View Full Version : Electrical Protection

13-05-2004, 09:25 PM
I want to ensure maximum protection for a Copeland Scroll compressor.

I am building a control panel. What accessories are vital. ie: overload devices, etc

Any thoughts? or bemusements?

13-05-2004, 10:33 PM
Well a number of safeties come to mind, it all depends how far you want to go....

Obviously as Marc says you need something to stop the refrigerant moving and hopefully filling the compressor when stopped.

Also, overload protection, phase failure protection, in theory low voltage should be covered by the overload but.. just in case.. add a low voltage device.

If the system is on a pump down ensure that when pumped down it stays OFF until required.

You could also add a start delay timer to prevent too frequent starting.

13-05-2004, 11:15 PM
To add to Brian's phase failure/voltage protection - make sure you use a device that can detect phase sequencing to prevent reverse rotation.

14-05-2004, 12:10 AM
I want to ensure maximum protection for a Copeland Scroll compressor.

I am building a control panel. What accessories are vital. ie: overload devices, etc

Any thoughts? or bemusements?


How about the time-delay nonpayment safety lockout? :)

(I only see scrolls on commercial AC with my customer base: no LLSV and I thought scrolls were most forgiving of liquid.)


14-05-2004, 09:41 AM
HP/LP, phase reverse protection, compressor overload thermal relay, rest is fitted inside the compressor and on the special Kriwan.

Time delay non-payment device? ;)
We had a client (meat factory) where some other contractors (plumbing , steam..) warned me that we had to be carefully with the client that the longer you worked for him, the longer the delay time would become for the payment of the invoices.

We therefore programmed in the PLC (S5 Siemens) a routine - the non-payment routine - which counted the running hours of some cold rooms. As soon they came reached a preset programmed time, we closed all the SV's of the whole factory (+/- 15 cold rooms) for 15 or 20 minutes during the day.
This happened +/- once a week.
After a cycle of 5, we divided the counting with 2 so that it happened twice a week, after 5 non-payment delays 4 times a week and so on...

The moment they realized that the cold rooms weren't running anymore and went to the racks to figure out what was going on, everything went on again.

Time was thus random.

They had a second factory in the same city so we were there +/- once a week. We then bridged with a wire 2 inputs of the PLC and resetted the internal non-payment timer.

So, as long they payed correct, nothing happened. If we should decide that we n longer wanted help them, we then could connect that specific input so that the non-delay timer was shut off.

Payments became 60 days, then 90 days and I send him a letter that we wouldn't come any longer if he didn't payed the invoices as correct as we serviced his machines.
He payed some of the invoices
He finally decided to call someone else (did the same thing with them) after payments became again 90 days and we told him that we no longer wanted to help him.
He still needed to pay some open invoices.
But...our timer was running.
They finally removed the PLC (almost 3 ft long, so very expensive) and ordered the company that replaced the PLC that they never wanted Siemens anymore.
Siemens was a bad piece of electronic because it always failed. :D

14-05-2004, 07:53 PM
Ive learnt a lot from this thread, Ive printed it out, and will see how I get on. Its a 6.5 Hp scroll, and lot of money, hence my anxiety.

Thx all

14-05-2004, 11:33 PM
phase reverse protection,HP/LP, compressor O/Lthermal relay, LLSV etc, all were point out,
but just be sure about the proper oil heater in off mode (for a normal /low LRA )many time i exp the scroll fails because of over heating and rotter jammed most of the time because of lack of lubricant.
i am sure u have this things in yours notice. :)