Combi vs Heat-only boiler for a 5 bedroom house

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Dear Forum,

We are very confused as to which boiler to installed for our home. We invited two registered corgi engineer/ plumbers.
1) One recommended the condensed boiler as he said the combi boiler is not good for large house. The other boiler recommeded Worcester combi boiler which he said is fine for large houses.

2) A bathroom designer suggested us to have a pressurised hot water tank in the loft as we need the space on the first floor if we were going to have a condensed boiler

Your advice/sharing of experience is always appreciated.

Lin
 
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A combi boiler in any shape or size is a compromise. Combination suggests a combined unit that supplies heat and hot water. One does not need to be a brain doctor to realise a failure could end up with household having no hot water or heating. Also, combi boilers give finite amount of hot water flow. Run two taps will result in water flow dividing as boiler can only give you what flows from a tap (when it is at full flow).

On the other hand an unvented (installed by someone who is registered to fit such a system) and heat only boiler (what you call condensing- combis are also condensing) can fail but electrical heating of water in cylinder will give you that belt and braces system.

Final thought is that a lot of so called engineer cannot even repair a simple boiler. Combi to such people become challenging. Combi condensing then become rocket science. Add to this fact you have makers making boilers for maximum profit and have forgotten how their boiler easily passed 15 birthdays without too much trouble.
 
hot water unvented cylinder :!:

don't put a combi in that size house!! :LOL:
 
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A Worcester Bosch Highflow 550 has a heating output of 30Kw (100,000 BTU) which is normally suitable for a mid sized house. What do you have now in terms of boiler output.

This model can deliver up to 25 litres a minute of hot water, for the first 200 litres of draw off. It recharges quickly, and we tend to use hot water in bursts rather than continuously.

If you look at your water supply, if it is not significantly over 25 litres per min, then the floor standing Highflow 550CDi will be comparable in performance to an unvented connected to the same water main.

The Highflow 440/550 and Vaillant 937 are hybrid combination boilers, they combine a small internal unvented cylinder with a large power combi to give better hot water flow rates, from a single box.

It is true without a separate cylinder you do not have the luxury of an electrical backup heater.
 
All the eggs in one basket again, when the boiler breaks down you're left with nothing other than an expensive repair bill.

I would devalue a 5 bed house by a least 10-20k if it had a combi boiler.
 
I would devalue a 5 bed house by a least 10-20k if it had a combi boiler.
That my dear chap, is total nonsense.

It would imply that scrapping a good, large combi and replace it by a 300 pound Ideal and a 200 pound tank would increase the price by 10 grand.

Upgrading a backboiler to an Atag with an 300 litre stainless unvented and the latest digital controls including wc would at the very best increase the price by a couple of thousand.

A bit theoretical anyway at the moment as the only people who are buying property are speculators and those who get it paid for by the employer; that would be politicians, and politicians.

In case you missed it;
The total amount of houses sold under the government support/guarantee scheme to date is: 0.0
 
Not nonsense, if I viewed a 5bed property that is what I would knock of the asking price, if, I even considered it in the first place.

How much would you charge to scrap a combi, and fit a decent boiler and unvented cylinder. £5k perhaps ? Then you have re-decorating and the mess of ripping up floor boards to run new pipes etc.

Houses will start to sell again, once we get rid of Brown Nose, mind you we, sorry you will be paying back the debt on the borrowing for the next 50 years.
 
I would always advise a system boiler and unvented cylinder for a property this size.

I have put a un-vented cylinder in a loft before, but I had to have the trusses strengthened and a strong base built.

300 litres of water is an awful lot of weight to have up there :eek:
 
Houses will start to sell again, once we get rid of Brown Nose, mind you we, sorry you will be paying back the debt on the borrowing for the next 50 years.

They are now. House prices went up by 1%. Brown is our only chance as he has the experience. A world-wide financial tidal wave hit us, and people blame Brown for all the world's problems and that he caused it. Take no notice of party political TV pundits and tabloid papers. Brown is the right man for the right time. History will prove that.
 
I was put onto the large ATAG combi, the Q51C, as a customer wanted high hot flow and didn't have much space. A combi was the only way to go. A top quality piece of combi at 51 kilowatts. It gives 23 litres a minutes and has an internal 15 litre tank to reduce the lag to the taps. It is wide on the wall with being slim enough. It fitted fine and the case looks quality.

This was doing two bathrooms and does 2 showers on together with no hassle at all. A bit slow filling two baths but OK. The chance of 2 baths being filled together was slim in this house. It is not cheap to buy as a boiler but savings over cylinders, pipes, time and other controls. It came out cheaper than a quality boiler and unvented cylinder. You get what you pay for as this is very well made. I would recommend one up to 2 bathrooms. I was mightily impressed.

The only negative is that if the boiler is down there is no DHW backup with electric immersion. This is so well made I can't see it breaking down much at all.

Here is the web site. Well worth looking into as it will solve many problems in some jobs.
http://www.atagheating.co.uk/default.aspx?cp=products_select&id=27&productgroepnaam=Combi+boilers
 
I would always advise a system boiler and unvented cylinder for a property this size.

I have put a un-vented cylinder in a loft before, but I had to have the trusses strengthened and a strong base built.

300 litres of water is an awful lot of weight to have up there :eek:

This is where the big flow combis come in. They solve a lot of problems and expense like strengthening. I now never say "I always advise", as in this situation, as each job is a valued decision.
 
All the eggs in one basket again, when the boiler breaks down you're left with nothing other than an expensive repair bill.

I would devalue a 5 bed house by a least 10-20k if it had a combi boiler.

I would say the opposite if anything, if the space you gained is used to maximum effect. Use a cylinder cupboard for an ensuite shower room or extra shower cubicle and use a quality combi like the ATAG and the price will rise.
 
you have to decide what you are after, economy or comfort.

point 1: a combi does both things, as said. it heats your DHW and your heating. you only heat the water you use. therefore, your in control of water useage. best type to maximise storage.

point 2: unvented hot water is similar to "old" y plan systems, ie you heat up **gallons of water a day. can be wasted. and these systems take up a lot of room.

Point 3: intsallation cost. depends what you want to spend. a combi system will be a fair bit cheaper than an unvented system.

so you are the person who needs tio decide. you pay the bills and live in the house.
you never mentioned how many bathrooms you have, ie water oulets which is ultimately more important than the number of beds you have.

and for the person saying you'd knock 20k off a house with a combi, you need to do your homework, i think its a foolish thing to say.
 

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