Hot water not turning off

[colled]

I'm hoping someone here will know what the problem is. My setup is a Megaflow system heated by an Ideal classic boiler with 2 port valve to the heating circuit and another 2 port valve to the hot water cylinder (indirect). I've noticed that even with the hot water and heating switched off at the main controller/programmer the hot water is still being heated up to the same temp as normal, which is very hot but not enough to trigger the T&P valve. The heating remains off as expected. The boiler is firing up about every 10 mins or so for about 30 seconds all day and night so is getting demand from somewhere, I assume from the hot water circuit as that's what is still being heated despite being selected as off. I'm thinking the 2 port valve to the hot water is stuck on/open, but I've checked this and the manual lever is in the off (and is sprung open) position and doesn't seem to ever go into the on position even when the boiler is fired. Also I assume the boiler gets it's demand signal from this valve so if on all the time the boiler would fire all the time? or could it be the valve is opened and demanding all the time but the boiler is using it's own inbuilt thermostat to switch on and off? But then with the hot water switched off at the controller, why would a demand signal be sent to the boiler anyway? I assume demand is sent electricallly rather than just water flow? Anyway, does anyone have any suggestion as to why it's doing this?

many thanks for any help given!!

 

[Kimou]

Have you had it working normally before to your knowledge?

 

[colled]

I've only moved into the house recently and only noticed it because I went on holiday and turned the hot water and heating off, but still had piping hot water when I came back. I think it's been like this since I moved in. It's possible it's been doing it for years an noone has noticed.

 

[diamondgas]

sounds like one of your zone valves is faulted 'colled' cauzing the boiler to cycle around the bi-pass. Quite common with 'S'Plan heating design. Anyone you know competent with diagnosing electrical faults on heating system wiring?

 

[Kimou]

That's why I asked. It may be wired up incorrectly. Or faulty programmer. It powers up from there via the wiring centre. Call someone round to check is the best idea. You're wasting your money heating water that way.

 

[plumbdoctor]

does it still heat up even if you hot water stat is turned right down ?

 

[Kimou]

Ah, or what Diamond says...he's the artist :4:

 

[colled]

Changing the thermostat temp doesn't seem to make a difference to the water temp or boiler firing. My original thought was that the hot water 2 port valve was the problem (I assume that's what you mean by zone valve Diamond?), but it seems to be switched off at the manual switch even when the boiler is firing, although hot water must be getting through somehow so I guess it's on at somepoint. I assume if it was the controller or thermostat I would hear or see the valve opening and closing but it's not. I'm not sure whether to get in a plumber or an electrician (I don't know anyone) or just change the valve myself and see if it fixes it? I could try and take the head of it and turn it manually to off and see if it stops the water from heating and the boiler from coming on? Or maybe the valve gate inside could be broken and still lets water through even in the off position, but AFAIK the valve should only send a demand signal via a wire when fully open.

 

[steadyon]

You've probably already checked this, but are you sure there isn't an electric immersion heater in the Megaflow left on? I know it wouldn't provide a reason for the boiler to fire, but you could have more than one fault.

 

[stevetheplumber]

should be easy enough to trace back from boiler to find the fault my bet is its wired wrong from the of especially as you say stat has no effect

 

[diamondgas]

Hi Colled, soz for late reply ... had to go make some pennies!

Moving the head manually usually makes no difference what so ever... The microswitches inside the valves tend to fuse together so the valve turns off but the switch stays on!

Get someone in to verify this, it can be either valve and you wouldn't know unless you test them!

 

[diamondgas]

You may be able to change just the head --- usually they cost about the same as the whole valve but save the issue with draining! If you're confident with wiring then you'll be able to tell which one is giving grief by independently checking which 'orange' wire is live when controls or off and tracing that one back to the 2 way valve causing he grief! Only do this if you're confident with wiring though as it could cost you big time if you start pulling wires out and forget where they go back!!

 

[colled]

I'm fairly sure the valve to the central heating circuit is ok. That one switches on and off ok (I can see the lever move) and the heating is only on when I tell it. The hot water valve however never seems to move to the on position but the water is still being heated in the tank so somehow hot water is getting past it and the boiler is being demanded like I say about every 10 mins. Very odd.

 

[Kimou]

You might have the common live connect direct to the zone valve bypassing programmer switch. So only cyl stat is breaking the circuit? But then the cyl won't lose it temp every 10 mins. Interested in knowing as well.

 

[John The Rad]

Your cylinder cannot heat up if the 2-port valve is permanently closed.
If the boiler fires up every 10 minutes for 30 seconds then there must be a fault in the wiring. The cylinder stat is probably calling for heat.
The only way the cylinder can have hot water all the time is if the 2-port valve is fitted backwards. The pump can force the hot water from the boiler into the circs this way. Check the arrow on the valve.
Also check the arrow on the pump. If that’s on the wrong way round it can force the hot boiler water backwards through the 2pv via the return.
The 2-port valves are not designed to hold the water back if it is travelling in the wrong direction.

 

[diamondgas]

I'm fairly sure the valve to the central heating circuit is ok. That one switches on and off ok (I can see the lever move) and the heating is only on when I tell it. The hot water valve however never seems to move to the on position but the water is still being heated in the tank so somehow hot water is getting past it and the boiler is being demanded like I say about every 10 mins. Very odd.

Hi colled, If the valve is closed then, as mentioned, it's unlikely that the boiler is heating the hot water. Also as mentioned before, you may have an electric immersion heater switched on. That doesn't solve the reason why the boiler is cycling... There's a wiring fault that needs tracing, if you are not able to do this then I suggest you get a gas engineer in... 🙂

 

[colled]

Ok cheers guys I really appreciate your help, I'll check the fitted direction on the valve (I assume the arrow is easy to find on the brass section of the valve). If the programmer/controller is off however, then even with a valve the wrong way round why would there be demand to boiler as presumably the controller overrides the thermostat and valve microswitch?

The valve is a honeywell v4043h series which according to the spec has a grey wire for the boiler demand signal, so presumably I can check if this is live to see if the microswitch on the valve is dodgy? The orange wire is apparantly always live and is used to be switched to.

 

[diamondgas]

OOps! Soz 'colled' ... orange and grey switch between each other, got them wrong way around did I... I was only working on one last week too!! My memory cells are depleting!! LOL

Please let us know how you get on ... :charming: