Hi, I was wondering if anyone could help me. I have a conventional
boiler with a large storage tank.
I have two swiches on the system -- one for hot water the other hot
water/ central heating.

When I press "ho****er/central heating", the radiators only seem to
heat up for a short burst then go off and never come back on. Meanwhile
the water heats up and the radiators never seem to come back on. If I
then use a large amount of hot water by having a bath, the radiators
will start becoming hot again.
Is this normal. I fear that there is a problem with the valve? Can
anyone help explain in very simple terms. Many thanks. Will.

In an earlier contribution to this discussion,
wrote:

Hi, I was wondering if anyone could help me. I have a conventional
boiler with a large storage tank.
I have two swiches on the system -- one for hot water the other hot
water/ central heating.

When I press "ho****er/central heating", the radiators only seem to
heat up for a short burst then go off and never come back on.
Meanwhile the water heats up and the radiators never seem to come
back on. If I then use a large amount of hot water by having a bath,
the radiators will start becoming hot again.
Is this normal. I fear that there is a problem with the valve? Can
anyone help explain in very simple terms. Many thanks. Will.

Are you referring to a motorised valve? If so, how many are there in the
system, and what type? [Clue: There is likely to be either one 3-port valve
or two 2-port valves]

If you describe the system more fully, we can tell you what to look for.
However, it's pretty obvious that the CH is only coming one while the HW is
being heated, and goes off as soon as the HW demand is satisfied. This is
very likely a problem with a motorised valve, unless it's always been like
it - in which case it could simply be wired wrongly.
--
Cheers,
Roger
______
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wrote:

Hi, I was wondering if anyone could help me. I have a conventional
boiler with a large storage tank.
I have two swiches on the system -- one for hot water the other hot
water/ central heating.

When I press "ho****er/central heating", the radiators only seem to
heat up for a short burst then go off and never come back on. Meanwhile
the water heats up and the radiators never seem to come back on. If I
then use a large amount of hot water by having a bath, the radiators
will start becoming hot again.
Is this normal. I fear that there is a problem with the valve? Can
anyone help explain in very simple terms. Many thanks. Will.


I am guessing you have a fire backboiler and no room
thermostat........Is that right?

hi Roger, thanks very much for replying and your explanation.

I have just checked the system and have a motorized valve. It's pretty
old, I think -- a sundial y plan 3 position diverter valve. I think
it's been here for about 20-30 years -- do they often break down? Are
they easy/ cheap to repair, or is it best to get an electrician in?


many thanks for your swift reply. Kind regards, Will.
Roger Mills wrote:
In an earlier contribution to this discussion,
wrote:

Hi, I was wondering if anyone could help me. I have a conventional
boiler with a large storage tank.
I have two swiches on the system -- one for hot water the other hot
water/ central heating.

When I press "ho****er/central heating", the radiators only seem to
heat up for a short burst then go off and never come back on.
Meanwhile the water heats up and the radiators never seem to come
back on. If I then use a large amount of hot water by having a bath,
the radiators will start becoming hot again.
Is this normal. I fear that there is a problem with the valve? Can
anyone help explain in very simple terms. Many thanks. Will.

Are you referring to a motorised valve? If so, how many are there in the
system, and what type? [Clue: There is likely to be either one 3-port valve
or two 2-port valves]

If you describe the system more fully, we can tell you what to look for.
However, it's pretty obvious that the CH is only coming one while the HW is
being heated, and goes off as soon as the HW demand is satisfied. This is
very likely a problem with a motorised valve, unless it's always been like
it - in which case it could simply be wired wrongly.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
wrote:

hi Roger, thanks very much for replying and your explanation.

I have just checked the system and have a motorized valve. It's pretty
old, I think -- a sundial y plan 3 position diverter valve. I think
it's been here for about 20-30 years -- do they often break down? Are
they easy/ cheap to repair, or is it best to get an electrician in?


