Plumbing: Hot water gravity system
David Cawkwell
I've recently replaced my cold and hot tanks moving them
from first floor bathroom to the loft. Previously if I switched the
boiler on I would have a tank of steaming hot water within
about an hour or so. Now I seem to get a few gallons of luke warm
water.
The system has two boilers an oil fired boiler the pipes of which
come into the house on the first floor and a rayburn.
Just after the pipe enters the house pipes from the rayburn joint the hot
water
boiler pipe so that the rayburn can be used to heat water. A few inches
after this
the pipes go up the wall and to the tank in the loft. I notice
that the from the boiler going up the wall to the loft is hot and the
returning
is cool which is what I was expecting. However feeling the pipe just after
the
rayburn joins these are both hot. The pipe going to the rayburn are both
hot.
Therefore I seem to be heating the rayburn rather than the water in the hot
water
tank (I did have the setting on the rayburn set to hot water so I changed
this
and may have sorted by problem I'm currently waiting to see. It depends
on if the dial on the rayburn actually opens and shuts a value on the
rayburn
like a radiator which I don't know)
Can anyone explain why the hot water from the boiler is choosing to decend
to the rayburn and heat it rather than ascent up the wall to the hot water
tank?
Could I put a value in the cold return to the rayburn so that it would
stop all flow this way if the rayburn is not on?
Thanks for any help.
David Cawkwell
system via a pump which is triggered by a thermostate on the rayburn.
I've closed the values on the pump and switched it off. But it apprears
that the heat from the boiler is going into the central heating
radiators rather than the hot water tank.
I suppose my question now becomes how can I integrate the rayburn into
the central heating and hot water system (separate systems). I am fairly
sure that if I cut the pipes leading from the rayburn to the central heating
pipes that the gravity feed hot water would start working.
"David Cawkwell" <da...@dcawkwell.freeserve.co.uk> wrote in message
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Dave Plowman
David Cawkwell <da...@dcawkwell.freeserve.co.uk> wrote:
> I suppose my question now becomes how can I integrate the rayburn into
> the central heating and hot water system (separate systems). I am fairly
> sure that if I cut the pipes leading from the rayburn to the central
> heating pipes that the gravity feed hot water would start working.
Gravity feed is a bit of a gamble. Sometimes even a minor alteration can
cause it to stop working. Personally, I'd convert to a pumped system -
it's far more tolerant of iffy pipe runs.
--
*Great groups from little icons grow *
Dave Plowman dave....@argonet.co.uk London SW 12
RIP Acorn
Robert Laws
> from first floor bathroom to the loft. Previously if I switched the
> boiler on I would have a tank of steaming hot water within
> about an hour or so. Now I seem to get a few gallons of luke warm
> water.
Let's look at this another way:
You have an oil-boiler and a rayburn at the same (ground) level
connected by a loop that goes up to the first floor level and down
again. From the top of the this loop goes a loop up to the calorifier
in the loft.
The upgoing part of the loop up to the loft is now not getting as hot
as it used to (being longer) so it is not conventing properly. Let's
pretend that loop to the loft is not there: the rayburn is now
behaving like a radiator in one of those convective systems where the
boiler is at the same height as the rads. To make such a system work
you have a loop in the flow-pipe from the boiler that goes up several
metres and then turns down again. There is some heat-loss in this
loop and the temp difference in the up and down branches makes the
convective pump that drives the water round round the system, even
though the rads are at the same height as the boiler.
I think that's what is happening.
Check valaves in the oil and rayborn branches should solve it as long
as they don't impede the flow too much in the forward direction.
RObert
David Cawkwell
Can I use check values in the pipes from the boilers?
Or are these non return values? Is there a difference?
From what I've read they look to be spring loaded would
a gravity system be strong enough to push these open?
If non return values are what I want can some one tell me where to
find them. My piping is 28mm.
"Robert Laws" <la...@bcs.org.uk> wrote in message
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IMM
> A few more questions
>
> Can I use check values in the pipes from the boilers?
> Or are these non return values?
Only if it is not in the line of the open vent.
> Is there a difference?
> From what I've read they look to be spring loaded would
> a gravity system be strong enough to push these open?
Spring loaded are no good for gravity. Gravity seated non-returns need some
pressure created via the heat in the boiler to open them. They usually open
eventually.
> If non return values are what I want can some one tell me where to
> find them. My piping is 28mm.
You may find it is better to have a 3-way valve (not mid-position) on the
piping between the two boilers. When energised the valve takes flow from
the oil boiler to the cylinder and not to the Rayburn. De-energised it
springs back to the gravity fed Rayburn.
Robert Laws
> "David Cawkwell" <da...@dcawkwell.freeserve.co.uk> wrote in message
> news:auhl73$mv8$1...@newsg3.svr.pol.co.uk...
>
One further thought: You don't say how well lagged the hot feed to
the loft is. If the lagging is poor you might find that improving it
will do the job.
Removing the lagging from the cold return from the loft moight also
help - to maximise the temperature difference between the two pipes
and thus maximise the circulation.
Robert
David Cawkwell
Simply switch the rayburn to another circuit which isn't used when the
rayburn
is not in use.
"IMM" <I...@NOOSSPPAM-IMM.com> wrote in message
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