A/C internal unit freezing?
 

Hi,

One of those small wall mounted Season A/C units suffering lots of ice
formation upon the heat exchanger matrix. The diagnosis is that the
system needs to have the gas topped up.

Being as I am the type of character who likes to understand the logic
behind the diagnosis, rather than just accept it... Why does the ice
form if the gas is low?

My problem with the diagnosis is that if the gas were low, then surely
the chilling effect on the internal matrix would generally be poorer.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org

In article ,
Harry Bloomfield writes:
Hi,

One of those small wall mounted Season A/C units suffering lots of ice
formation upon the heat exchanger matrix. The diagnosis is that the
system needs to have the gas topped up.

Sounds like BS to me.
It should have a temperature sensor on the heat exchanger to detect
freezing, which should switch it off. Cause might be airflow blocked,
or operating it when air temperature is well below its designed min
operating temperature.

--
Andrew Gabriel

Andrew Gabriel explained on 07/02/2005 :
In article ,
Harry Bloomfield writes:
Hi,

One of those small wall mounted Season A/C units suffering lots of ice
formation upon the heat exchanger matrix. The diagnosis is that the
system needs to have the gas topped up.

Sounds like BS to me.

...and me too.

It should have a temperature sensor on the heat exchanger to detect
freezing, which should switch it off. Cause might be airflow blocked,
or operating it when air temperature is well below its designed min
operating temperature.

They do sound like more logical reasons, thanks..

--


--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org

"Harry Bloomfield" wrote in message
...
Hi,

One of those small wall mounted Season A/C units suffering lots of ice
formation upon the heat exchanger matrix. The diagnosis is that the system
needs to have the gas topped up.

Being as I am the type of character who likes to understand the logic
behind the diagnosis, rather than just accept it... Why does the ice form
if the gas is low?

My problem with the diagnosis is that if the gas were low, then surely the
chilling effect on the internal matrix would generally be poorer.

--


--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org

The temp drop is caused by expansion of pressurised gas into a lower
pressure area through a fixed or sometimes (rarely) variable tiny hole. If
the pressure after the hole is lower than it should be (due to low gas) then
the expansion rate is higher and the temperature lower and the evaporator
freezes. This is easy to prove by overfilling a system, whereby it ceases
to work, since the high and low pressures are the same. Cheaper units do
not have a sensor to detect ice build-up.

Get an engineer to put the gauges on and the problem is very obvious. Or
buy your own gauges and a bottle and fill it yourself. (read a book on safe
procedures first.)

mrcheerful

mrcheerful
. brought next idea :
Get an engineer to put the gauges on and the problem is very obvious. Or buy
your own gauges and a bottle and fill it yourself. (read a book on safe
procedures first.)

Thanks for the explanation as to how, that does seem to hang together
now.

No need for me to worry about fixing it, a specilist engineer will
attend to it. I just wanted to understand why it should happen and
confirm we had the correct diagnosis.

--


--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org