EcoRenovator  

Go Back   EcoRenovator > Improvements > Geothermal & Heat Pumps
Advanced Search
 


Blog Register 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 04-22-10, 03:13 PM   #1
Piwoslaw
Super Moderator
 
Piwoslaw's Avatar
 
Join Date: May 2009
Location: Warsaw, Poland
Posts: 926
Thanks: 176
Thanked 101 Times in 80 Posts
Default Dual compressor heat pump

Anyone know where I can find info on heat pumps with more than one compressor? There are models with 2 compressors which come on independently depending on load. I wonder how they are plumbed together: just plain parallel, or with some complicated valves?

Googling shows that often "dual heat pump" mean either a split (both heating and cooling) or a heat pump assisted by an electric/gas heater.


Last edited by Piwoslaw; 04-23-10 at 12:17 AM..
Piwoslaw is offline   Reply With Quote
Old 04-22-10, 09:55 PM   #2
NeilBlanchard
Journeyman EcoRenovator
 
NeilBlanchard's Avatar
 
Join Date: Dec 2009
Location: Maynard, MA Eaarth
Posts: 383
Thanks: 78
Thanked 39 Times in 32 Posts
Default

These are the best commercially available dual stage heat pumps I know of:

Hallowell International - Heating and Cooling Systems
NeilBlanchard is offline   Reply With Quote
Old 04-24-10, 12:16 AM   #3
Xringer
Lex Parsimoniae
 
Xringer's Avatar
 
Join Date: Feb 2009
Location: Woburn, MA
Posts: 4,875
Thanks: 106
Thanked 245 Times in 225 Posts
Default

At that Hallowell site is this paper. http://www.gotohallowell.com/images/...te_PaperLR.pdf

It has diagrams showing the dual pump setup..


I'm glad that I can get away with just one compressor in my Sanyo..
It's never Maine Cold down here in Massachusetts.
Xringer is offline   Reply With Quote
Old 04-24-10, 05:22 AM   #4
NeilBlanchard
Journeyman EcoRenovator
 
NeilBlanchard's Avatar
 
Join Date: Dec 2009
Location: Maynard, MA Eaarth
Posts: 383
Thanks: 78
Thanked 39 Times in 32 Posts
Default

But, their efficiency is almost as good as a groundwater geothermal heatpump, so it would be great to have this down here in "warm" Massachusetts! Especially, if you were powering it with renewable electricity...
NeilBlanchard is offline   Reply With Quote
Old 04-24-10, 10:06 AM   #5
Xringer
Lex Parsimoniae
 
Xringer's Avatar
 
Join Date: Feb 2009
Location: Woburn, MA
Posts: 4,875
Thanks: 106
Thanked 245 Times in 225 Posts
Default

If the Sanyo keeps working, I foresee using very little oil during the coming years.

With NStar charging about 20 cents per kWh, my single compressor Sanyo seems
to be burning up about 1/4 to 1/3 the money needed for oil heat alone.

It's April, but still cool around here. So we are still heating the house.
http://ecorenovator.org/forum/projec....html#post5090
And, we are using less than 4 kWh per day..

So, even if NStar is someday forced by Cap-n-Tax to increase our rate to $0.40/kWh
we will still be saving money using the Sanyo mini-split.
(And, I'll bet that oil prices will not have dropped)..

Maybe by then, my wife will become more accepting of PV on our roof..

This week, we saw a local install by these guys..
Where We Work - Massachusestts and New England - SunBug Solar

It sure looked sweet to these old eyes..
I have a feeling that even a small array on my small roof would pay
for heating & cooling this small house..


IMHO, the inverter type mini-split ASHP is nearly the equal of GSHP
when used in the Boston area. But, it's the installer cost that makes
the old GSHP take a lot longer before break-even.

Last edited by Xringer; 04-24-10 at 10:38 AM..
Xringer is offline   Reply With Quote
Old 02-16-11, 05:44 AM   #6
Piwoslaw
Super Moderator
 
Piwoslaw's Avatar
 
Join Date: May 2009
Location: Warsaw, Poland
Posts: 926
Thanks: 176
Thanked 101 Times in 80 Posts
Default

I found a picture of a heat pump with dual compressors.


