Dear all

I have a conventional heating system, comprising an Ideal gas boiler,
with gravity flow and return (hot water circuit) and pumped flow and
return (central heating circuit).

I'm getting no hot water out of the taps at present, central heating
is ok.
Can anyone advise me on how to fix this please?

Thermostat on boiler is ok, and the control panel is asking for hot
water as it should. The gravity flow pipe from the boiler is not
heating up. So I guess it might be the heat exhanger that's the
problem?

Yours in hope
John

"John Andrews" wrote in message
m...
Dear all

I have a conventional heating system, comprising an Ideal gas boiler,
with gravity flow and return (hot water circuit) and pumped flow and
return (central heating circuit).

I'm getting no hot water out of the taps at present, central heating
is ok.
Can anyone advise me on how to fix this please?

Thermostat on boiler is ok, and the control panel is asking for hot
water as it should. The gravity flow pipe from the boiler is not
heating up. So I guess it might be the heat exhanger that's the
problem?

It looks like two points:

1. sludge in the gravity flow and returns

2. An air lock ( is there an air vent above the gravity pipe to the
cylinder)

Get rid of the gravity DHw and make the system more efficient by fully
pumping.

In an earlier contribution to this discussion,
John Andrews wrote:

Dear all

I have a conventional heating system, comprising an Ideal gas boiler,
with gravity flow and return (hot water circuit) and pumped flow and
return (central heating circuit).

I'm getting no hot water out of the taps at present, central heating
is ok.
Can anyone advise me on how to fix this please?

Thermostat on boiler is ok, and the control panel is asking for hot
water as it should. The gravity flow pipe from the boiler is not
heating up. So I guess it might be the heat exhanger that's the
problem?

Yours in hope
John

Does the CH use entirely separate pipes from the HW, connected to the
opposite side of the boiler?

Do you have a small fill & expansion tank in the attic, with pipes connected
into the HW circuit? Does it have any water in it?

There is a possibility that the ball valve may have stuck, allowing the
level to drop through evaporation/leaks etc. to the point where there's an
air lock in the HW circuit.

If this is the case, freeing the ball valve should fix it.

Failing that, are there any controls on the HW circuit - such as a motorised
valve driven by a cylinder stat to stop the HW from getting too hot?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

In article ,
"IMM" writes:

"John Andrews" wrote in message
m...
Dear all

I have a conventional heating system, comprising an Ideal gas boiler,
with gravity flow and return (hot water circuit) and pumped flow and
return (central heating circuit).

I'm getting no hot water out of the taps at present, central heating
is ok.
Can anyone advise me on how to fix this please?

Thermostat on boiler is ok, and the control panel is asking for hot
water as it should. The gravity flow pipe from the boiler is not
heating up. So I guess it might be the heat exhanger that's the
problem?

It looks like two points:

1. sludge in the gravity flow and returns

2. An air lock ( is there an air vent above the gravity pipe to the
cylinder)

3. Ball valve has got stuck up in header tank (smaller
tank), and water level has dropped below the top of the
hot water cylinder coil so it no longer circulates.
Check the small header tank.

--
Andrew Gabriel

"Andrew Gabriel" wrote in message
...
In article ,
"IMM" writes:

"John Andrews" wrote in message
m...
Dear all

I have a conventional heating system, comprising an Ideal gas boiler,
with gravity flow and return (hot water circuit) and pumped flow and
return (central heating circuit).

I'm getting no hot water out of the taps at present, central heating
is ok.
Can anyone advise me on how to fix this please?

Thermostat on boiler is ok, and the control panel is asking for hot
water as it should. The gravity flow pipe from the boiler is not
heating up. So I guess it might be the heat exhanger that's the
problem?

It looks like two points:

1. sludge in the gravity flow and returns

2. An air lock ( is there an air vent above the gravity pipe to the
cylinder)

3. Ball valve has got stuck up in header tank (smaller
tank), and water level has dropped below the top of the
hot water cylinder coil so it no longer circulates.
Check the small header tank.

Good point. Usually the highest rad is above the coil, and if this was the
case the upper rads would not work. Maybe that the coil is above the
highest rads.

"Andrew Gabriel" wrote in message
...
In article ,
"IMM" writes:

"John Andrews" wrote in message
m...
Dear all

I have a conventional heating system, comprising an Ideal gas boiler,
with gravity flow and return (hot water circuit) and pumped flow and
return (central heating circuit).

I'm getting no hot water out of the taps at present, central heating
is ok.
Can anyone advise me on how to fix this please?

Thermostat on boiler is ok, and the control panel is asking for hot
water as it should. The gravity flow pipe from the boiler is not
heating up. So I guess it might be the heat exhanger that's the
problem?

It looks like two points:

1. sludge in the gravity flow and returns

2. An air lock ( is there an air vent above the gravity pipe to the
cylinder)

3. Ball valve has got stuck up in header tank (smaller
tank), and water level has dropped below the top of the
hot water cylinder coil so it no longer circulates.
Check the small header tank.


You got to it first Andrew. It was (is) a common problem with gravity
primary hot water and pumped CH systems. It sometimes occurred with an
intermediate stage where the HW only warmed up when the heating was on and
provided just enough water movement within the boiler to persuade the
primary to move sluggishly before giving up entirely.

In an earlier contribution to this discussion,
John wrote:


You got to it first Andrew. It was (is) a common problem with gravity
primary hot water and pumped CH systems. It sometimes occurred with an
intermediate stage where the HW only warmed up when the heating was
on and provided just enough water movement within the boiler to
persuade the primary to move sluggishly before giving up entirely.

