Combi ignition switching on and off

[Aaron83]

Hi all,

I have Worcester 35cdi combi boiler and when the heating is on the "flame detection indicator" turns on and off every approximately every 2 minutes.

The heating does seem to work as the radiators are hot. It just doesn't seem right that it keeps going on and off. Is this normal?

Also (as previously posted) the shower goes cold occasionally. It was doing it more often until I changed the shower head. Not sure if it could be related so thought I should mention.

Would appreciate any guidance.
Thanks in advance.

 

[Agile]

It is not normal and you need a gas reg engineer to investigate the cause of the fault.

Left like that could cause further damage to the boiler.

Tony

 

[Agile]

But is it really a flame detection indicator? Or is it just a flame on indicator?

It is quite normal on a small load for the boiler burner to need to cycle on/off at approximately 2-4 minute interval if the heating load is less than the minimum boiler output which is probably about 12 kW. That's more than th heat loss of a three bed semi when it is -1 C outside!

Tony

 

[Aaron83]

Hi Agile. Thank you for your reply.

Well the manual says that it's the flame detection indicator. When it turns back on it sounds like the boiler is lighting again. I thought maybe it's related to the temp set on the stat but continues to do the same when set a max.

So you think I need an engineer to look at it? Only had it serviced 4 weeks ago

 

[Agile]

Sounds as if it is intended as a flame on indicator!

When did it start doing this?

I would expect it will be correct operation in relation to your house size.

If there was a fault it would be most likely to be there on hot water as well. But you have not mentioned hot water delivery!

The boiler needs a minimum HW flow of about 2.5 litres per minute. If the boiler is deteriorating it may need a higher flow rate. The service engineer SHOULD have checked that. But some don't.

If your shower flow is inadequate that can cause the boiler to turn on/off. But the correct minimum flow rate is a very poor shower.

On CH only, it can be caused by a wrong minimum gas setting.

But without knowing your house heat loss its impossible to reach any conclusion. I can only guess it may be the typical UK semi.

Tony

 

[Aaron83]

Well it's the first time we have used CH as bought the house in May. The shower going cold started around 3 weeks ago.

No it doesn't do it with hot water, only with the shower but the hot water light also goes off.

It's a 3 bed semi with a large conservatory and single storey extension. Have underfloor heating downstairs.

Not sure if that extra info helps