You can clearly see that the compressors are simply plumbed in parallel, with no valves. This is not a cascade of two heat pumps, this is one HP with two compressors, everything else is common.

From what I've read, the controller turns on only one compressor at a time (in an alternating fashion). Some controllers keep an account of how much on-time each of the compressors has had and turns on the one which was used less often. When one compressor takes too long to do its job, then the second one kicks in.

So building one of these can't be much harder than a normal HP: two identical compressors plus everything else sized for a compressor twice as big. Making the controller would be a little harder, but still doable.
Attached Thumbnails
Click image for larger version

Name:	2compressor_hp.jpg
Views:	5119
Size:	70.6 KB
ID:	1266  
__________________
Ecorenovation - the bottomless piggy bank that tries to tame the energy hog.
Piwoslaw is offline   Reply With Quote
Old 11-18-11, 10:44 AM   #7
charlesfl
Helper EcoRenovator
 
Join Date: Dec 2009
Location: Pensacola Florida
Posts: 38
Thanks: 17
Thanked 5 Times in 4 Posts
Default

mcquay dot com application guide ag 31-11
refrigerant piping design guide
application guide technical bulletins
charlesfl is offline   Reply With Quote
Old 11-18-11, 10:48 AM   #8
charlesfl
Helper EcoRenovator
 
Join Date: Dec 2009
Location: Pensacola Florida
Posts: 38
Thanks: 17
Thanked 5 Times in 4 Posts
Default

I tried to put website in but wasn't allowed.
Hope this helps. charlesfl
There are more application guides available if needed
charlesfl is offline   Reply With Quote
Old 11-19-11, 08:35 PM   #9
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 712 Times in 532 Posts
Default

Quote:
Originally Posted by Piwoslaw View Post
You can clearly see that the compressors are simply plumbed in parallel, with no valves.

From what I've read, the controller turns on only one compressor at a time (in an alternating fashion). Some controllers keep an account of how much on-time each of the compressors has had and turns on the one which was used less often. When one compressor takes too long to do its job, then the second one kicks in.
I'm really not an HVAC technician, but I think that they work differently...

Here is a quote I found on this page:

Quote:
...two compressors of these Trane Heat Pumps help with the efficiency rating because when there is a mild day, the smaller compressor of the two will work while the large compressor will work on the days that it may be extremely hot.
...and on this page:

Quote:
Two compressors are better than one. That's the message from HydroDelta, the latest manufacturer to announce a dual-compressor, ground-source heat pump. Most of the time the smaller of the two compressors can meet the house's heating or cooling load. Running the smaller unit closer to its capacity uses less energy. When the smaller compressor can't keep up, the larger one takes over.

And there is another efficiency booster. The evaporator and condenser coils are sized to match the larger compressor, so they are oversized for the smaller one. The dual compressors help HydroDelta's Meg-Tek heat pump reach very high efficiency with COPs up to 4.1 and EERs as high as 20.7.
So, I think that it would be needed to use a simple check valve on the compressor output line of each compressor.

It also seems to me that with an arrangement like this would work pretty well:
  • Compressor #1 = 400 watts
  • Compressor #2 = 650 watts
  • Compressors #1 + #2 = 1050 watts


An arrangement like this could give you three speeds with only two compressors.

-AC_Hacker

* * *
Attached Thumbnails
Click image for larger version

Name:	three-speed.gif
Views:	3701
Size:	13.7 KB
ID:	1876  
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker...
AC_Hacker is offline   Reply With Quote
Old 01-19-12, 02:37 PM   #10
kbonk
Helper EcoRenovator
 
Join Date: Aug 2010
Posts: 44
Thanks: 10
Thanked 4 Times in 2 Posts
Default

Looks like Hallowell is out of business? anyone confirm? How do they cascade compressors?

kbonk is offline   Reply With Quote
Reply


Thread Tools
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

Forum Jump


All times are GMT -5. The time now is 11:39 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design