We have a thirty year old gravity system, with an Ideal Concord WRS 255A
boiler and a Switchmaster 350 timer/controller.
At the moment the temperature of the hot tap water can only be the same as
the radiator water temperature, in the colder months this is really too hot
Is there any way to adapt/add to the system to give us independent
temperature control for the tap water?
IANA plumber, but it sounds a simple job of adding a motorised valve in
the gravity loop to the hot water tank heat exchanger, controlled by a
thermostat on the tank. That will limit the hot water to be the lesser
of the boiler thermostat and the thermostat setting. The valve and
thermostat could both be in the airing cupboard, next to the tank and
get a supply from a spur off the immersion heater - so it may be dead
easy and quick to do.
Depending on the system, you may want to use a two-port valve, so the
flow is diverted from going through the hot water heat exchanger, into a
"short-circuit" additional pipe that returns the water to the boiler.
Putting a manual valve in that additional pipe will let you set the flow
to the lowest level that works. This basically leaves the entire system
working as before - but with the heating water going through the pipe,
rather than through the heater exchanger in the tank. You could even
consider putting a heated towel rail in the pipe - I do like nice hot
A couple of things. Best practice says all the boiler controls should be
turned off by one switch and immersion heaters should not really have things
spured off them (even small loads)
You would need a diverter valve not a 2 port valve for that :) (A typo I
It is still very inefficient. The boiler would be cycling on and off and
wasting gas when the tank is up to temperature but the boiler cools down and
also hot water is still being produced even if you just want the radiators
on. Also look at lagging an uninsulated hot water tank if it is not already
lagged. The savings are quite good.
The C plan on the link below is the minimum you should be looking at.
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