DIY Home Improvement Forum banner
1 - 7 of 7 Posts

·
Registered
Joined
·
191 Posts
Discussion Starter · #1 ·
Hello fellow DIYers. I am in southern Illinois and have a 20 y.o. heat pump. Earlier in the winter I had been having all sorts of trouble getting it to defrost, but solved the problem. It's all documented here: http://www.diychatroom.com/f17/older-carrier-heat-pump-freezing-over-229489/index3/#post1684129

Today we are running in the 25-35 deg. ambient range with high humidity, and it's getting loaded up with frost, between defrost cycles. I wonder if it's defrosting often enough. The Carrier board has options for 30 minute, 60 minute, and 90 minutes. It's currently set on 90.

As I understand the system, the board does a frost check every 90 minutes. IF it senses the coil is frozen it goes into defrost.

My question for you guys, what disadvantage is there in selecting a shorter time frame, the 60 or 30 minute checks. If the board detects a frost condition wouldn't it make sense to get rid of it sooner than later? I assume inefficiencies play into this formula.

Thanks!
 

·
Registered
Joined
·
2,449 Posts
Hello fellow DIYers. I am in southern Illinois and have a 20 y.o. heat pump. Earlier in the winter I had been having all sorts of trouble getting it to defrost, but solved the problem. It's all documented here: http://www.diychatroom.com/f17/older-carrier-heat-pump-freezing-over-229489/index3/#post1684129

Today we are running in the 25-35 deg. ambient range with high humidity, and it's getting loaded up with frost, between defrost cycles. I wonder if it's defrosting often enough. The Carrier board has options for 30 minute, 60 minute, and 90 minutes. It's currently set on 90.

As I understand the system, the board does a frost check every 90 minutes. IF it senses the coil is frozen it goes into defrost.

My question for you guys, what disadvantage is there in selecting a shorter time frame, the 60 or 30 minute checks. If the board detects a frost condition wouldn't it make sense to get rid of it sooner than later? I assume inefficiencies play into this formula.

Thanks!
If the outdoor temps are low enough (sensor closed) it will go into defrost even when it's not frosted up. It does this according to the time frame of the the jumper setting. That's what is nice about an "on demand" defrost board. It won't go into defrost until needed.

Mine has been set to 90 minutes (default) since 1983 when it was installed but it would freeze up in cold humid conditions. This past year I changed it to 60 minutes and it has helped but I don't think it's worth the extra cycles so I'm going to change it back to 90 this spring.

ETA: I might even retrofit an on demand board if I get motivated enough. It makes a big difference in wear & tear and electricity bills.
 

·
Administrator
Joined
·
42,290 Posts
As long as the defrost stat is colder then its temp setting. It will go into defrost every 90(your current setting) of accumulated compressor run time.

Setting it to a lower time, will cause it to defrost more often, which means it will be cooling your house, and the aux heat will be used to counter that. Which can raise your heating bill.

As long as its completely defrosting the coil, I would leave it set to 90.
 
  • Like
Reactions: MurphyMan

·
Registered
Joined
·
191 Posts
Discussion Starter · #4 ·
Setting it to a lower time, will cause it to defrost more often, which means it will be cooling your house, and the aux heat will be used to counter that. Which can raise your heating bill.

As long as its completely defrosting the coil, I would leave it set to 90.

Okay - thanks for clarifying that for me. 90 minutes it is! :thumbsup:
 
1 - 7 of 7 Posts
Top