central heating not working

[delboybully]

As part of my pre winter home check i tried my central heating, unfortunately it does work.

I have some knowledge of my system in a DIY capacity, In the past(over 2 houses) i have changed a pump, 3 way valve, 2 way valve, moved and added rads. I apologise if i havent used the correct terminology for various parts

I have a non pressurised system (have a header tank) with a back boiler (behind the fire) with thermostatic valves and no thermostat There is a 3way valve that goes to hot water or central heating or both. The boiler was fitted about 6 years ago. The header tank is full to where is normally is. I have bled the rads and they are all full of water.

The controler has 4 settings for hot water and 4 for central heating , 24hrs, timed, on and off

If i turn both of them to off and them turn the water on, I can hear the 3 way valve move and the pump turn on. If, on the other hand, i turn both of them off and turn the central heating on, i cant hear the 3way valve move and the pump stays off, 2 of the rads have been turned up to max(6)

I think this points to the 3 way valve being faulty. However when the boiler was fitted, a new 3 way valve was fitted, this failed after just over 2 years (the central heating came on when the only the hot water was being called for) which i replaced. This could be a coincidence but i suspect not. Also I was under the understanding that these valves are designed to fail on rather than off

The only other problem i have had was when the pipe that comes down from the header tank blocked where it meets the horizontal pipe of the system

Thanks

 

[looneyfitter]

Right so it sounds like you have a MID position 3 port valve.. Does the boiler have a pilot light or is it self igniting? Does the boiler fire? IS the boiler stat turned up? Does the HW get hot at all?

 

[delboybully]

the boiler has a electric starter- no pilot light

the boiler does fire

if the boiler stat is the dial on the front of the boiler that goes from low to high, then it is turned up

We do have hot water

There is a lever on the 3way valve. It can be on auto or manual. It is on auto, but whatever i set the controller to (both off or both on, water on heating off, water off heating on), when i pull this lever to manual the lever goes back to auto. But when the controller is set for water off and heating on, as soon as i pull this lever to manual, the pump starts until the lever goes back to auto then the pump stops. does this help?

 

[looneyfitter]

Actuator has gone mate. Check you have 240v on the brown or white wire (dependant on what valve/actuator you have) If you pull the lever over, there is a slot to allow it to stay in position so you can at least keep you tutsies warm till you fix it.

If no 240 to the brown check you have 240 to the C at the room stat (ch on) then turn the stat up, should have 240 at terminal 3.

 

[delboybully]

Thanks

What is the actuator? From reading your reply it seems to be the 3way valve

I have a done a lot of home electrics (re-wired a house etc) but the only electrics i have done with the heating was straight replacements of the pump, 3way valve etc. When i last replaced the 3way valve the box that the cables went into were numbered, is that the terminal numbers.

Also i dont have a multi meter. I have one of those screwdrivers that you touch then end off and it lights up if its live- will this suffice to check the power or do i need to get a mulit-meter. I am aware of the limitations of these screwdrivers in that they will only tell you if the power is live and the screwdriver is working.

Thats for the advice on the manual override, i dont need the heating yet.

Is there anything that could be causing all these failures of the 3way valves. A new one was fitted with the boiler which failed after approx 2 years and now that has failed after about 4 years? or have i just been unlucky

These sort of problems are why i do a pre winter check on things. You dont want to find out your heating system dont work when its cold

 

[looneyfitter]

The actuator is the motor matey. Bin the screwdriver they are useless. You can pick up a cheap meter of under a tenner.

The motors just die with ware and tear mate. You could also just swap the syncron motor if you liked.

Gareth

 

[delboybully]

I put the valve onto manual and the heating works!!!! I think i am getting really close to finding the cause and thus a fix. You have been a great help

I remember now. The last time the 3way valve went the plumbers merchants said you can replace the motor (thats the top part). However they couldnt get the same motor so i had to replace the whole lot

Thanks for that, you have possibly just save me draining the system down and replacing the whole lot

I will check the terminals for power hopefully tomorrow evening

Will keep you updated

 

[looneyfitter]

no problem mate always happy to help.. What is the name of the valve you have? Is it grey? Honeywell? by any chance?

When you check the terminals dependant on what is there.

You want (with CH on at programmer and room stat up)

Either 240 v between N Blue and Brown or N Blue and white. if you have 240 then its defo the motor. If not then look at the stat then the programmer.

Gareth

 

[delboybully]

Its a Salus motorised valve MV322

It has 5 cables. An earth which goes to earth, orange goes to terminal 12, grey to 14, white to 15 and blue goes to a bank of cable connectors which have no numbers. Terminals 1 to 9 have nothing connected to them

I get home tonight and go to the terminal connector box and open it up. As i dont have a multi meter, I decided to check if there was voltage at various terminals when the water was on, CH on and both off using the screwdriver with a light. i had 2 of them and checked they worked by trying them on the live terminal of a socket.

However the screwdrivers kept giving me different readings for a couple of terminals for the same situation- they are useless. Then i remembered i had my dads old multi meter in the loft. so i go and find it, but then when i come down i noticed the heating was working on the timer. Now i am confused!!!!! The Ch works whether the system is also calling for HW or not. When i put the timer onto CH i can hear the sway valve moving and the pump starting and the rads heat up

Any ideas?

 

[looneyfitter]

It sounds to me like the actuator switch in the valve is sticking mate.

Basically How mid position valve works is this.

Mid pos has 5 wires

White should have 240v when CH calls

Blue- Neutral

Yellow/green Earth

Orange boiler/pump Switch live

Grey, HW off. (connects to HW off and terminal 2 of cylinder stat) Basically recieves 240v when either the programmer HW is off or the cylinder stat is satisfied.



Basically If white recieves 240 only then the motor moves to mid position,

When it recieves 240 on the grey and white it moves to CH only.

 

[delboybully]

I get it now and i understand what each wire does and what i should be looking for.

As I dont like spending money unnecessary, I am tempted to leave things as they are and wait until the heating fails again (maybe it wont- i should be so lucky) and then i can check to be sure its the actuator that is the problem or do you think i should replace the actuator now. If it does fail I can always turn the valve to manual to keep warm!!! I shall bookmark this page for future reference!!

Thanks again for your help

And if you keep tropical fish especially oscars and you need help or advice, come over to oscarfishlover.com where i am a moderator and I can return the favour. Delboy

 

[looneyfitter]

if its started working again mate then leave it be. you will be fine. I will be setting up a tank in the future funny enough so ill come find you . \


Thanks for the thanks too.

Cheers

 

[delboybully]

Checked to see if the Ch was working tonight and it wasnt.

Checked with mulit-meter. Results are

With CH and W off , white and orange 0v, grey 240v as expected

With W on, white and grey 0v and orange 240v, as expected

With CH on, white and grey are 240v, and orange 0v

Now i was expecting orange to be 240v with CH called for. Having thought about it, if the 3way valve is faulty and not moving to the CH position then the boiler/pump wont come on -is that right? When CH is called for i cant hear the 3 way valve move

With all this, is seems to me your are correct and the 3way valve is faulty? Can i check its the actuator and not the actual valve (the bit with water in it), by removing the actuator and putting the programmer to various settings and seeing if the actuator moves?

 

[looneyfitter]

Yes there is usually 2 grub screws as per your 1st note, you should have 240 to White with ch on tho

 

[delboybully]

I have 240v at white and grey with CH on, orange 0v