low high-side pressure, help

[Gary]

no i didnt have a chance, but i would expect the pressure to rise since the refrigerant has nowhere to go, it would be compressed in the coil, hense the pressure should skyrocket.

When you shut off the suction the compressor has nothing to pump into the high side... and the high side is still cooling off and draining off into the evaporator. If anything the high side pressure should drop.

[Gary]

the only other orifice i have is a .73, but when i installed it before it acted like it had too much restriction to flood the coil with enough refrigerant to keep it cool.

Trust me, it will provide enough flow.

[mackking]

at this point i have nothin to loose so ill try the .73 again

[tonyelian]

hi
ithink there is miss matching btw the comp&air handler unit it appear that u have a large air hanling unit condenser came with this small orifice should b too small to handle the load u can check the comp brand & serial #

[Gary]

hi
ithink there is miss matching btw the comp&air handler unit it appear that u have a large air hanling unit condenser came with this small orifice should b too small to handle the load u can check the comp brand & serial #

I tend to agree about the mismatch. The evap seems oversized for the compressor, but then this could be simply an orifice mismatch.

More worrisome is that the condenser seems oversized for the compressor.

If the compressor is undersized (under-capacity) for both the evap and the cond, that probably means the compressor is inefficient.

At this point I'm still hoping that the right sized orifice will show a good condenser load, but that may be just wishful thinking.

As mackking says, at this point there is nothing to lose by trying another orifice.

[mackking]

i put in the .73, set it to 15f superheat but i still have a high pressure on the low side (85psi with a 66f suction line)
the high side psi did rise but only to 225 psi. i couldnt get any more readings because it started pouring on me, but its still not bring the room temp down.

[mackking]

are u telling me that u think goodman installed the wrong compressor from the factory?

[Gary]

i put in the .73, set it to 15f superheat but i still have a high pressure on the low side (85psi with a 66f suction line)
the high side psi did rise but only to 225 psi. i couldnt get any more readings because it started pouring on me, but its still not bring the room temp down.

Any idea what the indoor and outdoor temps were at the time you took those readings?

[Gary]

are u telling me that u think goodman installed the wrong compressor from the factory?

No... an inefficient compressor is one with broken valves. The symptoms are the same as having an undersized compressor.

[mackking]

yeah the air in evap was 79 and the air out was 62, i know there is a good difference but it still dont seem cold enough to me.

[mackking]

how would i confirm an inefficient compressor

[Gary]

yeah the air in evap was 79 and the air out was 62, i know there is a good difference but it still dont seem cold enough to me.

And what was the outdoor temp?

[mackking]

i couldnt check it at the time because of the rain but i thinkit was around 85

[Gary]

As the temp in the house comes down the superheat will drop, so you should remove some refrigerant to keep it up around 15F.

[Gary]

i couldnt check it at the time because of the rain but i thinkit was around 85

225 psi at 85F would be an improvement. There may be hope for this system yet.

[mackking]

there may be hope but it hasnt brought it down and shut off yet, do u think this is any indication of how its gonna perform?

[tbirdtbird]

I have to wonder if pix would help. There may be a surprise in store. It has happened with other threads.

[mackking]

what kind of pics do u want?

[Gary]

there may be hope but it hasnt brought it down and shut off yet, do u think this is any indication of how its gonna perform?

To get the charge just right, you need to adjust to 15F superheat when the house is down to your shutoff temp. We've been just ballparking it to compare orifices.

[mackking]

is the superheat effected by night time or daytime?

[mackking]

it just shut off!!

[mackking]

from 830 to 12 to drop it 8f

[Gary]

When it comes back on would be the best time to adjust the charge.

[mackking]

will the superheat skyrocket during the heat of the day? or should it stay pretty much the same?

[Gary]

will the superheat skyrocket during the heat of the day? or should it stay pretty much the same?

The superheat will be higher when the house is warm.

[Gary]

from 830 to 12 to drop it 8f

You are not only cooling the air in your house... you are cooling everything in your house. And you are also dehumidifying everything. It has been very humid lately.

