member
Posts:17
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| 16 Jan 2011 07:28 PM |
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Hi Curt... thanks for the comments.
Please disregard the copper line temps... these lines are for the hot water heater. As identified by ICFHybrid " I have a DX (Direct Exchange) unit which means that copper loops with refrigerant go directly into the ground without using water as a cooling fluid. There is no "Entering Water Temperature" per se."... my rookie mistake.
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vkykam
New Member
Posts:60
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| 16 Jan 2011 11:02 PM |
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Are you SURE you're not drawing AUX heat? On the assumption of 5 tons, and on an assumption of a COP of 3.6, you should only be drawing just under 5kWh per hour, or 117kWh per day, if the unit was running full tilt 24/7. It's certainly possible you're drawing another 60kWh for the rest of the house, but that will really depend on your lighting (halogen vs CFL), how many computers, appliances, etc. I'd get a baseline by getting a Kill-A-Watt and start measuring your appliances to know how much you are drawing, and unplugging everything else at least for a day to get a better reading of how much the GSHP is using.
But that's all based on an assumption of a COP of 3.6, which may not be the case if you're down a loop.
Victor
www.ecobuilthome.ca
A 4350sqft Net Zero Energy initiative |
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vkykam
New Member
Posts:60
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| 16 Jan 2011 11:07 PM |
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Just noticed another thing... Nordic themselves on their web site says vertical systems require a 3" bore 120' per ton. I'm now really wondering if your loop size is inadquate for the heat demands of the house and the 5 ton unit, since it looks like you needed 600' but you only have 400' working in the field.
For what it's worth; I'm no expert in geothermal.
Victor
www.ecobuilthome.ca
A 4350sqft Net Zero Energy initiative |
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KimKong
New Member
Posts:17
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| 17 Jan 2011 05:38 PM |
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Thank you Victor...
I am planning on measuring the power draw on each circuit to try to isolate the problem.
I will report my findings later!
Kim |
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KimKong
New Member
Posts:17
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| 17 Jan 2011 09:08 PM |
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Victor... looks like you are right. Even thought my thermostate is not registering any AUX Heat use like it use too, I have identified that they are in fcat turning on.
When I measured the AMPS from each circuit I got the following;
17.8 Amps Compressor
39.9 Amps AUX heater #1
43.8 Amps AUX heater #2
When I turned the breakers off for both AUX Heaters I get 0 Amps but the Compressor continues to climb to 28.5 Amps for about a minute then turns off. I beleive that this must be a safety feature. I have turned off the breaker to the compressor and have requested a service call for tommorrow.
According to my calculations the 88.7 Amps generated by the Aux heaters is equal to 20.088 kWh... no wonder my consumption is so high.
Wish me luck with the servcie techs... I will keep you all informed.
Thanks for the help so far...
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KimKong
New Member
Posts:17
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| 18 Jan 2011 07:34 PM |
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The servcie tech came today and made the following observations and comments;
- the relay for the Aux heaters is not stuck
- he confirmed that the Aux heaters are comming on but without any regularity of temp differential
- he stated that my particular model will call for Aux Heat when the temp drop 2 degrees F below the requested temp (for example if we are asking 72 F then the Aux Heaters will come on if the temp reaches 70 F)
- I advised him that this would always be the case since those are the limits on the thermostate.
- He stated that the the compressor should go on when 0.5 f difference is reached (for example if we are asking 72 F then the compressor will come on if the temp reaches 71.5 F)
- He checked everything else and is suggesting that he thinks there is a problem with the thermostate
- He is ordering a new thermostate
- In the interim he disconnected the relay wire so it will not call for the Aux Heaters.
We will monitor the system to see if it can sustain a 72 F temp without the Aux heaters and if my power consumption goes down.
FYI... this past Sunday my total power consumption for the day was 234.26 kWh with an outside temperature of 5 degrees F (-15 degrees C).... OUCH!
I can't wait to solve this problem!
