> If the blower is used to cool a tube pa the thermostat detection
> hardware is probably way to slow.
I was assuming a SS PA, but maybe that was a mis-assumption.
> Many vane indicators are of the long arm micro switch type. Easy
> enough to make your own but you can probably find them through
> companies like McMaster, C&H Sales Company, Grainger (all in
> Southern California) and many Heating & Air Conditioning Supply
> Stores.
I hate vane switches, having seen way too many failures over the years.
Vanes breaking off, microswitches getting stuck due to all of the gunk that
accumulates, etc. Good transmitters use differential pressure sensors to
measure the difference between the two halves of the tube compartment. Too
much differential and you've got a blockage in the tube fins or socket. Not
enough differential and either the blower isn't running, the intake filter
is clogged, or the chimney is blocked. I always monitor stack temperature
too as a backup.
For a SS PA, I still think a thermostat is the most reliable.
I had a 5kW watt FM transmitter that somebody bypassed the air interlocks
on. The squirrel cage blower lost a blade and jammed up. Looked like a
miniature version of Cheryobyl in there after all was said and done...and
off to the scrap yard it went (it was 30 years old and due for retirement
anyway).
--- Jeff
