Received my new thermostat today and planning on fitting it this evening.
Couple of quick questions...
Firstly, the old thermostat had marked on it 16A 250V~ and T107oC. I assume
that means that it can switch 16A at 250V AC and switches at 107oC. The new
one (the part suggested by Baxi Spares and KeepTheHeatOn.com) has lots of
figures on it (with what appear to be first 3 chars of part number) but the
one for this part says 2(2)A 250V~ 90oC. Can I assume that this switches 2A
@ 250V AC and switches at 90oC? Seeing as Baxi said this was the part, I'm
tending to believe them that 2A switching is okay - and I guess that it just
means that the water reaches 90oC rather than 107oC now? Does this sound
Secondly, I drilled out the old siezed probe and the hole is now nice and
clear. I used an 8mm drill and it fitted fine. 7mm was too small and 8mm
was tight, but not too tight. This new probe is just under 8mm in
diameter - so it should fit. My only question is whether I just insert it
or whether I need to put anything like heat transfer stuff. From memory,
when a similar probe was removed from a similar Baxi boiler it was dry
without anything on it - so I'm assuming that's right - but I just wanted to
To send email to me - remove references to NoSpam, and Spammer from my email
Well, I replaced the thermostat and it is working fine now. Noticed that
its short cycling far more than it used to. Its not a room thermostat
problem as it was constantly calling for heat, its that the new thermostat
is switching off when it reaches temperature and then switching on again
about 1 minute later. Still, not bothered too much with it.
Anyway - I noticed when I inserted the thermostat probe that there were
small droplets of rusty water clinging to the sides of the hole. Either its
condensation or its leaking slightly. Seeing as the old one siezed in
there, I guess it was doing it before, and just was kept hot so water never
had a chance to sit there. I'm planning on removing the probe every so
often and cleaning the hole so this new probe doesn't seize as well. Sound
On Wed, 03 Dec 2003 09:46:19 +0000, David Hearn wrote:
I'd make sure the water is moving around well in the system.
How long do you intend keeping the old boiler going?
If you do have a small leak in the sensor pocket on the main heat
exchanger this is all reason to change it next summer.
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Well, everything appears to be working fine - rads are getting nice and hot
and the house is warm, so I doubt there's any problem in the water flowing
How long to keep it going? Well, the truth is as long as possible. I have
no plans on replacing the boiler for another few years - though that doesn't
mean it won't give up the ghost before then!
Obviously, if I had the money to do it, I'd get it changed ASAP - however
our situation is that we just don't have the money to spent on it - at
least, not unless it died and wasn't repairable. I guess that's the joys of
a mortgage in Guildford and a baby on the way... ;)
The thermostat switches the gas valve on your boiler** - which is very
unlikely to require more than 2 amps - so the one you have should be fine. I
don't think that you can deduce anything about the switching temperature
from the hieroglyphics in the part number - the old one certainly didn't
switch at a water temperature of 107 degC, by which time it would be well
and truly boiling! If it's a boiler stat, and if it fits, it should do the
job. I assume that the end with the electrical contacts has a knob which you
can twiddle to set the switching temperature?
It's a long time since I fitted one of these, but I seem to remember that
you are supposed to use some conducting paste to make sure that the bulb
makes good thermal contact with the pocket in the heat exchanger.
** The term "boiler" is somewhat of a misnomer - since if it *boils* the
water it is malfunctioning! A flow temperature of around 80-85 degC is what
you need for the central heating.
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