Daikin u4 VRV HELP!

[maxcool]

Got sent to a job today which consists of 2 Daikin 3 pipe systems RSEY8K7W1 which have 4 internal units ,with 4 bs boxes and 4 seperate controls on each system.

Over the past 2 weeks some builders have been in an revamped the whole office area. Whilst on site they moved all controls to a corner in office by extending control cable.

A U4 fault is present on one system now and will refuse to run. It may be possible that this was present before the work was carried out but the landlord said it was working fine before.

I have power to condenser, power to all 4 indoor units, power to bs boxes and power to each control. As soon as you turn one of the four controls on, it goes into U4 fault with flashing led. The indoor unit fan runs but that is it.

I know that on each bs box and control terminal there should be 16v dc. On the bs box indoor f1 and f2 on board i only get 13v dc and the outdooe f1 and f2 inside bs box i get 15v dc. On the condenser I get 15.4 v dc with or without the wires connected on the condenser pcb.

I have gone through all of the extended cables and all looks fine. I can only access 2 of the 4 bs boxes but the other two i can see have power and cables look to be fine.

I cant seem to find any damaged cables nor does any control cable seem to be next to power cables as such.

I have carried out a full system reset by isolating all power, then turning internal units and bs boxes on, leaving for 10 mins and then turning condenser on and leaving for ten mins before trying to run system up.

This is really playing on my mind as usually i correct U4 faults quick but cant get my head around this one. Any help, ideas or previous experience would be great to try and put my mind at rest.

Thanks in advance...

[Reffnut]

Have you checked that the transmission isn't shorting somewhere? ie: checked with your meter?

[maxcool]

Iv checked where I can but i cant get to two of the bs boxes... Everywhere seems to be low on voltage.

[Reffnut]

Disconnect the transmission at the condenser and bell out between f1 and f2 and if the transmission is shorting anywhere along the system you will see it there! ive had this problem before! then ull have to work you way through the transmission cable with you tester!

[sumsor]

Hi Maxcool,

we had a similar fault on a Daikin VRF, simply crossed wiring between transmission and remote.
No chance of getting to the two Bs boxes?
Sumsor

[ktm]

Have u tried to take all the units off the condenser and then add them one at at a time? Just do a complete reset every time u add another unit. Mite help u narrow it down to were your problem is.

[r0ss]

Have you tried counting bs boxes / indoor units by the condenser led dipswitch display?

Though i havnt done this on a min-vrv, i would assume its the same as on a larger vrv system.

From memory it is; (but you may need to ring daikin to confirm)

mode once
set 5 times (for indoor units) or set 6 (for bs box)
return once

the total is counted in binary from right to left


Its the problem when building work has taken place and you're called to a new site. You have absolutely no idea about the system and you can spend a whole day sussing everything out :confused:

[AbsoluteWDJ]

Iv checked where I can but i cant get to two of the bs boxes... Everywhere seems to be low on voltage.

If you can't get too these two bs boxes then how do you know you have mains power present at these points? I would concentrate on accessing these first.