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Sly
Premium
join:2004-02-20
Chuckey, TN
kudos:1
Reviews:
·Callcentric
reply to DarkLogix

Re: [HVAC] Issue with AC

Ok I think I found it... It looks like you can cut a jumper and it will allow the unit to operate at a lower ambient temperature. If you install the baffle it will go even further. Do you know exactly what outdoor model you have?

I found this PDF that has instructions for cutting the jumper. »www.daikinac.com/content/assets/···nual.pdf
Page 8 says
Cutting jumper 3 (J3) on the circuit board will expand the operation range down to 5°F (–15°C). However it will stop if the
outdoor temperature drops below –4°F (–20°C) and start back up once the temperature rises again.
1) Remove the 3 screws on the side and remove the top plate of the outdoor unit.
2) Cut the jumper (J3) of the PCB inside.
I think I found the baffle at Johnstonesupply.com: »www.johnstonesupply.com/storefro···=X72-145

I'm not 100% sure this is the correct baffle and so that's why I need the outdoor model number.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
It was "0" here this morning and my unit was humming right along. Not putting out much heat but running.


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
reply to Sly
Thanks I'll see if I can get the model number of the outside part tonight (I thought that split mini's were sold as a pair so didn't think the outside would have such info, but I'll look)

BTW again today I woke up to my room being 78F and the server fans revving up (not constant but intermittently the servers would rev up then down)

BTW I'm taking that temp from this clock I have by my bed.

the weather station said it was 31F outside.
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pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast
Once again.... is there no way you could blow some of that excess heat into the rest of the house and reduce the heating cost for them?

Someone is paying twice here: first power to run the computers in your room then again for the power AC to remove this heat.
--
The difference between genius and stupidity is that genius has its limits.


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
Well then in summer I'd need to undo it.

Sure its "Possible" but would cost alot to do in a way that would keep my room cool.

basically not gonna happen.

The central Unit does have the fan set to on currently to keep air circulating some when nether heat or cold is active (it runs slower than when cooling/heating)

So I guess technically I could have an exhaust fan pull air out and send it to the central intake, but the logistics of doing that would make it costly.

I formerly had a "portable" unit that was ducted to push heat into the attic, but that thing was loud and didn't cool very well.

there just isn't a way to do it logistically that would be effective.

And ya I know its paying 3 times, because then there's also the cost of heating the house.

The air intake for the central unit is at floor level and under the furnace with very little clearance between the furnace and the wall around it, so feeding a duct to it would be difficult and be very small.
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pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
·Comcast
Could you put a fan at the supply vent in your room and "backfeed" the house through that? Or put a fan on the supply duct in your room and pull air from the house through the ducting system into your room? I assume there is a return path some where from your room to the central HVAC system so the air drawn into the room could escape.
--
The difference between genius and stupidity is that genius has its limits.


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
AFAIK the only return path is at the base of the door, when standing at my door I can feel air rushing out.

All the vents in the house are home run to the plenum on top of the furnace, though I doubt a fan would compete very well with the furnace fan.
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HarryH3
Premium
join:2005-02-21
kudos:3
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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HarryH3
Premium
join:2005-02-21
kudos:3
Reviews:
·Suddenlink
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:1
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
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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)
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