Upgrading an open vented system to a combi boiler?

[JayS]

I'm sure this question have been asked before...I've tried to search the forum, but haven't come up with anything really helpful.

Anyway, I've just bought a 2 bedroom semi. It's got a fully pumped open vented CH system with a loose lagged hotwater cylinder. I'm note sure when it was installed, however my guess is mid 70's. The boiler is a Concord WRS model, so that would make it about 25-30 years old...

Being a very old boiler I want to upgrade it to a modern (preferably a condensing) boiler. I think for my needs a combi would be quite suitable, don't take baths that often, and the mains water pressure is good.

As I understand the combi boilers tend to run on sealed CH systems, with higher water pressure. The pipe work is 15 mm connections to the individual radiators, and the 'back bone' is 22 mm (might even be 1"...).

Questions:
- I presume a conversion should not involve too much work? Mainly disconnecting loft tanks, etc.?
- Will the pipes be up to the higher water pressure?
- Is it possible to check this in a non destructive way?

I'm considering one of Worcester, Vaillant, or Baxi for the boiler. Favouring the Baxi 130HE at the moment because of its slim design (boiler is in the kitchen)!

Many thanks in advance for any help!

 

[boilerbeasty]

I'd really try to avoid buying a boiler cos it looks nice !
I think you have to look at the problems on here and decide whether lots of problems demonstrates a rubbish boiler, or just that lots of people have them and therefore more problems will be reported (even if the percentage of failures is the same).
Does any one publish MTBF figures for boilers ??
From what I can see on the forum, Worcester Bosch give good service/post sales warranty support. Baxi/Potty have loads of problems reported ! But see my comment above.

 

[taydo]

the pipes are almost certainly able to accept the increased pressure you may however have minor leaks on joints etc yes this can be tested with a dry pressure test
the only trouble is it will tell you that you have a leak not where the hell it is

 

[DP]

I would suggest wet pressure test at three bar. After all a sealed system will go to three bar under fault condition.

 

[COG]

As DP ,but i would advise all new rad valves and a good system flush.

 

[oilman]

Will the pipes be up to the higher water pressure?

The static pressure should be not much more than the open vented system pressure. Most sealed systems seem to be set up for a pressure thats more than twice whatit needs to be. 1 bar is 34 feet!!!

Radiator valves - unless they are already thermostatic, building regs part L require your valves to be thermostatic, and the installer will be committing a criminal offence in signing the paperwork if they aren't (The nice Mr. Prescott says so)

 

[JayS]

Thanks for the info guys. Very much appreciated!

oilman, no there are currently no TRV's fitted, but I was going to do that at the same time.