Daikin E4

[Slim R410a]

Been to a server room callout today, system installed by myself 18 months ago. FAQ71B & RZQ71B9.
Got called out two weeks ago to the E4 fault but when got there customer had restarted sytem and it was running away as normal. So I ran up fault history, cleared the E4 by holding on/off, did a complete restart and all was fine again, waited around for an hour, no faults, outdoor leds all ok. System showing all signs of a full charge of refrigerant.
Got there today with the E4 back up and outdoor red led solid (protection device activated) went though E4 flow chart checked dc voltage (X64A on pcb) going to l.p sensor was 5V, coming back, 0V. Spoke to daikin tech he thought was definately faulty l.p sensor.
So my question is, has anyone had this before and if so is it a case of complete recovery or is the l.p sensor somthing that just screws on and off quickly?

[Obi Wan]

Hi slim
I am 80% sure that on the B9 models the pressure sensor is a screw on compression fitting. An easy was to tell is if there is a brass nut between the pressure sensor and the piping stub. If yes than you can remove the pressure sensor without having to recover the gas. If not then it’s a braze in type. (like on the new RZQ – C series)

Happy New Year

Obi Wan

[hyperion]

If you go onto the Daikin Extranet, you will be able to access the exploded diagram. I think that this unit has a mechanical fitting LP sensor. It is a fairly common failure, the insulation on the sensor breaks down and moisture gets in causing intermittent failure. Daikin spares department may be able to help identify which type of fitting it has before you order it.

[puddleboy3]

Can you tell us what the pipe length is between the indoor and outdoor?

[Slim R410a]

Thanks for the replies, yes there is a brass nut inbetween the sensor and piping stub so thats good I wont have to recover.

Pipe run from what I can remember, allowing for bends etc, is around 35m. Additional 410a charged was 500g, as per chart on outdoor unit cover: +500g for 31-40m pipe run.

[nicolacozma]

Happy New Year!

If this phenomena still remain after LP sensor replacement then maybe there is some moisture in the refrigerant system. If LP value drops below 1,5bar then you will get E4 allarm.

All the best,
Nicola

[brunstar]

i don't think it will be the lp sensor at fault.
check that the expansion valve is opening and closing ok and check the reading of the indoor coil thermister, as the system is in a low humidity application the indoor coil will not evaporate the refrigerant quick enough causing the exv to close off prematurly to cause this, it could also be a blockage in the filter before the expansion valve or a refrigerant leak.
Also make sure that the indoor unit is not short cycling as this will cause the exv to close off prematurely.

[puddleboy3]

i don't think it will be the lp sensor at fault.
check that the expansion valve is opening and closing ok and check the reading of the indoor coil thermister, as the system is in a low humidity application the indoor coil will not evaporate the refrigerant quick enough causing the exv to close off prematurly to cause this, it could also be a blockage in the filter before the expansion valve or a refrigerant leak.
Also make sure that the indoor unit is not short cycling as this will cause the exv to close off prematurely.

Even if this system is installed within a low humidity area you would be able to adjust the EDP setting as this unit is desgined for use in computer rooms etc.

[brunstar]

Even if this system is installed within a low humidity area you would be able to adjust the EDP setting as this unit is desgined for use in computer rooms etc.

EDP true true yes i just assumed that this was already set but you should never assume..

[Slim R410a]

Fitted the new low pressure sensor on monday, cleared the E4 and everything has been back to normal.
In the end i decided to reclaim the lot to change the sensor, I dont think I would of have to but wasn't 100% sure of the fitting it was like a T piece inside the brass nut?? and this would also rule out any signs of a leak. Reclaimed 3.3kgs which was exact charge.
Another point aswell I recovered from the suction shut off valve schreader, when my gauges got to zero I'd only got around 2kg in the bottle. Then I remember reading a thread on here about someone getting nitro trapped on an RZQS condenser, so i put gauges onto the suction port pass the eev and there was gas stuck inside. Powered up the outdoor which obviously opens the eev and reclaimed the remaining 410!
Passed nitro through every schreader to double check was ok and there were no signs of a blockage, so in this case was definately a faulty sensor!

[Brian_UK]

Thanks for the update, glad that you've got it sorted.