Logic Combi ESP1 35 always showing demand for Central heating

[theboyroberts]

Hi folks,

I've got a potential problem with my Logic Combi ESP1 35. When the boiler is set to Central Heating and Hot water mode, the boiler indicates that there is a constant Demand for Central heating.

When the thermostats (TP5000 Si) are turned off (both pulled from the wall and also simply by turning off the heating either via temperature or timer) boiler continues to fire. The boiler indicates that the temperature of the system is always around the 50c mark and as soon as the temperature drops, the boiler kicks in and heats the water again.

I have a dual zone system with some form of valve system which is controlled successfully via the thermostats (photo attached) and as the radiators do not get hot unless triggered by one of the two thermostats i can only assume that it is working as expected.

Initially I believed that this was by design, however after finding a similar post on this site, I'm now not too sure.

I suppose my question is this; when the two thermostats are set to off, should the boiler be continuing to heat that water system or should it go into standby mode and allow the temperature of the system to drop until the thermostat kicks in to show a demand for central heating?

I've also included a picture of the thermostat wiring, which I believe to have been correctly wired.

Thanks in advance for any advice.

Shaun

 

[Scott_D]

Sounds like it’s not wired correctly.
How old is the house?

 

[Deleted member 120897]

Sounds like a link may have been left in.

 

[John.g]

Zone valves normally give the run signal to the boiler via auxiliary (end) contacts which switch a permanent live to fire it, the motorized valves are closing but one of the contacts may still be closed, the boiler will then continue to fire controlled by its own thermostat.

 

[theboyroberts]

Morning folks,

Thanks for the quick replies; its appreciated.

OK, so the boiler shouldn't be be receiving the demand for heating call until the thermostats kick in. At least I now know that its not wired correctly.

I can see that the zone valves have a wire which drops through the floor and I believe to the boiler, so this may be where the problem is as John.g mentions. I'll open the floor plate (white box near the valves) later to see if I can spot the problem.

As for the age of the house; its just over 2.5 years old and has just left the warranty period. I have dropped the builders a mail about this as if the system has been wired incorrectly, it should be covered by them, either as a good will gesture or perhaps via the 10 year NHBC building cover.

 

[Deleted member 123817]

It could still be wired correctly but one of the zone valves may be faulty and not opening it's end switch when it closes, tne HW will still work as it takes priority over the CH.
If it's always behaved this way then probably wiring problem.

 

[Deleted member 120897]

Yeah, I’m pretty sure nhbc wouldn’t cover it. I think they’re more for the building works, eg roofs etc.

 

[exedon2]

I would go for failed valve danfoss aren't the best.
Check to see if manual lever moves freely they are pronne to sticking open.

 

[John.g]

Should be relatively easy to check out at the junction box in front of the two zone valves. Each valve actuator will have 4 or 5 (if earth wired).
Brown&blue and grey&orange. (+yellow/green earth wire).
The brown wire is live from the room stat etc with call for heat and opens the valve via the motor and the blue neutral.
The grey wire is always (permanently) live and the end switch connects this supply to the orange wire and on to the boiler when the valve opens.
With motorized valve de energised (Shut) there should still be 230V at the grey wire but nothing at the orange wire, a multimeter can easily check this out.

 

[theboyroberts]

Hi folks,

Attached is a picture of my floor junction box.

John.g - to perform the test you mentioned above, I believe I need to connect the multi-meter (also shown in a picture) to 3rd and 4th points in the connector block when both of the thermostats are powered off?

If the wiring is correct (which it looks like it is), I should get a 0 reading?

Thanks again

Shaun