oil combi boilers

[Roger Welton]

I would also say I'd prefer a heat only boiler rather than system, then fit correctly sized external expansion kit and pump.

 

[WHPES]

Depends if you have suitable space for it.

 

[Roger Welton]

Like anything there are always compromises to be made, just seem to find internal vessels on oil boilers seem to fail quite frequently, I put it down to the heat, plus a lot of them are marginally sized bearing in mind the volume of water in the jacket (combi's in particular)

 

[StillLearnin]

I've had a few internal vessel failures too, including on Grant machines .... replaced them with external vessels and touch wood no problems. I think you are correct about the internal heat causing the problem.... one Grant combi I replaced the internal vessel twice in 3 years before moving to an external vessel.

 

[kimbo]

The problem with combis I think is due to the heat. Most of the components have plastic in them or rubber or nylon, the heat makes it brittle over a period of time and then it leaks or breaks or just gives up prematurely.

 

[WHPES]

You will get the problem with internal vessels on all makes of boilers as they are all pretty much the same. The square shaped ones seem to be the worst.

Always best to have an oversized external expansion vessel if you can fit it somewhere.

 

[DustyM]

I've fitted a couple of WB's recently on larger sized properties. On each occasion, due the system volume, I have fitted an additional external vessel; it takes the 'pressure' off of the standard fitted one and hopefully will ensure they last longer!

 

[lame plumber]

and when the internal one fails, which it will the other one will allow the boiler to continue to function.

 

[kimbo]

The cheap external ones last a lot longer than the internal ones that come with the boiler.

 

[peteheat]

We are supposed to size the vessel to match the volume of water in the heating system, I haven't seen any problems with two vessels.

Is that one waiting for me lame plumber?