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Tayters
05-01-2009, 10:04 PM
Could anyone shed some light on this please.

I have replaced a few relays which control the compressor on the above chiller. The relay sticks on causing the compressor to run continuously resulting in too low a temperature and eventually icing of the coil.

Upon inspection of the relay, the contact are burnt and presumaly sticking them together causing the fault.

Replace the relay and all is well. Some seem to last a while, others only a few months.

The relay is rated at 16A and has about 6A running through it when operating.

I presume the initial start current is what eventually ****s the thing up. Is that correct?

nike123
05-01-2009, 10:33 PM
Yep! Relay should be rated for 5-6 times higher current than FLA!

If it is for PCB mounting, this (http://components.omron.eu/en/products/catalogue/relays/pcb_power_relays/up_to_30a/g4a/default.html) is good one.

If it is not than this (http://components.omron.eu/en/products/catalogue/relays/general_purpose_relays/g7l/default.html) is good one:

Tesla
06-01-2009, 06:07 AM
Hi Tayters
It sounds like a vibration problem, is there another problem with chiller causing excess vibration? U could use a solid state relay or isolate relays from vibration. Snubbers or suppressors could be used across coil to minumise spikes to control circuit. Almost forgot low coil voltage will also cause contacts to chatter.

tony--1
06-01-2009, 09:08 AM
I just fit a smalll contactor to take the load of the comp after relay . No more problems.

tony--1
06-01-2009, 09:11 AM
If it has 2 comps fit a timer .Set at about 1 min for delay.

Tayters
06-01-2009, 07:19 PM
Thank you chaps.

Also suggested to me was to fit a contactor (as suggested above) and link across any spare poles so all 3 of them take the current thereby reducing the load on each individual set of contacts.

MR CVP
07-01-2009, 11:59 AM
This has been a problem with Linde cases for years,I always used to replace these relays with a 16 Amp Contactor and never used to get a problem after that.

tony--1
07-01-2009, 06:44 PM
Not just linde cases . Iv had it on verco cases too and very cheap cases