What is a High suction pressure ?

[kfjoe]

hi all

was just wonderihat exactly is a High suction pressure , people talk about suction pressure being too high,

But what exactly is too high ?

A high heat load / Temperature will give a high suction pressure , but when is it too high ? if the compressor isnt pumping to capacity wouldnt the Suction pressure rise , but how do you define this ?

Thanks

[nike123]

hi all

was just wonderihat exactly is a High suction pressure , people talk about suction pressure being too high,

But what exactly is too high ?

A high heat load / Temperature will give a high suction pressure , but when is it too high ? if the compressor isnt pumping to capacity wouldnt the Suction pressure rise , but how do you define this ?

Thanks

High suction pressure is when suction pressure is converted to saturation temperature and if that temperature is higher than result of this equation.
SST= evaporator entering air temperature - evaporator TD

SST=suction saturation temperature
TD=evaporator designed Temperature Diference
http://www.refrigeration-engineer.co...75&postcount=5

[mad fridgie]

hi all

was just wonderihat exactly is a High suction pressure , people talk about suction pressure being too high,

But what exactly is too high ?

A high heat load / Temperature will give a high suction pressure , but when is it too high ? if the compressor isnt pumping to capacity wouldnt the Suction pressure rise , but how do you define this ?

Thanks

I think you have the right understanding!
So I think you asking about the practical side.
You are asking 2 questions,
1; The compressor is working correctly?
Suction pressure is to high, if it is higher that the manufactures working enverlope (specs)
Most of the time you will not have this with you, so practically, it is to high if the moter current is equal to that of the name plate, or if the discharge pressure is too high (similar result increased moter current) This why you install CPR say for instance on a large freezer.
2; The compressor in not working correctly?
No finite number, First thing to look for is high suction and low discharge pressures, this can give an indication that the comp may be faulty (but is not the only fault that can give this set of readings)

[mad fridgie]

In service you should always use your 4 best tools first,
Brains, Eyes, Ears, and fingers

[Peter_1]

Hey Mad Fridgie, that's really a good one to remember.

[mad fridgie]

Hey Mad Fridgie, that's really a good one to remember.

Hi Peter_1, I wish somebody had given this advice to me early on in my trade, It would of saved a bit of wear and tear on the old knees and back

[powell]

Here's a link to some quick references for troubleshooting systems. Check out the "High Suction Presure" section.

http://www.hvacrinfo.com/system_trouble.htm

[Blythe Warland]

A high suction pressure would be dependant on the expected pressure / temperature of the evaporator.

If the pressure / temp is higher than designed then it would be a high suction pressure. Just remember that for a freezer, cool room or a/c these pressure / temps all differ, then you have the different refrigerants as well

Blythe