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Old 2009-11-25, 11:47 AM   #1
coaster
 
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Question Heat Pump not delivering energy savings

We own a split-level 1500 sq ft home with electric baseboard heating.We installed a Fujitsu

12RLS mini-split in September 09. The installer and the Home Energy Audit claim a 30% saving in

heating costs with this unit.

The energy audit revealed some air leakage areas and with that list and a little DIY I managed

to reduce the heat loss by 10% qualifying for additional Federal grant money plus the heat pump

grant. So, all things being equal, I would save 10% on heating costs?

On the upper lever we have 7 baseboard heaters totalling 7500 watts on digital thermostats.

These heaters are set at 5 C as the heat pump has been in heat mode for the past month. The heat

pump is set at 66 F or 18.8 C and the upper level is comfortable. The lower level is heated by 3

Convectair convection heaters set at an average of 20 C, set back at night, same as previous

years.

Now comes the problem/question. Our latest electric bill shows an increase in consumption of 106

kWh over the same time period last year. The average outdoor temps for both periods are about

the same. I'm not looking forward to -10, -15 C when I have to add supplementary heat.

Changes from last year.

-heat loss reduced
-upper level baseboards essentially off
-heat pump installed
-increased electrical comsumption

What am I missing or doing wrong here?

Do I shut the unit off until cooling season arrives and heat with baseboards?
Do I turn the baseboards on and put the unit in fan mode for air circulation?
Do I lower the temp setting on the unit even lower?

Any assistance would be appreciated and apologies for the lengthy post.
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Old 2009-11-25, 12:59 PM   #2
57
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This unit has a very good HSPF:

http://en.wikipedia.org/wiki/HSPF

http://housesmartheating.com/hp-faq.html#2

This means that on average, it will be about 2-3 times as efficient as radiant heat. However, the efficiency does drop off as the temperature drops. Also 106 kWh in a couple of months is not much difference if your typical use is say 2000 kWh+... What was your overall usage when you saw the 106 kWh difference?

A small change in indoor requested temperature or in the heating degree days (outside temperature) and you'd see that much change. If you have the exact weather data, then you may be able to compare but to simply say the weather was about the same is not accurate enough.

If you've still got baseboards downstairs on, then that heat will rise and the split heat pump doesn't really need to work that hard - at it's minimum inverter rate it's only using about 900 Watts (3.4 W/BTU/h) So, this is really a supplemental unit which may only affect some (small) percentage of your overall electrical usage. There are other factors that also come into play in your electrical usage - stove, DW, dryer, etc...

You/they have overestimated how much savings you'll get from this unit since it's only supplying a (perhaps small) portion of your overall use.

You should continue to use your unit down to -10C since it's more efficient than radiant heat, however, you should monitor your overall usage for the entire winter to see how things go. Where is the heat pump located? If it's upstairs, then it'll not affect the downstairs usage very much since heat rises and it'll only affect a small portion of your overall usage, again because heat rises.
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Old 2009-11-25, 01:47 PM   #3
Sylvain
 
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Location: Gatineau Quebec
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Arrow Heatpump not very effective

Quote:
Originally Posted by coaster View Post
(...) What am I missing or doing wrong here?

Do I shut the unit off until cooling season arrives and heat with baseboards?
Do I turn the baseboards on and put the unit in fan mode for air circulation?
Do I lower the temp setting on the unit even lower?

Any assistance would be appreciated and apologies for the lengthy post.
You may have seen the thread I started a while back http://www.digitalhome.ca/forum/showthread.php?t=42544
I have not been very pleased with the 3.5ton heatpump I got installed in 2006. I just had to have $400 of maintenance done on it (fall 2009) and am still not sure if it is going to make a big difference (looks like it was not configured properly and did not have enough gas; original installer went out of business BTW). It seems to me that heatpumps are only effective between 5 and 15C, that's not a long time in Canada...
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Old 2009-11-25, 02:40 PM   #4
coaster
 
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My second try at a reply. Got timed out before. Note to self...use Notepad when composing.

Quote:
"If you've still got baseboards downstairs on, then that heat will rise and the split heat pump doesn't really need to work that hard"
Actually the heat does not rise that well. I'm going to open up the stairwell to help with that.

Quote:
"So, this is really a supplemental unit which may only affect some (small) percentage of your overall electrical usage."
The unit is located upstairs and, at present, is the only heat source on that level.

Quote:
"What was your overall usage when you saw the 106 kWh difference?"
1357 kWh compared to the same time period last year at 1251 kWh but 1357 kWh compared to the previous month of 867 kWh. We do not reach the 2000+ mark before December. Our Dec/Jan/Feb last winter average was 2888 kWh per month. I expect by December the inside unit will be nothing more than a means to circulate the warm air provided by the electric baseboards.

Quote:
"they have overestimated how much savings you'll get from this unit"
A four year, net after grants, payback does seem ambitious even though EfficiencyNB is promoting heatpumps as an option. I'll have to monitor this all winter to see the effect on billing.
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Old 2009-11-25, 03:03 PM   #5
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Quote:
I'm going to open up the stairwell to help with that.
You don't want to do that if you wish to maximize the use of the heat pump, which should be more energy efficient (2-300% heat pump, vs 100% for baseboards)

Edit: I suppose if you have a large enough delta T between upstairs and downstairs (upstairs warmer), then you may be able to "move" some of the heat from upstairs to downstairs, perhaps with additional air circulation.
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Old 2009-11-25, 07:43 PM   #6
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The new mini-splits have inverter drive compressors and are designed to maintain output as the outdoor temperature drops; they are better than their central counterparts in cold climates.