[mackking]

yeah i know

[mackking]

so far its holding 70f in the room, but it has been overcast and raining today too. so far so good

[Gary]

Got a full list of temps/pressures?

[mackking]

nope still rainin, but its running about 35-45 minutes during cycles

[Gary]

Did you trim the charge to 15F superheat?

[mackking]

i got in contact with goodman tesh support, they said the system required a .73 orifice(which i installed) and a superheat of 22f because uf the humidity. i did this yesterday and it has worked the best today but like i said it was overcast and raining. anyways here are the reading-
suction temp=62f
liquid line=83f
condensor in=77f
condensor out=88
evap in=66
evap out=53
lowside=72psi
highside=175psi

[mackking]

this was taken at 10pm and it was wet, 95% relative humidity

[Gary]

Low delta-T's... high suction... low head... I'm thinking this compressor is inefficient.

The only other possibility would be a leaking reversing valve, but you checked the suction pressure on both sides of the reversing valve and they were identical.

[Gary]

I found a Goodman service manual:

http://www.hvacpartsshop.com/asc%20series.pdf

[tonyelian]

hi
ur air handler is 3.5 tons&condenser is 3 tons there is a miss match
gary tanks for the link&the way u guide him
i think every thing is clear now

[Gary]

The air handler is rated at 2.5 to 3.5 tons, based on 400CFM per ton. It is currently set on low speed (1000CFM) which should result in a low suction pressure... but the suction pressure is in fact high.

One more thing we can try is to measure the temps of the two cold pipes at the reversing valve. If the valve is leaking across, the temp on the side towards the compressor will be considerably higher.

[mackking]

would a leaking reversing valve of an inefficient conpressor still pull a vacuum when the suction line is closed?

[mackking]

you asked if it would pull a vacuum, it did but it didnt do it fast and it wasnt much. ive seen systems with a clogged orifice and they would pull a hard hacuum very quickly.

[mackking]

also as a bit of info, the tech at goodman said he didnt think the highside pressure was low. but as im learning more of how the system works, it seems it would need a higher pressure to keep the refriderant from boiling in the liquid line, right?

[Gary]

Where are you measuring the evap air in and air out temps? Best would be at the air handler.

[mackking]

the return air is right above the air handler about 1ft and the closest out is at a vent 3ft away. its a downdraft.

[mackking]

i cant measure the out temp right from air handler because it mounts to the floor so i have to use the closest vent

[Gary]

3 ft away should be accurate.

[Gary]

it seems it would need a higher pressure to keep the refriderant from boiling in the liquid line, right?

Uhhh... No.

[Gary]

also as a bit of info, the tech at goodman said he didnt think the highside pressure was low.

I would disagree. Generally the SCT is 20-35F above the temp of the air entering the condenser (20-35F TD), depending upon load and relative coil size. I have yet to see the TD hit 20F despite the high suction pressure.

[mackking]

Uhhh... No.

in reading your post in a/c 101, you explained that the boilding of refrigerant in the evaporator removes the heat from the air(which i understand) but i also understood it to say by raising the pressure in the condensing coil it returned the refrigerant back to a liquid(by increasing pressure and removing the added heat) so i guess my question is, is the system raising the pressure enough to maintain the proper liquid state?

[mackking]

my next question is, by overcharging and having the wrong orifice, could that have damaged the valves in the compressor?

[Gary]

in reading your post in a/c 101, you explained that the boilding of refrigerant in the evaporator removes the heat from the air(which i understand) but i also understood it to say by raising the pressure in the condensing coil it returned the refrigerant back to a liquid(by increasing pressure and removing the added heat) so i guess my question is, is the system raising the pressure enough to maintain the proper liquid state?

R22 at 175psi gives you a saturated condensing temp (SCT) of 93F. In order for the liquid in the liquid line to boil off, its temp would have to be higher than 93F. Its temp is 83F. Not going to happen... and since the two temps go up and down together, it can't happen.

[Gary]

my next question is, by overcharging and having the wrong orifice, could that have damaged the valves in the compressor?

Yes... it could.