Daikin VRV

[matt.yelland]

Hi all,

On a site I went to recently which has had a new Daikin VRV system installed, there is 6 wall mounted A/C units. I checked the controller for the fault code and 5 of them had a U9 Fault code, Comms error between Indoor Unit and Outdoor Unit in the same circuit. 1 had a U5 fault code, Comms fault between the Indoor Unit and the Remote Control.

Two of the units are in a staff canteen. 1 had been switched off on the Fused Spur….. which has “ Don’t switch off ” plastered all over it.

My question is why, when switch 1 unit off does it put up a fault on all the other controllers and shut down the condenser and would it be possible to stop this?

Many thanks

Matt

[Clk320_Greg]

Are you turning the unit off at the mains? This is a NO NO, as if you cut the mains then you have no control over the EEV. If you want to turn a unit off then do so by the remote/forced off pins.

[multisync]

Hi all,

On a site I went to recently which has had a new Daikin VRV system installed, there is 6 wall mounted A/C units. I checked the controller for the fault code and 5 of them had a U9 Fault code, Comms error between Indoor Unit and Outdoor Unit in the same circuit. 1 had a U5 fault code, Comms fault between the Indoor Unit and the Remote Control.

Two of the units are in a staff canteen. 1 had been switched off on the Fused Spur….. which has “ Don’t switch off ” plastered all over it.

My question is why, when switch 1 unit off does it put up a fault on all the other controllers and shut down the condenser and would it be possible to stop this?

Many thanks

Matt

Switching off one indoor sends a signal to the outdoor unit -usually a U4. this is transmitted to all those indoors which are running at the time to flash up the U4 fault too. Those not running will not U4 till they are switched on (not the mains but the remote)

Fit fused spurs without a switch to stop on/off occuring but your main question remains :

No this is part of the system setup and a U4 automatically stops the whole system and connot be bypassed.
Only switching that particular unit back on or a sw reset will enable the rest to run

[acnerd]

In addition to the above answers: Daikin explained to me that if you switch the power off to one indoor unit, the system no longer knows what position that unit's EEV is in. For all we know it could be wide open! So if the rest of the system keeps running in cooling ..... well we all know what happens to an evaporator coil with refrigerant running through it, and zero airflow.

Incidentally, I have discovered that U9 basically means: 'I have a comms error on this system, but not on this controller, look on another.'

[brunstar]

if this is a continuing problem within a system or a set of appartments you can install and additional printed circuit board to each of the indoor units.
When one of the units is powered down, it will not lose communications as the slave board will be kept powered up and the system can continue to run.
The easiest way is to not turn the power off!

[Thermatech]

The Daikin VRV system has no way to shut down the EEV when 240v switched off at the indoor unit.
The indoor unit control circuit board goes dead & the outdoor unit cannot communicate with the indoor unit.

In this case if the indoor unit was operating with an open possition at the EEV then with 240v off then liquid will flood through this unit & liquid flood back to the outdoor unit.

So the system stops on a comms fault to force you to investigate & switch 240v power back on at all indoor units.

Mitsubishi City Multi overcome this by using 30v dc communication voltage.
In this case when 240v is switched off at any indoor unit the indoor unit can use the 30v communication voltage to shut down the EEV instead. So the system is safe & no risk of liquid flood back & the system does not need to shut down on any fault.
The outdoor unit still has full communication with the indoor unit with 240v off & the outdoor unit continues to operate with the other indoor units which still have 240v switched on. But the indoor unit will not operate with the 240v off & remains at standby untill 240v is switched back on.

Most other VRV / VRF systems use 5 - 12v d/c comms which is too low voltage to drive the EEV so they must stop on a fault instead to prevent liquid flood back.

[brunstar]

The Daikin VRV system has no way to shut down the EEV when 240v switched off at the indoor unit.
The indoor unit control circuit board goes dead & the outdoor unit cannot communicate with the indoor unit.

In this case if the indoor unit was operating with an open possition at the EEV then with 240v off then liquid will flood through this unit & liquid flood back to the outdoor unit.

So the system stops on a comms fault to force you to investigate & switch 240v power back on at all indoor units.

Mitsubishi City Multi overcome this by using 30v dc communication voltage.
In this case when 240v is switched off at any indoor unit the indoor unit can use the 30v communication voltage to shut down the EEV instead. So the system is safe & no risk of liquid flood back & the system does not need to shut down on any fault.
The outdoor unit still has full communication with the indoor unit with 240v off & the outdoor unit continues to operate with the other indoor units which still have 240v switched on. But the indoor unit will not operate with the 240v off & remains at standby untill 240v is switched back on.

Most other VRV / VRF systems use 5 - 12v d/c comms which is too low voltage to drive the EEV so they must stop on a fault instead to prevent liquid flood back.

Daikin have the exact same additional printed circuit board to over come this as stated above.

[Thermatech]

City Multi dont need any extra circuit board & have been like this with 30v d/c control voltage since last 17 years.

Standard operation is to close LEV valve using 30v d/c when 240v power is switched off.

Some contractors opt for low cost time clock control by using time clock & contactor for 240v ring main to the indoor units.
Set the indoor units for auto restart & when 240v ring main come back on all the indoor units operate.

No need for any extra circuit boards or wiring because the units will do this as standard out of the box.

BTW
How much does the Daikin optional circuit board cost for each indoor unit ?

[brunstar]

City Multi dont need any extra circuit board & have been like this with 30v d/c control voltage since last 17 years.

Standard operation is to close LEV valve using 30v d/c when 240v power is switched off.

Some contractors opt for low cost time clock control by using time clock & contactor for 240v ring main to the indoor units.
Set the indoor units for auto restart & when 240v ring main come back on all the indoor units operate.

No need for any extra circuit boards or wiring because the units will do this as standard out of the box.

BTW
How much does the Daikin optional circuit board cost for each indoor unit ?

Not too sure about the cost but realistically, it should only be needed in a multi tenanted building where they are sharing the same VRV systems, where there is a possibility of them turning their mains supply off.

[matt.yelland]

Hi all,

Thanks for the replys.....

It makes sense, thanks. Its a Waitrose site in Southend, Essex.

CLK Greg, they are switching the unit off in the staff canteen as it is blowing onto their heads... All together,,, Arrrr.

[matt.yelland]

The Install was done by the Install part of the company, we dont have the contract, but got asked to go back in and look at the problem. With regards to the spurs, if the do carry on switching them off, I will be changing them over