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HarryH3
Premium
join:2005-02-21
kudos:3
reply to DarkLogix

Re: [HVAC] Issue with AC

Perhaps a jump duct and a fan could be used to route the extra heat into the hall, the next room, etc.


pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Yup. Suggested that a few days ago.


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
reply to HarryH3
said by HarryH3:

Perhaps a jump duct and a fan could be used to route the extra heat into the hall, the next room, etc.

Not logistically do able.
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semper idem
1KTzRMxN1a2ATrtAAvbmEnMBoY3E2kHtyv

HarryH3
Premium
join:2005-02-21
kudos:3
said by DarkLogix:

said by HarryH3:

Perhaps a jump duct and a fan could be used to route the extra heat into the hall, the next room, etc.

Not logistically do able.

So you can dump heat from a portable A/C into the attic, but not back into the house?


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
no


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
Ok the model of the outside unit is
RXN12JEVJU


Sly
Premium
join:2004-02-20
Chuckey, TN
kudos:2
Reviews:
·Callcentric

1 edit
I've looked at the Engineering Data manual and the installation manual for that model and neither mentions a jumper for low ambient conditions.

»www.google.com/url?sa=t&rct=j&q=···64,d.eW0
»www.google.com/url?sa=t&rct=j&q=···64,d.eW0

After doing some more reading, models that have that jumper will operate in low ambient conditions because they have a built in head pressure control similar to what I posted above. When you cut that jumper, the inside fan defaults to high speed to warm up the evaporator as much as possible. Then the outside unit will pulse on and off as needed to keep the pressures high so that the compressor doesn't freeze up.

At this point I don't know if there's anything you can do, short of bypassing the outdoor temperature sensor and blocking the airflow. I'm not sure that I would recommend either. It may still be possible to install your own head pressure control if you don't mind doing some minor rewiring. I know I said earlier that you couldn't use one but after familiarizing myself with your system, I think you may be able to. The head pressure control has a thermocouple that monitors the outside coil temperature. As the temperature drops, it slows down the outside fan until the temperatures come back up. Then it raises it as needed so that the compressor doesn't overheat.

What's involved in hooking one up is basically attaching a thermocouple to the outside coil, hooking the head pressure control up to your low voltage wiring so that it knows when you are in heating vs air conditioning, and then relocating the wires that go to your outside fan to the head pressure control so that it can vary the fan speed. If you do this, then it would probably be safe to bypass the outdoor ambient temperature sensor so that it will operate below 40 degrees. The head pressure control will protect the compressor and so you won't need that sensor.

If you are willing to investigate, I would suggest just pulling the cover off the system to see if it has those jumpers. If it has jumper 3 in the same location as the above mentioned drawing, then if you are brave you might try cutting it to see if it works in low ambient mode. Like I said, your model may not have this feature but it is possible that it does and they just left it out of the manual. I can't say that this is a risk free thing to do. It's possible that it may have that jumper but it may do something else. But I would be willing to bet that if it does have the jumper and you do cut it (with the power off), and it doesn't work, you could always solder it back together.

You might also try calling a dealer to see if there is anything they can suggest. A low ambient baffle is just one of the things that will help. However none of it will matter unless you can bypass that outdoor temperature sensor that cuts the system off at 40...


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
Thanks for the info, I think the sub 40F days are past for the year, and I think I will take some action before next winter or if another sub 40F day comes.

Its a bit hard to see the area where the cover is as its right next to the wall, and I'd feel better having the installer do some of that, its good to know there are/might be a good option to fix this issue (had to use my phone to take a pic to get the model number)

BTW I have the inside fan set to always bee at highspeed even when not calling for cooling, and though its a heat pump I only ever have it in cooling mode (Told the HVAC people to use ac or Heat pump whichever was actually cheaper)
--
semper idem
1KTzRMxN1a2ATrtAAvbmEnMBoY3E2kHtyv