Daikin Inverter Board / Compressor issues

[Greengrocer]

Hi Guys.
I’m looking for some 2nd opinions / advice to help us resolve an issue we have on a client’s RXYQ14P7W1B outdoor unit. It’s a 2-pipe VRVIII R410a unit serving a bunch of Cassettes. Warranty ran out in January this year (wouldn’t you just know it).
There’s a U2 fault up which indicates system power failure. Our engineer reckons the Inverter board is dead & new one’s required. However, we have been advised by Daikin that the compressor may have been the reason for the Inverter board blowing.
Our engineer has tested the comp windings but can’t find anything obviously wrong e.g. nothing down to earth or open circuit. The chances are that if the comp is faulty it will blow the new inverter board as well. So customer has to pay for two Inverter boards & a compressor.
Question how can you test the compressor fully without a functioning Inverter board and without risking blowing a new board? At £440 the board isn’t much less than a new compressor!! An expensive part if we have to replace twice.:eek:

All contributions gratefully accepted.

[Brian_UK]

Don't know if things have changed but always used to swap out compressor as well as inverter board, just in case.

That way, just one site visit and one repair.

[AbsoluteWDJ]

I had a similar problem with an old R22 Hitachi VRF system a year or so ago. It had an inverter compressor and direct compressor but the inverter control side was damaged. I carried out the relevant checks on the inverter compressor....i.e 500volt insulation test and resistence all passed. The distributor told me that the inverter compressor would have to be changed. The customer had had a quote from another company that came in over £9000! This is due to compressor needing a crane to get to roof. In the end I run a lead from the three phase power down to the inverter compressor windings, powered it up for around 30 seconds whilst measuring amps and checking for any unusal noise. The Inverter compressor worked fine. So I changed the Inverter control side and operated system. That was over a year ago with no issue. So you could try this but I would make the customer aware of what your doing and why you're doing it.

[nike123]

. In the end I run a lead from the three phase power down to the inverter compressor windings, powered it up for around 30 seconds whilst measuring amps and checking for any unusal noise. The Inverter compressor worked fine. So I changed the Inverter control side and operated system. That was over a year ago with no issue. So you could try this but I would make the customer aware of what your doing and why you're doing it.

Generally speaking, you could do direct on line three phase test only if compressor is AC inverter.
If compressor is DC inverter, you cannot do that!
So, care mast be taken to know for sure what type of compressor is used.

[AbsoluteWDJ]

Generally speaking, you could do direct on line three phase test only if compressor is AC inverter.
If compressor is DC inverter, you cannot do that!
So, care mast be taken to know for sure what type of compressor is used.

Good point!

[Greengrocer]

Thanks for the input. I think we are going to play it safe and replace the inverter board and the compressor. This can be done in without having make multiple visits and limits the parts to only one inverter board instead of two - if the comp is dead.
Customer is not too happy about the cost so we have approached Daikin to see if they are feeling generous (the warranty only ran out in Jan this year). Curiously there are other 2 & 3-pipe outdoor units installed on the same site at the same time who's warranty has another 9-12 months more to run. Very strange that there should be nearly 1 year difference in the manufacturing dates. More investigation needed I think.

[nike123]

More investigation needed I think.

Off course, after compressor or inverter defect, you need to find what was the cause of trouble or it will happen again sooner or later.

[Greengrocer]

Off course, after compressor or inverter defect, you need to find what was the cause of trouble or it will happen again sooner or later.

Too right Nike. As it happens I might now know what caused the problem. One of the server room split systems has never been run because the main phases were out of balance. The customer said that they were going to get the power re-wired / balanced so the split could be brought on line.
I wonder if this work was done recently - could be the cause of this Inverter board blowing if someone screwed up the mains power work.
I think I'll do a bit of detective work.

[Thermatech]

An alternative method to test run the compressor is to use an industrial inverter to run the compressor.

I use a Mitsubishi Electric 500 series inverter which has loads of programable options & has ground fault protection which means you can connect it to a compressor even if you think the windings are suspect.
You can start the compressor in forward or reverse to rock it free if its locked & you have infinate options for high torque or low torque start up & run speed settings.
The inverter control displays hz & amps so you can monitor if the amps go too high.

You wire 3ph power into the inverter & connect it to the compressor.
As this is an independant test of the compressor you cant run it for long without the system operating as it can be running with valves closed so you need to keep watch with pressure gauges. But all you are looking for is for the compressor to start & run without excessive amps & that only really takes a few seconds.

The only problem with this is the cost
£1500 - £2000 depending on which model.
As many service managers are reluctant to provide proper mega meters for their engineers they are not likely to be prepared to spend that kind of money for a daignostic tool which will spend most time on a shelf in the workshop.

I have been using the industrial inverter now for about 7 years & think its a great way to prove the comprssor without risking damage to any new inverter components.

[robin r33 gtr]

An alternative method to test run the compressor is to use an industrial inverter to run the compressor.

I use a Mitsubishi Electric 500 series inverter which has loads of programable options & has ground fault protection which means you can connect it to a compressor even if you think the windings are suspect.
You can start the compressor in forward or reverse to rock it free if its locked & you have infinate options for high torque or low torque start up & run speed settings.
The inverter control displays hz & amps so you can monitor if the amps go too high.

You wire 3ph power into the inverter & connect it to the compressor.
As this is an independant test of the compressor you cant run it for long without the system operating as it can be running with valves closed so you need to keep watch with pressure gauges. But all you are looking for is for the compressor to start & run without excessive amps & that only really takes a few seconds.

The only problem with this is the cost
£1500 - £2000 depending on which model.
As many service managers are reluctant to provide proper mega meters for their engineers they are not likely to be prepared to spend that kind of money for a daignostic tool which will spend most time on a shelf in the workshop.

I have been using the industrial inverter now for about 7 years & think its a great way to prove the comprssor without risking damage to any new inverter components.


This sounds a very good tool.
Can you get the model number please as I would like to search and read up on this.
Does this machine test all a/c and d/c compressors or just d/c ?

[nike123]

This sounds a very good tool.
Can you get the model number please as I would like to search and read up on this.
Does this machine test all a/c and d/c compressors or just d/c ?

Probably only AC!

[robin r33 gtr]

So if it is a/c only I might aswell save my money and just wire it into the isolation switch.

Do the new fujitsu r410a wallmounted units have a d/c compressor ? (12 000 btu)

I borrowed a inverter machine from fujitsu to test the compressor ,but had no settings or display you can change. just 1 flashing light meaning all is ok.

[nike123]

So if it is a/c only I might aswell save my money and just wire it into the isolation switch.

Yes, with some overload protection!


Do the new fujitsu r410a wallmounted units have a d/c compressor ? (12 000 btu)

It is stated in catalog!