I now need to fit a pump and thermostat to an existing gravity fed
HW system (gas cooker/boiler cuts out occasionally before the tank is
really up to heat, so I suspect the gravity loop isn't that efficient
at moving the water round - it was OK through last winter, but we've
had a few cut-outs this summer) So... Can anyone suggest where to get the
thermostat from? I've only found tank thermostats when looking online
and really need something that I can fasten round the 28mm pipe that
comes out of the unit, with normally open contacts, which will close
(ie turn on the switch) when the pipe gets to a certian temperature
(thus supplying power to the pump) and breaks the contact when it falls
to a preset temperature (ie. some time after the boiler is turned off)
Also, the pumps I've seen (standard CH style pumps, any to avoid?) all
seem to have 22m connections, but I've seen isolating ball-valves which
are 28-22m conversions - I presume this won't really have any effect on
the flow through the system, given that it'll now be pumped...
Thanks for any advice,
is one example, but not the one I remember finding last year.
(I have an ancient one which is selectable for normally
open or normally closed, which in the end I got working.
I presume this is for hot water only, not radiators too).
Maybe I should have made myself a bit more clearer. This is a gas fired
range cooker which in addition to cooking, heats the hot water tank. It's
got nothing to do with central heating. The range replaced a coal fired
rayburn which was capable of boiling the water in the pipes. It was
installed in the winter and worked fine, but this summer it's cut-out a
few times because it's internal temperature sensor has gotten a bit too
hot. The manufacturer (Stanley) suggests a pump and a pipe thermostat
connected to the exit pipe, but when it was installed, both Stanley and
the plumber thought it would be OK with gravity feed only, as there was
an existing gravity feed system and pipe-work in-place. It was fine in
the winter, but not so fine in the summer. If the tank is full of hot
water and I run it off, it's also fine (but a waste of a tankfull of
hot water) Actually, it's not that hot which is why I'm thinking the
flow thorugh the gravity loop isn't that efficient.
The pipes go to the hot water tank upstairs through the tank coil and
back again. There is a separate heat-sink radiator in paralel with the
tank coil. There are a few more bends in the (28mm) pipe-work with the
new cooker than were in the old one, so maybe thats a factor.
I do also have a separate gas CH unit which can heat the tank via a 2nd
coil fitted in the tank, but thats fully programmable to work either CH or
HW or both. No point using it to heat the water when the cooker can do it.
Thanks to others for the links so far, but best I have is possibly:
If that has a normally open set of contacts which close when it reaches
the set-point I think I'll go for that.
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