Externally equalised expansion valve

[Daz man]

Morning,

A very simple question!

I have a gas fired 'Reznor' AHU with a retro fit cooling battery which has four stages of cooling.

The four stages are Airedale condensers - twin condenser fan, single Copeland compressors.

Each stage has obviously an expansion valve.

The valves are Danfoss externally equalised TE5's with a number 3 orifice.

Question is - when pressure testing with OFN, would you expect to see a slight pressure drop between high pressure side and low pressure side of the system?

When gauges are closed off I have 150psi (10.34 Bar) HP side then 100psi (6.89 Bar) LP side

Many thanks

[NewmanRef]

Daz man,

Are you applying pressure from both high and low sides of system? If you increase low side pressure does high side rise? If so is it a constant 50psi diff? are there any other valves in circuit? Regulator valves?

I have never seen this with just an expansion valve.

[passandscore]

The pressure should equalize across the system over time as long as you don't have a check valve holding you up. Recommend that you pressure test from high side to low side, following system flow in order to see flow through the metering device.

"The maximum test pressure to be used should be the maximum allowable pressure, which should be stated on the equipment label. On smaller systems the suction and discharge pressures will be the same, however on larger equipment the maximum allowable suction pressure will be lower and the system will need to be tested in several sections." See attached PDF for source info

[Daz man]

Appreciate the response men.

no there are no check valves in the system. I'm applying the ofn pressure down the correct flow that the gas would travel, down the liquid line.

when I apply the ofn pressure down the liquid line the suction gauge does increase, so the ofn is coming back up the suction line.

i am back on site today so will check to see if it has equalised out.

[nike123]

Check your gauges, also!