readydave8
re member
- Location
- Clarkesville, Georgia
- Occupation
- electrician
I think the heat strips kick in every time outdoor unit goes into defrost?
Owner gc/ and bad hvac company
- Thread starter AC\DC
- Start date
solarken
NABCEP PVIP
- Location
- Hudson, OH, USA
- Occupation
- Solar Design and Installation Professional
Is the Hot tub really included in the general loads with the first 10@100% and 40% remainder?
4-20mA
an analog man in a digital world
- Location
- Charleston SC
- Occupation
- Process Control, Instrumentation & Electrical
Yes, also, can and will get stuck on and stop a home from cooling and create a service call... lol...
Really though, they are a wonderful back up if the condenser fails.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
They can.
All that defrost cycle really needs to do is to switch to cooling mode for long enough to defrost the outside coil - this will result in cold air coming out the inside registers, if they do kick heat strips on during defrost it primarily to keep inside outlets temperature from getting as cold. But this shouldn't really last more than a few minutes anyway.
If outside ambient is low enough that aux heat becomes necessary to keep up - the compressor won't be drawing anywhere near it's RLA either, and good installers set them up to lock out the compressor when temp is low enough that is no longer more cost efficient than running the aux heat, let alone the heat pump probably won't keep up with heat losses in that situation either.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
My personal experience is with minisplit heat pumps in my home. But I've noticed the greatest need for outside coil defrosting when the outside air temperature is right around 32F.
Air hold more water when it is warmer, so there is more water to condense on the coils. And the outdoor coil must be colder than the air to be able to absorb heat from the air. So I'd expect peak icing on the outdoor coil on a humid day when the outside air is in the mid 30's, not below when the outside air is below freezing.
One of the details that may matter: does the heat pump defrost based on a timer, an algorithm, or an actual frost sensor. I don't know enough to know how common each approach is.
Air hold more water when it is warmer, so there is more water to condense on the coils. And the outdoor coil must be colder than the air to be able to absorb heat from the air. So I'd expect peak icing on the outdoor coil on a humid day when the outside air is in the mid 30's, not below when the outside air is below freezing.
One of the details that may matter: does the heat pump defrost based on a timer, an algorithm, or an actual frost sensor. I don't know enough to know how common each approach is.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
In order for it to bring heat into the house, the coil needs to be colder than the outside air so it will absorb heat from that air. Chances are it will be cold enough for frost to form on the coil when it runs.
The fact it doesn't get too extremely cold probably allows for it to defrost between run cycles most the time though. Simply running in cool mode for pretty short time will clear the frost off the coil as it is bringing heat from inside and putting it through the outdoor coil when in cooling mode. System with variable speed indoor blower likely is running at a low speed during defrost to keep output air from being too noticeably cold during defrost.