mr slim

[Andy AC]

Hello guys, just a quick question about a couple of old mr slim cassettes. A customer of ours has a very old mr slim 14Kw ish, cooling only system that has a leak in the condenser coil. We also have a previously cherished mr slim 7-8 Kw heat pump cassette that our customer wants us to fit in place of the other system. I know the original system is twice the capacity, it was grossly oversized anyway, and this other system hasn't cost us anything.We are basically doing this job for nothing, well I'll get paid for fitting it, its part of some favour/deal between my mate and the customer.
As its not a real money making scheme, we want to keep it as cheap and quick as possible. I was wondering if we could keep the 3/4 inch suction pipe, the pipe run is only about 6-8 metres, but a pig to get to as it is in the ceiling above machinery. So i would rather not run an additional 5/8 pipe if we could get away with it.
The newer machine is a plh3 5/8 suction, the older one was a pl6? 3/4 suction both on R22

Andy

[frank]

Hi Andy

The 'h' in the model number refers to a heat pump.

As you only have a relatively short suction line, oil return should not be affected to a great degree by the lower velocities within the 3/4" pipe. Providing the pipework is not, say, all vertical, I don't see any problem.

To help with oil return though, it may be of benefit if you could replace any of the 3/4" line with 5/8" wherever possible. You will have to anyway at the connection points.

[Andy AC]

Hello Frank, vertical pipework is an absolute minimum, the condenser is high level on the wall outside with the connections approximately the same height as the cassette unit indoors.
I'll go for it

Andy