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Old 09-05-18, 01:59 PM   #10
Elcam84
Apprentice EcoRenovator
 
Join Date: Jun 2013
Location: TX
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Quote:
Originally Posted by u3b3rg33k View Post
something is wrong. a heat pump should be more efficient than strip heat until 0F or lower. if it stops working at high temperature like 35F, well... wow?

for example:
https://www.energy.gov/sites/prod/fi...40616-1135.pdf

COP of 2.0 down to -13F. that means for every $1 you spend on strip heat, you get $2 of heat with that heat pump.

the average heat pump you buy now will have a COP >1 until it shuts down due to low outdoor temp. switching over to strip heat at 35F = you need your unit serviced/replaced.

I would look at something like the Bosch BOVA 5 ton outdoor inverter unit. it will modulate compressor capacity from 25%-110% to maintain a 47F/108F indoor coil temp regardless of outdoor temp or AHU airflow. seen it online for $2400.

Been through this before the unit is operating properly and not just this unit its a common issue with conventional heat pumps here. the heat pump function is still basically an afterthought on them but they don't have the issues with constantly failing reversing valves anymore.

Yes the heat output is better per dollar for a heat pump however you negate that benefit by the blower motor running and running and running. Its not uncommon for heat pumps to be replaced with conventional electric units here especially when overall ROI is looked at. Even with a high end heat pump that delivers on its efficiency it doesn't pay for itself as 10 years is replacement interval time here because of the extreme long summers.

You would only save a couple dollars over maybe 4 months here so it just doesn't make sense just like having a 25 seer ac in canada. And of those 4 months it only gets below 35 for a very short period of time most winters.

Some have also replaced theirs with gas units if they have gas available in their neighborhood which most all do.
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