View Full Version : Mitsubishi city multi VRF incorrect daisy chain

12-09-2017, 12:32 AM
New guy here, I've been contracted by a company to fix a botched VRF install, besides multiple leaks I've already found they daisy chained the communications wire incorrectly instead of indoor unit to indoor unit they ran all indoor units to the condenser. All of the wires were ran under ground and the house is nearing its final inspection and they cannot not run new wire.

My question is will the below set up work. I am unable to test the system as is due to the fact that they will not have power to the building for another two weeks.

IDU 1 --- Condenser --- IDU 2

This system is a part of the S series M/N PUMY-P60NKMU

12-09-2017, 01:28 PM
I would suggest a large junction box where you can reconnect the wiring tails to correct the bad wiring.

I hope that the hidden data cabling is not run alongside any power cablibg.

12-09-2017, 01:36 PM
The problem is going to be trying to create a series daisy chain from each air handler when only one set of cables has been run from each air handler.
Trying to get the communication to operate through a star point is going to be fraught with problems and it is likely to cause random Comms errors and not necessarily just when first powered up.

12-09-2017, 04:08 PM
Sorry, what I meant was to create the daisy chain by connecting the wires as pairs from one unit to the next.

13-09-2017, 09:11 AM
Make sure that you keep the polarity the same on each pair of wires as sometimes crossing them over can cause spurious Comms errors as well.
The only problem might be potential interference due to the extended cable runs. Try to keep the junction point away from mains sources.

16-09-2017, 07:43 PM
Best option would be to use 1 of the cables from the condenser to 1 of the indoor units and then run new interconnecting cables between each indoor unit. You could use the condenser as a star point but this could cause comms issues.