Combi Modulator? hot/cold/hot water

[rednaxela]

Yesterday, my Vokere non condencing boiler had a fault.
In hot water mode, the water would come through hot, then over a minute or so, would go cold again, then it would go hot, then repeat over and over.
The flame seemed to be either on or off and the temperature dial was getting to just below 60°C
This morning, the temperature regulation seemed ok again.

The boiler was moved a few weeks ago and has been fine up to now.
Would it be worth checking all the electrical connections are sound, or could it be the modulator? I am not sure if they fail intermitantly.

any thoughts would be great.
Alex.

 

[chrishutt]

Tell us more about the boiler move. Was it carried out by a Corgi installer? Was the heating system flushed and cleansed? It could be that heating system corrosion debris has been disturbed by the work and has caused problems in the boiler.

 

[rednaxela]

The boiler was moved upstairs by a Corgi guy and has been registered etc. I helped out with flushing of the whole system. Its about 8 years old. (don't have the boiler number with me)
I was at the wet end of the flush when we did each radiator. The water went grey for a few moments, then went clear. The guy said it was very good.
Apart from that, nothing else really to report.

 

[chrishutt]

Was a chemical cleaner used? Typically such a cleaner would need to be circulated for at least a day or so to help loosen sludge. Just physically flushing through might dislodge the bulk of the sludge, but there would be plenty left behind (not that even chemical cleaning is 100%).

 

[rednaxela]

(thanks for your comments Chris)
no chemical was used, he just used mains water pressure and went round the house switching each radiator on in turn until the water ran clean.
Could debris in the system affect the burning? perhaps thats why it was ok this morning.. it may have moved on.
I do know that the cover on the flame chamber was never taken off. Would it be worth getting this cleaned?

 

[ChrisR]

Boiler model name would be useful, like Excel, Flowmatic...

 

[chrishutt]

I don't know Vokeras well enough to comment further. It might be nothing to do with system cleanliness, although I've come across situations where sludge coatings on temperature sensors have seriously upset hot water performance. Heat exchangers are vulnerable to sludge too. Others have more experience with Vokeras and will hopefully comment.

 

[DP]

You asked for the boiler to be moved. Boiler would have been moved as a unit. Only access would have been to lower half for electrical connections.

The boiler (I suspect) is either Excel or Maxine. The boiler make or model is not important as most boilers (other than cheapos) use plate to plate HEs. Almost certain muck in the system will be a contributing factor (which effects this type of heat exchanger).

If the system is functioning again, it would be worthwhile to chemically cleanse the instal and consider additional controls for fuel efficiency.

 

[ChrisR]

I would agree, I was just thinking about this guy DP, who answered, about a Vokera, which was going hot and cold, ...

"Sorry Chris, I doubt if sludge is the culprit here. HW HE rarely plays up." (Flowmatic)

 

[rednaxela]

Excel rings a bell..

 

[Agile]

It might be a flue assembly fault causing the boiler to think that the fan is not working.

Is the flue length less than one metre ?

As it is likely to be connected with the move then you should call the CORGI back to look at it.

Tony Glazier

 

[rednaxela]

Called my Corgi Guy, He thinks it could be the Heat exchanger (£80) or a sensor (£7) he asked me to run the central heating side tonight. If the temperature is also low, then it could be the sensor, or if its normal, then it could be a blocked heat exchanger.
He advised that it is better to change for new rather than clean, as he has never had much luck or long lasting results from cleaning.

(thinking about it, I have had a couple of black bits come out of the hot tap) I had assumed it was dirt on the tap. Perhaps it is rubbish coming right through..

 

[ollski]

Was a chemical cleaner used? Typically such a cleaner would need to be circulated for at least a day or so to help loosen sludge. Just physically flushing through might dislodge the bulk of the sludge, but there would be plenty left behind (not that even chemical cleaning is 100%).

for salamander fast cleanse they say 2 hours circulation at max system temp is ideal.

 

[weareleeds]

My guess is dirty fan.To prove it get corgi guy to loosen front panel in one corner & ease forward to allow air in from room.Switch on tap to see if it goes from high gas (11mb to low gas 1.6mb) if it does screw front back on & re-check if it then goes from high gas to off again then remove fan & thoroughly clean or replace