Cylinder stat

[Johntheo5]

What model Vaillant and age?

 

[noddy997]

What model Vaillant and age?

Ecotec 438, 2009 model

 

[Harry Bloomfield]

But doesn't the boiler tell the pump to fire?

So will that be a wiring issue?

That, depends upon how it is wired - Some pumps are directly controlled by the 3-port valve, others are wired to the boiler, so the boiler turns the pump on. That allows the boiler to keep the pump running after the demand is satisfied, to remove residual heat from the boiler.

 

[Johntheo5]

Ecotec 438, 2009 model

If you have Mis for that model, please post them, if they are anything like the ones for the Ecotec PLUS then there is some very useful information in the S (status) codes which should be interrogated when the pump starts but not the boiler, on the PLUS model the boiler certainly seems to control the pump, you can see certain ones inhibit the boiler firing (but there will be no alarm), these are just status codes.

 

[noddy997]

I just remembered my wiring centre is bagged to prevent any moisture entering it. With the cover screwed on and then bagged. This was done few months ago.

Any moisture would now be entering the pump wiring, cylinder stat or the 3port valve (where the lever is). Pump works fine.

 

[noddy997]

The problem reoccurred this evening when HW turned off at 650pm the CH turned off too despite being set to turn off at 8pm. Happened last Friday as well!!

I did some testing today (from the boiler end).

The yellow wire (No7) connected to the orange got 240v for CH only and HW only and also for CH with HW. However a few times it got 140v too. Boiler did not fire up nor did the pump despite getting 240v.

The "HW on" cable sent 240v when HW was turned selected on programmer. Similarly when selecting CH the thermostat cable sent 240v. Cylinder stat is at 60 so there would be demand for HW and the water in the cylinder was cool (unless cylinder stat faulty).

I then checked the PCB on the boiler the switch live was getting 140v (via the yellow cable connected to No 7) and the wire connecting the PCB to the pump was getting 140v too. Other occasions I was getting 240v.

The pump and boiler then decided to fire up.

240v is going up to the 3 port valve but on occasions only 140v is being sent down.... Why would this be??

This morning same issue again but was 240v where needed but boiler and pump not firing up despite getting 240v on pcb switch live and the pump from pcb.