Hot water won't come on by itself

[Ivan Android]

I wonder if anyone can help diagnose a problem I'm having.

My hot water won't come on by itself.

The system is a pretty bog-standard gravity fed type with the cylinder, pump, 2 port valve etc in a first-floor airing cupboard.

If I switch on the heating by itself it works.

If I switch on the heating and hot water together the pump switches off. If I then turn down the cylinder thermostat the pump switches back on and I start getting a supply of hot water to the cylinder. This isn't ideal though because supposedly there's nothing to tell the 2 port valve when there's enough hot water? Could this be harmful?

The 2 port valve seems to be switching to direct water to each part of the system without any problem so I don't think that's the issue. As far as I can tell the problem lies with the controller which is a pretty ancient looking Potterton EP2002.

Anybody able to offer any thoughts?

 

[Burger]

Are you sure it’s a 2 port? Any photos of cylinder cupboard? Has it always done this or just started?

 

[Ivan Android]

I'm no expert but I think this is a 2 port.
It's just started a few days ago.

 

[chris watkins]

So it is a 3 port & system is fully pumped, not gravity hot water but apart from that you were spot on Ivan

 

[Ivan Android]

Haha. What's in a number and a little bit of relativity?

 

[chris watkins]

It is more like to be the motor in the zone valve than the programer.

 

[Ivan Android]

How would I check that?

 

[SJB060685]

Dodgy cylinder stat? If you switch HW and CH on at programmer and turn cylinder stat to max do you get a feed to orange wire? I’m saying this but really someone with electrical knowledge should be testing this.

 

[Ivan Android]

Dodgy cylinder stat? If you switch HW and CH on at programmer and turn cylinder stat to max do you get a feed to orange wire? I’m saying this but really someone with electrical knowledge should be testing this.

I replaced the cylinder stat this morning as the plastic mechanism inside had broken. I was hopeful this would sort the problem but alas....

 

[SJB060685]

Ok when calling for hot water on it’s own do you get a feed to cylinder stat from programmer and then to boiler live?

 

[Ivan Android]

Ok when calling for hot water on it’s own do you get a feed to cylinder stat from programmer and then to boiler live?

That's beyond my capabilities to check safely. Have ordered a new 3 port valve head, I'm comfortable swapping that out. We'll see if that helps. Thanks for helping out.
If that doesn't resolve the issue what would you suggest? I have a spare Drayton controller on standby if necessary...

 

[SJB060685]

I suggest get someone out who can diagnose it. These valves are pretty simple inside, I’ll attach an image. With what you’ve said I would be suspicious of the programmer not supplying feed to cylinder stat (of course I could be wrong). I don’t think changing the valve head will fix it but again I might be wrong.

 

[Burger]

I replaced the cylinder stat this morning as the plastic mechanism inside had broken. I was hopeful this would sort the problem but alas..

Not that I don’t trust what you have done, but did you wire up the cylinder stat correctly?

 

[garygvl]

I'm no expert but I think this is a 2 port.
It's just started a few days ago.

View attachment 37154

strange pipework the 15mm pipe that comes back in the middle of pic????

 

[chris watkins]

strange pipework the 15mm pipe that comes back in the middle of pic????

15mm was often used to pipe to the old cylinders, when it was a couple of turns of pipe for the coil it provided enough heat.

 

[garygvl]

15mm was often used to pipe to the old cylinders, when it was a couple of turns of pipe for the coil it provided enough heat.

yes but if thats the hot water return in middle of pic strange pipework

 

[SJB060685]

As Chris says I’ve seen quite a few old cylinders with a 15mm flow and return, at a time when cylinders had a longer reheat time it was deemed acceptable, as you know nowadays cylinders have a coil output in the much higher KW outputs, sometimes even larger than boiler output itself and we wouldn’t get away with 15mm pipework. As for the the pipework in picture it’s hard to make out the arrangement lol

 

[Ivan Android]

Not that I don’t trust what you have done, but did you wire up the cylinder stat correctly?

100% it was 3 wires like for like.

 

[Ivan Android]

Regarding the 15mm pipe in the middle, if it helps to solve the mystery there's a shut-off valve just below and out of shot.

There appears to have been quite a few alterations to the pipework in the airing cupboard. Partially to accommodate some new rads in an extension and partly to add a couple of showers, the Aqualisa types that sit up in the loft.

We moved in last summer and for month or two were convinced we had a leak somewhere inside the house because even after all toilets had finished filling up the meter was still spinning. I eventually realised that the first floor toilets and showers were being fed by pipes coming out of the main loft tank so it was this that was filling up for a good half hour after everything else had.

 

[Burger]

Might be time to get an engineer in.

