Drayton LP241 Problem - Pump and Boiler Constant Running

Talk Electrician Forum

Help Support Talk Electrician Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Stephen_o

New member
Joined
Apr 30, 2020
Messages
3
Reaction score
0
Hi, I have had a Drayton 241 System installed for the last 15 years. Room Stat and Tank Stat controlling the boiler and pump. 

Other than having to replace the pump twice in recent years all has been good with this until this last week. 

I noticed the hot water was even hotter than normal, on investigating the thermostat was switching between calling for heat and not calling for heat but the 2 way valve was not closing fully to stop the flow when heat not needed. Last night I noticed that the hot water ran all night 24/7. 

I removed the head of the valve and it was rattling, took it apart and discovered a spring was loose in the head, a plastic lug had fractured and so the valve was not springing back shut again. I fixed this by drilling a self tapper in and reattaching the spring. The valve then worked fine open and closed as does the heating valve. Both valves are responding to their thermostats but I seem to still have a problem and it has stumped me. 

The pump and boiler are still running even with the valves shut and stats not calling for heat, They are even still running independently of the control programmer. I've not had this happen before. I took the programmer off the wall so there was no circuit and the pump and boiler still run independantly. With the valves shut the pump will be pumping against a dead end and the boiler firing means I will have a problem with pressure let alone wear and tear and waste of gas. Can anyone shed any light on this for me. In the wiring centre, with the programmer switched off wires 6 (HTG and HW Orange), 7 (HTG and Hot Water Grey), 11 (Boiler Live) and 12 (Pump Live) are all active at 240v.

Thanks in advance 

Stephen

 
It will be the microswitches that has failed and stuck on. Orange and Grey connect just to the microswitch and I bet that is stuck.  It could be either the heating or the HW valve head that has the stuck switch.  Disconnect the orange and grey from one valve at a time to work out which head has the stuck switch.  If you are adventerous you can usually replace just the microswitch inside, if not replace the whole head.

For a more reliable outcome, but more work, change the whole valve and body for a Honeywell.  More metal less plastic tat.

There will usually be an automatic bypass valve somewhere so with both valves shut the water will pump around a short loop of pipe.  It will still waste some gas keeping that loop of pipe hot for no reason.

 
Last edited by a moderator:
Hi Dave

I had a break for an hour out of frustration and came to the same thinking as you said. And it was right, the HW Valve was not stopping the pump and boiler whereas the heating valve did. I guess I was just unlucky to have 2 faults in the same divertor valve and think I had fixed one to save replacing it and will end up replacing it after all. 

I have removed it from the system and will run with the programmer on CH only to control both the water and CH until a replacement valve comes, I will shop around, I have no qualms about flirting the old valve off and putting a new honeywell on other than the mess of a slight drain down (my drain cock downstairs has leaking glands if I open it) so it boils down to price and amount of energy I feel I will have on the day. 

Thank you for your help.

Regards

Stephen

 
I guess I was just unlucky to have 2 faults in the same divertor valve and think I had fixed one to save replacing it and will end up replacing it after all. 
You probably disturbed the switch  or operating cam in some way whilst doing the other repair.

I've fixed these things myself and they are really finicky to work on, and given the cost of a new head not really worth the trouble.

 
You probably disturbed the switch  or operating cam in some way whilst doing the other repair.

I've fixed these things myself and they are really finicky to work on, and given the cost of a new head not really worth the trouble.


Yes thats my thinking as well. Ive seen the replacement motors online at £16 but bearing in mind ive already patched it I will buy a replacement head from toolstation and job done, its the first trouble i've had since I put it in 2005 so I suppose I can't complain. I was just utterly stumped this morning as to why the valves would be live when they weren't calling for heat or even switched on. what a crazy set up. I am minded to rip the lot out and do it with a better quality system but ££ is the issue. I will keep the old valve - I know it works to a point and then if I have trouble with the new one or the CH valve then I can swop stuff around. 

Stephen

 
That is the normal way to wire a heating system.

The programmer and thermostats control when heating or hot water is demanded and open the appropriate motorised valve to achieve that,

The microswitches in the motorised valves are wired in parallel and perform a logical OR function and demand heat from the boiler when heating OR hot water OR both are demanded.

There is not really any other way to do it.

 
I was just utterly stumped this morning as to why the valves would be live when they weren't calling for heat or even switched on. what a crazy set up. 

Stephen


You have to keep in mind the concept of typical heating arrangements...

[ Power supply ] ---> [ Timer/Programmer ] ---> [ Thermostat (Cylinder or room) ] ---> [ Motorised valve, to open up flow to required pipes ( Water or heating) ] 

[ Power supply ] ----> [ Switch inside motorised valve,  (switch should only be on when the valve has opened) ] ---->  [ Boiler & Pump ]

So in your case if a micro switch has failed in the on position inside a valve, even with programmer and thermostats 'off'..

you sill have a direct supply through to the boiler & pump.

The valves are used as relay switches to prevent back-feed from the boiler holding all valves in the on position.

:coffee    

 

Latest posts

Top