Almost.g

[My post suggesting the same thing was actually sent 12 minutes earlier than
Andrew's. Let's hope we both got it right!]
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

3. Ball valve has got stuck up in header tank (smaller
tank), and water level has dropped below the top of the
hot water cylinder coil so it no longer circulates.
Check the small header tank.


Good idea, I hadn't thought of that. But no, that's not the problem.
Water level and ball valve are fine - in fact I replaced the ball
valve assembly about six months ago. The important point is that the
hot water supply to the cylinder is not working - i.e. cold.

Cheers
John

It looks like two points:

1. sludge in the gravity flow and returns

2. An air lock ( is there an air vent above the gravity pipe to the
cylinder)

Get rid of the gravity DHw and make the system more efficient by fully
pumping.

Thanks for your ideas. I guess with (1) I can have a go at
disassembling to check it out. There is a vent, so that takes (2) out
of the picture, right?

Excuse my ignorance, but why is a pumped system more efficient? Surely
by definition an unpowered system, if it's working ok (which it's not
obviously), is more efficient?

Cheers
John

Does the CH use entirely separate pipes from the HW, connected to the
opposite side of the boiler?

Yes and yes. Gravity flow and pumped return go in one side, pumped
flow and gravity return in the other.

Do you have a small fill & expansion tank in the attic, with pipes connected
into the HW circuit? Does it have any water in it?

Yes and yes. Ball valve/expansion tank are A-OK.

....

Failing that, are there any controls on the HW circuit - such as a motorised
valve driven by a cylinder stat to stop the HW from getting too hot?

There's nowt apart from what's in the boiler unit itself. I'm
beginning to feel like I should take this apart and see, but as much
steer as I can get from the knowledgable folks out there the better!

Cheers

In article ,
John Andrews wrote:
I have a conventional heating system, comprising an Ideal gas boiler,
with gravity flow and return (hot water circuit) and pumped flow and
return (central heating circuit).

I'm getting no hot water out of the taps at present, central heating
is ok.
Can anyone advise me on how to fix this please?

Thermostat on boiler is ok, and the control panel is asking for hot
water as it should. The gravity flow pipe from the boiler is not
heating up. So I guess it might be the heat exhanger that's the
problem?

No - the heat exchanger is the same one as for the heating. Only different
feeds off it.

Has it got provision for bleeding? Any air in there? Has the system been
worked on recently necessitating draining down?

If the system once worked normally, then it can only be:-

Airlock caused by the water level being too low at some time.
Blocked pipe.

--
*A conscience is what hurts when all your other parts feel so good *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
John Andrews wrote:
Thanks for your ideas. I guess with (1) I can have a go at
disassembling to check it out. There is a vent, so that takes (2) out
of the picture, right?

These can block. Check there is water there by partially dismantling.

--
*Sometimes I wake up grumpy; Other times I let him sleep.

Dave Plowman London SW
To e-mail, change noise into sound.

In an earlier contribution to this discussion,
John Andrews wrote:

3. Ball valve has got stuck up in header tank (smaller
tank), and water level has dropped below the top of the
hot water cylinder coil so it no longer circulates.
Check the small header tank.


Good idea, I hadn't thought of that. But no, that's not the problem.
Water level and ball valve are fine - in fact I replaced the ball
valve assembly about six months ago. The important point is that the
hot water supply to the cylinder is not working - i.e. cold.

Cheers
John

I think that you may have misunderstood the point. You should have *two*
header tanks - a big one and a little one.

The big one feeds cold water into the bottom on the cylinder expelling hot
water out of the top to your hot taps. Is this the one with the new ball
valve?

The small one keeps the primary heating circuit full of water. This is the
water which circulates from the boiler by gravity to the heating coil inside
the hot cylinder, and pumped action to the radiators. If the water in *that*
circuit becomes depleted for some reason, the first thing to suffer will be
the gravity circulation to the heating coil - followed by the central
heating.

Are you *sure* that you have located the *small* tank, and that it has water
in it?

--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

"Set Square" wrote in message
...
In an earlier contribution to this discussion,
John wrote:


You got to it first Andrew. It was (is) a common problem with gravity
primary hot water and pumped CH systems. It sometimes occurred with an
intermediate stage where the HW only warmed up when the heating was
on and provided just enough water movement within the boiler to
persuade the primary to move sluggishly before giving up entirely.

Almost.g

[My post suggesting the same thing was actually sent 12 minutes earlier
than
Andrew's. Let's hope we both got it right!]

Your other post still hasn't surfaced to me - ain't usenet grand:-)

"John Andrews" wrote in message
om...
3. Ball valve has got stuck up in header tank (smaller
tank), and water level has dropped below the top of the
hot water cylinder coil so it no longer circulates.
Check the small header tank.


Good idea, I hadn't thought of that. But no, that's not the problem.
Water level and ball valve are fine - in fact I replaced the ball
valve assembly about six months ago. The important point is that the
hot water supply to the cylinder is not working - i.e. cold.


Its worth checking that the "fill" pipe from the tank to the primary loop
isn't blocked with crud.
This is not too rare IME

I think that you may have misunderstood the point. You should have *two*
header tanks - a big one and a little one.


Bingo! You read my tiny mind - ballcock in the little one was floating
in the air! I'll keep an eye on water heating working less efficiently
than before - I guess I might have some air in the system now - but
normal service has been resumed so I'm happy.

Thanks to everyone for their help - very much appreciated.