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Krups
13-07-2005, 06:53 PM
chigo ducted unit model KFR-150FhW
10.3 kw heating
9.8kw cooling..


Went to a nursery today, complaining rooms not getting cold enough;
on walking into the the 3 seperate rooms, i found they were pretty warm, even though 1 of the rooms was not used at the time.
each room has 3 supply grilles.(no extract?)
the remote control was set on 21c(not flashing), and it showed the room temp as being 29c(this was flashing and is the highest temp reading available for room).
manager told me its always been flashing on 29c.
Didnt have a thermometer to check air off at grills, but didnt feel cold enough.
Suction pressure is 80psig, and discharge was 130psig(sound abit high?), R22
suction was sweating.
Set remote to 18c made a little difference although nothing acceptable.
found that the extract ducts were left in the roof space. so this explains why the remotes always showing 29c ?
outdoor unit bottom fan is spinning fast throwing off alot of heat, although top fan is not spinning much...
could this be a problem? (fan speed controller?)

what would your next steps be from here ?

frank
13-07-2005, 07:15 PM
The outdoor unit only having the bottom fan running is not really a problem as the top fan cycles off to maintain liquid sub-cooling.

What other measurements did you take?


Suction pressure is 80psig, and discharge was 130psig(sound abit high?), R22
suction was sweating.

This does not make sense. On R22 with the suction sweating then I could accept 80psig as being a little high. But a discharge pressure of 130psig - way too low. With suction at 80psig I would expect the discharge to be nearer 275/300. Dont want to tell you how to suck duck eggs but are you sure you were not measuring the liquid line pressure?

More info is required.

If the ducted unit return air is drawing from the ceiling void then it can't possibly maintain any sort of room temp. I would expect it (in this current weather) to over cool the rooms as the return air sensor would only see the ceiling void temp. As you say, there aren't any return air grilles so none of the conditioned air is able to effect the sensor.

rbartlett
13-07-2005, 07:17 PM
don't worry Frank it's just over charged that's all...

cheers

richard

frank
13-07-2005, 07:21 PM
don't worry Frank it's just over charged that's all...

Not with a discharge pressure of 130psig it isn't :)

rbartlett
13-07-2005, 07:26 PM
Not with a discharge pressure of 130psig it isn't :)


that's because it's not discharge pressure as I will bet your next weeks wages he's on the suction and pre-expanded connections on the condenser...

it's over charged -I've seen it soooooo many times it's not funny any more..(well it is a little bit ;-)

cheers

richard

Krups
13-07-2005, 07:43 PM
lol it is funny, as i meant liquid line pressure, sorry for the confusion guys...
i did suspect overcharged, what should the suction be reading something more like 50/60 psi?

rbartlett
13-07-2005, 07:45 PM
lol it is funny, as i meant liquid line pressure, sorry for the confusion guys...
i did suspect overcharged, what should the suction be reading something more like 50/60 psi?

no more like 0-5 deg'c

cheers

richard

Krups
13-07-2005, 08:01 PM
haha my boss told it should be 50/60psi,
thanks for ur help guys, il see what they make of it...
ne1 know where to get a comparitor from ? :p

rbartlett
13-07-2005, 08:05 PM
The outdoor unit only having the bottom fan running is not really a problem as the top fan cycles off to maintain liquid sub-cooling.

What other measurements did you take?



This does not make sense. On R22 with the suction sweating then I could accept 80psig as being a little high. But a discharge pressure of 130psig - way too low. With suction at 80psig I would expect the discharge to be nearer 275/300. Dont want to tell you how to suck duck eggs but are you sure you were not measuring the liquid line pressure?

More info is required.

If the ducted unit return air is drawing from the ceiling void then it can't possibly maintain any sort of room temp. I would expect it (in this current weather) to over cool the rooms as the return air sensor would only see the ceiling void temp. As you say, there aren't any return air grilles so none of the conditioned air is able to effect the sensor.


frank the ceiling return is a mute point.

if used correctly it's a perfectly acceptable method..however it can be abused and spec'ed incorrectly in which case your concerns apply

cheers

richard

Krups
13-07-2005, 11:03 PM
mrmagiccooling =
no i fully understand what richard was saying,
just laughing due to the fact that i dont have a comparitor, and it just goes to show that although overtime im sure u can remember the most common temp/pressure conversions in your head, for a person like me a comparitor is an essential tool...
or how else am i sposed to memorise these things ?

:)

(ps it was the bosses son who overcharged the system in the first place but shhhhh)

frank
14-07-2005, 08:26 PM
just laughing due to the fact that i dont have a comparitor,

You should always charge the system to temperatures - not pressures :)

How can you attend a system and confirm it's correct operation without a comparator? How would you set the superheat? etc.

Brian_UK
14-07-2005, 10:59 PM
No compartitor, no employment. Get one from any wholesaler or gas supplier.

With the return air ductwork drawing air from the ceiling space instead of the conditioned space means that you are wasting energy. Also the airflow into each of the rooms will vary whenever someone opens any of the doors to relieve the pressure.

Krups
14-07-2005, 11:28 PM
thanks for ur reply brian, 1st thing 2moro im foning agas, see if i can get 1 out of them...