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Power draw of external compressor when off

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#44 ·
drees said:
Anyone know what compressors don't? As an end-user, this type of information is very difficult to find.
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I remember reading a copeland service bulletin and I believe that the need for a crankcase heater is dependent on the total refrigerant charge in pounds. With that being said even if a unit is designed without one if the additional refrigerant charge required because of line set length put you over that threshold one will need to be added.
 
#45 ·
Drees, I applaud the way you are analyzing your electric load and what uses it. This is a difficult thing and not many people know how to do it. Weather effects for example, make it much more difficult to know whether one's hardware or nature is responsible within a range of +/-10 or 20%. That may not apply to your case, but would you please explain to us how you judge that 150W load is added? Spell it out step by step so we can understand.

I am an admirer of the TED series of load analyzers and think a couple hundred may not be too much in a case like this.

Best of luck -- Pstu
 
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#46 ·
My hunch is that the data logger, decent analysis software, and accessories might cost more than leaving the crankcase heaters run for a year, maybe two.
 
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Discussion starter · #47 ·
pstu said:
This is a difficult thing and not many people know how to do it. Weather effects for example, make it much more difficult to know whether one's hardware or nature is responsible within a range of +/-10 or 20%.
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I am simply looking at my monthly utility bills and comparing last year's usage to this year. Yes, I know it's not perfect (which is why I'm looking for an easy way to track the electricity usage of the compressor directly), but when looking at multiple months, it's pretty easy to find a pattern as our bills are normally very consistent.

Last year, our winter electricity bills took a jump in Nov/Dec because we tended to use plug-in electric heaters to warm up the bathroom during bath time or a kids room instead of heating the whole house. Then in January we stopped using those as it wasn't too cold. This year, we didn't use the portable heaters at all after the new HVAC system was installed in early Dec. But electricity usage was the same or higher as last year.

We attribute the Jan bill to be higher because we were used the heat-pump for a week or two before setting the lockout temp to 60*F (it was 45*F). Our setback temp at night is 62* and normal temp is 66*. There may have been a few odd occasions when the heat-pump kicked in with the ambient temps were above 60*, but it wouldn't have run for long.

Here's our monthly electricity / gas data (kWh/therms):

Code: 
     2009    2010
Dec 459/20  430/10
Jan 458/72  533/18
Feb 356/31  494/21
Mar 378/44  479/12
The billing dates were in the middle of the month, so Dec this year didn't include more than a week's time of the HVAC system installed.

In non-heating months last year, our electricity usage averaged 350 kWh/month. March this year was pretty mild so the furnace rarely ran. Our gas usage this March was lower than it was last year with the old furnace not running but with the pilot lit! Summer time gas usage (without the old furnace pilot lit) is well below 6 therms/month.

shophound said:
My hunch is that the data logger, decent analysis software, and accessories might cost more than leaving the crankcase heaters run for a year, maybe two.
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I think you're right. But if it helps us save energy in other areas, it may be worth it. IMO, they are worth it for the geek factor alone (love having that kind of data), but convincing my wife is a different story!
 
#48 ·
You also need to look at what the temps. were last year vs. this year, during the months you're comparing. Because the temps. are never going to be the same, it's hard to say how much extra money you're saving/spending. There are different amounts of sunlight that gives radiant heat, etc. There are other areas in your home that you can save electricity. I think you're over-thinking this way too much.
 
#49 ·
Does your utility use those smart meters, and if so can you view usage data thru Google Powermeter? If the cards fall right then you may get detail data without the expense of TED.

I have not digested the data you just posted, will hope to get to that soon. Can you use Weather Underground to verify the degree-days are similar between those months you compare?

Best wishes -- Pstu
 
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Discussion starter · #50 ·
With net metering, I don't think I get one of those smart meters. Actually had a smart meter installed for a couple weeks, then when I signed up for net metering to install my PV system, they swapped it back out for a regular meter. I'll have to call up and check with SDG&E to confirm.

Looking at Wunderground, if anything it was slightly warmer last year than this year from Dec through Mar.
 
#51 ·
capecool said:
I remember reading a copeland service bulletin and I believe that the need for a crankcase heater is dependent on the total refrigerant charge in pounds. With that being said even if a unit is designed without one if the additional refrigerant charge required because of line set length put you over that threshold one will need to be added.
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does this mean that copeland thinks a compressor on a system at outside ambient will not have refrigerant migration at 10* F if it only has a pound or two? Or is it that the small amount will not be enough to displace enough oil to matter?
 
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#53 ·
Lennox includes them as standard in all heat pumps 3 ton and larger. They are an optional item for smaller heat pumps and must be ordered as a separate line item. Why that is, I don't know.
 
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