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Peter_1
25-01-2013, 09:12 PM
I have a RZQ200 on a OEM coil in an AHU which starts a defrost at an ambient of -5C, Te at -11C every 27 to 30 minutes but there's not a single drop of ice on the coil. The defrost then lasts >15 minutes and it takes then +/- 7 to 10 minutes before coil is hot enoiugh to start the fans.
What triggers faulty the defost in this case? Charge is OK.
We've taken IR-scan during the defrost and after 5 to 6 minutes, the whole coil still is at -1C. I have pictures of it.

flyinkiwi
25-01-2013, 09:16 PM
Faulty coil thermistor, perhaps?

Is your 4-way valve changing over correctly?

install monkey
25-01-2013, 09:29 PM
Freeze protection function
Start Te ≤ -1C for 40 minutes
accumulated
OR
Te ≤ AC for 1 minute
continuous
(Indoor decision)
Te ≤ -1C for 40 minutes
accumulated
OR
Te ≤ -3C for 1 minute
continuous
(Outdoor decision)
Te ≤ -1C for 40 minutes
accumulated
OR
Te ≤ AC for 1 minute
continuous
(Outdoor decision)
End Te > 7C for 10 minutes
continuously.
(Indoor decision)
Te > 7C for 3 minutes
continuously
OR
Te > 4C for 20 minutes
continuously
(Outdoor decision)
Te > 7C for 3 minutes
continuously
OR
Te > 4C for 20 minutes
continuously
(Outdoor decision)

Peter_1
25-01-2013, 09:29 PM
Thermistor was checked by Daikin itself and the 4 way is 100% working. It's the trigger for the defrost that botters me.

Peter_1
27-01-2013, 02:29 PM
I.M., what's Te ≤ AC for 1 minute?
As far as I can conclude now, there's no real detection if the coil is iced up at all. We can run under the present conditions at least 3 hours before we need a defrost. We're losing now a lot of energy and I'm wondering in how far this was considered in the overal COP of the machine!

marc5180
27-01-2013, 07:05 PM
Hi Peter I think AC is the 'timer A'. In other words what ever the defrost interval settings are at.
These can be changed by using 'mode 2' on the outdoor unit.

r.bartlett
27-01-2013, 08:07 PM
http://daikintech.co.uk/Daikin-Zoom/Split-Sky-Outdoor/RZQ-CY.html#

manual here

Peter_1
28-01-2013, 08:49 PM
http://daikintech.co.uk/Daikin-Zoom/Split-Sky-Outdoor/RZQ-CY.html#

manual here
Thanks Richard, I think I will need someone form Daikin to check and more specific to monitor while running at low ambients trying to analyze what triggers the un-needed defrost cycle wand why it last such a long time before we reach end defrost. There as too much variables to monitor finding out what's happening.

r.bartlett
29-01-2013, 02:01 PM
Are you sure it's defrost and not oil recovery ?

Peter_1
29-01-2013, 04:59 PM
It's 100% for sure a defrost Richard (even Daikin followed once this machine) + sign on remote controller indicates defrost + 4 -way valve reverses and we took several IR-pictures while unit defrosted. Can post those. Takes a long time before defrost ends: 29 minutes running, shut down for a defrost and then +/- 22 to 24 minutes before units blows heat again. Not that good for the SCOP or SEER I presume.

r.bartlett
29-01-2013, 07:05 PM
Most defrosts are a version of the old

instigate defrost
Time+ temperature

Terminate defrost
Time or temperature

If this isn't happening it's most likely the board...Rough part changers guess but from where I am sitting it's my best shot :-)