Combi Boiler Gas Supply

[dpensox]

Hi All,
Do all combi boilers have to be fed by a 22mm Gas supply ?

Sorry if this seems a stupid question, but I 've had a quote to replace my existing Conventional Back Boiler with either a Vaillant EcoMax 828E or a Glow-Worm 30cxi, and been quoted to re-run 22mm from meter to new boiler site.
After reading the Vaillant Bolier Spec, it say 15mm gas connection(the Glow worm doesn't specify).

Can anyone shed any light on this ?

Also, from the 2 boilers mentioned, which would you go for - or is there another(more reliable one) that you'd recommend.

Thanks

Dave

 

[ChrisR]

22mm if it's between almost nothing and several metres, 28mm or more if further than that. Proper sums have to be done taking bends etc into account, as well as cookers, fires etc.
V and GW are owned by the same company now, and the boliers are similar, though the GW has more probs it seems.

 

[Gasman1015]

There are several boiler manufacturers that specifiy a 15mm gas connection,
but this only relates to the actual boiler connection not the size of the pipe required to supply the boiler, rest as ChrisR has said.

 

[ollski]

I come across at least one blocked hw heat exchanger a week on the glow worm cxi, don't know why they are so much more prone to blocking so quickly when compared to everything else, but I wouldn't take the risk on the gw.

 

[timbalcombe]

up to 1.5 m can be 15 mm any more will have to be 22mm

 

[Agile]

I hope you are not CORGI registered Tim! A bland statement like that can only confuse! It all depends on the number of elbows and other connectors.

The only thing that you can specify is that there must be less than 1 mB pressure loss between the gas meter and the boiler gas valve test point.

Since plate heat exchangers are virtually all the same they will all be equally prone to blockage. Just the result of failure to power flush the system as usual.

Tony

 

[ollski]

Since plate heat exchangers are virtually all the same they will all be equally prone to blockage. Just the result of failure to power flush the system as usual.

Tony

You would certainly assume that, but the cxi's are the only boilers I'm replacing dhw hxs on in less than 2 years on a regular basis. I did one last year on a complete new system installed 18 months ago.

 

[dpensox]

Thanks for the replys - just wanted to check - (makes sense when I thought about it - same as volt drop!)

Ollski, just out of interest, do they block on the Primary (heating) or Secondary (hot water) Side of the HW Heat Exchanger ?


Thanks

Dave

 

[Agile]

I think the answers would become apparent if you investigated who installed them, what power flushing was not done, why YOU are getting called to them and the proportion of that model which were being installed in your area 1-2 years ago!

They were one of the most popular boilers with a lot of installers then. More recently problems particularly with condensate traps and connections have made them less popular.

The cheaper Vaillant Ecotech model seems to have made that one of the favourites now with many installers.

Tony

 

[ollski]

I think the answers would become apparent if you investigated who installed them, what power flushing was not done, why YOU are getting called to them and the proportion of that model which were being installed in your area 1-2 years ago!

Its not a question Tony, I have never had anything block up like them and that is my bugbear with them without even going into the leaking filling loops, manifolds, condensate traps, failing pcbs, duff overheat stats etc.

That said I very rarely see vailliants, round here we are pretty heavily worcester.

 

[Agile]

I still think that the problem is not specifically associated with the boiler.

They are the same HEs as all the other boilers so there is no reason they would block more than any other model.

I am quite convinced that its a function of the installer and his lack of water treatment.

Tony

PS Plate HEs always block on the primary side due to rusty debris from the rads when the system has not been power flushed.