Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 01-23-2010, 04:54 PM   #16
Member
 
Join Date: Jan 2010
Location: Acworth Georgia
Posts: 77
Rewards Points: 75
Default

Heat Pumps


Quote:
Originally Posted by Marty S. View Post
That's no joke. Went on three calls this week about high bills ($400+) and every one of them had electric back up with a HP lock out set at 25 degrees. Same sized and insulated houses with lock out set to zero were $125.

I had a house that had the crossover point at about 28 degrees, the electric strip heat would not come on till the outside temp got below that. It would take a while to warm up but it rarely got below that. I pity those who lock out their heat pump at such a warm temp.

I think this must have come from way back when accumulators were smaller and they did not heat the accumulator. They would overflow and liquid freon would harm the compressor.

H. Phillips is offline   Reply With Quote
Old 01-23-2010, 05:13 PM   #17
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,025
Rewards Points: 3,714
Default

Heat Pumps


In the old days.

Yep, I'm going back to the 70's.

When you did a balance point graph. Most heat pumps couldn't heat the house when the outdoor temp got to 47/45. So the first bank of aux heat had to come on.

And at 17 they were barely more efficient then the strip heaters. Quiet often the COP was only 1.1 to 1.3 at 17F outdoor temp. With a time and temp defrost board. Running the heat pump below 17 was often a wash because of defrost. And sometimes cost more.

It was then, and still is now in many areas. A common practice to bring on the next stage of aux heat 2 to 3 before its needed. So the customer doesn't have a lag in heating.

So, after a while, many contractors just started locking out the heat pump at 20 since at 17 it didn't save much if anything because of the defrost, and poor efficiency of the heat pump.

A 20 lock out temp became a standard temp because people still think heat pumps are inefficient at that temp and lower. When the improvements in efficiency has made them much more cost effective then strip heaters at temps far colder.

PS: Accumulators are not heated on residential heat pumps. Unless its a special application. Which would put it on the border line of being commercial.
beenthere is offline   Reply With Quote
Old 01-24-2010, 12:54 AM   #18
Member
 
Join Date: Jan 2010
Location: Acworth Georgia
Posts: 77
Rewards Points: 75
Default

Heat Pumps


Most of my experience is with commercial and not much in the past 19 years, so pardon me if I get it a bit confused.
H. Phillips is offline   Reply With Quote
Old 01-24-2010, 01:01 AM   #19
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,025
Rewards Points: 3,714
Default

Heat Pumps


Quote:
Originally Posted by H. Phillips View Post
Most of my experience is with commercial and not much in the past 19 years, so pardon me if I get it a bit confused.
Won't find heaters on accumulators on commercial anymore either(except for some special applications). They didn't wok for the most part in the first place.

Some manufacturers don't even use accumulators on a lot their commercial heat pumps anymore (Trane for one).


Confusion is allowed.
beenthere is offline   Reply With Quote
Old 01-24-2010, 11:32 PM   #20
Member
 
Join Date: Jan 2010
Location: Acworth Georgia
Posts: 77
Rewards Points: 75
Default

Heat Pumps


Accumulators work, but not needed with the newer electronic expansion valves. If they have to they would simply close up almost completly to avoid liquid refrigerant. Heating the accumulator? Not sure it was that much help, maybe some extra insurance for special applications.
H. Phillips is offline   Reply With Quote
Old 01-24-2010, 11:40 PM   #21
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,025
Rewards Points: 3,714
Default

Heat Pumps


Its the heaters on accumulators that I was referring to .

Trane doesn't use an accumulator on a lot of their RTU's. And they're using regular TXV's.
They been doing that for several years now.
beenthere is offline   Reply With Quote
Old 01-25-2010, 08:06 AM   #22
Member
 
Join Date: Jan 2010
Location: Acworth Georgia
Posts: 77
Rewards Points: 75
Default

Heat Pumps


Quote:
Originally Posted by beenthere View Post
Its the heaters on accumulators that I was referring to .

Trane doesn't use an accumulator on a lot of their RTU's. And they're using regular TXV's.
They been doing that for several years now.

Well I guess it would go for a good mechanical TXV as well, they may be more accurate and relaiable than they were.
H. Phillips is offline   Reply With Quote
Old 01-25-2010, 03:22 PM   #23
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 26,025
Rewards Points: 3,714
Default

Heat Pumps


A bit of improvement on all refrigerant components.

Better heat transfer from the outdoor coil boils off the refrigerant better(rifled coils, more fins per inch, etc).
Slightly larger coil can hold more liquid so less chance of flood back.

beenthere is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Heat Pumps?? cambishop HVAC 5 12-30-2009 06:42 PM
Heat Pump Blower always on gg_daman HVAC 1 12-16-2009 07:15 AM
Programmable thermostats, heat pumps and aux heat Crunkleton HVAC 3 04-21-2009 06:17 PM
Are Trane heat pumps and Am Std exactly the same? jgtaylorjr HVAC 1 06-01-2008 10:35 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.