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swampy84
12-06-2016, 11:25 AM
Hi all! I've recently converted from being a transport tech for 10+yrs and ventured into the World of commercial. Long story short I've got a small single phase coolroom I wanna store beer in. Got a condensing unit and evap unit and just going to pipe up and run. It came with an older type thermostat that I'd like to change over to digital and just as an exercise to help me understand control circuits a whole lot more... I'd like to change it from direct on/ off to a pumpdown system also.

Questions.....

When setting dual pressure controls how do you know what to set the cut in on the LP side? Assuming cut out would be 5 - 10psi (134a for this particular system)

Want the pipe work to look really neat & tidy. What are the best ways to run & fasten pipe work that look nice & neatly done?

Any other help, questions, input welcomed!


Thanks in advance!!

chemi-cool
12-06-2016, 01:41 PM
If you place the SV close to the TXV you don't need pump down at all.
The idea of pump down is to protect the compressor from liquid floodback.

Without the pumpdown time you can save quite a bit of electricity, the dual pressure control will protect the system from playing in and out and too high discharge pressure.

Dr._Fleck
12-06-2016, 11:39 PM
Cut out at 5psi cut in at 25psi. If the cut in is too low it will switch back on a couple of times before staying off, so as long as it doesn't do that the cut in is high enough.
Pipe clips, you can use RPC clips (Rapid Positioning Clips) on aluminum channel or unistrut. These are good because they hold the pipe nicely while you're still brazing/lagging etc.

mikeref
13-06-2016, 10:02 AM
On R134a? As Chemi says, Pumpdown is not necessary on a coolroom, * Depending on LLSV location.

You can use the HP/LP as a means to limit an iceup, TX failure, loss of refrigerant or excess high pressure.

swampy84
14-06-2016, 11:04 AM
So... Forgive me for being such a newbie but...
Cos I'm so new at controls... Replacing an older type tstat with digital would mean I'd need to grab a neutral from somewhere, correct?!
If I place the LLS right next to the tx and just make the controller power the solenoid whenever cooling is required.
That way I'll only need to set the HP/LP as a safety then?

Dr._Fleck
14-06-2016, 11:16 AM
Check the controllers power supply, it might be a 12v one and you would need a little transformer.
What you've described is a pump down arrangement. The other way people are suggesting would be to power the compressor or compressor contactor from the controller - then the LP would be for safety. You can wire the Solenoid in to open when the compressor is running, or just remove it.