Replacing conventional gas boiler v.installing combi

[Late Learner]

Please save me from learning life the hard way; I've learnt from past experiences with plumbers and the like (no offence to honest professional plumbers) which is why I am turning to you good folks who selflessly devote time to advising less clued up people like me. I don't seem to be able to find a trustworthy heating engineer in East London, so if you know one you can recommend, please kindly pass on the name and tel.no.

Seems the boiler packed up on New Year's Day. It's a small studio flat on the third floor. Just before I moved in less than two years ago, a power shower and new bathroom was installed. I believe the boiler is very old as it's a Myson Apollo. There could be a number of reasons why there was suddenly no hot water and replacing the boiler might seem a bit drastic. I am mindful of costs and have learnt from past mistakes that a simple problem never has a simple solution and in the end, the no. of call-outs plus labour and parts equate to paying for something new upfront.

The hot water was timed to run at certain times of the day, everyday and circulated the radiators, keeping them lukewarm (I never needed to turn on the CH) and kept the small flat warm enough. It is wasteful to heat up a whole cylinder of water just for a shower and washing-up for

1 person. I'm thinking a combi is more suitable in my case. However, I have to think of the costs of ripping out the conventional system plus new-ish power shower, hidden pipework,etc.

Would replacing with another conventional boiler be cheaper than installing a condensing combi system? I am worried about the condensing plume of steam affecting neighbours in my block of flats. I also don't have plans to stay in the flat for more than say, 5 years.

Please advise me as to a suitable make and size of boiler. I have looked at Alpha and Vaillant but seems the heat output is way too much for a 1-person studio flat but what do I know. How do I calculate the size of boiler I need? The studio dimensions are 7.5m X 4.37m X 2.62m ( or 24'4" X 14'4" X 8'7.5" ceiling height ).

I would be most grateful for any advice. Thank you.

[Doctor Drivel]

A combi is ideal for you. You can have non-condensing combis if the plume is a nuisance. The CH side may appear too large. But they modulate the burner down so get one that modulates quite low. The hot water? If mainly showers a 12 litres per min on a 35C temperature rise is adequate if mainly showers are used. If you take baths all the time then a higher flow is needed. Make sure the pump is removed from the shower if the combi is fed from the mains. Have a wall stat/programmer to control the heating. If you have a cylinder in the studio then the combi will release valuable space.

[Christian McArdle]

Absolutely, if there was any installation that is crying out for a combi it is a single person studio flat with a shower.

Possibly not. Your existing system appears not to have modern controls (i.e. rads come on when hot water is required etc) and would need to be brought up to date. It is probably cheaper to install a combi and remove the old cylinder than to bring the old system up to scratch.

That would depend on the flue position etc. We couldn't possibly comment without a more detailed knowledge of the layout.

A combi is sized by the hot water requirement, not the space heating requirement. A studio flat probably only needs a few kW to keep warm. However, you should be looking at 28kW for the hot water to get a lovely powerful shower that doesn't go tepid in winter.

I've got a Worcester-Bosch Greenstar. Not a combi, but an excellent boiler and available in combi form.

Some possibilities ideal for studio flats:

you need to route the flue through a long and circuitous path, then the Keston allows you to do this with standard high quality drainpipes, rather than expensive flue extension kits. Costs a little more to start with but it includes the flue terminals (which are extra with most boilers). With any flue length or with a few bends, it starts looking much cheaper.

[Late Learner]

Thanks, doctor, but as of April 2005, I must only install condensing combis. I need to base my final decision on cost more than space as I do not plan to stay in this flat for longer than 5 years. Also, there's a bath, but I only take showers.

I would appreciate anyone else's input as regards other points raised in my query. Thanks.

[Late Learner]

Thanks for the links, Christian. I'll look them up right away. Meanwhile, anybody knows somebody who knows a reliable heating engineer in East London? Thanks.

[Ed Sirett]

Have a look through the boiler choice FAQ Come back with any issues not covered.

[Doctor Drivel]

I know that. I did say, "You can have non-condensing combis if the plume is a nuisance." There is an exemption, and a nusiance plume is one.

A 12 l/min combi will do. A bit slow on the bath but still OK.

[Late Learner]

Thanks again. Now that puts a new complexion on things. Is exemption granted automatically or does a higher authority need to assess the situation?

Pls tell me, apart from removing the pump, cylinder and tank, will pipes need to be changed to accomodate a new shower that is suitable for a combi. I'm asking this because the bathroom is relatively newly refurbished - so am I looking at quite a big job? Thanks.

[Late Learner]

Thanks Ed. Have just taken a look. Is very informative and will print out to seriously read tonight.

[Late Learner]

Thanks Ed. Have just taken a look. Is very informative and will print out to seriously read tonight.

[Doctor Drivel]

If the plume can enter other windows it is clearly exempt. Also if you fit a condensing boiler and a neighbour complains you may be made to remove the boiler.

Check the shower make and model. They usually make high and low pressure versions. If low pressure get a high pressure cartridge. Virtually straight exchange and no pipework.

[Ed Sirett]

There is an exemption procedure for avoiding a condensing boiler install. Essentially points are given for the type of property. More points are given if the boiler has to have a new location. More are given if the location must move due to condensate drain problems. If get enough points (1000) then the installer can fill in a form declaring the reason for the Part-L non-compliance.

If you are diying then the form would/should get building control off your back.

The exact details are on the ODPM site.

[Late Learner]

Thanks. Sounds more promising now. Will let you know outcome. I have also written to the management of the block of flats for some guidance

- I was warned to apply to them first before I do any work on the flat.

[Late Learner]

Thanks, Ed. With all these hints, I may end up sounding more knowledgeable than the installer. That'll may him think. I'll keep you informed of progress.

[Late Learner]

Thanks, Ed. With all these hints, I may end up sounding more knowledgeable than the installer. That'll make him think. I'll keep you informed of progress - probably not soon as I still have to pin down a reliable heating engineer or next best person.

[Doctor Drivel]

That I would not doubt.

[Ed Sirett]

A possible case for the exemption procedure applies to a job that I am currently looking at.

The flat is on the first floor and is part of a conversion from a large early C20 mansion. The flat has a kitchen window at the side where the existing broken balanced flue boiler sits. The side is about 2m away from a very similar converted property next door. The only exterior walls are the side and the front. The only way to install a condensing flue would be to extend the flue above the roof line some 10m above ground level. This will cost a small fortune in scaffolding costs alone. It would make a lot of sense to simply install a normal F/F conventional combi. (There is no question about a combi here - there's no pressure and flow from the "top cupboard cisterns" on the existing system anyway).

Since the boiler is not being moved the points for exemption add up:

700 for a flat with gas boiler. 210 for a long flue.

There is no need to relocation the boiler and every reason not to. There is no problem with the condensate drain.

Apparently the procedure does not allow for this, except by the straight declaration - "the flue cannot be installed". There must be a cut off for the expense of installing the flue. I estimate the additional flue costs will be around £1000-£1500!

I will be doing two quotes that are £1250 different!

[Late Learner]

Ed, the more I read, the more respect I have for you guys. There's no way I would be allowed to spoil the look of the building by sticking a long flue up another 4 floors, so it seems I could be exempt. The boiler is on the inside of the exterior wall (and the cylinder and tank are inside a cupboard about 5 metres away on adjacent internal wall). I'm still digesting the information you asked me to read. This is a great way to learn. Thanks.