If you have correctly identified the SL as coming from the programmer then, yes, a programmer/wiring fault but the boiler should then just run continuously.
What did you short between and what is "no difference" ?.
Vaillant ecotec plus 438 no heating or hot water
- Thread starter noddy997
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Go read the event chain again posted in this thread.
For systems with wired thermostats:
When needed, Programmes sends a GO signal to the zone in question = 240v ---> Thermostat.
If the thermostat is warm (ie hot enough) the voltage stops there.
If the thermostat is cold, the switch is closed and the 240V continues on to the zone valve actuator.
This energises the actuator which opens the valve fully.
On full open, the valve closes a microswitch connected to a seperate 240V feed. On closing the switch, the 240V is returned to the Boiler SL.
On seeing SL go 240+, the boiler gets the go signal and wakes up.
If you are measuring 240V at the terminal on the boiler marked "SL" and the system components are all marching to that tune, then the boiler should be running.
If you are getting 240V and any one of those links in the chain should be broken (ie you unplugged the programmer, or the thermostat is off) then you have a short circuit somewhere.
Unless the SL is normally 240V+ and detects current changes (odd but whatever) i cant see how you would have SL positive and the boiler sat still.
I am not a plumber/Gas eng. So take this with a pinch of salt.
Your wiring diagram shows a brown wire, presumably from the programmer? in terminal 3 so shorting between this and the PL (as shown) should start the pump & boiler, presuming you have 230V on the PL??.
But the boiler schematic shows no brown wire in 3 but one in 4 which suggests that this may be the SL?.
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You have to remove the jumper if using a external control. (IE a 240 signal from a zone valve)
SL then goes to 4.
The number 4 on mine has been connected to the motorised valve.
Been like this for 15 years and had no problems. Same with all other wiring in wiring centre too.
Apologies, number 4 was the switched live and voila from L to 4 direct boiler and pump fire up immediately as soon as I turned on mains power
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That is the way it should be
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So go backwards. Go to the switched live from the motorised valve.
It should have permanent live on one side and be switched on the other.
When the valve is open, the switch should close.
Easy to test with a multimeter
Thats coming from the 3 port Orange or grey wire.
Yes, the grey wire that comes "directly" from the programmer via the HW cylinderstat is connected in parallel with the orange wire that comes from the 3 port valve when CH only required.
Do the simple test first, with HW only requested and the cylinderstat calling, does the boiler fire up, if so, turn the cylinderstat down, does the boiler then shutdown?
Yes it does fire up and then shuts down when stat is turned down
With this amount of testing going on, were it me, I would be making use of something a little more permanent to connect to the SL. Such an item, might be as simple as a small light bulb, a lamphholder, with a bit of flex. Connect the ends of the flex, between SL and N, and it is immediately obvious when there is a call for heat, to the boiler.
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