Hi there,
Hopefully someone will be able to help me out with this CH/HW system.

I don't know what my stsem is called. It's not a combi though.

The components a- Potterton Boiler, Potterton Controller, Grundfos Super Selectric Pump, Honeywell v4073a motorised valve and a honeywell room thermostat.

The pilot light is still on in the boiler but I can't get it to fire up. I thought it was the pump so I changed it but it didn;t make any difference. The two things I'm wondering about now are either the thermostat in the boiler or the motorised valve are faulty. A friend of mine doesn't think it will be the valve because there is obviously some power getting to it. When the power is switched on the manual overide lever is quite loose and only seems to have any resistance at the last couple of millimetres. When the power is switched off the lever moves to about halfway and has resistance all the way when I push it. I'v not sure whether I should change just the motor or the whole valve to see if it works.

Any suggestions would be appreciated.

Cheers,

Jon

In an earlier contribution to this discussion,
YellowPlanet wrote:

Hi there,
Hopefully someone will be able to help me out with this CH/HW system.

I don't know what my stsem is called. It's not a combi though.

The components a- Potterton Boiler, Potterton Controller, Grundfos
Super Selectric Pump, Honeywell v4073a motorised valve and a honeywell
room thermostat.

The pilot light is still on in the boiler but I can't get it to fire
up. I thought it was the pump so I changed it but it didn;t make any
difference. The two things I'm wondering about now are either the
thermostat in the boiler or the motorised valve are faulty. A friend
of mine doesn't think it will be the valve because there is obviously
some power getting to it. When the power is switched on the manual
overide lever is quite loose and only seems to have any resistance at
the last couple of millimetres. When the power is switched off the
lever moves to about halfway and has resistance all the way when I
push it. I'v not sure whether I should change just the motor or the
whole valve to see if it works.

Any suggestions would be appreciated.

Cheers,

Jon

You have a Y-Plan system [See
http://content.honeywell.com/uk/homes/systems.htm and scroll down to Y-Plan]

You should also have a thermostat on the hot water cylinder - which you
didn't mention.

A few questions:
* Has it previously worked ok, and suddenly stopped - or has it never
worked?
* What happens if you select Hot Water but not Heating on the programmer -
does the boiler fire up then?

If the boiler works for HW for not for CH, it is either a wiring problem or
a problem with the 3-port mid-position valve (most likely with the
electrical acuator part of this).

If HW doesn't work either, it sounds like a boiler problem. As Christain
says, check whether the boiler is getting a demand signal on its Switched
Live input.

A few more things to check:
* Switch off all power to the system (at the FCU, not the programmer). The
3-port valve should return all the way to the HW position - and you should
feel immediate resistance on the manual lever. Does it do this?
* Remove the actuator from the valve and check that the shaft of the valve
isn't seized. [The 2 parts are separate, so no water will leak out when you
undo the screws holding the actuator on]. The shaft should move fairly
smoothly through 90 degrees from the HW to CH position - either by gripping
it with a finger and thumb or, at most, using light pressure with a pair of
pliers.

Let us know what you discover, and we'll help you to home in on the problem.

[Sometimes, when the actuator gets 'confused', the simple act of removing
all power and then turning it on again will get it going - a bit like
re-booting your computer!]
--
Cheers,
Set Square
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In message , YellowPlanet
writes

Hi there,
Hopefully someone will be able to help me out with this CH/HW system.

I don't know what my stsem is called. It's not a combi though.

The components a- Potterton Boiler,

Potterton have made, in the past, a number of different boilers.

What is it, a Netaheat, a Profile ?

You've just said the equivalent of "My ford doesn't go"

Is the fan coming on, can you hear a clicking of the spark, is the water
pressure high enough, is the boiler getting a switched live from the
timer ?? etc

--
geoff