Having just moved into this house I have not fully had time to explore
the central heating system yet, so details might be a little bit
brief..

But hopefully someone may have had this problem before!

Normal (not combi) potterton bolier in the kitchen that looks a good
10-15 years old, with hot water tank upstairs.

Timer is one of the really old fashined ones with the red/blue pins
for on/off on the dial, and thermostat in the living room.

Problem..

Even with thermostat down as far as it will go, radiators remain hot,
only way to cool them down is to turn off the central heating fully.
Have not yet confirmed whether they cool down if we turn c/h off but
leave water on... thats next on my list!

(When you turn the thermostat up you can hear the pump start, but the
rads are hot anyway)

Given that the rads remain hot, even when the pump is not pumping,
could it be a faulty pump valve allowing hot water to circulate via
convection, or is likely to be more serious?

anyone else had this weird problem?

On 17 Mar 2004 02:14:41 -0800, in uk.d-i-y (Tony
Commander) strung together this:

Having just moved into this house I have not fully had time to explore
the central heating system yet, so details might be a little bit
brief..

But hopefully someone may have had this problem before!

Normal (not combi) potterton bolier in the kitchen that looks a good
10-15 years old, with hot water tank upstairs.

Timer is one of the really old fashined ones with the red/blue pins
for on/off on the dial, and thermostat in the living room.

Problem..

Even with thermostat down as far as it will go, radiators remain hot,
only way to cool them down is to turn off the central heating fully.
Have not yet confirmed whether they cool down if we turn c/h off but
leave water on... thats next on my list!

(When you turn the thermostat up you can hear the pump start, but the
rads are hot anyway)

Given that the rads remain hot, even when the pump is not pumping,
could it be a faulty pump valve allowing hot water to circulate via
convection, or is likely to be more serious?

Pumps don't have automatic valves. What sort of system have you got,
do you have a valve and possibly cylinder stat in the cylinder
cupboard or do you have a gravity system. If the latter it's more than
likely just convection from having the water on.
--

SJW
A.C.S. Ltd.

(When you turn the thermostat up you can hear the pump start, but the
rads are hot anyway)

Possible solutions:

1. Stick a zone valve on the heating circuit.

2. Stick a gravity (non-sprung) non return valve in the system. This may
require you to reverse the pipes (or simply pump direction if external to
boiler) if the pump is currently set to assist gravity convection, rather
than oppose it, and the convection flow is strong, as the convection flow
might actually be strong enough to open the NRV.

Christian.

Tony Commander wrote:
Having just moved into this house I have not fully had time to explore
the central heating system yet, so details might be a little bit
brief..

But hopefully someone may have had this problem before!

Normal (not combi) potterton bolier in the kitchen that looks a good
10-15 years old, with hot water tank upstairs.

Timer is one of the really old fashined ones with the red/blue pins
for on/off on the dial, and thermostat in the living room.

Problem..

Even with thermostat down as far as it will go, radiators remain hot,
only way to cool them down is to turn off the central heating fully.
Have not yet confirmed whether they cool down if we turn c/h off but
leave water on... thats next on my list!

(When you turn the thermostat up you can hear the pump start, but the
rads are hot anyway)

Given that the rads remain hot, even when the pump is not pumping,
could it be a faulty pump valve allowing hot water to circulate via
convection, or is likely to be more serious?

anyone else had this weird problem?

Do you have a pump? It sounds like it may be a gravity fed system. If so its
a lot older than 10-15 years, more likely to be 20-30 years. So probably the
boiler is near or at its end-of-life. Will be horribly inefficient too..

Pumps don't have automatic valves. What sort of system have you got,
do you have a valve and possibly cylinder stat in the cylinder
cupboard or do you have a gravity system. If the latter it's more than
likely just convection from having the water on.

bog standard gravity fed....

convection could heat most rads in the system then?

don't doubt you at all, but am shocked that they could get so hot
without phsically having water pumped through them...

hmmm, will have to check the temperature setting for the hot water
now, to see if i can turn that down in attempt to cool the rads down..

mind, it's better than freezing i guess, even if the gas bill could be
horrendous

On 17 Mar 2004 07:28:13 -0800, in uk.d-i-y (Tony
Commander) strung together this:

Pumps don't have automatic valves. What sort of system have you got,
do you have a valve and possibly cylinder stat in the cylinder
cupboard or do you have a gravity system. If the latter it's more than
likely just convection from having the water on.

bog standard gravity fed....

convection could heat most rads in the system then?

don't doubt you at all, but am shocked that they could get so hot
without phsically having water pumped through them...

hmmm, will have to check the temperature setting for the hot water
now, to see if i can turn that down in attempt to cool the rads down..

mind, it's better than freezing i guess, even if the gas bill could be
horrendous

If it's a bog standard gravity system the hot water temp will be
controlled by the boiler thermostat.
I didn't think that convection would heat the rads from cold but once
they're warm I suppose the convection is helped along a bit by this.
It does all depend on the actual piping of the system and the size of
it as well really.
--

SJW
A.C.S. Ltd.

