Hot water won't come on by itself

Ivan Android · Feb 22, 2019

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 · Feb 23, 2019

chris watkins said:
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 · Feb 23, 2019

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 · Feb 23, 2019

CBW1982 said:
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 · Feb 23, 2019

@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 · Feb 23, 2019

SJB060685 said:
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 · Feb 23, 2019

No worries Chris

Burger · Feb 23, 2019

Ivan Android said:
@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 · Feb 23, 2019

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 · Feb 23, 2019

Ivan Android said:
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 · Feb 24, 2019

SJB060685 said:
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.

Ivan Android · Feb 24, 2019

Solved!

The connection from terminal 1 in the cylinder stat had worked its way free of its connection inside the junction box. The lead from the stat is hanging free and had not been secured at or near the entrance to the junction box so multiple knocks over time had caused it to work itself free.

Now to run it for a while to generate some hot water and then I can power off and tighten up all connections and secure the loose leads.

Thanks to all who got involved!

SJB060685 · Feb 24, 2019

Like I said initially it was going to be something like this. These valves are very basic and once you have a good understanding it’s easy to find the fault. Glad you’ve found the cause and sorted it

Welcome to PlumbersTalk.net

American Visitor?

Hot water won't come on by itself

Ivan Android

Burger

Burger

Ivan Android

Ivan Android

chris watkins

SJB060685

Plumbers Arms member

Burger

SJB060685

Plumbers Arms member

garygvl

Ivan Android

Ivan Android

SJB060685

Plumbers Arms member

Similar plumbing topics