Honeywell ST9400C

[cambsdiy19]

Hi,

I have the aforementioned programmer which is working fine for hot water but not for CH. It seems that no matter what setting the CH is on (timer, continuous, override) it will not come on unless it is a particular time in the evening.

For example, if I set the timer to come on at 2pm, the green light will come on at 2pm but the heating will not. If I set it to continuous the green light will come on but the heating will not until it hits this random time in the evening (around 5ish). At that point it will come on roughly from 5pm-10pm. It's as if it's being controlled by a timer program but not the ones I have set in my programmer and these times cannot be overridden.

The hot water works fine on all settings. Is it possible there could be another programmer somewhere controlling only the heating? I know nothing about plumbing but I wouldn't have thought so?

Should add this is a rented house so I didn't install any of it and the handyman favoured by the lettings agency is pretty useless so I'm keen to gather as much info as possible before calling them.

Any thoughts/suggestions would be much appreciated! Thanks in advance

 

[JohnD]

please post a photo of the room thermostat which will be on a wall somewhere.

I have a feeling it will be one with a timer, or it might just be set rather low.

 

[cambsdiy19]

please post a photo of the room thermostat which will be on a wall somewhere.

I have a feeling it will be one with a timer, or it might just be set rather low.

Hopefully that's worked. Thermostat has been set to 20 all day but right on cue just before 5pm the heating has come on despite the light having been on all day

 

[ianmcd]

As already said, sounds like you have a room thermostat somewhere

 

[JohnD]

turn the wall stat knob up and down. Does it click at about 20?

Put a thermometer by it and see what the room temp is.

If you turn it to a lower number, the heating should go off when it clicks; if you turn it to a higher number it should go on when it clicks.

It might be that your room temperature dropped around 5pm due to the sun going down.

It is less likely, but also possible, that there is another timer or stat somewhere, especially if the landlord is parsimonious and pays the heating bills.

 

[cambsdiy19]

I just tested it, the 'click temp' seems to be around 16-17 and heating responded accordingly so thermostat definitely working. Unfortunately I don't have a thermometer to check the room. Interestingly though whilst I left the stat at 20 today, on other days (including this week so not warm days by any standard) even if I turn it up to max the heating won't kick in if it's before the roughly 5pm trigger time.

I pay the heating bills but the boiler is in the loft and the landlord doesn't give off the impression that he knows this place inside and out so potentially something else on the boiler. Just odd that it's only affecting the heating if that was the case.

Thanks for your help so far in any case!

 

[JohnD]

if incorrectly wired, CH might not come on unless HW is also on

 

[cambsdiy19]

I’ve managed to fix the issue so just in case anyone else encounters this problem with this programmer:

Scrolling through the set up menu there is a reset parameter (parameter 8 ) which is set to 1 unless you’ve changed the on/off times in which case it will be 0. Mine was still set to 1 despite having changed the timings so I manually set this to 0 and then back to 1 to reset the timings to default.

This seemed to fix the error. The heating came on in the morning as per the default timing and has now come on again after I set up my own custom timings.