Viesmann 100-W boiler - pump keeps kicking in

[bensp]

Hi,

First post on this forum so go easy.

I have searched the forums for my problem and as I have found nothing I think it must be one of those silly niggles that is unique to me!

My boiler is a Vitodens 100-W WB1B regular open vent.
My controller is Honeywell, timer box on the wall and room stat separate.

I had the boiler fitted some months ago and am very happy with it other than the niggle I will describe.

When the boiler is turned (the button on the front panel) but the timer or stat are turned off then then every 20 minutes or so the burner symbol will flick on for a couple of seconds then go off. You can also here the boiler fan or such like spin up. Not and issue as such but when the burner flicks on the pump then kicks in. I would expect that when the boiler is "off" due to timer or temp from the stat then surely it does not need to flick the burner on and off? Therefore not keeping the pump running more or less all the time.

I have played with the controls and room stat and had the whole thing checked out by the installer and we can find anything wrong.

Any advice or thoughts would be appreciated.

Thanks

 

[Agile]

Did those tests include disconnecting the external controls?

Tony

 

[bensp]

To be honest I am not sure. I thought the boiler would not fire up if there was no signal as such from a controller.

I think because the weather has become a bit warmer I noticed it more so than when it was cold and the installer thought it might just be pump over run.

If there an easy way to disconnect the controls?

Thanks

 

[Agile]

Thats the whole point!

To disconnect the external controls to then decide if the problem is with the controls or the boiler.

Tony

 

[bensp]

Ok I take your point on isolating the controls.

I would think I have to remove the wire within the boiler or the control casing in effect. I will have a look.

On a side note do you know if there are any controls which work well with Viesmann? There site lists a couple but they only appear to be for sale on a handful of websites. I thought Honeywell was a reasonable brand.

Thanks for the quick answer as well.

 

[D_Hailsham]

My boiler is a Vitodens 100-W WB1B regular open vent. My controller is Honeywell, timer box on the wall and room stat separate.

So you have a hot water cylinder with a thermostat (see pic) and one or two motorized valves (see pics).

The problem could lie with one of those. Tell us which valve(s) you have.

View media item 10596
View media item 5946 View media item 11762

 

[bensp]

Hi,

I have a hot water cylinder with 3 way valve also honeywell. I had it replaced about 8 months ago and i can hear it switching between hot water and heating.


I have never seen the hot water symbol on the boiler but the water does get heated up fine.

Thanks

 

[D_Hailsham]

I have a hot water cylinder with 3 way valve also honeywell.

How a mid-position valve works explains how to fault find this type of system.

 

[bensp]

I will run through the guide but I don't have any issues with water/heating cutting over just the boiler triggering the pump. How would the valve cause that or is this just a good place to start checking?

Thanks

 

[D_Hailsham]

Reading your description again, I doubt if it is the motorized valve. You need to find out if the problem is boiler or controls related.

At the junction box (where the motorized valve etc are all connected) locate the terminal which has the orange wire from the valve connected. There will be a two other wires on the same terminal. One connects to the cylinder thermostat, the other goes to the boiler. Disconnect the wire to the boiler. (Turn power off before you do this, then turn on again.)

This means the boiler should not work at all. (OK, you may get cold and the cylinder won't get reheated. ) If the fault still appears, it is boiler related; if it goes away, it is controls related.

If controls:

Follow the fault finding in the link I gave.

If boiler related:

Is the boiler actually lighting when the problem occurs or do just the fan and pump which come on?

Where is the boiler located?

If it's in a cold area - loft, garage etc - it could be the automatic frost protection working.

 

[mysteryman]

Check that the 470nF capacitor is in place between 1 & N on plug 96. If not, you need one fiitted which is good for mains voltage. Some mid-position valves pass a low voltage enough to boot up the boiler, and the capacitor will slug this.

 

[bensp]

Sorry it has taken so long to post back I have been a bit caught up.

Anyway I did the trouble shooting as described and found think all components are working correctly. However I replaced the Honeywell ST699 controls, like for like, as I noticed some scorch marks on the PCB. Perhaps some water got in when the old boiler failed. Either way I thought it best to change them for the money.

I also rang Viessmann who are helpful and suggested I check for the capacitor as mysteryman suggested so that is my next job.

Incidentally Viessmann wanted £190 to visit and would waive the cost if the warranty covered the fault. Sounded a bit steep to me I was expecting more like £120 call out.

 

[Agile]

Check that the 470nF capacitor is in place between 1 & N on plug 96.

Hopefully this is now included on the PCB in all current boilers?

I usually add a resistor with these problems though.

Tony

 

[bensp]

I see 1 and N on the PCB where 96 is marked and just behind there are two small blue capacitors, does that sound right?

Thanks

 

[Agile]

Blue caps are often mains rated ( but not always! ).

But I dont know the answer to your question.

Tony