Daikin Atherma model EMRQ8AAY1

[Jayaka]

I was called to look at no heat coming from Rads. Initially there was an E5 fault so I checked the comp/inverter board to conclude the comp needs replacing.
I then coded out the faulty comp to run the left hand comp.
Here's the question I'm looking for help with

The left hand comp run and hot gas can be felt going down the pipework to the indoor unit and chilled air coming off both external coils. After a couple of mins a valve can be heard opening/closing and a rush of hot gas being directed into the left hand coil. So now we have warm air coming off the left hand coil and chilled air coming off the right. The hot gas going to the indoors down the pipe work becomes just warmish.
Any one got any ideas why hot gas is being diverted to the left hand coil?

Thanks

[seanf]

Is the left hand comp a fixed speed motor?
Could that be its way of capacity control? not enough heating required inside to run full whack.

[Jayaka]

thanks Sean,
the left hand comp is inverter driven.In theory once the faulty comp [right side] is coded out then it should run on the left only as an emergency mode. I'm wondering if it is going into defrost and that's why it's pushing hot gas into the left hand coil. Perhaps a faulty thermistor that is n't far enough out of range to throw up a fault code.

[seanf]

Be interesting to hear what you find.

[frank]

From vrv3 onwards, the defrost sequence was altered to allow individual coils to defrost seperately thus allowing heating to the indoor coils to continue. Prior to this, heating indoors stopped, sometimes leading to cold draughts and poor indoor temperature control.

I would start by checking your sensor readings (easy with a Service Checker) but by resistance without a checker.

Seems like the unit may be going into defrost.

The heat pumps are basically vrv with different software

[Jayaka]

That's really helpful.When i get back to site I will check the thermistors and report back

[Elizabeth]

Hey Guys,

The left-hand component operates through an inverter drive. The idea is that once the faulty component on the right side is addressed in the code, the system should function in an emergency mode using the left side alone. I suspect the system might be entering a defrost mode, causing it to push hot gas into the left-hand coil. It's possible that a faulty thermistor could be causing this without deviating far enough from the expected range to trigger a fault code.

[frank]

Hey Guys,

The left-hand component operates through an inverter drive. The idea is that once the faulty component on the right side is addressed in the code, the system should function in an emergency mode using the left side alone. I suspect the system might be entering a defrost mode, causing it to push hot gas into the left-hand coil. It's possible that a faulty thermistor could be causing this without deviating far enough from the expected range to trigger a fault code.

Hi Elizabeth
Welcome to the forum
Please see post number 5