When comparing heating costs, you have to subtract the base load and water use. (many hydro bills include water) Electric water heaters*, stoves, and dryers are large electrical loads and November tends to be mild, so the difference may not be very noticeable until it actually gets cold.

Improper charging reduces efficiency.

Also, you may not realise significant savings if you're heating half the place with baseboards. The mini-split units can have a COP of 3+ above zero, so they're superior to baseboard heaters; keep running it.

*Water heating can consume 500-1000kwh per month alone.

To compare operating costs:

1. Note the electric meter reading

2. Check the meter once a day at the same time, alternate between 100% electric resistance and the heatpump (daily)

3. Subtract each reading from the previous one to calculate kwhs consumed

4. Check an electricity bill which didn't include heating and calculate kwh consumed per day

5. Subtract base load from kwhs consumed between readings

6. Compare the results (electric resistance vs heatpump)
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Old 2009-11-25, 08:47 PM   #7
coaster
 
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Lots of good input folks. Thanks.

One other question. Is a setting of 66 F too low? I've seen references on web sites about setting the temp so low as to make the unit run inefficiently and thus negate any possible savings.
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Old 2009-11-25, 09:34 PM   #8
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66F is fine; the lower the setpoint, the lower your bill will be.
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Old 2011-10-16, 10:39 AM   #9
Jostudly
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Default temp in house hotter then on remote

I have a Fujitsu 15rls heat pump installed in my open concept 1200sq ft house. I have the remote for the heat pump set at 68F. How come the temp in the house on a thermometer shows 74F? This is a 6 degree difference here. I am wondering how accurate the temp on the remote is? Also I had the temp set at 68F on the remote last night and checked it again this am and was at 64F and no one changed it. Thought this was odd as the remote temp should not change on its own. I also was told to keep the fan set at auto all year round and heat setting in the winter and cool in the summer and not to use the quiet or economy modes as it does not work efficiently.
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Old 2011-10-16, 12:29 PM   #10
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Jostudly, I have no idea how your remote temperature changed itself, unless you have a cat or dog that stepped on the button. Our remotes - one each for 2 units -- have never changed any setting on their own.

As for the temperature difference on your remote contrasted to your thermostat, I often experience that condition too. We have thermostats in every room, since there are baseboard heaters in every room. The readings seem to fluctuate a degree or a little more from the remote's readings, as we discussed in earlier posts. I note the thermostat nearest the inverter changes the most, I assume because it reacts to the unit's output fluctuations.

I have only had our inverters on heat setting once this fall, however. I have changed from A/C to dry, depending on the day, but heat, even at low temperature settiing overnight, heats up the house too much. Dry has an auto override so the unit decides fan speed. I know it is a little warmer near Greenwood than Moncton but not so much that I would imagine you need the heat setting. I just checked weather network and we're 16C opposed to your 14C. You'll be a little cooler overnight but not much. I'll be sticking to dry until we get some consistently cooler nights -- it was only 20C overnight Friday and the humidity was 100%.

Finally, I can attest to TVX's post about the merits of inverters. We have been here 2 winters, one with baseboard heat, one with Fujitsu units. The energy saving s have been more than we anticipated, winter and summer. The baseboards have become a decoration and we never use them except to heat a bath towel towel in February.
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Old 2011-10-16, 02:31 PM   #11
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66F is fine; the lower the setpoint, the lower your bill will be

Not if you are married LOL
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Old 2011-10-18, 12:28 PM   #12
Jostudly
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So asd, you are suggesting that I set my mode from heat to dry? Also should I have my fan on auto or low? I find at night it feels cooler in the living room then what the temp on the remote says. I currently have the temp set at 68F.
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Old 2011-10-18, 12:51 PM   #13
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Jostudley, I suspect your house thermostat is more accurate than the Fujitsu remote setting since it reports the actual temperature not the desired setting; I go with the baseboard heater digital readouts and experiment with the remote setting to achieve the desired temp on the thermostat readout. I have found the "dry" setting more successful than "heat" over the last week or two so fan speed is not adjustable. When I did use heat setting this fall, it was a very cool night, down in low single digits; I put the fan on "high" but "auto" would likely work too. I find putting the fan on high and setting the louvres to shoot ahead not down forces heat down to the bedrooms from living room, where the unit is installed. I admit I play with the remote more than some might find practical, though. My wife says I like remotes too much, of course. I used to live in Calgary with forced air natural gas and programmed thermostat and never touched anything, except to turn off the heat for summer. I think heat pump mini-splits need a bit more tweaking on the part of the householder. I think with patience, by experimenting, you will find the settings that work for your situation.
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Old 2011-10-18, 12:58 PM   #14
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Okay thanks I will try the dry setting with fan on auto and see how that works.
Thanks. Also with the time setting if I have it turn on when I go to sleep to make the rooms cooler will this continue every night or do I always need to re set the timer?
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Old 2012-03-10, 10:39 PM   #15
Jostudly
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Default remote does not beep all the time

I have a fujitsu 15rls and the model of the remote is AR-RAH1U and I point directly at the wall unit about 5-10ft away and when I try and adjust the fan,mode and temp setting it does not always beep so I am wondering if there is something defective sending the signal from the remote to the fan unit? The batteries are also new. Also sometimes if I change the temp setting the unit stops heating meaning you can not hear any air flow coming cycling on and off even know the operation green light is solid.
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