scroll internal check valve

[codgy]

How many of you have seen multiple copeland scroll issues with discharge check valves failing to holdback during off cycle causing on/off cycling on low pressure. This kills contactors and start relays, caps etc.. I've had multiple compressors on different units w/ the same problem. Low temp 404a application. Units are 18-24 months old and out of warranty, customer is ticked that unit runs fine just kills wiring and components when load is satisfied. ZF15K4E model. Not a cheap compressor to replace.

I advise my customers of the high future replacement cost of scrolls and sell mostly semi-hermetic due to the ready access and rebuild cost.

[craig1]

You can get external check valves that braze into the discharge line rather than replacing the compressor.

I agree that semi hermetic compressors are the way to go if you can convince the customer to spend a little more up front.

[icemeister]

I've found this on two units with Copeland scrolls.

One is a 4 HP R22 high temp, the other is a 6 hp R404A low temp. Both are Heatcraft units.

Heatcraft recommended installing an external check valve or adding a delay on break time delay.

[codgy]

Already did the delay on break to prevent short cycling. This application is cold plates w/ only 20" between cpr and compressor w/ pressure control as the thermostat, this screws up the discharge check valve being external due to to much gas bleeding into suction. Only 10 psi diff. on control to maintain temp. Thought about moving pressure control to entering side of cpr then maybe external check valve would work.

[monkeyspanners]

I've had this problem on some copelands too, fitted a check valve in the discharge pipe and alls been well since.
Some other makes of scrolls need an external check valve as they don't have one as part of the compressor, so i don't see much wrong in fitting one in your example.

[Poodle Head Mikey]

And sometimes it is easier to install a suction check valve.

[ascj]

If you read the literature they say it's a low leak check valve. But say it's ok to use with pump down. I have seen many leak through. And we always end up with a check on the discharge.

[Poodle Head Mikey]

I think the scroll discharge checks are just a metal-to-metal seal because isn't it's primary function to prevent back-spin on shutdown?

A metal-to-metal design discharge check valve would also be cheaper to make and have no high temperature issues.

PHM
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If you read the literature they say it's a low leak check valve. But say it's ok to use with pump down. I have seen many leak through. And we always end up with a check on the discharge.

[IceVicious]

I agree that semi hermetic compressors are the way to go if you can convince the customer to spend a little more up front.

Craig you speak the truth , fortunately the margin on new cond units is the same lol. cause selling hot water in hell aint easy lol