Walk-in box control
Walk-in box control
(OP)
Hello friends, as may you know, the canonical method of controlling the compressor on a refrigeration system is by opening and closing the solenoid valve and letting the compressor trip the LP switch. On my system, I find that the pressure switch is making this strategy impossible. The switch is a manually-resettable type. To make matters worse, it has a hard-wired differential of only 10 psi. Even if I could jerry-rig it to self-reset, that diff would be way too small. So, short of changing the pressure switch (it is a Danfoss KP 15, btw), what are my options?
Here are my ideas so far:
1. The controller has an NO relay each for indoor, outdoor and defrost. I can put the solenoid and the compressor contactor on the indoor relay, with the compressor behind a delay-on timer. On a start this would open the solenoid before starting the compressor. The off would be simultaneous for both solenoid and compressor.
2. Same thing as 1, except without a delay. Solenoid and compressor would always start and stop simultaneously.
PS. Here is the diagram of the system.
Here are my ideas so far:
1. The controller has an NO relay each for indoor, outdoor and defrost. I can put the solenoid and the compressor contactor on the indoor relay, with the compressor behind a delay-on timer. On a start this would open the solenoid before starting the compressor. The off would be simultaneous for both solenoid and compressor.
2. Same thing as 1, except without a delay. Solenoid and compressor would always start and stop simultaneously.
PS. Here is the diagram of the system.
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RE: Walk-in box control
I'm not following your logic or reasoning at all. Help us out.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Walk-in box control
That is exactly the issue - in my case it is not. Both the low and the high have to be manually reset. Such is the pressure switch that is currently installed (see pic).
RE: Walk-in box control
You need to keep looking for the actual "low pressure control switch". Or install one.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Walk-in box control
RE: Walk-in box control
Does this system actually have a liquid-line solenoid controlling the temperature? If it does then really you should have a low-side pressure control. Possibly you can isolate the existing pressure switch with a valve that allows replacement of the pressure switch without evacuating the system, then TEE-in to the LSide with a control switch.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Walk-in box control
The switch connects directly to compressor, which can be isolated from the rest of the system to work on it. That would be the cleanest solution to just replace the switch, but either way it will take a little bit of time to source.
In the meanwhile, I will set the refg controller to minimum settings of 3 min ON / 4.5 min OFF -> 8 starts/hour max (as per manual). Let's see how it goes, wish me luck.
RE: Walk-in box control
Keith Cress
kcress - http://www.flaminsystems.com