I have a gravity hot water & central heating system with a rather
strange (from what I can see) setup. The hw cylinder has the standard
thermostat attached to it which operates a 2way valve, when the tank
reachs the set temperature. Unfortunately when the valve closes, this
also causes the central heating to stop. The ch pump is still spinning
(if room thermo wants heat) but it seems that no water is flowing
round the circuit as the rads go cold and the pipe leading to the pump
goes cold as well. Almost as if the circuit for the ch is shut as
well.

I have attempted a bodge, by turning the boiler gas control down, and
turning the tank thermo up high, so that the 2way valve does not close
easily. This all works fine, as long as some hot water is used, and
the house is fairly cold requiring ch. Else I get into a loop of
waiting for the tank to cool enough to open the valve, and thus give
me some ch.

Can anyone think of something I can do to remedy the situation ? Can I
put a link into the output from the room thermo that will open the
2way valve if ch is required, or will this cause problems ? If so
which of the 5 wires on the valve would need to be used ?

Thanks in advance

Paul..

On 6 Jan 2005 06:01:35 -0800, (Wordy) wrote:

I have a gravity hot water & central heating system with a rather
strange (from what I can see) setup. The hw cylinder has the standard
thermostat attached to it which operates a 2way valve, when the tank
reachs the set temperature. Unfortunately when the valve closes, this
also causes the central heating to stop. The ch pump is still spinning
(if room thermo wants heat) but it seems that no water is flowing
round the circuit as the rads go cold and the pipe leading to the pump
goes cold as well. Almost as if the circuit for the ch is shut as
well.

I have attempted a bodge, by turning the boiler gas control down, and
turning the tank thermo up high, so that the 2way valve does not close
easily. This all works fine, as long as some hot water is used, and
the house is fairly cold requiring ch. Else I get into a loop of
waiting for the tank to cool enough to open the valve, and thus give
me some ch.

Can anyone think of something I can do to remedy the situation ? Can I
put a link into the output from the room thermo that will open the
2way valve if ch is required, or will this cause problems ? If so
which of the 5 wires on the valve would need to be used ?

Thanks in advance

Paul..


Often the vaules have a manul leave to open them ....... this + gaffer
tape will make a top quality bodge.

Rick

I have a gravity hot water & central heating system with a rather
strange (from what I can see) setup. The hw cylinder has the standard
thermostat attached to it which operates a 2way valve, when the tank
reachs the set temperature.

All sounds good so far.

Unfortunately when the valve closes, this also causes the central
heating to stop. The ch pump is still spinning (if room thermo
wants heat) but it seems that no water is flowing round the
circuit as the rads go cold and the pipe leading to the pump
goes cold as well.

There clearly should be a system so that when the CH is calling for heat,
the boiler should fire. Unfortunately, we need many more details to make an
educated guess as to why it isn't.

See if you can answer the following:

1. Has the system ever worked? (i.e. could it be a design/installation
fault, rather than a failed component).

2. What sort of zone valves do you have? You mention one for the hot water.
Are there more like this one? How many pipes emerge from the valve you have
located? Are there any markings on the valve?

3. Does the pump run for hot water as well as central heating, or is it
purely for the CH?

4. What is the make and model of boiler?

Christian.

In an earlier contribution to this discussion,
Wordy wrote:

I have a gravity hot water & central heating system with a rather
strange (from what I can see) setup. The hw cylinder has the standard
thermostat attached to it which operates a 2way valve, when the tank
reachs the set temperature. Unfortunately when the valve closes, this
also causes the central heating to stop. The ch pump is still spinning
(if room thermo wants heat) but it seems that no water is flowing
round the circuit as the rads go cold and the pipe leading to the pump
goes cold as well. Almost as if the circuit for the ch is shut as
well.

I have attempted a bodge, by turning the boiler gas control down, and
turning the tank thermo up high, so that the 2way valve does not close
easily. This all works fine, as long as some hot water is used, and
the house is fairly cold requiring ch. Else I get into a loop of
waiting for the tank to cool enough to open the valve, and thus give
me some ch.

Can anyone think of something I can do to remedy the situation ? Can I
put a link into the output from the room thermo that will open the
2way valve if ch is required, or will this cause problems ? If so
which of the 5 wires on the valve would need to be used ?

Thanks in advance

Paul..

Do you mean that the *primary* hot water circuit uses gravity (convection)
circulation, whereas the heating circuit is pumped?

If so, it sounds as if someone has tried to install a C-Plan system (See
http://content.honeywell.com/uk/homes/systems.htm) and got it wrong!

If there is a zone valve in the HW circuit to stop any further circulation
in that circuit once the water is hot, it shouldn't affect the CH circuit.
It sounds like either the valve is in the wrong place or (more likely) it
has been wired wrong.

If I'm right, and it *is* a C-Plan system, have a *careful* look at the
wiring diagram on the Honeywell site - and bring yours into line with that.
Have a careful look at the 3 wires which go to the volt-free change-over
switch in the valve (which switches when the valve is open). Orange needs to
go to the boiler, white to the pump, and grey to permanent live. My guess is
that one or more of these are wrong!
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Christian McArdle wrote:
I have a gravity hot water & central heating system with a rather
strange (from what I can see) setup. The hw cylinder has the
standard
thermostat attached to it which operates a 2way valve, when the
tank
reachs the set temperature.

All sounds good so far.

Unfortunately when the valve closes, this also causes the central
heating to stop. The ch pump is still spinning (if room thermo
wants heat) but it seems that no water is flowing round the
circuit as the rads go cold and the pipe leading to the pump
goes cold as well.

There clearly should be a system so that when the CH is calling for
heat,
the boiler should fire. Unfortunately, we need many more details to
make an
educated guess as to why it isn't.

See if you can answer the following:

1. Has the system ever worked? (i.e. could it be a
design/installation
fault, rather than a failed component).

2. What sort of zone valves do you have? You mention one for the hot
water.
Are there more like this one? How many pipes emerge from the valve
you have
located? Are there any markings on the valve?

3. Does the pump run for hot water as well as central heating, or is
it
purely for the CH?

4. What is the make and model of boiler?

Christian.