Denco Johnson control

[sparrow]

Hi I have Been trying to work something out in my head for a while but am unsure as to the correct action.
I was looking at an old Denco unit it had tripped out on the duel Johnson control low pressure due to a lack of R22 ref.
My question is this I put a set of gauges on but although some psig was present standing, I could not get the relay to reset, I did attempt to engage it,this ran the compressor for a fraction but as I let go it stopped and the relay popped again. Would I have had to Isolate the system take out the Refrigerant, take care of the leaks and then try and secure the relay with new virgin refrigerant in place. Would the Johnson control allow this or would some attention be needed to the low pressure control.
Regards

Sparrow

[nike123]

Could you set low pressure control to lowest setting and try if it holds. Also make differential as high as possible to check this because, cut out is cut in minus differential.

P.S. Before any action, note current pressure settings, to be able later set these again as they were.

[Brian_UK]

Surely this indicates that the LP control is working correctly.

Low pressure in system and the pressure switch is preventing the compressor from running.

You will have to recover the refrigerant anyway so that you can find/fix the leak.

When you recharge the system the LP switch will be reset automatically as the pressure rises.

[sparrow]

Ok that makes sense, Thanks Nike 123 , Brian.

Sparrow.

[Denco Technical]

Surely this indicates that the LP control is working correctly.

Low pressure in system and the pressure switch is preventing the compressor from running.

You will have to recover the refrigerant anyway so that you can find/fix the leak.

When you recharge the system the LP switch will be reset automatically as the pressure rises.

On any denco units we have a LP delay timer, this is fitted to prevent unnecessary trips when the unit is starting in cold ambients, if the unit trips off straight away when you start up from isolation i would suggest that the timer has not been set up or has been bypassed.