"Paul Coyne" wrote in message
.. .
snipped
So it looks like the way forward to be compliant is to put the towl
rails
onto the heating circuit and work out how much pipe would be needed
to
lose
10 degrees of temp in a bypass loop and just have a big long pipe run
off
the bypass valve...
Paul
Yes !!! Someone's got the idea.
Pain in the butt though....
If it's just 4 metres it's not so bad; I've just got visions of this
stuffing great pipe looping it's way round the house to burn off the
required heat...
;-
Paul
But if there is a stuffing big radiator within the loop, then heat is burned
off easily and then the pipework doesn't have to be all that long. All a
manufacturer asks is for you to make an unrestricted loop of some kind,
which will dissipate a required amount of heat so that if a fault occurs on
the boiler itself, the heated water is not circulating directly back into
the boiler to quickly and is loosing a required amount of heat to stop it
steam venting or splitting through the build up of pressure. I've actually
seen it done with a heated towel rail on the other side of a wall from the
boiler and no more than four feet away in the actual run of pipe, but it was
enough to satisfy the requirements for that system.
Because it asks for a loop, the loop itself doesn't have to be a loop of
pipework running all around the house. All it is, is an unrestricted
circuit which will dissipate the heat required and do it by what ever means
possible for the situation. A valve doesn't have to be used either, as a
normal open unrestricted loop will more than usually suffice for a domestic
system.
How I was taught to do it was, place a circuit on the flow and return pipe,
but make it so that, that one particular circuit heated when a call for heat
request was given to the boiler even if the motorised valve or pump failed
to activate. The easiest way to do this, is to install a three port valve
that when de-energised, defaults to room heating closed and water heater
open. This makes the circulating coil for the hot water storage tank your
unrestricted loop. It is the perfect unrestricted loop between flow and
return with a perfect medium for dissipating heat from the boiler. Yes, you
got it. The "Water" in the storage tank.
Tell me how many times you've turned a conventional central heating system
on and not wanted it to heat the water you use at the sink or in the bath.
You've probably wanted hot water without heating the radiators in the house,
so you would fit a motorised valve to the radiator circuit to stop the flow
from circulating around the house, which is what it is supposed to do. But
I'd really like a show of hands on how many people call for room heating and
don't want the hot water tank heated to go with it.
The thermostat on the hot water storage tank is fixed in line with the three
port motorised valve and when it call for heat when only hot water is
required, then the valve is already in the default open position for that
circuit, so the valve doesn't have to move at all. When a call for heat is
made by both the room heating circuit and the hot water, then the valve
moves to mid position to give both circuits a flow of water. When the
thermostat on the tank reaches its setting, it then moves the valve to close
only the hot water side to stop the flow to the tank. This would only
happen when both the heating and hot water setting is selected on the
programmer or timer system by the connections to the switching of the valve
itself. When only the hot water is on, then the tank 'stat tells the boiler
to shut down.
We have a water flow underfloor heating system and it works perfectly by the
method I've just described above. It also exceeds the manufacturers
requirement of heat dissipation by a few degrees using the open loop through
the hot water storage tank, and our tank is only a couple of yards away from
the boiler. The main test on our system, consisted of the engineer
by-passing the thermostat from the boiler and allowing the system to run
itself silly for about half an hour with only the unrestricted hot water
loop in play, no heating circuit.
I'm glad to say that the water returning to the boiler never got hotter than
83 degrees centigrade, which I'm now reading from the pass certificate from
Scottish Gas, so it never allowed the boiler to boil already boiling water,
but we did have clouds of steam blowing out through the expansion pipe of
the hot water storage tank and the floor did heat slightly, and only
slightly, under the first half of the kitchen floor. The system was given a
good pass certificate and has been running merrily and economically for many
years.
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