 

[chris watkins]

100% it was 3 wires like for like.

So it is a diverter valve not a mid-position (which would be a 5 wire)? are you sure the valve is the right way around, as normally heating can not be on without hot water.

 

[Ivan Android]

Well, changed the controller this morning and still have exactly the same problem so will change the 3 port head unit tomorrow. With the cylinder stat having already been changed I'm guessing there's not many components left to change??

If I need to get an engineer in so be it but would prefer the satisfaction of sorting it myself if I can.

 

[Ivan Android]

So it is a diverter valve not a mid-position? are you sure the valve is the right way around, as normally heating can not be on without hot water.

I assume it is as this has only been a problem in the last few days.

 

[Ivan Android]

The problem is that with both HW and CH on together the pump and boiler shut down until I turn down the cylinder stat. CH works fine by itself

 

[SJB060685]

So it is a diverter valve not a mid-position (which would be a 5 wire)? are you sure the valve is the right way around, as normally heating can not be on without hot water.

Chris he said it has three wires for the cylinder stat, he didn’t mean the valve. I believe he means this is a mid position valve.

Ivan with these valves, if HW and CH are on at same time or just HW then power to boiler is through the cylinder stat. When you turn down the cylinder stat this satisfies the stat and the grey HW off wire becomes energised, this then motors over to CH only and power to boiler and pump is through valve orange wire

 

[Burger]

So it is a diverter valve not a mid-position (which would be a 5 wire)? are you sure the valve is the right way around, as normally heating can not be on without hot water.

The wiring was relating to the cylinder stat

 

[Burger]

Ivan,

If you insist on doing the work yourself and are competent and can work safely, I suggest you head to this website for a better understanding:

Y Plan central heating system

Just don’t listen to video before bed unless you want a good nights sleep

 

[Ivan Android]

Ivan,

If you insist on doing the work yourself and are competent and can work safely, I suggest you head to this website for a better understanding:

Y Plan central heating system

Just don’t listen to video before bed unless you want a good nights sleep

Thanks will have a read

 

[Ivan Android]

@CBW1982 Reading through that site you posted, looking at the first section "Hot Water Only". I've turned power off and back on again so that the 3 port valve is in position B. I've then turned on HW only and it doesn't run. Bearing in mind that I have replaced the cylinder stat and controller and assuming I've done this correctly does this point to a wiring fault somewhere? The boiler and pump run for CH only so can I rule out any problem with that?

 

[chris watkins]

Chris he said it has three wires for the cylinder stat, he didn’t mean the valve. I believe he means this is a mid position valve.

Ivan with these valves, if HW and CH are on at same time or just HW then power to boiler is through the cylinder stat. When you turn down the cylinder stat this satisfies the stat and the grey HW off wire becomes energised, this then motors over to CH only and power to boiler and pump is through valve orange wire

Sorry to all for any confusion caused.

Note to self, read the back posts again before you open your big mouth.

 

[SJB060685]

No worries Chris

 

[Burger]

@CBW1982 Reading through that site you posted, looking at the first section "Hot Water Only". I've turned power off and back on again so that the 3 port valve is in position B. I've then turned on HW only and it doesn't run. Bearing in mind that I have replaced the cylinder stat and controller and assuming I've done this correctly does this point to a wiring fault somewhere? The boiler and pump run for CH only so can I rule out any problem with that?

It could be, but not necessarily, you don’t know for certain that the valve is returning to position B. This might be why getting an engineer in might be more beneficial. Boiler and pump should still come on for HW, if you look at the flashing brown wires diagram. Also like you have said if you have replaced the other components correctly.

 

[SJB060685]

Something just doesn’t add up. Are you sure that you have wired programmer and cylinder stat in correctly? This valve is very basic and even if not returning to HW position only then the stat should still bring on the boiler. Am I wrong?

 

[garygvl]

100% it was 3 wires like for like.

was the make of the cylinder stat like for like. some have terminals c 1 2 and others have terminals 1 2 3

 

[Ivan Android]

Something just doesn’t add up. Are you sure that you have wired programmer and cylinder stat in correctly? This valve is very basic and even if not returning to HW position only then the stat should still bring on the boiler. Am I wrong?

I'm as certain as I can be that I've wired both correctly.

The cylinder stat was a like for like replacement and I'm sure I put everything back in the same place.

The programmer I was replacing was a Potterton EP2002 and I've put a Drayton LP522 in its place. I've attached a pic of the back plate before I remove it. When I wired in the Drayton backplate I wired it identically to the old one with the one exception of removing the link between live and 5 on the Potterton - as per the comparison chart supplied with the Drayton. Is this wrong? Seems spot on to me.

I'll switch the power off later on this morning and double check all wiring I can.