Compressor safety valve opens

[PRADYUTGHOSH]

Sir,
I am installing 7 nos 5TR condensing unit with reciprocation compressor, emerson make, in our one site in India. Unfortunately, we are observing one problem which I never faced. Kindly advise me.
During charging of refrigerant when suction pressure reaches 50-55 psi & discharge pressure reaches 260-70 psi the safety valve opens & compressor trips.

[sedgy]

i DONT KNOW WHAT REFRIGERANT YOUR ON, but it looks like a faulty compressor?

[monkey spanners]

What Sedgy said, also where are you measuring the pressure and how quick are you charging?

I'm not familiar with these safety valves, do they work on temperature or pressure differential?

Jon

[Tycho]

-are the safety valves rated at 250 psi or higher?
-Where is the HP manometer connected?

I had a problem on a twin howden unit (2 compressors on one oil sep) where we measured the HP on the common HP line, both compressors had danfoss NRV/CHV valves fitted
http://img641.imageshack.us/img641/5647/148g15011218217731.jpg

The SFV valve was fitted between the compressor and NRV.

When the compressor reached 70% capacity the gas detector in the safety line tripped.

I fitted a manometer on the line next to the sfv, and while we had a normal 10 bar in the common line it was 22 bar before the NRV.

being in south america and parts were hard to come by, I took the lid of the NRV, and took off 10 mm in the lathe so that the valve could open further and problem solved.

[PRADYUTGHOSH]

Sir,
It is Hermatically sealed reciprocating compressor. Refrigerant is *****-22. The safety valve setting is factory setting of Emerson.
Is there any relation with condenser size?

[Tycho]

Sir,
It is Hermatically sealed reciprocating compressor. Refrigerant is *****-22. The safety valve setting is factory setting of Emerson.
Is there any relation with condenser size?

and what is the factory setting? is the valve set to open at 250 psi?

seems kinda low for the HP side

[monkey spanners]

and what is the factory setting? is the valve set to open at 250 psi?

seems kinda low for the HP side


I think they work on differential pressure too so it would be operating at around 200/210psi which seem way too low to me!

What is the run currnet when it trips? and what is the max run current for the compressor? would give an idea of how hard the compressor is working when the valve lets go. Maybe the compressor is seeing a higher pressure than your gauges due to a restiction in the pipework, where are you measuring the high side pressure?

I think on these hermetic compressors the valve is fitted on the muffler inside the compressor body and not on the head, i know some scroll comps valves work on temperature so thats why i wondered about the discharge superheat, if the system is low on charge it would have a high superheat.

Jon

[powell]

PRADY,

I believe you're referring to the IPR (internal pressure relief valve) which is designed to open when the discharge to suction differential exceeds 450 to 550 psid.

Check for restrictions in the discharge line or an overcharged system.

Here's a link that will help you out.

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

section 4-1329.