Vaillant Ecotec Plus 637 Pump over run problem- Please Help !!!!

[sam smith]

Thats the boiler

 

[The831Bunny]

Two things you need to do before we can diagnose this. When the pump is running (when you think it shouldn’t) press the i button and make a note of the code, press the i button again to get back to the main screen. Press the i and + together, the display should say d.0. Press the + button repeatedly to go to d.9, press i and make a note of the figure. Post back and we can go from there.

 

[sam smith]

Hi, ok sure thing. I will run through that sequence once the pump comes on again. I do know that when it came on before without any demand the code was S7 which I believe is for pump overrun. I have not recorded the D9 value but will do this once it comes/plays up again. Many thanks

 

[sam smith]

@The831Bunny

Just to give u an update. The pump has come on the S code is S7 and the D 9 value is 10?

 

[sam smith]

The temperature on the boiler display then dropped to 18 c and the pump over run stopped. The room stat is reading 19c and now so is the boiler

 

[Johntheo5]

@The831Bunny

Just to give u an update. The pump has come on the S code is S7 and the D 9 value is 10?

d.009 is the "target temp from external eBus controller", its most unlikely that any WC curve would go that low, at 10C, most only start at 20C.
d.047 should show the actual outside temperature.

If the boiler is getting a target temp of 10C (remotely) then it may tell the boiler to fire up, the circ pump will then start but the actual flow temperature would then IMO have to be, or fall to 5C, (SP-5C) to fire the burner, which it clearly won't (get to5C)
One would think then though that the circ pump might just keep running and not display S7, pump overrun?.

 

[sam smith]

I just noticed the pump had come on randomly yesterday so checked the S and D values. This morning after the radiators were timed to turn off at 9.00am I came downstairs and the pump was running until 9.30am. Is it normal to have the circulation pump running for so long after a heating demand time has lapsed? Would the pump come on normally during normal boiler operation (heating or hot water) and can it run for so long afterwards? Or do you think it is a fault ?

 

[Johntheo5]

If everything was/is normal then the pump overrun time is, as set in d.001, 1 to 60 minutes, default time 5 minutes, easily checked out, you don't really know whats going on there especially since input d.009 is "wrong", at least you can check d.047 to see what actual outside temperature its reading.
Because of all this the boiler may be "firing" and then doing multiple anti cycles + pump overrun, whether its displaying a s7 or not.
the anti cycle time depends on its setting (default, 20 minutes, set in d.002) plus the boiler target temp, it only goes as low as 30C so don't know what it thinks if it sees a apparent target temp of 10C, a 30C target temp + 20 min setting gives a actual anti cycle time of 16.5 minutes.

 

[The831Bunny]

As previously stated you need to check for any bad connections on the eBus wiring and the controller, especially the pins on the back of the controller. If the boiler loses connection or sees a blip in the requested temperature, even for a split second, then the boiler pump will start. It then runs for the duration set in D.1. At this point, that is the S.7 pump over-run you are seeing. S.7 always follows S.1, S.2, S.3 or S.4. An intermittent connection is the most likely cause, followed by a controller and/or boiler PCB fault.