It's unusual for them to last as long as 20 years!

The valve is in two parts - the wet bit which directs the water to the HW or
CH circuit or both together, and the actuator (the electrical bit which
rotates the paddle in the wet bit to make it do its business. With many
valves, you can replace the actuator without getting wet - but if you've got
an early Honeywell valve you may not be able to do this.

Several things can go wrong with these valves. The wet part of the valve can
seize up such that the actuator's rather weedy motor and return spring can
no longer move it. The motor and/or the microswitches in the actuator can
fail.

Before attacking the valve, it would be as well to check the wiring very
carefully to make sure that nothing has come adrift. You can find a wiring
diagram by looking under 'Y-Plan' in
http://content.honeywell.com/uk/homes/systems.htm

One feature of Y-Plan systems is that there needs to be a positive signal to
indicate that the HW demand is satisfied (or not required) - because that's
what drives the boiler and pump in CH-only mode. So your programmer must
have a HW-off output which is live when HW is switched off, and is connected
to Pin 7 in the wiring centre. Likewise, the cylinder stat must have a
change-over switch (rather than a pure on/off) which switches the HW signal
from the programmer either to Pin 8 when the HW is being heated or to Pin 7
once the tank is hot. In CH-only mode, a microswitch inside the 3-port
valve's actuator connects the grey and orange wires together - thus using
the feed from Pin 7 to power the boiler and pump via Pin 8.

In your case, the feed isn't getting to Pin 8 for some reason. This could be
due to:
* a wiring fault
* a cylinder thermostat problem or
* a 3-port valve/actuator problem

If you are competent with a mains voltmeter (forget neon screwdrivers!) you
should be able to work out where the problem lies.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Hi Roger, thanks for your message and details on how I should go about
rectifying the problem. From what you have said, I'm pretty sure the
valve is faulty.

Kind regards, Will.
Roger Mills wrote:
In an earlier contribution to this discussion,
wrote:

hi Roger, thanks very much for replying and your explanation.

I have just checked the system and have a motorized valve. It's pretty
old, I think -- a sundial y plan 3 position diverter valve. I think
it's been here for about 20-30 years -- do they often break down? Are
they easy/ cheap to repair, or is it best to get an electrician in?


It's unusual for them to last as long as 20 years!

The valve is in two parts - the wet bit which directs the water to the HW or
CH circuit or both together, and the actuator (the electrical bit which
rotates the paddle in the wet bit to make it do its business. With many
valves, you can replace the actuator without getting wet - but if you've got
an early Honeywell valve you may not be able to do this.

Several things can go wrong with these valves. The wet part of the valve can
seize up such that the actuator's rather weedy motor and return spring can
no longer move it. The motor and/or the microswitches in the actuator can
fail.

Before attacking the valve, it would be as well to check the wiring very
carefully to make sure that nothing has come adrift. You can find a wiring
diagram by looking under 'Y-Plan' in
http://content.honeywell.com/uk/homes/systems.htm

One feature of Y-Plan systems is that there needs to be a positive signal to
indicate that the HW demand is satisfied (or not required) - because that's
what drives the boiler and pump in CH-only mode. So your programmer must
have a HW-off output which is live when HW is switched off, and is connected
to Pin 7 in the wiring centre. Likewise, the cylinder stat must have a
change-over switch (rather than a pure on/off) which switches the HW signal
from the programmer either to Pin 8 when the HW is being heated or to Pin 7
once the tank is hot. In CH-only mode, a microswitch inside the 3-port
valve's actuator connects the grey and orange wires together - thus using
the feed from Pin 7 to power the boiler and pump via Pin 8.

In your case, the feed isn't getting to Pin 8 for some reason. This could be
due to:
* a wiring fault
* a cylinder thermostat problem or
* a 3-port valve/actuator problem

If you are competent with a mains voltmeter (forget neon screwdrivers!) you
should be able to work out where the problem lies.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!