pump on

[fire]

my pump stays on and when i turn off the cylinder stat it switches off, thought cylinder stat was faulty so put a new one and still does the same.

i then disconnected the zone valve and its still on.

its controlled by a drayton LP722 and we have not set any demand on it (its off) when i switch the hot water on even the raditors come on.

i was all working fine till one day when the 3A fuse on the spur blew and all the above started after replacment.

any help on this please.

 

[BillyTheSparks]

Has the valve got stuck in the open position? have a look at the little arm that sticks out from the valve, it should move freely.
The valve could be faulty and need replacing.
The internals of the valve could be jammed.

I hope this helps

 

[fire]

i stripped the valve, tested all the micro switches and the mech its all fine and works perfectly when i set the demand on the controller. also checked the pump wiring and look ok as it was, surly what could affect it to work this way after a fuse blows??!!

 

[sambotc]

Where are you located?

Do you have a frost stat fitted, or is the boiler fitted in an outhouse or similar?

What make and model of boiler is it?

 

[BillyTheSparks]

is the pump wired from the boiler? could the boiler be knackered and that is what caused the fuse to pop?

 

[fire]

its a well maintained back boiler and the tank located in the airing cupboard on the upstairs landing. the central heating works perfectly its only the cylinder stat the keeps the pump running. disconnect the cylinder stat and everything works fine.

if i disconnect the cylinder stat permanatley will i still be able to controll hot water from the contorller?

 

[sambotc]

Is this a 3 port valve or a zone valve (2port)?

Y plan's (3 port valve) have 3 cores on the cylinder stat which goes to the hot water off on the programmer and 3 port valve, are you sure these are correct?

 

[BillyTheSparks]

so you have a programmer which is switching on the heating via a room theromstat. which turns on the valve. which in turn switches the pump to run.

the programmer also switches on the hot water via the cylinder stat. which turns on the valve. which again switches the pump to run.??


Just want to get it clear in my head.
Do you have two separate valves or a 3port valve?

 

[fire]

its a 3 port valve,

the pump runs when everyhting else is off i.e. the control and even the boiler is off. the pump will only switch off if you turn off the cylinder thermostat. and when i switch just hot hot water on the controll the raditors also get hot.

 

[jase]

when the stat is on the pumps is on and when the stat is off it switches off, well surely that is normal then cos the stat when on is calling for heat so the pump and boiler should be wired together so that the boiler comes on and the pump pumps the water round, when you disconnected the zone valve it was still on, thats cos the zone valve dont tell the pump what to do, the stats do, although if the programmer is switched of then yes, nothing should be happenning at all.
as for the rads coming on with the hot water after a fuse replacement, are the programme settings the same or did they reset to a default when the fuse blew?

 

[sambotc]

With the programmer off for both hot water and heating, do you have 240v on C at the cylinder stat? check when stat is calling and satisfied

 

[jase]

its a 3 port valve,

the pump runs when everyhting else is off i.e. the control and even the boiler is off. the pump will only switch off if you turn off the cylinder thermostat. and when i switch just hot hot water on the controll the raditors also get hot.

when you say turn the control off and even the boiler off, do these have seperate spurs?

 

[5544]

i know you said back boiler but just checking, is you pump fed from the boiler. modern boilers have pump overrun so the pump is fed from the boiler circuits regardless of everything else. if it is then youneed to confirm where all the voltages are coming from. youhave a number of switched live options with three port valve systems. i think the tank stat is a read herring. just make sure you have wired the hot water off on the tank stat correctly. i would put money on either the three port valve or the boiler if it has pump overrun

 

[GT1]

How long does the pump stay on for. ?
Just to rule out the obvious, it's not the overrun on the pump is it !

They can run for some time after the system stops calling for heat....

 

[GT1]

Doh !!
Sorry 5544. You beat me to it !