Central Heating Wiring - Weird Stuff Happening

[noswar]

Hi,

My gas central heating and water seemed to come on and stay on randomly. So I sat down and went through every combination of Timer Setting / CH Thermostat / Tank Thermostat to see precisely where the issue was.

If you look at the attached matrix, you'll see that there are two specific scenarios that causes 'weird stuff' to happen.

Untitled

• noswar
• 9 May 2014
• 1

The first is where the CH & HW are OFF at the Timer, but when the Room Thermostat calls for heat the Boiler fires up.

The second is where the CH is ON and HW is OFF - Room Thermostat is NOT calling for heat but the HW thermostat is - this results in the boiler firing up but the valve stays at H meaning!

From the info provided, can anyone suggest what may be wrong with the wiring?

Thanks,

Nozzy

 

[Agile]

Faulty valve?

 

[D_Hailsham]

Is this a new fault, i.e the system worked correctly before?

 

[noswar]

Yes... it did work before...

 

[D_Hailsham]

Yes... it did work before...

Has any work been done recently on the system?

How many motorized valves do you have?

View media item 5946View media item 11762

 

[noswar]

Sorry for massive delay in replying...

1). No work done.

2). Just the one.

 

[noswar]

The thing that is massively spooky is that with the... CH and HT both OFF at the timer, the boiler still comes on when the room thermostat calls for heat AND the tank thermostat doesn't...

 

[picasso]

Boiler a worcester bosch by any chance ?

 

[noswar]

Boiler a worcester bosch by any chance ?

No - an old Ideal Elan 2

 

[noswar]

And some more info...

I have checked the voltages from the cylinder stat...

1(C) - 2(NC) = 240v when heat NOT required,

1(C) - 3(NO) = 50v when calling for heat

 

[picasso]

What voltage do you have to the switched live on your boiler when both the heating and hot water are switched off at the programmer ?

 

[jeff the gasman]

Faulty actuator head. Microswitch shorting out between on and off.
Had it a while ago on a Drayton Valve.
Jeff

 

[ALCPlumbing]

Definitely a bit of an enigma.

I love your chart BTW.

 

[ecowarrior]

If it has defo been working properly, draw out the Y plan os S plan and see whats the ways it can supply a S/L to the boiler.

Perm live to HW on from the timer on a Y plan is an interesting one - does this but with the cyl stat not the room stat.

Also lots of Y plans wired up wrong for years. Then a fault appears & u r looking at two faults?
Draw it out & apply you matrix to the drawing.

 

[matt1e]

Morning all
never posted on here in a while so I will give a little input on this then go and ave a catch up to see what I've been missing

Noswar, this is strange indeed can you confirm that your table is correct especally the first four entries on it as it seems to suggest that the room stat is in series with the cylinder stat common/normally open conntact

Untitled

• noswar
• 9 May 2014
• 1

do you have a multimeter?
start with the 11th one down (off,on,no,yes) the boiler should be on it's a simple circuit to trace through and it doesn't involve the valve actuator
hw on > cylinder stat com/call for heat> boiler call

Matt