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

[sam smith]

Hello Folks and Especially those that are averse to Vaillant prooblems

I have an Ecotec plus 637 systems boiler not sure if its S or Y plan but will poost pictures. Theres a wireless room stat in same room and a Valliant control center too. All has been running fine for absolutely ages until the pump decided to come on of its own accord at random times and for what seems like ages (20-30 plus minutes) it would even come on when there was no demand for heating or hot water.

I ran through the overun time settings but this didnt help. And the pump was making loud noises (fan/propellar on its way out?)

Anyway as the boiler was still functioning (heating water and radiators ok) we decided to ignore it and thought it must be due to the pump being 'on its way out' . Anyway the pump noise got louder so I have just had that replaced yesterday but the overun still occurs. I think it mainly occurs on the heating side rather than when there is a demand for hot water - also I have not noticed it coming on of its own accord but while testing the pump the boiler would heat up to 50C and not get any warmer no matter if the dial for the heating was turned all the way up! And the pump was obviously on too. The heating engineer said it could be do with the 'settings' on the stat/controller but I know this is not the case as the settings have not been altered. Then he said it could be due to a faulty weather compensator? But I am not sure if this is correct

I have read somewhere on this forum that it could be a 3 way port valve issue? Can anyone tell me if this could be the case here?
Also the pump over run has been doing my head in so much that I am not sure if the pump symbol SHOULD be on when its calling for heat or HW? or should it come on afterwards?


Any help would be greatly appreciated

 

[CBW]

AFAIK - pump overun comes via the PCB. Is it firing at all for a demand? The temperature setting I believe is down to the vaillant controls being used. @ScottishGasMan might have more clarity for you.

 

[sam smith]

Hi @CBW,

Thanks for your prompt reply. Yes pump overrun most likely does come via PCB but I read on a previous thread a couple of times that it could be a faulty micro switch on a port valve sending false info to the boiler thereby sending into circulation/over run mode. Im not sure how I would check which one is at fault as I have 2 ports not sure which is which in my case ? And yes to answer your question it seemed to fire up fine on hot water demand and then switch off at the set time but for heating when I set the time tge boiler would heat up to 50c and then stay at that temp while the circulation pump came on and it stayed like that for ages. I havent rechecked this morning (as pump was changed last night) but im guessing it will do the same thing. So the old noisy pump wasnt the cause of the over run problem. Hence why I am looking for other solutions. Yes by all means if any vaillant experts can give their valued input and opinions I am willing to try their advice

 

[CBW]

Test equipment would assist in a microswitch stuck situation. Try moving the lever on the valve(s) if they have resistance then likely ok, if move freely then potential issue

 

[sam smith]

I can possibly get someone to check the terminals for output etc but they would need to know what to look for etc. the lower valve definately had resistance but not checked the top one. I will do when I get home and update

 

[The831Bunny]

Check D.9 diagnostic code on the boiler. This is the boiler flow temperature requested from the controls. If it doesn't deviate from 50ºC, then that’s the temperature requested in absence of the normal operation, an emergency mode if you like. It could be bad contacts of the controller in its backplate, bad contacts at the VR65 or any eBus wiring. There doesn’t appear to be any display on your controller, which would cause the issue. Maybe get somebody to check it out who is conversant with Vaillant controls.

 

[sam smith]

Hello The831Bunny,

I will check the D.9 diagnostic code and see what is says.

As suggested by CBW I physically checked both port valves and the one above also has resistance, although now that I have pushed the lever to the other side, it is in effect much looser, I am guessing this is because I have shut (or opened) the valve?

The lower port valve lever as options : auto or manual and that is quite hard to push.

I will see what the Diagnostic code says. One other thing that comes to mind, the stat in the room currently reads 18.5c and the outside temp is around the same (reading on weather compensator) so would this “prevent” the boiler from reaching temperature if it “thinks” too much heat is not needed? The thermostat is set to 23c

 

[CBW]

Check D.9 diagnostic code on the boiler. This is the boiler flow temperature requested from the controls. If it doesn't deviate from 50ºC, then that’s the temperature requested in absence of the normal operation, an emergency mode if you like. It could be bad contacts of the controller in its backplate, bad contacts at the VR65 or any eBus wiring. There doesn’t appear to be any display on your controller, which would cause the issue. Maybe get somebody to check it out who is conversant with Vaillant controls.

I thought I’d read somewhere in a manual that 50 is the maximum when using ebus, I had a similar situation last year, customer had a Vaillant wireless stat, couldn’t get the temp higher, I fitted her a 3rd party controller as she’d damaged hers, and after messing with D codes the temp was ok after that.

 

[sam smith]

Hi, thanks for that. I would have to look up what you mean by ebus but will certainly look at the D values and update you. Thanks to both of you guys

 

[Harry Bloomfield]

I thought I’d read somewhere in a manual that 50 is the maximum when using ebus,

I have ebus and I can assure you my system is not limited to 50C..

 

[The831Bunny]

Flow temperature request to the boiler via eBus is not limited to 50ºC.

With weather comp it can be anything from 20ºC to 80ºC, depends on the heat emitters and the curve set. Usually radiators require a curve around 2.4, this gives a mean temperature of 75ºC at the rads with a -1ºC outside temperature. Lower curves may well work if the rads are oversized. This time of year when outside temperatures are as warm as 16-20ºC and the required inside temperature is 21ºC the flow temperature could be as low as 30-40ºC. That’s all the heat you need to raise the property temperature, and indicates the system is working correctly.

As to the 50ºC issue, it may be by absolute coincidence that was the required temperature at that time and all is well, or as I said, in absence of a proper connection to the thermostat, the controls default to a mid temperature of 50ºC as an emergency feature.

 

[The831Bunny]

Other things to point out: The zone valves don’t use any switched lives (orange and grey wires) to feed back to the boiler and turn it on, the boiler gets the request to light from the eBus flow temperature. They are 100% controlled from your VR65/6. Also the heating and hot water knobs on the boiler should both be set to maximum. The hot water temperature for your cylinder and room temperature is then set on your Vaillant controller.

 

[sam smith]

Hi @The831Bunny

Thanks for this. I see what you mean about how the weather compensator will affect the boiler in the warm weather we are having. As the previous person mentioned to check the port valve, I checked both and noticed when i pushed the lever of the top valve to its opposite position, when the boiler came on to heat the water, I found that the upstairs radiators also came on! The next day I pushed the lever back to its original position and it fixed the problem.

 

[sam smith]

I will see if I can find the post about a similar problem to what I had (pump coming on - without any heating/hot water demand) and you can let me know what you think as in that case it happened to be a faulty port valve

 

[sam smith]

Ok so the pump has come on again theres no demand for hot water or heat (timers are off for each) but the radiator symbol is flashing and the pump is on, the reading on the room stat is shown too. Is this the same “fault” or is this happening as the boiler thinks theres too much “heat” in the system to get rid of (due to higher outside temp??)