(Clive Long,UK) wrote in message . com...
Hi,

Does anyone have experience of extraction fans that use the heat
from the outgoing air to warm the in-coming air? Hi,

Does anyone have experience of extraction fans that use the heat
from the outgoing air to warm the in-coming air?

I have 2 such systems one in my current place ... and one in the new build
that is coming to the end.
Both work are MHRV (Mechanical heat Recovery & Ventilation) ... suck air
from rooms with moisture or smells. ... utility, kitchen, wc's bathroom
.... plus over hob extract a swell.

This goes via filters into centrifugal fans pushing the air through large
plastic heat exchanger in the loft (aprox 1.5m x 0.6 x 0.6) ... and is then
expelled outside through a tile vent.

Incoming air comes in through filters through the exchanger into a separate
fan unit, and then through sound dampers before being distributed to all
other rooms.

In summer you flick a switch downstairs and it operates a bypass unit ..
taking heat exchanger out of the loop.

I have been running this system 24 Hr. a day for more then 20 yrs ..... no
faults, and the only problem is that if it close to freezing or below the
incoming air is too cold and I have turned it off .... probably only 3 or 4
nights in 20 years.

In the kitchen there is a 0-2 Hr boost that doubles extract in kitchen and
cuts it by half elsewhere, in the lounge there is a 0-4Hr boost switch that
does the same for supply air.
This system is made by Greenwood Airvac.


In my new build the design has moved on ... the ducts are flexible aluminium
rather than plastic, fully insulated. The incoming air goes through a 4
stage filter process then via an electrostatic filter which will take out
particles at the micron level (smoke dust, pollen etc.)

The heat exchanger has an electric pre-heater in the event of incoming air
being too cold, I also have a LPHWB (Low pressure hot water battery) this
is like a car rad with a 225mm pipe through it ... the heating system hot
water is circulated through this and therefore anytime the heating is 'on'
it will a also warm incoming air.
(I may think up a temp differential circuit to control this in the future
via a simple 2 port valve.)

The extract & supply is similar to before, the big benefit of the new system
is the greatly increased efficiency of the heat exchanger - now an aluminium
cross flow device, the fans are variable speed low current consumption
devices.

It also has an addition (or will have when I install it) of an air
conditioning unit, not big enough to provide full air-con, but it can drop
incoming temp by several degrees and dehumidify the air.

The system this time is supplied by Villavent http://www.villavent.co.uk/

They did the CAD design, I did the install.
They also supplied the central vacuum cleaner system.

I was so pleased with the system in current place that I had to have it in
the new build, it also allowed me to meet building regs ventilation
requirements without having to fit damn ugly trickle vents.


Rick