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tevs
22-06-2016, 03:56 PM
Hi everyone

Very new to hvac and I am after some advice.

How do I know what the pressures/gauge temp should be on different refrigerants.

I know I will likely get shot for this question as there are a lot of variables and has probably been asked loads of times before. It's just driving me insane on how I work this out.

I am in the UK so would appreciate answers in Celsius

Thanks

Tev

Brian_UK
22-06-2016, 03:59 PM
If you use a pressure/temperature chart it will help

The temperature of the refrigerant depends on what it is cooling or heating.

tevs
22-06-2016, 04:40 PM
Thanks for the reply for example then if I am cooling a cold display counter refrigerant is r404a.

The ambient temp is 30oC in the kitchen area

The cold display counter should be running at approx 3 to 4 degrees

I know how to work out my sub cooling and super heat etc but it's just this what is really baffling me.

Brian_UK
22-06-2016, 04:59 PM
If the sub cooling is within expected limits then don't try and change it.

The superheat reading at the evaporator will only settle out when the unit/system is down at design temperature.

You have told the kitchen temperature and what you want the cold counter to be but......

Is the counter in the kitchen?
Where is the condensing unit?
What readings have you recorded from the system?
Was it working before you were asked to look at it?

We can't see what you have so need a little more info please.

tevs
22-06-2016, 05:18 PM
The counter is in the kitchen the condenser is located under the unit in a cupboard with louvered doors.

The gauge temp is -10 and the suction temp out of evap is -7

40 degree gague temp and 46 line temp out of condenser

The unit was working last week but had a leak. I found the leak and repaired.

Brian_UK
22-06-2016, 08:10 PM
So, the leak was repaired, did you acheive a good vacuum before you recharged it?

Did you recharge by weight?

tevs
22-06-2016, 08:19 PM
So, the leak was repaired, did you acheive a good vacuum before you recharged it?

Did you recharge by weight?

Vac down to 2 torr, the cold display was changed using reference documents from when it was installed, I believe it was made for the canteen so no data plate is available.

Apreciate you taking the time to reply, I am really keen to become clued up in all this as I have finally found something I enjoy doing. Much more than repairing lifts 😂

Gary
22-06-2016, 11:35 PM
Hi everyone

Very new to hvac and I am after some advice.

How do I know what the pressures/gauge temp should be on different refrigerants.

Tev

You might want to check out this thread: http://www.refrigeration-engineer.com/forums/showthread.php?19701-Refrigeration-101

Brian_UK
22-06-2016, 11:44 PM
Thank you Gary, I had forgotten about your little thread. ;)

Gary
23-06-2016, 12:45 AM
Hopefully, a few people have found it helpful. :)

Magoo
23-06-2016, 01:45 AM
tevs,
did you recharge 404a in liquid phase, there is a danfoss app available on line free from danfoss site. " refrigerant slide rule " very handy for every refrigerant .

tevs
23-06-2016, 06:20 AM
Thanks everyone much appreciated