City Multi pipe sizing problem

[Putte]

Hey!

I'm project managing on a project where we have installed 2 City Multi systems i.e. PURY-P300YHM-A outdoor units each connected to a master BC box and 1 slave BC box. The pipework between the outdoor units and the master BC boxes should be 7/8 & 3/4 but the pipe installer has somehow managed to install both gas and liquid with 7/8 on both systems! The pipe run is approx 30m total but the last 5m to the outdoor units are not finished so we can do this bit with the correct pipe sizes.. Before i start frantically changing both the liquid lines down to 3/4 (a big job!) i was wondering if anyone can give me some advice/thoughts on whether it is necessary? All other pipe sizes between BC boxes and to indoor units are correct.

Thanks in advance!

[stufus]

To be honest i'm not too sure of the exact implications,however at least the pipe's are not under sized.
Personally i've never been in your situation.The only advice i could offer would be change the liquid line if at all possible.
If its not possible the only thing you can do is calculate the additional charge using the figures for a 7/8 liquid line.
That in itself may cause issues with overcharge faults.
Do the math for 3/4 and 7/8 liquid lines and weigh up the options, then if its a big difference make an educated guess.
I dont have a manual to hand to do it myself at the moment but ill have a look around.
30 mtrs of 3/4 = 30x 0.16=4.8kg of refrigerant
I cant remember the multiple for 7/8 if you have it do the same and weigh up the difference , it will give you some idea of what to expect.
Cheers
Stu

[marc5180]

I would rip the 7/8th out and replace it with for 3/4, the pipes are that size for a reason.

Imagine trying to run it up and having problems with any of the indoors not cooling properly upon commissioning it would be even worse then.

Just my 2cents.

[stufus]

I almost forgot , your warranty will be shot as its not installed as per manufacturers specifications.
As Marc says it's not worth the risk and accompanying grief.
Cheers
Stu

[croc1774]

Best practice is as Marc said but it really wont make a differance if you don't change it.
Stu this is true with warranty but i dont think mitsi would come to site over a compressor
Regards Croc

[install monkey]

to achieve finesse- do th job properly and weigh in all that oversized 7/8-pity they didnt lash in 1 5/8

[big bear]

If in Doubt read the instructions lol . Yeah always stick with the spec like guys say ! It will only come back to bite you on the derierre ! :-)

[Thermatech]

There have been cases over the years when manufactures have specified 1 inch pipe & here in the UK we dont use 1 inch. In this case maunfactures tend to advise use next size up @ 1 1/8.
R22 replace systems can also operate with larger pipe sizes but there are limits to the pipe lenghs & some impact on system performance depending on the pipe lenght.

In your case changing from 3/4 to 7/8 is not likely to have a big impact on system performance
But
What if there is a problem with the system & you need on site technical support from the manufacturer ?
A very good chance that you could end up with no warranty & a system not working properly.

It will be easier to change the pipework now rather than after handover as remedial works.