Combi boilers

[Bazza]

SWMBO has just given me my project for next spring - revamp the bathroom, she has already selected the suite she wants. Now me and the kids have showers (over the bath at the mo) but she prefers a bath so I want a fitted shower cubicle The only place I can fit a separate shower is in the corner where the airing cupboard is with the hot water tank. I have nowhere else I can put the tank so I was thinking of a combi boiler system for the rads and hot water. I am sure lots of you have experience of these but I have a few questions.

At present I have a 20 year old Wickes boiler 45k btu(works fine apart from replacing the pilot stat every few years) on a Y plan system, this is hung on the wall in the kitchen, would a combi be a fairly straight forward replacement.

The present shower over the bath is a pumped system, can the pump be dispensed with when using a combi (understand combi's use mains pressure, mine is ok but with hard water)

The loft tank only feeds the hot water cylinder and the power shower, all cold taps, appliances and WC's are mains fed

Combi(condensing) boilers used to have a bad reputation for failing, has this improved on recent models?

Any recommendations

Bazza

[Dave Plowman (News)]

If you still want to have the bath you'll find the time it takes for the average combi to fill it very much longer than with a decent storage system (especially in cold weather where the incoming mains water is very cold) as a combi can't heat the same volume of water at the same temperature instantly as a storage system can dispense.

If you look at the spec of a combi it will give the water flow at a certain temperature. You can measure your present flow (and temperature) to the bath to compare. And since you already have all the parts in place for a decent storage system which presumably works pretty well, beware of prats like Drivel who will be along shortly to tell you a combi is the answer to world peace. ;-)

[Cicero]

================================== Not a *recommendation* but a possible alternative worth considering.

A multipoint water heater could be installed as a completely independent unit to supply domestic hot water only. You could then remove the hot and cold water tanks (except for the existing CH header tank - probably in your loft) thus leaving space in your bathroom for a shower cubicle. You would then have your existing boiler for CH and the multipoint (mains pressure - no storage) for HW thus giving you two completely independent systems.

Many people look down at multipoints because of their lower delivery rates but there are thousands of them in use by satisfied users.

Cic.

[Doctor Drivel]

Not this pillock again!! There are high flow combis around. This man should eff off.

[Bazza]

Waiting for the bath to fill is not really a big problem as we mostly take showers, it's just that I would "really" like to have a separate shower and the only way is for the tank to go, have already told the wife that the boiler is old and could fail at anytime and with the new regs the airing cupboard is not an option anymore ;-)

I have no other problems with the system but as I will be totally gutting the bathroom anyway I may as well go the whole hog. I await to hear what the good doctor has to say, I do keep an open mind

[Doctor Drivel]

You want one on the wall. There are quite a number of decent boilers that will do.

The RRs are Atag, Atmos, ACV, Buderus, ECO-Hometec, Viessman. Middle of the road along with Vaillant, Glow Worm are Worcester Bosch.

My favourite combi is the Atmos (well the Intergas range) - comes with a weather compensator too. Not cheap, but this sort of quality and design never is, but you can get a good deal if you look around. A very simple well thought out boiler built like a tank. The whole back panel is the heat exchanger. They only go to around 12.5 litres/min. Higher flows you use the floor standing Multi.

High flowrate wall mounted combi?

- Eco-Hometec - V Good and expensive.

- Glow Worm 38 kW

- Worcester Bosch Greenstar 40kW

You will not be disappointed with any of the above three and in a one bedroomed house they are fine. They all do around 16 litres per minute flowrate. If you want to go less than 16 litres/min for for the Atmos.

There are physically larger combis like the Worcester Bosch 937 and the Alpha CD50 which deliver flowrates as good as any storage system - as they have internal storage.

Have you thought of fitting a combi in the loft?

[Doctor Drivel]

See my post on this.

[Doctor Drivel]

A very good suggestion. Try the Rinnai which gives high flow rates and can be fitted outside to save space. High quality Japanese product that is taking off in the UK.

Look at the Rinnai which has high flowrate deliveries:

[Doctor Drivel]

He has an inefficient 20 year old boiler, which really needs replacing with a modern cheap to run model. In his case. He may as well go for a good quality high flowrate combi.

[Jim Alexander]

There's two characteristics of a combi system I'd flag up. Firstly the time for hot water to arrive at the bathroom basin can be frustrating and unlike storage can't be shortened by increasing flow. You're bound to notice this because your existing storage is adjacent to the bathroom. Made worse if backfeeding from the new combi position over existing 22mm pipework. The other issue is that you will now have a single point failure for DHW and CH. You need to have contingency plan. Perhaps a maintenance contract, but that's another issue...

Jim A

[Dave Plowman (News)]

There are indeed. At a high cost. And both the gas and water main might need replacing to supply them.

Isn't about time you went away again? You're still obviously not well in the head.

[Dave Plowman (News)]

Right - if you need the space and realise the limitations of a combi (or rather your wife does) it could well be the way to go.

The best advice is to ignore totally what he says as he knows the value of nothing and would love to spend other's money on his 'quaint' ideas. But plenty others will give you good advice based on your actual requirements.

[Bazza]

Is the time taken to get hot water to the tap due to the run of the pipes or the heating time of the combi? the combi would be mounted in the kitchen directly below the bathroom. I have an immersion heater but never had to use it, if the boiler has failed I have always managed to fix it the same day, admittedly it is old with not much gubbins, are combi's much more complicated?

[robgraham]

Well I don't know anything about combis, but I do have three people I know who have them, and they are aways giving bother. My mother's neighbour loses hers monthly - I had friend's daughter on the phone this morning asking for assistance with hers yet again, and it requires professional input this time, and another friend regards his as the spawn of the devil. I don't know anyone who has one that works without breaking down !

The was a time on this forum when there was a move to ban this particular 'C' word.

Rob

[Jim Alexander]

Its due to the volume of water in the pipes and the limited flow rate of the combi. The water heats as near as dammit instantly at the combi but changes in flow rate at a remote tap take time to be reflected in the temperature delivered at the tap, unlike storage systems where the temperature is independent of flow rate. Sorry didn't mention that earlier. Some top of the range combis have a limited reservoir of hot water but never installed one so no idea if that helps.

BTW not dead set against combis but best to understand their characteristics.

Jim A

[Dave Plowman (News)]

Yes they are - but them so are most modern boilers. You can say goodbye to your near total reliability with simple fixes if anything goes wrong.

[David Hansen]

On Mon, 12 Nov 2007 14:25:16 GMT someone who may be Bazza wrote this:-

Have you warned SWMBO that a combination boiler is likely to take two to three times as long to fill the bath? Is SWMBO happy with this?

Do you really want to have one in the bathroom? Would it not be better/possible to put one elsewhere and cut the bathroom queue?

The sort of combination boilers one tends to see in houses are fine for one or two people, but any more than that and their limitations tend to show up.

[Bazza]

I have a 3 bed house but only 1 bathroom, hot water will be used for shower and bath (not at the same time) kitchen sink not used for washing up, have a dishwasher for that.

They all do around 16 litres per minute

Could be a way to go fitting it in the loft, not much room anywhere else in the house unless it can fit on a wall in a space 600 wide x 600 high, If I floor mounted it I would have to take out a kitchen unit, don't think she would let me get away with that.

[Bazza]

No space for a downstairs shower, the bathroom it has to be, garage is the only other place but on a cold morning walking up the garden to the garage Brrrrrr

[Bazza]

Just been upstairs and filled a bucket for a minute (with the shower that is) 10 ltrs per min so the 16 should be adequate