would love some help with freezing evap

[VTP99]

for my own sanity- if you put a low temp compressor in a medium temp cooler, it will gain btu capacity right? why would i lose 1/3 capacity with this. compressor btu ratings go up as evap temps go up right.

Horsepower! As a rule of thumb a 1HP compressor is good for 12.000 btu's at high temp.(a/c)
Same 1HP is good for 8,000 btu's at medium temp.
As well 1HP is good for 4,000 btu's at low temp.
So you can see where you lose capacity.
You are correct that the capacity will go up within any given range.
Do a pump down test for your sanity. That compressor could still be good. Sell it to someone else in the correct application.

[IRBH]

Horsepower! As a rule of thumb a 1HP compressor is good for 12.000 btu's at high temp.(a/c)
Same 1HP is good for 8,000 btu's at medium temp.
As well 1HP is good for 4,000 btu's at low temp.
So you can see where you lose capacity.
You are correct that the capacity will go up within any given range.
Do a pump down test for your sanity. That compressor could still be good. Sell it to someone else in the correct application.

Horsepower?? Don't you mean Displacement??

[VTP99]

Horsepower?? Don't you mean Displacement??

Consider R22 for a medium-temperature application. A popular Copeland Discus, in-line compressor is the 3DS1500. For a low-temperature R22 application, the compressor need only be a 3DS1000. This equates to a one-third drop in horsepower potential.
Why so if the refrigerant is unchanged ?

[IRBH]

Consider R22 for a medium-temperature application. A popular Copeland Discus, in-line compressor is the 3DS1500. For a low-temperature R22 application, the compressor need only be a 3DS1000. This equates to a one-third drop in horsepower potential. ?

3DS3-1000 LO TEMP R22 = 2120cfh
3DB3-1000 EXT MED = 1620cfh
equals a 24% loss in pumping capacity between same hp units.

Your logic of 10hp vs 15hp escaped me.
If the OP simply amped the unit thru an operating cycle, this thread could RIP.

[VTP99]

3DS3-1000 LO TEMP R22 = 2120cfh
3DB3-1000 EXT MED = 1620cfh
equals a 24% loss in pumping capacity between same hp units.

Your logic of 10hp vs 15hp escaped me.
If the OP simply amped the unit thru an operating cycle, this thread could RIP.

Give it up ! You seem to have a hard time answering questions.
Let me try again.
A low-temperature, central rack system was short on capacity. Two people decided to replace a 10HP compressor with a 15HP model. They had monitored the original amp draw. When the compressor change out was accomplished, the rack was still short and the amp draw was unchanged.
Why ?

[IRBH]

Give it up ! You seem to have a hard time answering questions.
Let me try again.
A low-temperature, central rack system was short on capacity. Two people decided to replace a 10HP compressor with a 15HP model. They had monitored the original amp draw. When the compressor change out was accomplished, the rack was still short and the amp draw was unchanged.
Why ?

simple... DISPLACEMENT !!!!!!

My friend, I agree that one of us has some difficulty understanding the written word.

moving on, case closed.

[VTP99]

Consider R22 for a medium-temperature application. A popular Copeland Discus, in-line compressor is the 3DS1500. For a low-temperature R22 application, the compressor need only be a 3DS1000. This equates to a one-third drop in horsepower potential.
Why so if the refrigerant is unchanged ?

HERE'S THE ANSWER !
The answer is that a low-temperature condition utilizes a thinner gas. In other words, it's specific volume has increased, which results in a density decrease.
Seems all you know is DISPLACEMENT. How then in my previous post example, did the same 1HP compressor with the same DISPLACEMENT have three different Btu ratings ?

[Tinbrook]

Your idea of a time clock will fix it. But, you're just giving it an 'off cycle'. Maybe the high ambient temp is infiltrating into the case and forcing this unit to run for long periods of time without any air defrosts. I would consider ways to lighten it's thermal load like: Upgrading the lighting to LED or swapping out the old shaded pole fan motors for PSC fan motors. You could sell a customer on the fan motors just by comparing the Watt consumption.

Which would also raise superheat. I have an 8' case on account which iced over during the recent heat wave in the north east. Figure all that humidity and heat made perfect conditions for ice making. Weather has cooled, we defrosted the coil, and it's running good. But it made me think that thermal isolation is very important when troubleshooting the cause of ice over.

[kklobas]

i ended up putting a paragon 9000 clock with 2 fifteen minute defrosts durring the day, 2 1/2 hour ones at night 10pm, and 4am.
Mainly because we now know i have the wrong and undersized condenser, and it really never shuts off on temp. Owners trying to get money together for new condensing unit.....

[primmers]

kklobas how long has this system been in use?

[kklobas]

4 wks

[kklobas]

Well getting back to this old case with known wrong compressor. Called today. Not cooling. Found pressures for 416a at 60 degree box 16 low, 140 high. Suction line 80 degrees. Subcool 12 degrees. I closed suction service valve on compressor and suction actually went up to 35 never pulled any lower in 15 seconds or so.

Guess they finally have no choice now.

Did suction go up because discharge valves also are leaking by ? I would have expected it to at least stay the same ?

[VTP99]

[QUOTE=kklobas;16373661
Guess they finally have no choice now.

Did suction go up because discharge valves also are leaking by ? I would have expected it to at least stay the same ?[/QUOTE]

Well you could change out the valve plate. Your suction reed is bad.
Pull the head and have a look.

[kklobas]

I told them they need to get the correct 3/4 hp condensing unit. Stop wasting any more money on this. Federal said it needs 3/4 hp.
I am curious why my superheat went so high compared to 3 weeks ago. I'm thinking drier plugged(had lots of bubbles with 14 degrees subcool) glass after drier. I tried warming txv bulb before i valved off comp. no change in suction pressure. Drier did not show a temp drop at all with fluke clamp.

Recomended new 404a condenser and txv .