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jdunc2301
16-01-2015, 11:04 PM
Hi all,Could someone shed light on a Mitsi heavy hyper inverter.On a 16kw system the data I have shows a steady drop off in output down to -2'c, during this drop off the compressor is limited to a maximum 85Hz, once a temperature below -2'c is achieved the compressor is allowed to reach maximum of 120hz, this increases the output back to around 14kw. The output then drops off until around -20'c at which point the Kw output is 6-7..ish kw.Can anyone explain why? Or care to have a stab at it

install monkey
16-01-2015, 11:20 PM
on a hard wired controller you can see actual freq,lev position,coil temps and running current,lev position,
set the controller to work on the thermistor in the controller

jdunc2301
16-01-2015, 11:25 PM
It's not run by a controller...it seems to be done automatically on outdoor unit..

install monkey
16-01-2015, 11:32 PM
unplug the return air sensor and get a hard wired room sensor, external interface , get an eco controller on it- can do loads on it

install monkey
16-01-2015, 11:40 PM
page 117 system limits page 118 on adobe reader
on the indoor pcb main 1 not power pcb, terminal labelled CNT - your contacts for heat/cool fault
page 160 section W room temp compensation adjust it to 1 deg preset at 2

jdunc2301
16-01-2015, 11:42 PM
Yeah I'm gonna try a controller, but I don't understand why we would have such a drop off

install monkey
16-01-2015, 11:45 PM
hook a controller upto it and press the diamond button- you can adjust the indoor fan static pressure - maybe its been slowed down to prevent cold draughts- you can prog fixed /lock any of the louvres independantly

install monkey
16-01-2015, 11:53 PM
During heating, it is operated with the maximum required frequency until the indoor unit heat exchanger temperature
becomes 40C or higher.

Rob White
16-01-2015, 11:55 PM
Hi all,Could someone shed light on a Mitsi heavy hyper inverter.On a 16kw system the data I have shows a steady drop off in output down to -2'c, during this drop off the compressor is limited to a maximum 85Hz, once a temperature below -2'c is achieved the compressor is allowed to reach maximum of 120hz, this increases the output back to around 14kw. The output then drops off until around -20'c at which point the Kw output is 6-7..ish kw.Can anyone explain why? Or care to have a stab at it

Are you talking about in heating mode and ambient at -2 to -20 or
are you on about the evaporating temperature?

Regards

Rob

.

jdunc2301
17-01-2015, 06:54 AM
Yes in heating mode and outdoor air temp

Rob White
17-01-2015, 11:17 AM
.

I might be totally wrong about this, but is it anything to
do with what happens to moisture in air.

Ambient air is funny to control because above freezing it
reacts differently to the way it reacts below freezing.

Heatpumps work really well down to +5 and then under freezing
at about -2 they start to get really efficient again and it
is all down to what happens to moisture as it goes through the dew
point. Sensible and latent heat reductions ect.......

So I might be completely wrong but at +2 to -2 the heat pump will
ramp down to reduce temperature difference over the evaporator (outside cond)
and then when air temp is -2 it can ramp up to full power because
the moisture issue has gone.

At -20 the heat pump will struggle with heat exchange again so will start
to ramp down.

Only my thoughts and not an official answer, but I remember a conversation
with somebody once who designed heatpumps and he commented on the
fact that at +2 to -2 the heat pumps work differently because of what
happens to moisture in air.

He went on to explain about how they are actually more efficient at -2 than at
+5 because of the ice on the heat exchanger interfering with heat flow.

regards

Rob

.

jdunc2301
17-01-2015, 05:24 PM
Hi,

Seems like a good explanation, I have lowered the outdoor temperature using a variable resistor..no luck with that, there must be other sensors coming into play on this! I'll dig out the explanation from a manual and post it up..see if we can make sense of it!

install monkey
17-01-2015, 05:34 PM
jay, is this a foreigner? (cash job):p

jdunc2301
17-01-2015, 05:44 PM
Nooo, I'll explain out of a public forum