I went out to the Tempstar N4A360 condenser with the Internal pressure
relief opening problem today.
By the way, this unit is a one speed condenser motor and has NO low
pressure or high pressure switch, no high temp switch or anything
Owner said it had been opening and making noise several times a day
now. I unload my tools from the truck and after about 10 mins the A/C
still hasnt cycled on, on its own. I went in and turned the stat down.
It was set on 76 and it was 76 in the home. The unit came on and
immediately I heard it running with the relief valve opened. I already
had gauges on it and it was showing about 175 on the suction and about
275 on the head. I pulled the disconnect, waited about 5 secs and
turned it back on. Unit ran just perfect and quietly. I checked the 11
degree subcooling and it was right on. For shits and giggles I pulled
the condenser fan wire and watched the head pressure climb. About 25
seconds later with me stepping slowly backward I watched it climb to
750 psi before the relief opened. (So now you all know what they open
up at). Cant quite say I want to stand near a unit that does that
again. Anyways, word is that a certain batch of units may need to have
the factory installed R-410a refrigerant charge removed and recharged
with new virgin refrigerant. I pulled the crap out and saved it so I
can do a press/temp check on it to see if it jives with the R-410a
chart. (Yes, I pulled a vacuum on the tank and my recovery machine
before I dumped the crap in the tank). Pulled a 500 micron vac on the
system. While waiting, I found the sensing bulb on the Aspen coil was
mounted horizontal at the 6 oclock position with no insulation on it.
Not sure if it came that way or we mounted the bulb but that was our
fuquer up. (I did the outside unit. Employee did the inside unit.)
Corrected that and put it at the 4 oclock/8 oclock position and
insulated it. Measured the 22 ft lineset and recharged the unit.
Works fine now but time will tell if that does the trick or not??
It is really wierd that it would do that immediately upon startup. FWIW,
I have seen factory installed TXVs with the bulb mounted in about every
position you can imagine, some insulated and some not. I doubt if that
is going to make much difference. With insulation the valve should
actually close down a little more and give slightly higher superheat
than if it was not insulated. One more thing-- we have made it standard
on all 410 systems to install a sight glass-- not so much for the charge
itself, but for the moisture indicator. So far all have stayed clean and
green. Did you replace the drier when you recharged the unit? Well, I
guess if you got it to 500 microns and it held, moisture wasn't the
problem anyway. Larry
On Thu, 26 Jun 2008 00:07:50 -0500, email@example.com (lp13-30) wrote:
They didnt say why to change the charge but Im guessing that means
there was a bad batch of factory charged units. (Thats my guess).
I dont use sight glasses except on commercial stuff. Supposedly, the
sight glass is not a good indicator of charge anymore on the high
efficiency stuff? I didnt change the drier on the change-out of the
refrigerant. Just recovered it, evacuated to 500 (which took over 2
hrs) and then recharged it.
I have the old stuff and just checked it at 78 degrees. It should
register 233 psi and it shows 231 psi so I think even the slightest
gauge error puts that batch in the good category.
I havent a clue now but I havent heard from the
Is it possible the RV is intermittently sticking half way?
That could create the same symptoms especially the fact that shutting off
the power & back on solved it. That would be more likely if it were a 240v
coil on the RV but I thought they all were 24v on the newer units. Anyways
the fact that it went right into by-pass immediately makes me wonder about
the RV. Either that or there's got to be a blockage in the system which
pretty much goes back to the TXV. Hopefully doing what you did solved the
problem by getting whatever trash was in the system. Good luck
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