Some Combi boiler questions

[Mark Hewitt]

How do I find out if I have any or not? Or is it a case of interrogating the installer?

[Dave Plowman (News)]

Many installers will leave it out, since that's not going to cause a failure in the normal year's warranty. But the long term implications - well, you know. A system so blocked with crap it has to be totally replaced.

It might also just cure your leaks - and quieten down your TRVs.

[Taz]

I had a combi installed last year. It meant that the cupboard in the corner of my bedroom containing the hot water tank was replaced by a shower unit etc. The tanks in the loft came out, letting me convert the loft into a gigantic bedroom for my 17 y/o son to hang out in with his mates and not annoy us with his mega hifi noises. It meant more storage space in the kitchen where the old boiler used to be. The combi lives in the loft with my son now. Get the most powerful combi you can find, otherwise the flow of hot water diminishes if you use more than one hot tap at the same time. This one will happily run the power shower, and fill the bath at the same time. It has some kind of dual output apparently, fires up more gas when needed. This is where combis are the same as autos, both need the biggest engine/power output available on the market for them to work well. One of my mates bought a budget combi, and has regretted it ever since, much the same as someone buying a 1 litre auto would.

[John Rumm]

If in doubt, then add some anyway, too little is a problem, too much is not.

[raden]

In message , John writes

This is becoming increasingly true

[Uno Hoo!]

Just don't expect to have a bath if you're in a hurry!!!!

Kev

[Uno Hoo!]

Now this I can't understand because you are not supposed to use power showers with combi boilers. The combi boiler heats water as it passes through it. Because of this, the water has to be slowed down - otherwise it wouldn't heat up sufficiently as it passed through. (This is why it takes so long to fill a bath with a combi). A power shower (as opposed to an instant electric shower) uses a pump to force pre-heated and mixed water out of the shower head at a pressure much higher than normal. If you use a power shower with a combi boiler then you are trying to 'drag' hot water out of the boiler at a faster rate than it can produce it. Are you sure it is a power shower - or do you mean an instant electric shower (many people confuse the two). A power shower pumps pre-heated water, an instant electric shower (like a combi boiler) heats the water as it passes through.

Kev

[bangbangchicken]

How do you use a power shower with a combi? Did you mean a thermostatic mixer?

[Adrian]

Uno Hoo! ( [e-mail]) gurgled happily, sounding much like they were saying :

You need to try a decent combi boiler.

Mine seems to manage one of the most powerful showers I've ever had, or will fill the bath quickly, without the aid of bodges like pumps.

[Uno Hoo!]

You may be right Adrian. I've never had one myself, but everyone I know who

*does* have one, runs them down continuously. Maybe they all have 'budget' combi's (although they are good makes like Worcester Bosch etc).

Kev

[Adrian]

Uno Hoo! ( [e-mail]) gurgled happily, sounding much like they were saying :

Aha... "Let's run 'em down, despite knowing nothing"

Mine's a Worcester. The one before it was an ancient (c. 1980ish) Vaillant. It supplied plenty much hot water, when it was working. Which got increasingly infrequent.

TBH, I've rarely had as powerful a shower in a house with a hot water cylinder as I've got with the combi. Certainly not without the bodge of a pump. Don't even start me on electric on-demand showers. Useless.

[Clive George]

Mains pressure water innit. It's what combis are good for. With a cylinder you're on gravity feed unless you pump.

I tried quite hard recently to persuade a friend who was installing a combi that he should run his shower off it rather than have an electric one, since that was the one thing a combi boiler was really good at.

Depends a bit on how chunky they are - 7KW is too small, 8.5KW is just about ok. Combi at 20KW+ is going to laugh at this.

cheers, clive

[Mark Hewitt]

Hi Kev, I regularly have baths (no shower!) and it fills within about 5-6 minutes, which is certainly fast enough for me. Probably slightly slower than the old system, but there isn't much in it.

[Mark Hewitt]

Depends really. Having an electric shower means you at least have some hot water if the combi is offline, also anyone/thing else using the hot water in the house isn't going to affect your shower.

[Christian McArdle]

But given that the only really good thing about combis is the shower performance, it seems like a bit of a waste to swap that for a "pathetic drizzle from a wringed out flannel" level of performance from an electric shower.

Christian.

[Dave Plowman (News)]

True they *can* be good. At considerable cost. But in practice the vast majority ain't.

[Ian Middleton]

Be careful when re-siting. My neighbour at my last place (a row of terraced houses) replaced his backboiler and gas fire, in centre of lounge, with a new boiler in his kitchen, mainly because it would be cheaper that a new back boiler and fire. Was quoted £2K for new back boiler and fire and only £1K for boiler in kitchen. Problems were:

- Couldn't remove the chimney breast completely as rising main came in there and there was the stop c*ck. Also there were some cental heating pipes going off to the lounger radiator. So ended up with a 10inch type chimney breast/boxing in lounge rather than flat wall and a stupid tiny door to get access to stop c*ck.

- Holes were made in ceilings and cuts in tongue and groove floor boards upstairs to re-route pipes to kitchen.

- Lost a cupboard to a boiler in the kitchen.

- Suffered from boiler fumes in garden in summer as now vented into back garden rather than via roof.

- I could hear the boiler in my house as it was on the party wall and was noisy !!! (which is how I know about what was done as I mentioned the noise one day at a BBQ).

Also

- A leak occured in the pipes in kitchen ceiling causing damage.

- The plumber damaged the flat roof causing more leaks whilst fixing the first leaks, being convinced it was not his plumbing but the roof leaking.

[Uno Hoo!]

Clearly there are some combi systems that are much better than others! Pleased that you are happy with yours.

Kev

[Tim S Kemp]

You need a more powerful shower...

[Philip]

We are changing a conventional for a combi due to a loft conversion - to do away with the water tanks and the hot water cylinder.

Do I site the combi where the old boiler was - downstairs with a vertical flue all the way up the chimney, or do I site it where the HW cylinder was - in loft with 4 foot vertical flue up chimney? TIA

Philip