Heat Pump Retrofit

[stryped]

I have a 2008 Goodman 2 ton slit system heat pump. It is an r-22 system but does not have any r-22 in it. I got it from an HVAC guy. It was removed from a house because the owners updated to a newer system. My intent is to put this in my detached garage/workshop. (Plus refrigeration interests me but my experience is limited to automotive.)
Anyway, my question is what is the best way to go in terms of retrofit. I can cut the lines holding the compressor and accumulator in and turn them upside down to drain, adding the same amount that is drained of POE oil and refilling with 407c. Or keep the system intact and use a more expensive gas, M099 which supposedly will work with the existing mineral oil.
I have also read conflicting reports as to if going to 407c, how much mineral oil can be left in the system and the unit still function appropriately. I have read there must be less than 5% and I have also read that it really does not matter.
Also, I know this is an oddball question, but has anyone installed 134a into a system like a heat pump that was designed for r-22? How would it perform? R134a is a lot easier to come by but I am sure it would not perform very well.
I appreciate the info!

[monkey spanners]

Personally I'd got with an oil change to POE and R407C, i'm not keen on drop ins such as MO99, R134a on its own will not work properly. Wouldn't bother with the accumulator, as doubtful there is much oil in it.

Try and find out how much oil the compressor had from the factory, typically 1.5 to 2 liters depending on make and model. The trouble with matching what came out is it could have lost oil in the decommissioning etc.
In an ideal world you would change the oil two or three times but its not practical in your system, I have many commercial refrigeration systems converted to R407F with just the one oil changes with not one problem.

[stryped]

Thanks so much for your help!
What is the best way to rid the system of old oil and install new poe? Is it necessary to change all the seals? I read that r22 causes seals to swell and when installing a different refrigerant they swell a different amount, causing leaks. Does this mean the service valves need to be replaced? What other seals are on this system?

By the way, my unit is a Goodman GSH130241AC. My air handler is a ARUF182416BA. I found that the evaporator looks new but has a leak in the small copper spider looking capillary tube fitting. I guess I need to find an inexpensive evaporator. NOt sure if my current one can be fixed, I cant seem to find that assembly....

[monkey spanners]

I'd remove the compressor and tip the oil out of the suction pipe (assuming its not a rotary compressor with inbuilt accumulator), then tip fresh oil back in and refit compressor. The oil is hygroscopic so once the compressor is refitted the system will want vacuuming and either refrigerant charging in or dry nitrogen holding charge putting in until the system is vacuumed again and refrigerant put in when you finally plan to commission it.

No idea on the seals in your goodman unit, it is generally rubber o rings that may leak, I would expect the service caps to keep and leaked refrigerant in the system but again not familiar with the equipment. Change all the shrader cores though.

The leaky spider might be able to be brazed up, but may make more sense to replace the coil if its not too expensive or if the rest of the old evaporator is in poor condition.

[stryped]

Is it ok to siler solder the connections when re installing the compressor or must they be brazed

[monkey spanners]

They need to be brazed.