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 01-15-2012, 05:27 PM   #1
Newbie
 
Join Date: Jun 2011
Location: Sacramento area
Posts: 18
Rewards Points: 0
Share |
Default

heat pump technical question


My Mitsubishi mini split service manual says:

In heating mode:

condensing pressure 309 psi
discharge temperature 139 F
condensing temperature 95 F


Question: if R410a is condensing at 95F, then the correct pressure is 309 psi. But if the refrigerant is discharging from the compressor at 139 F (which would correspond to 500+ psi) where is the pressure drop occurring between the compressor and the inside unit? There is no serious restriction in that line.

Maybe there is something I don't understand, or this is just a misprint in the manual.

Ron

rwfegley is offline   Reply With Quote
Old 01-15-2012, 07:31 PM   #2
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 25,058
Rewards Points: 4
Default

heat pump technical question


It doesn't discharge from the compressor at 500 PSIG. The hot gas from the compressor is super heated.

beenthere is online now   Reply With Quote
Old 01-23-2012, 08:41 PM   #3
Newbie
 
Join Date: Jun 2011
Location: Sacramento area
Posts: 18
Rewards Points: 0
Default

heat pump technical question


I have done some reading and studied the R410a phase diagram. I keep coming up with the compressor discharge pressure being 550 psi when the discharge vapor is 139 F. Since the line goes directly to the inside unit condenser through an oil separator, a 4-way valve, and a muffler (no serious restrictions), I can't understand why the pressure in the inside unit condenser wouldn't also be 550 psi.

Yet the specs from Mitsubishi say the condensing pressure and temperature is 309 psi and 97F.

I just don't understand!

Ron
rwfegley is offline   Reply With Quote
Old 01-23-2012, 10:26 PM   #4
Newbie
 
Join Date: Jun 2011
Location: Sacramento area
Posts: 18
Rewards Points: 0
Default

heat pump technical question


I just studied the manual more, and I now see that the Discharge Temperature is determined by a thermistor located near the compressor output. It may not the temperature of the vapor??
rwfegley is offline   Reply With Quote
Old 01-24-2012, 04:19 AM   #5
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 25,058
Rewards Points: 4
Default

heat pump technical question


The compressor discharge gas is super heated, and will not be at saturated pressure.
beenthere is online now   Reply With Quote
The Following User Says Thank You to beenthere For This Useful Post:
rwfegley (01-24-2012)
Old 01-24-2012, 11:06 AM   #6
Newbie
 
Join Date: Jun 2011
Location: Sacramento area
Posts: 18
Rewards Points: 0
Default

heat pump technical question


Thanks for your help.

I finally "got it" that you can have a 139F vapor out of the compressor at a pressure of 309 psi. So I guess Mitsubishi is recommending that the superheat be 139 - 97 = 42 F.

Ron

rwfegley is offline   Reply With Quote
Old 01-24-2012, 05:33 PM   #7
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 25,058
Rewards Points: 4
Default

heat pump technical question


That sounds about right for discharge super heat.

beenthere is online now   Reply With Quote
The Following User Says Thank You to beenthere For This Useful Post:
rwfegley (01-24-2012)
Reply

Tags
heat pumps


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
Hello I have a heat pump question? pennie100 HVAC 7 01-11-2010 11:08 AM
How to test apartment Heat Pump tbrubes HVAC 7 02-04-2009 03:05 PM
Heat Pump set back GEAF HVAC 6 01-26-2009 07:49 AM
Heat Pump vs Aux Electric Heat batolson HVAC 16 01-17-2009 10:28 AM
Easy Heat Pump Question brutis HVAC 6 11-03-2008 10:06 AM




Top of Page | View New Posts

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