heat strips for a heat pump?
Are the heat strips more efficent than the pump or less efficient?
Also are they a necessity or luxury?
I am finishing my attic which is 2/3s the size of the downstairs. I will be installing an extra hvac unit. We live in a mild climate, sacramento CA, I am guessing the upstairs will have a very small heat demand since the heat will go up. It would be difficult but not impossible to run an extra wire for the heat strips. So I was kind of hopeing to avoid them.
Less effecient under most circumstances. A necessity usually, but in your case maybe not,with another system in the house.
If everything was always done "by the book"....the book would never change.
Even though you could probably get by with out them, it sure wouldn't hurt to throw some small one's in there (like 5kw or so). Just something to help the HP when it goes into defrost or on that unusual night every 5 years that gets really cold.
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I would be using a minimum of a 13 seer unit outside temp would rarely be freezing.
What electrical load does a 10kw strip normally run, 30 amp 220V?
10 Kw is rough fully around 40 to 42 amps on 220 volts.
Originally Posted by my65ffrcobra
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They are great to have if the heat pump fails and in defrost mode when the HP switches over to AC for a predetermined period of time to defrost the outdoor coil. I say get them now and dont regret not having them later. As far as efficiency they arent even on the chart but will get you through in a pinch.
You'll need the strips to temper the air during defrost and to supplement the pump on those cold foggy nights that happen in Sacramento. Electric heat is 100% efficient, but more costly than running the pump.
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Heat strip ( 1.0 ) is much less efficient that heat pump
Originally Posted by my65ffrcobra
(~ 3.4 @ 47'F and perhaps 2.7 @ 30'F)
Your choice to install heat strips or not.
However, most regions of the US do not have the option that you do.
With less than 500 hours < 40'F,
the heat pump is likely to handle the load > 95% of the time.
Sacramento CA temperature bin data
25' F ______ 30
30' F _____ 116
35' F _____ 333
40' F _____ 660
45' F _____ 924
Alternate: Use one or two high quality 1.5 kW - 110 V portable heaters for the ~20 nights that temperature is < 35'F.
Might NOT be a good option where children are living.
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Why would it be difficult to run a new wire?
You have to run a new wire from the panel to the heat pump, right? Well, you also have to run refrigerant lines from the pump to the airhandler.
Why not run the proper size wire from panel to the ref. lines, then follow them to the air handler?
Note: Proper wire and breaker sizing should be determined by a qualified electrician.
Unless you want freezing air coming out all the ducts during defrost (about 10 minutes of every hour all winter long), install the 10 KW strip. Here in Seattle, my HP frosts very easily when the temps are between 30F and 40F. At 50F, it doesn't seem to need defrost anymore.
I have my defrost timer set for 60 minutes, but it is often quite frosty by then. Seattle and SFO are pretty similar in climate (high humidity when temps are 32F - 50F), but not terribly cold nor very humid in the summer.