Central heating and boiler question

[AndersonC]

Good afternoon all.

We have a Vokera Syntesi 35 combi that has been installed for about 6 years. Over that time it has been rather reliable but there have been a couple of niggles that I have never got to the bottom of despite visits from a couple of heating engineers. I thought I'd see if I could get a second opinion by posting a thread on the forum before getting another engineer visit sorted out.

The first question relates to the amount of gas that seems to be ignited when the boiler fires up. Sometimes the ignition is silent, as if the ignition and gas inflow have occurred simultaneously (which is what I would consider to be normal). Other times, there is a click when the gas inflow starts however ignition seems to be delayed, resulting in a larger quantity of gas entering the boiler before ignition and then a much louder "thump/whoomph" when the gas ignites. Is there a possibility that there is something not right with the ignition mechanism? Could this be repaired?

Secondly, the boiler has a room stat wired into it. A couple of weeks ago I noticed that the boiler was repeatedly going stop-start-stop-start. I thought that it didn't seem right so adjusted the thermostat and the boiler settled down. Is it normal for a boiler to keep starting and stopping when a room thermostat is wired in? How could I rectify this - would installing a new thermostat help or could I remove it entirely and control the temp using rad valves and the CH temp control on the boiler?

Many thanks in advance for any feedback/consideration.

 

[ianmcd]

from what you have told us it sounds as though you need an RGI to check out the set up of your boiler, it sounds like your combustion set up is incorrect, the room thermostat should not have any bearing on the clicking you have told us about, why not get Vokera out to re-commission the boiler and then you know it has been done correctly, too many installers take it for granted that when they install a boiler that it is correctly set up but this is not always the case Im afraid

 

[dcawkwell]

The vokera boilers usually although I can't speak for this model.
Need the fan speed settings adjusted when first installed so that it
is running correctly. Worth checking.

As for the cycling
it could be the boiler isn't modulating correctly for the reason above.
Or that there is a lack of circulation going on if you have a lot of TRV on the radiators meaning the temperature is going up and down a lot rapidly.

 

[bolshy]

Is the start/stop cycle over a matter of seconds, or is it cycling on and off for a few minutes at a time? Could be a roomstat with TPI?

 

[AndersonC]

Thanks for the replies, very helpful as ever on this site

Bolshy - The stop start cycle was occurring over several minutes, with only a few seconds elapsing between each stop/start. I got sick of hearing it so went and turned the room stat in the landing which then stopped it.

dcawkwell - I have seven rads of varying sizes each with a TRV fitted - is this considered a lot?

With regards to getting the boiler combustion set-up correctly, fan speed adjustment and modulation sorted out - I am happy to get this sorted by a RGI (registered gas installer?) as recommended by ianmcd. I am pleased that someone recognises that the combustion may be set wrong. We had a Vokera person out to it not long after it was installed and he told my missus that "the differences in time are due to oxygen level variations". I'd have told him what I thought of that suggestion if I'd been there!

So, with regards to getting an RGI out, I have choices from - local heating service engineers, or an engineer provided by Npower off a "care package" we signed up for a couple of years ago, or do I get on to Vokera again and make sure I am at home if mr "oxygen theory" arrives?

Once again thank you for taking the time to respond to my initial questions.

 

[dcawkwell]

Thanks for the replies, very helpful as ever on this site

Bolshy - The stop start cycle was occurring over several minutes, with only a few seconds elapsing between each stop/start. I got sick of hearing it so went and turned the room stat in the landing which then stopped it.

dcawkwell - I have seven rads of varying sizes each with a TRV fitted - is this considered a lot?

With regards to getting the boiler combustion set-up correctly, fan speed adjustment and modulation sorted out - I am happy to get this sorted by a RGI (registered gas installer?) as recommended by ianmcd. I am pleased that someone recognises that the combustion may be set wrong. We had a Vokera person out to it not long after it was installed and he told my missus that "the differences in time are due to oxygen level variations". I'd have told him what I thought of that suggestion if I'd been there!

So, with regards to getting an RGI out, I have choices from - local heating service engineers, or an engineer provided by Npower off a "care package" we signed up for a couple of years ago, or do I get on to Vokera again and make sure I am at home if mr "oxygen theory" arrives?

Once again thank you for taking the time to respond to my initial questions.

No 7 rads is perfectly normal.
So should have taken more than 2 minutes between cycles.

 

[Agile]

Thanks for the replies,

We had a Vokera person out to it not long after it was installed and he told my missus that "the differences in time are due to oxygen level variations". I'd have told him what I thought of that suggestion if I'd been there!

So, with regards to getting an RGI out, I have choices from - local heating service engineers, or an engineer provided by Npower off a "care package" we signed up for a couple of years ago, or do I get on to Vokera again and make sure I am at home if mr "oxygen theory" arrives?

Once again thank you for taking the time to respond to my initial questions.

I am very sorry that you encounted such a nupty!

Its embarassing when I read that.

Equally that so many installers walk away if it works without properly checking it and setting it for optimum performance in that property.

There is currently a thread about a Vaillant which is seriously oversized and still with all the factory default settings!

I would always say a good independent. But how to find one unless you make up some test questions to ask them on the phone!

Tony