"Tony Commander" wrote in message
om...
Having just moved into this house I have not fully had time to explore
the central heating system yet, so details might be a little bit
brief..

But hopefully someone may have had this problem before!

Normal (not combi) potterton bolier in the kitchen that looks a good
10-15 years old, with hot water tank upstairs.

Timer is one of the really old fashined ones with the red/blue pins
for on/off on the dial, and thermostat in the living room.

Problem..

Even with thermostat down as far as it will go, radiators remain hot,
only way to cool them down is to turn off the central heating fully.
Have not yet confirmed whether they cool down if we turn c/h off but
leave water on... thats next on my list!

(When you turn the thermostat up you can hear the pump start, but the
rads are hot anyway)

Given that the rads remain hot, even when the pump is not pumping,
could it be a faulty pump valve allowing hot water to circulate via
convection, or is likely to be more serious?

You say the pump is definitely not running when the system's providing hot
water only.

There are no zone valves (motorised valves) in the system?

You will, I expect, have 28mm / 1" pipework between the boiler and the hot
water cylinder.

Therefore (as others have surmised) the hot water is heated by gravity
circulation alone. Maybe there is some partial blockage in the hot water
pipework, encouraging water to circulate around the heating circuit? You
should have a non-return valve in a vertical section of the flow pipework
from the boiler to the HW cylinder - maybe this is partially blocked?

In the short term* you could try turning down the valves on all the
radiators so that they still heat up when they're supposed to i.e. the pump
is running, but discouraging gravity circulation.

* i.e. if it works, indefinitely :-)

Thanks to everyone for your help on this...

and to answer some questions, but not all as we couldn't experiment
with all ideas last night as once things had heated up, you have to
wait for them to cool down again before trying something else!

couldn't find any valves (unless they are hidden under the
floorboards) but certainly nothing near to either boiler, pump, or hot
water tank.

Certainly agree that the boiler could be 20-30 years old.. looks like
it could be - but when we moved in the plumber who's fitting our new
bathroom suite in a couple of weeks looked at the boiler and said -
'yeah, they're tops.. nothing to go wrong on them - so don't replace
it unless you have too' which implied it was old, but ok.

pump appears to drag water around the system (cold side of boiler) and
you can definitley feel it start when everything is cool and you turn
the thermostat up.

Just the hot water on, does heat most rads.. overriding the thermostat
for central heating.

anyway, we're going to replace the very old timer (to give independant
c/h and water heating) and have a digital thermostat...

only have the water heating for a couple of hours a day, as opposed to
most of the time we have the c/h on ( baby in the house so need to
keep it ticking over)

and hopefully the time that the water being heated 'overrides' the
central heating heat will be greatly reduced..

else it's going to be a rip out and replace i suppose...

else it's going to be a rip out and replace i suppose...

No. It sounds like you have a complete lack of zone valves. You need to add
some, and a cylinder thermostat. Does the hot water circuit have its own
pipes back to the boiler, or does it share the fully pumped ones for the
radiators?

Christian.

On 18 Mar 2004 01:49:50 -0800, in uk.d-i-y (Tony
Commander) strung together this:

couldn't find any valves (unless they are hidden under the
floorboards) but certainly nothing near to either boiler, pump, or hot
water tank.

If there were any they'd be by the cylinder, unlikely to be any if you
can't find them.

pump appears to drag water around the system (cold side of boiler) and
you can definitley feel it start when everything is cool and you turn
the thermostat up.

Sounds about right.

Just the hot water on, does heat most rads.. overriding the thermostat
for central heating.

anyway, we're going to replace the very old timer (to give independant
c/h and water heating) and have a digital thermostat...

Not without major repiping you won't, if you just replace the
programmer and stat you won't be able to do any more than you can now.
To be able to have independent control you need to upgrade the whole
system to a Y-plan or similar.

only have the water heating for a couple of hours a day, as opposed to
most of the time we have the c/h on ( baby in the house so need to
keep it ticking over)

and hopefully the time that the water being heated 'overrides' the
central heating heat will be greatly reduced..

else it's going to be a rip out and replace i suppose...

That's your only option really, if you want it to do anything
different to what it does now.
--

SJW
A.C.S. Ltd.

In an earlier contribution to this discussion,
Lurch wrote:


Not without major repiping you won't, if you just replace the
programmer and stat you won't be able to do any more than you can now.
To be able to have independent control you need to upgrade the whole
system to a Y-plan or similar.


No, the best bet is to go for a C-Plan (See
http://content.honeywell.com/uk/homes/systems.htm)

You can keep your existing pipework, just inserting a zone valve into the
gravity hot water system and adding a cyl stat. If you still get gravity
circulation through the radiators when the pump is not running, you'll also
need a null flow (anti-gravity) valve in the CH pipework.
--
Cheers,
Set Square
______
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