Merging two refrigerant circuits - URGENT advise needed

Dear All,

Please help with this, a lot is at stake!

I have about 48 Free Standing Units to be installed each of 8.0TR capacity. The units are arriving in 2 days.

The refrigerant piping has been done. The pipes passed through sleeves in the wall. The plastering is done and there is no more provision for extra pipes.

Just now, I discovered that the units that are arriving are all Double Circuit Units! Is it possible to merge the pipes after the ODU and split them again before entering the IDU? What would be the effect on the machine? Any extra measures to be taken before attempting this?

Please share your experience and insights. I shall be forever indebted to you.

This one is just to catch attention. I so desperately hope that some replies.

Short answer is no. Long answer is also no.

Think of it as two motorcycles with one gearbox.

Two engines with one gearbox and two driven back wheels.

You want to drive somewhere so you start one engine, you put it in gear and the other back wheel starts going round. After a little while your wheel starts moving but not enough to get you home before the end of the week.

Your friend comes along and starts the other engine but only puts the gearbox in second gear when you want top gear to get home before dark.

Now you get home and switch off your engine but because the other engine is still running it sucks all of the oil out of your engine and drives off into the distance.

Next time you start your engine it runs for a short while and then seizes up due to lack of oil and contaminates the other engine which also fails and short while later.

Only plastered walls? Do what needs to be done, get a quality drill and drill bit, drill the holes that you need and do the job properly.

Thank you Brian, for taking the time to reply.

Its not just about plastered walls. There are no more sleeves to pass the additional pipes.The ODUs has to be on the rooftop.

This is one big hall with a mezzanine floor.

I'm still looking for options.

Please refer to the attached image.

If I use a solenoid valve and a non return valve on each line before merging, wouldnt it ensure that when one compressor is off, the corresponding line is also closed and no backflow takes place?

Dont we apply the same concept with pumps?When multiple pumps are connected to a common header and then distributed?Attachment 15231

You will probably have oil return issues

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Also what will happen to all the refrigerant from unit 1 as it is pumped into unit No2? If there is no provision for it you will have overcharge scenarios and possible high head pressures.

No easy way round this. But you say double circuit units??

Are you definitely sure that it is 2 outside and 2 indoor?
Double circuit could still mean 1 outside and 2 indoor which means
your problem is solved.

Rob

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Quote:

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Originally Posted by frank

You will probably have oil return issues

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I'll describe the idea I have as of now.

Merge the 2 lines and introduce solenoid valves so that the line is cut off when the corresponding compressor is OFF.

Short the Y1 and Y2 in the board of the outdoor unit so that both compressors are always working at the same time. This will avoid pressure difference in both lines.

Does this eliminate the chances of oil return issues?

Or should I consider an oil separator or a U in the pipeline?

Can you confirm that each ODU does have two separate circuits to feed two separate evaporators?

Also can you provide details of the ODUs please, make/model?

What are the pipe sizes for each circuit and the pipe sizes through the sleeves?

Other option is to convert to a 'pack' system perhaps.

Post details of units, indoor and out, as Brian says a pack option could work very well

Quote:

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Originally Posted by tsf31

Thank you Brian, for taking the time to reply.

Its not just about plastered walls. There are no more sleeves to pass the additional pipes.The ODUs has to be on the rooftop.

This is one big hall with a mezzanine floor.

I'm still looking for options.

Please refer to the attached image.

If I use a solenoid valve and a non return valve on each line before merging, wouldnt it ensure that when one compressor is off, the corresponding line is also closed and no backflow takes place?

Dont we apply the same concept with pumps?When multiple pumps are connected to a common header and then distributed?Attachment 15231

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NRV is what you need, SV will not help as the pressure from the running compressor is higher then the pressure in the discharge line of the still compressor.

Thank you all for the inputs.

Anyway, I went for the safest option, which is having dual circuits.

Which means, I cant give a feedback on how the system functions had the solution I proposed above was implemented.