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vkykam
New Member
Posts:60
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| 18 Jan 2011 11:10 PM |
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There are thermostats that are programmable that can reduce the "swing" that might alleviate the problem. I know my Ritetemp one (that I bought at Home Depot) at my last place was adjustable, but you need one that works with geo.
BUT, your Sunday usage of 234.26kWh, to me, indicates an undersizing problem, and my guess is that the heat loss of the house is much greater than 4 or 5 tons at design temp. If your house was a typical build, I'd be pretty sure that would be the case. Unless your house was super-insulated or air sealed, 60kBTU heat loss @ -20C design temp on the square footage you indicated is unlikely, and on a cold -15C day you'd be on aux heat, driving up the kWh with COP of 1.
What I'd be very concerned with is, if you meant that in the interim the service technician disconnected the relay wire so it WON'T call for aux heat, then you may be in a situation where you won't be getting enough heat in a day or two, given the forecast temps in the mid -10C's. I didn't look at Ottawa weather specifically, but in Toronto where I am, we're expected below -15C in two days I think, so Ottawa temp will be fairly close, if not colder. The thing you need to watch for is that without aux heat, you might not be able to keep the hosue warm, or worse, that the compressor shuts off in a similar fashion as when you had flipped off the breakers to the aux heaters during your test, in which case you have no heat at all.
To add insult to injury, natural gas this year is crazy stupid cheap, while our electricity rates have been going up no thanks to the time-of-day metering and the debt retirements and other related charges that we have to pay now, in order to pay for the past sins of the province. To break even this year with natural gas, you would need a COP in the mid to high 3's during off peak hours (achievable with geothermal, assuming your loop lengths are not undersized), but during peak rates, you'd need greater than a COP of 5 to be ahead of natural gas, which just isn't feasible. So don't expect to save any money with geothermal this heating season compared to natural gas...
For what it's worth, keeping in mind I'm no expert in geothermal, just enough knowledge to be dangerous... :-)
Victor
www.ecobuilthome.ca
A 4350sqft Net Zero Energy initiative |
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ICFHybrid
Veteran Member
Posts:3039
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| 18 Jan 2011 11:37 PM |
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he stated that my particular model will call for Aux Heat when the temp drop 2 degrees F below the requested temp (for example if we are asking 72 F then the Aux Heaters will come on if the temp reaches 70 F) Doesn't the main board have an Aux Heat Delay built in, or is the thermostat you have capable of overriding that? |
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engineer
Veteran Member
Posts:2749
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| 18 Jan 2011 11:39 PM |
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This quote needs analysis:
"When I turned the breakers off for both AUX Heaters I get 0 Amps but the
Compressor continues to climb to 28.5 Amps for about a minute then
turns off. I beleive that this must be a safety feature. I have turned
off the breaker to the compressor and have requested a service call for
tommorrow"
Why did compressor amps continue to rise? Did opening aux heater breakers also kill the blower? That would likely cause compressor to draw excessive current and shut down on overload
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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joe.ami
Veteran Member
Posts:4377
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| 20 Jan 2011 07:58 AM |
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I wondered about that as well.
The way it is said suggests that the unit is shutting off on pressure or temp.
A previous measurement for compressor amps was 17.8a.
While there are systems where aux breakers also disconnect control circuit, I know of no compressor control circuit that is independant of fans transformer.
Joe |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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KimKong
New Member
Posts:17
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| 20 Jan 2011 03:57 PM |
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I don't know... he is bringing in another thremostat so I will ask him then. |
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KimKong
New Member
Posts:17
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| 20 Jan 2011 03:58 PM |
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Posted By engineer on 18 Jan 2011 11:39 PM
This quote needs analysis:
"When I turned the breakers off for both AUX Heaters I get 0 Amps but the Compressor continues to climb to 28.5 Amps for about a minute then turns off. I beleive that this must be a safety feature. I have turned off the breaker to the compressor and have requested a service call for tommorrow"
Why did compressor amps continue to rise? Did opening aux heater breakers also kill the blower? That would likely cause compressor to draw excessive current and shut down on overload
Yes the blower also shut down when the aux breakers where turned off. |
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