AC Hacks a Heat Pump

AC_Hacker · 04-27-13, 10:27 PM

New parts have arrived for the conversion...

The photo above is the TXV, that is sized for about 1-Ton, which is the nominal output of the Heat Pump.

The photo above is the nice-sized Brazed Plate HX (fork for scale). Not so visible is that the HX has sweat fittings (brazed) on the refrigerant side and water pipe fittings on the water side. I used a Brazed Plate sizing tool and this BPHX is pretty darn close to the one that is called out by the program. I also used this Brazed Plate sizing chart to cross check. I didn't want the HX to be the bottle neck of the machine. There were a fair number of BPHXs that were of a fair price, and in the aproximate size that I needed, but getting one that had appropriate connectors for refrigerant AND that had a substantial pressure rating really narrowed the choices.

I still have questions about how I should best handle the issue of 'frosting up', when the machine runs during the high humidity Western Oregon winters, and the evaporator is running much colder than the ambient air.

I was inclined to remove the reversing valve, just to make the whole job simpler... but it occurred to me that the reversing valve could be useful for melting off frost during the long, wet winter.

So I need to collect a bit more information before I start cutting & brazing.

Another issue that I'm mulling over is the location of the Brazed Plate HX itself. It would be really handy to mount it inside the Heat Pump case, but we do have cold snaps that could freeze it solid, and ruin it.

An alternative would be to put the BPHX inside the house, out of the weather. Which could admit the remote possibility of hydrocarbon refrigerant leak inside the house.

A third choice would be to build a Hydro Box (not an original term) that would be attached to the house, but outside the envelope. This would keep all refrigerant outside the envelope and would put the BPHX water loop nearly inside the house. I could insulate the Hydro Box and put a freeze-point thermostat inside the box to guard against freezing. The perfect-storm disaster would be a loss of power during extremely cold weather... it has happened here before.

Best,

-AC

04-27-13, 10:27 PM	#33
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	New Parts Have Arrived... New parts have arrived for the conversion... The photo above is the TXV, that is sized for about 1-Ton, which is the nominal output of the Heat Pump. The photo above is the nice-sized Brazed Plate HX (fork for scale). Not so visible is that the HX has sweat fittings (brazed) on the refrigerant side and water pipe fittings on the water side. I used a Brazed Plate sizing tool and this BPHX is pretty darn close to the one that is called out by the program. I also used this Brazed Plate sizing chart to cross check. I didn't want the HX to be the bottle neck of the machine. There were a fair number of BPHXs that were of a fair price, and in the aproximate size that I needed, but getting one that had appropriate connectors for refrigerant AND that had a substantial pressure rating really narrowed the choices. I still have questions about how I should best handle the issue of 'frosting up', when the machine runs during the high humidity Western Oregon winters, and the evaporator is running much colder than the ambient air. I was inclined to remove the reversing valve, just to make the whole job simpler... but it occurred to me that the reversing valve could be useful for melting off frost during the long, wet winter. So I need to collect a bit more information before I start cutting & brazing. Another issue that I'm mulling over is the location of the Brazed Plate HX itself. It would be really handy to mount it inside the Heat Pump case, but we do have cold snaps that could freeze it solid, and ruin it. An alternative would be to put the BPHX inside the house, out of the weather. Which could admit the remote possibility of hydrocarbon refrigerant leak inside the house. A third choice would be to build a Hydro Box (not an original term) that would be attached to the house, but outside the envelope. This would keep all refrigerant outside the envelope and would put the BPHX water loop nearly inside the house. I could insulate the Hydro Box and put a freeze-point thermostat inside the box to guard against freezing. The perfect-storm disaster would be a loss of power during extremely cold weather... it has happened here before. Best, -AC Attached Thumbnails __________________ I'm not an HVAC technician. In fact, I'm barely even a hacker... Last edited by AC_Hacker; 04-30-13 at 12:41 PM..