[jashton]

Hi. I have a problem in my new house. It's a 'standard' gas boiler feeding the heating and a DHW tank. There's a 3-way solenoid valve on the exit from boiler to control flow to DHW, CH or both.
There was a DHW tank thermostat fitted but missing the cable. The input for the thermo, in the controller panel, had been bypassed so that DHW is heated to the same temp as CH water, ie too hot for me.
The problem is that, when I wired the DHW thermo back in, when it reaches the set temp the hot water cuts off as expected but so does the CH.
Is this down to the way the programmer and controller panel have been installed? The panel has a number of wires around the edge, some of which have been clipped. I assume they are left intact/clipped to select various options during installation. I don't have instructions to decipher though.
Thanks.

In an earlier contribution to this discussion,
jashton wrote:

Hi. I have a problem in my new house. It's a 'standard' gas boiler
feeding the heating and a DHW tank. There's a 3-way solenoid valve on
the exit from boiler to control flow to DHW, CH or both.

More likely, a 3-port mid-position motorised valve.

There was a DHW tank thermostat fitted but missing the cable. The
input for the thermo, in the controller panel, had been bypassed so
that DHW is heated to the same temp as CH water, ie too hot for me.
The problem is that, when I wired the DHW thermo back in, when it
reaches the set temp the hot water cuts off as expected but so does
the CH.
Is this down to the way the programmer and controller panel have been
installed? The panel has a number of wires around the edge, some of
which have been clipped. I assume they are left intact/clipped to
select various options during installation. I don't have instructions
to decipher though.
Thanks.

You have a wiring problem. Your system needs to be wired as per the Y-Plan
diagram in http://content.honeywell.com/uk/homes/systems.htm (with the
possible exception that the pump may need to be controlled by the boiler
rather than being wired exactly like the diagram).

The important thing is that the cylinder stat *must* have 3 contacts - and
be of the change-over variety - and all 3 wires must be connected. When the
HW is hot, the stat *must* provide a HW-satisifed signal, which must be
connected to the 3-port valve's grey wire. The valve needs to turn the
boiler on when only CH is required, and cannot do so unless its grey wire is
powered.

There should also be a HW-off connection to the programmer. If this is
connected correctly, you may find that the CH works when you turn HW off at
the programmer. This may offer a short-term solution while you sort out the
stat wiring.
--
Cheers,
Set Square
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On Mon, 12 Dec 2005 16:25:01 +0000, Set Square wrote:

In an earlier contribution to this discussion,
jashton wrote:

Hi. I have a problem in my new house. It's a 'standard' gas boiler
feeding the heating and a DHW tank. There's a 3-way solenoid valve on
the exit from boiler to control flow to DHW, CH or both.

More likely, a 3-port mid-position motorised valve.

There was a DHW tank thermostat fitted but missing the cable. The
input for the thermo, in the controller panel, had been bypassed so
that DHW is heated to the same temp as CH water, ie too hot for me.
The problem is that, when I wired the DHW thermo back in, when it
reaches the set temp the hot water cuts off as expected but so does
the CH.
Is this down to the way the programmer and controller panel have been
installed? The panel has a number of wires around the edge, some of
which have been clipped. I assume they are left intact/clipped to
select various options during installation. I don't have instructions
to decipher though.
Thanks.

You have a wiring problem. Your system needs to be wired as per the Y-Plan
diagram in http://content.honeywell.com/uk/homes/systems.htm (with the
possible exception that the pump may need to be controlled by the boiler
rather than being wired exactly like the diagram).

The important thing is that the cylinder stat *must* have 3 contacts - and
be of the change-over variety - and all 3 wires must be connected. When the
HW is hot, the stat *must* provide a HW-satisifed signal, which must be
connected to the 3-port valve's grey wire. The valve needs to turn the
boiler on when only CH is required, and cannot do so unless its grey wire is
powered.

There should also be a HW-off connection to the programmer. If this is
connected correctly, you may find that the CH works when you turn HW off at
the programmer. This may offer a short-term solution while you sort out the
stat wiring.

Note that the boiler cuts out for a delay of a few seconds or so after
the DHW thermostat has satisfied until the 3-port valve has gone all the
way to CH only.

It is always better to wire the controls understanding how they work
than to use some sort of "simplified" wiring centre which supposedly makes
the task easier.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

Set Square wrote:

You have a wiring problem. Your system needs to be wired as per the Y-Plan
diagram in http://content.honeywell.com/uk/homes/systems.htm (with the

Oh good, they've put it right again! Anyone notice that Honeywell had re-
(or rather dis)-organised their web site about a week ago so that their own
links went to 404s and Directory Listing Denied-s all over the place?

Ed Sirett wrote:

It is always better to wire the controls understanding how they work
than to use some sort of "simplified" wiring centre which supposedly makes
the task easier.

Or better still, both: I like the Drayton wiring centres (only about sick
squid from bee and queue) since you can see what the links do (unlike the
honeywell PCB types) but they make it fairly idiot proof, both for you when
you're wiring it all up at the end of a long day/week and your brain's
already clocked off, and for whoever comes after you. Don't you hate trying
to debug a mass of spaghetti crammed into a single socket box? :-)

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

Set Square wrote:

You have a wiring problem. Your system needs to be wired as per the
Y-Plan diagram in http://content.honeywell.com/uk/homes/systems.htm
(with the

Oh good, they've put it right again! Anyone notice that Honeywell had
re- (or rather dis)-organised their web site about a week ago so that
their own links went to 404s and Directory Listing Denied-s all over
the place?

Yes, I remarked on it at the time - but checked that it had been restored
before quoting the link in this thread.
--
Cheers,
Set Square
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