In message , Brian Reay
writes

"raden" wrote in message
...
In message , Harry Bloomfield
writes
raden explained :
I sold someone a fan for his CH boiler a couple of months ago and he
swears that it causes RF interference. I sent him another one which he
says is OK. We've also changed his pcb for him (to eliminate the
possibility of it being a relay problem

Now given the fact that it's a shaded pole motor and the connections to
it are sound (i.e. electrically, it's just a coil of wire) does anybody
have an explanation ?

None... Except the connections were not in fact tight, or a fault on the
PCB.

Changed the pcb, checked the fan ctrl relay first

swapped the fan over several times

The fan works without generating RF when back at the factory

It's only when it's in the boiler


When you test it back at the factory, is it installed in way similar to in
the boiler?

It could be that the bonding arrangements are different

In which case, the other fan I sent him should suffer from the same
problem. The two fans are identical (FSVO of course). The wires coming
of the fans are of the same construction and are fast into the
connections to the coil.

(eg the bonding in
the troublesome boiler isn't so good) and the fan is marginal- OK in a well
bonded installation but not in a marginally bonded one.

To generate RF really requires a spark of some sort if it's coming from
50Hz. This would represent a loss which would present itself as a less
efficient fan motor (I would think) and therefore would not activate the
air pressure switch)

It's a total mystery
--
geoff