John Rumm wrote:
On 27/10/2020 15:14, Theo wrote:
"Dave Plowman (News)" wrote:
If you have a well insulated house in the UK, just how often would you
need air-con?

The problem is heat sources inside the house. If it's 25-30C outside and
someone's had a shower, you're roasting a joint in the oven, and the kids
are using their 600W gaming PCs, that's heat input and nowhere for it
to go.

Plus solar gain (windows etc) can be a problem, even if you're well
insulated.

Not to mention that AC does mote than just cool - it also lowers RH
which can make a big difference to comfort levels, especially in a
typical hot wet UK summer.

And this is why you don't want an AC system which is "over-capacity".

A high capacity system drops air temperature rapidly. Once the
air gets to around 22C or so, you don't want to go lower
so that the AC won't be damaged at the coil (freeze up).

If you drop the capacity of the system, there is sufficient
time for the dehumidification effect to take place.

On my current system, when it was new, it would remove a
summers-day of heat in 3 hours. This is too fast. The
air would feel clammy (still has moisture).

Now that the machine has aged, it takes 7 hours this year
to do the same thing. Now the household RH drops to 40%
or so, and the air is both dry and cool at the end of
the process.

The trick then, is to estimate the capacity required,
but also compensate for the aging effects on the equipment.
The newer systems seem to be pigs in this regard (big
performance drop after being new). Refilling them with
R134, doesn't seem to help all that much. (The refilling
process just does not seem to be good for the
equipment - the compressor is running while the
technician weighs in a charge. The pressures on either
side of the compressor are checked to determine when
sufficient material is inside the unit.)

Paul