Mini Split Install Questions.

buster · 04-18-12, 11:47 PM

I just installed a Gree Heat Pump 18,000 BTU. The outdoor unit was pre-charged for 25 feet of line set. The unit it rated for 208/230 volts which I have 246 volts. I happened to have a buck transformer, although not necessary, I wired in the buck transformer so since it's a minus 16 volt I have 230 volts. So I installed with 25 feet of total line set so I wouldn't have to adjust the charge. I pulled a vacuum to 20 microns and it settled after an hour at 196 microns. Yes, it took a day of running my vacuum pump to get it to that level. So I fired it up and it works really great. Here's my question - finally. I went out and grabbed the line set and they were HOT in heat pump mode. So I attached a Fluke thermal clamp to the 1/2" line (largest) and temperature ranged from 118 to 149 degrees F. On high, it finally settled down at 141 degrees. The current is supposed to max out at 12.49 amperes in heat mode. I measured 11.1 amperes maximum. The company that sold me the unit says I need to add freon due to the high temperature of the line set. I haven't taken pressure tests (only one fitting on the 1/2" line). I went inside to check inlet and outlet temperatures but the room was 86 degrees from my testing so I switched to cooling and the did some indoor measurements. Outside temp=51 degrees, inlet temperature inside=86, outlet temperature=61 for a 25 degree delta. Later inlet temperature=69 degrees, 40 degrees outlet for 29 degree delta. Does it sound like I need to do anything such as add some R410a? I didn't want to open the schrader valve to connect a pressure gauge if I don't have to. The Service Manual says it can only be charged by weight anyway so that's complicated. The seller says if it's low on freon, the compressor will burn up but I'm not seeing excessive current draws like I expected. Looking for any input and thanks so much.

Xringer · 04-20-12, 07:45 PM

If you are getting 149F on an R410A line, that's an indication of way too much pressure. (IMHO).

I wouldn't run it, until I found out what was going on..

BradC · 04-21-12, 02:40 AM

Quote:

Originally Posted by Xringer

If you are getting 149F on an R410A line, that's an indication of way too much pressure. (IMHO).

How would he know? He has not measured the pressure, only the temperature of the line.

In heat mode, the 1/2" line is the discharge from the compressor via the reversing valve. That temperature reading would be the superheated discharge vapor temperature, not the saturated condensing temperature.

149F is ~ 65C. That's low enough not to be even close to a problem. Most manufacturers don't even get slightly concerned until their discharge temps get up over the boiling point of water.

Your 1/2" line temperature is going to be your superheated discharge and your 1/4" line will be your subcooled liquid. A gauge will provide a pretty accurate picture of what is going on. On a system with a 25" line set, a gauge on your vapor line will not hold enough refrigerant to make a noticeable difference on the charge level and will give you significant peace of mind over what it is doing.

If your local store gave you advice on the system charge level based on the temperature of the pipe only, find a different store.

Xringer · 04-21-12, 11:03 AM

Wow.. 212F is pretty dang hot. Have to be careful hooking an R410A unit up to
a hotwater HX with regular 180f PEX tube!

On my Sanyos, I've only seen 126F on the output when I was doing that repair job testing.
I think the pressure was climbing towards 500psi, before I shut it off. It was using major amperes.

The average peak indoor coil temp on both my Sanyos is around 100F.
IIRC, the temperature of the larger service valve/lineset port never gets much above 120F.
Maybe I should check it on a mild day and crank it up to high power..?.

BradC · 04-21-12, 11:27 AM

Quote:

Originally Posted by Xringer

Wow.. 212F is pretty dang hot. Have to be careful hooking an R410A unit up to
a hotwater HX with regular 180f PEX tube!

Remember the superheat component is the excess sensible heat added to the refrigerant. It's why you can heat hot water with a desuperheater, but a relatively small quality compared to the heat of condensation.

When you next fire up your. Unit, measure the SCT with your gauge set and also look at the vapor line where it leaves the unit with an accurate thermometer. If you don't see 20-30 degrees C of superheat I'd be very surprised.

In reverse cycle mode my unit here condenses at about 40C but the discharge temperature is closer to 70C where it leaves the unit. So pressure at 40C and temp at 70C. In cool mode, the unit condenses at closer to 55C and discharge temp is in excess of 80C. You do burn your hand on the discharge pipe.

04-18-12, 11:47 PM	#1
buster Lurking Renovator Join Date: Apr 2012 Location: Oregon Posts: 2 Thanks: 0 Thanked 0 Times in 0 Posts	Mini Split Install Questions. I just installed a Gree Heat Pump 18,000 BTU. The outdoor unit was pre-charged for 25 feet of line set. The unit it rated for 208/230 volts which I have 246 volts. I happened to have a buck transformer, although not necessary, I wired in the buck transformer so since it's a minus 16 volt I have 230 volts. So I installed with 25 feet of total line set so I wouldn't have to adjust the charge. I pulled a vacuum to 20 microns and it settled after an hour at 196 microns. Yes, it took a day of running my vacuum pump to get it to that level. So I fired it up and it works really great. Here's my question - finally. I went out and grabbed the line set and they were HOT in heat pump mode. So I attached a Fluke thermal clamp to the 1/2" line (largest) and temperature ranged from 118 to 149 degrees F. On high, it finally settled down at 141 degrees. The current is supposed to max out at 12.49 amperes in heat mode. I measured 11.1 amperes maximum. The company that sold me the unit says I need to add freon due to the high temperature of the line set. I haven't taken pressure tests (only one fitting on the 1/2" line). I went inside to check inlet and outlet temperatures but the room was 86 degrees from my testing so I switched to cooling and the did some indoor measurements. Outside temp=51 degrees, inlet temperature inside=86, outlet temperature=61 for a 25 degree delta. Later inlet temperature=69 degrees, 40 degrees outlet for 29 degree delta. Does it sound like I need to do anything such as add some R410a? I didn't want to open the schrader valve to connect a pressure gauge if I don't have to. The Service Manual says it can only be charged by weight anyway so that's complicated. The seller says if it's low on freon, the compressor will burn up but I'm not seeing excessive current draws like I expected. Looking for any input and thanks so much.

04-20-12, 07:45 PM	#2
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	If you are getting 149F on an R410A line, that's an indication of way too much pressure. (IMHO). I wouldn't run it, until I found out what was going on.. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..

04-21-12, 11:03 AM	#4
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Wow.. 212F is pretty dang hot. Have to be careful hooking an R410A unit up to a hotwater HX with regular 180f PEX tube! On my Sanyos, I've only seen 126F on the output when I was doing that repair job testing. I think the pressure was climbing towards 500psi, before I shut it off. It was using major amperes. The average peak indoor coil temp on both my Sanyos is around 100F. IIRC, the temperature of the larger service valve/lineset port never gets much above 120F. Maybe I should check it on a mild day and crank it up to high power..?. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..