the whole system is working 3 port valve does the right thing when
told, thermostat on water tank does switch on and off if turned
manualy, pump is working, heating to rads works but....no hot water.

Hot water does flow into the tank and out of return pipe. both pipes
get hot, too hot to hold for very long but water in tank not heating

There is valve on the return pipe, currently this is fully open, should
this be closed to restrict the flow ? or is there some other problem.

Any advice appreciated?

On Mon, 27 Nov 2006 08:59:15 -0800, davem wrote:

the whole system is working 3 port valve does the right thing when
told, thermostat on water tank does switch on and off if turned
manualy, pump is working, heating to rads works but....no hot water.

Hot water does flow into the tank and out of return pipe. both pipes
get hot, too hot to hold for very long but water in tank not heating

There is valve on the return pipe, currently this is fully open, should
this be closed to restrict the flow ? or is there some other problem.

Any advice appreciated?

The valve could be broken in the mostly closed position (especially if it
a gate valve).

To hot to hold for very long (about 50-55C) the flow should be
scarcely touchable say around 70C and the return at least as hot as it is
now. So may be boiler thermostat nees to go higher.

Are there any dripping HW taps?






--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Ed Sirett wrote:
On Mon, 27 Nov 2006 08:59:15 -0800, davem wrote:

the whole system is working 3 port valve does the right thing when
told, thermostat on water tank does switch on and off if turned
manualy, pump is working, heating to rads works but....no hot water.

Hot water does flow into the tank and out of return pipe. both pipes
get hot, too hot to hold for very long but water in tank not heating

There is valve on the return pipe, currently this is fully open, should
this be closed to restrict the flow ? or is there some other problem.

Any advice appreciated?

The valve could be broken in the mostly closed position (especially if it
a gate valve).

To hot to hold for very long (about 50-55C) the flow should be
scarcely touchable say around 70C and the return at least as hot as it is
now. So may be boiler thermostat nees to go higher.

Are there any dripping HW taps?



Or is the tank just scaled up so much that its not transferring heat
properly?

In article .com,
"davem" writes:
the whole system is working 3 port valve does the right thing when
told, thermostat on water tank does switch on and off if turned
manualy, pump is working, heating to rads works but....no hot water.

Hot water does flow into the tank and out of return pipe. both pipes
get hot, too hot to hold for very long but water in tank not heating

Tank scalled up.

There is valve on the return pipe, currently this is fully open, should
this be closed to restrict the flow ? or is there some other problem.

Any advice appreciated?

New tank. Probably not worth trying to descale as it must be
quite old. If it's not old, then you may have been heating the
water up much hotter than required.

--
Andrew Gabriel

davem wrote:

the whole system is working 3 port valve does the right thing when
told, thermostat on water tank does switch on and off if turned
manualy, pump is working, heating to rads works but....no hot water.

Hot water does flow into the tank and out of return pipe. both pipes
get hot, too hot to hold for very long but water in tank not heating

There is valve on the return pipe, currently this is fully open, should
this be closed to restrict the flow ? or is there some other problem.

Any advice appreciated?

If the heat exchanger is effective, the return will come out at close
to the temp of the water in the tank, ie cool, and not hot. If it comes
out hot, theres little heat transfer to the tank of water. Presumably
either heavy scale or some kind of slime growth etc in the tank. Time
to replace the tank probably.


NT

thanks for these comments, I shoudl add that ti was working fine about
a week ago before i fitted a new 3 port valve, the new valve works as
does the stop cock on the return pipe, as did the heat transfer.

could air be preventing the heat transfer ?

could air be trapped within the heat exchanger?

is so how to get it out?

davem wrote:

thanks for these comments, I shoudl add that ti was working fine about
a week ago before i fitted a new 3 port valve, the new valve works as
does the stop cock on the return pipe, as did the heat transfer.

Ok, so it aint scale.


could air be preventing the heat transfer ?

no

could air be trapped within the heat exchanger?

not really

is so how to get it out?

the only other option I can think of is maybe its a very slow recovery
coil (very old tank) and youve got a hot water leak somewhere, so the
thing doesnt get a chance to heat up.

Cant say I really know exactly what the prob is tho.


NT