Combi or Conventional.

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I’m in the process of having my kitchen re-vamped and I need to replace my aged C/H boiler. I have a fairly standard set-up at the moment, conventional boiler in kitchen, hot-water tank/immersion heater upstairs, water tank and C/H header tank in the loft. Upstairs we have bathrooms/electric showers etc.

I need the new boiler to be of a size/spec that can be fitted and concealed inside a kitchen wall cupboard (i.e. 600mm wide x 900mm high;

...only me and er’indoors these days and I doubt we’ll ever move house at our time of life,...so the question is:- a ‘combi’ or a replacement conventional boiler?

I guess a combi is somewhat cheaper to run, but I’m not overly concerned about that aspect.

As ever, all replies gratefully received.
 
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I guess a combi is somewhat cheaper to run,

That could be a wrong guess, take everything into acount and a combi may not be cheaper to run. ( they were "invented" for use in flats and very small houses where there is no space for a hot water cylinder and airing cupboard )

Having a hot water cylinder has the advantage of being able to use an electric immersion heater when the boiler is faulty.

My Johnson and Starley Reno is 16 kW ( heat only ) and fits into a small space.

W = 380 mm
H = 800 including flue
D = 310
 
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Yes a combi would be your best bet, forget what Bernie says he hasnt a clue he just googles everything, there are a lot of combis on the market that will fit inside a kitchen unit, a consideration though is existing valves on rads, a new combi system will most likely be a pressurized system and the existing radiator valves might not be able to handle the higher pressure so might need replacing at the same time, your installer will be able to advise
 
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what Bernie says he hasnt a clue he just googles everything

Do I ? How come I built a house, totally DIY without the aid of Google ?

I agree Google is very useful for rapidly finding public domain documents and information. Other sources are available with far more accurate / useful information but these sources are not always in the public domain.
 
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Pipe work in general and the radiator themselves might not be able to handle the higher pressure.
pipework and radiators will be able to handle the higher pressure, however the Rads may pin hole if a cleanser is added but that is not because of the higher pressure and if an OV boiler was installed it should be cleansed anyway so the same would happen
 
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Many thanks for the replies;...plumber will be round in the next few days so I'll have a few more questions for him now. Thanks again.
 
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I have similar circumstances and had the same decision to make. In the end I decided to stay with the heat only open vented boiler. My reasons for doing so, some of which may also be applicable to you were:

1. I was able to keep the existing hot water cylinder, motorised valves, programmer and thermostats, so the installation wasn't at all disruptive.

2. I like to DIY. Open vented, heat only boilers have a lot of components externally mounted. Diverter valves, header tank, cylinder thermostat, pump, programmer etc. These can be easily repaired or replaced with parts readily obtainable from local plumbers merchants or DIY outlets. On the other hand, combi's generally have their equivalent components located internally, the components are usually specific to the manufacturer and not suitable for DIY as they require the attention of a gas safe registered engineer to replace them.

3. When heating hot water completely from scratch combi's have to heat up their main heat exchanger first, then transfer the hot water to a second heat exchanger before any hot water can even start its journey to the taps. My previous experience of a property with a combi that was located in the Kitchen and a long way from the bathroom, was that more often than not, the hot water never arrived before I had finished whatever I had originally wanted it for. A complete waste of the gas burned, and if I were to wait for it to run hot, a waste of water. On the other hand, my hot water cylinder is centrally located so hot water reaches all of the hot taps within a few seconds.

4. To have a Combi boiler, in order to get an adequate gas supply to heat hot water from cold instantaneously, I was told I would have needed the original 15mm gas supply pipe upgraded to 22mm. The installer wanted to run this ugly pipe from the gas meter at the front of the house, around outside of half of the property and a door frame, all on show, to reach the boiler at the back of the house. Classy!!

5. Mrs Stem loves her airing cupboard. Everything is well insulated in there so it doesn't get too hot, just warm enough for what's needed.

6. My cold main water supply isn't great, a single 15mm pipe pipe supplies all of the cold taps, WC’s, washing machine, dishwasher, etc., and can only really adequately supply one point at a time. With a combi it would also have to supply the hot water too. Keeping the hot water cylinder and associated feed tank means that there is a stored supply of water, which is unaffected by the use of the cold water elsewhere.

7. The open vented system doesn't require any manual topping up / re-pressurising. It is kept full by the header tank.

8. An immersion heater is a handy back up and can provide hot water when the boiler breaks down.
 
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I have similar circumstances and had the same decision to make. In the end I decided to stay with the heat only open vented boiler. My reasons for doing so, some of which may also be applicable to you were:

1. I was able to keep the existing hot water cylinder, motorised valves, programmer and thermostats, so the installation wasn't at all disruptive.

2. I like to DIY. Open vented, heat only boilers have a lot of components externally mounted. Diverter valves, header tank, cylinder thermostat, pump, programmer etc. These can be easily repaired or replaced with parts readily obtainable from local plumbers merchants or DIY outlets. On the other hand, combi's generally have their equivalent components located internally, the components are usually specific to the manufacturer and not suitable for DIY as they require the attention of a gas safe registered engineer to replace them.

3. When heating hot water completely from scratch combi's have to heat up their main heat exchanger first, then transfer the hot water to a second heat exchanger before any hot water can even start its journey to the taps. My previous experience of a property with a combi that was located in the Kitchen and a long way from the bathroom, was that more often than not, the hot water never arrived before I had finished whatever I had originally wanted it for. A complete waste of the gas burned, and if I were to wait for it to run hot, a waste of water. On the other hand, my hot water cylinder is centrally located so hot water reaches all of the hot taps within a few seconds.

4. To have a Combi boiler, in order to get an adequate gas supply to heat hot water from cold instantaneously, I was told I would have needed the original 15mm gas supply pipe upgraded to 22mm. The installer wanted to run this ugly pipe from the gas meter at the front of the house, around outside of half of the property and a door frame, all on show, to reach the boiler at the back of the house. Classy!!

5. Mrs Stem loves her airing cupboard. Everything is well insulated in there so it doesn't get too hot, just warm enough for what's needed.

6. My cold main water supply isn't great, a single 15mm pipe pipe supplies all of the cold taps, WC’s, washing machine, dishwasher, etc., and can only really adequately supply one point at a time. With a combi it would also have to supply the hot water too. Keeping the hot water cylinder and associated feed tank means that there is a stored supply of water, which is unaffected by the use of the cold water elsewhere.

7. The open vented system doesn't require any manual topping up / re-pressurising. It is kept full by the header tank.

8. An immersion heater is a handy back up and can provide hot water when the boiler breaks down.
Thanks for taking the time to post such a detailed and comprehensive reply;...really appreciated.

You’ve encapsulated my thoughts entirely,...and Mrs Harvey is dead set against a combi for the same (and more) reasons as Mrs Stem. :eek:

My conversation with the plumber may get heated...(no pun intended :mrgreen: .)
 
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Only you and the Mrs in the house plus you have a couple of electric showers. Combi all day long.

Your hot water demand isn’t much is it unless youse both like to take a bath everyday.
If your boiler was to break down, having an electric shower is a pretty good back up. You can always boil a kettle for the few dishes you need to wash. A decent brand combi installed correctly can be just as reliable as a conventional type boiler. There’s a fair few on the market that come with a 10year guarantee subject to T&Cs to offer peace of mind.

And as for the comment that states combis are only for small flats, that’s just not true.
 
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Do some research, go back to the 1960's when the first "combination" hot water and central heating systems were being developed.

https://blog.bosch.com/history/en/2016/09/30/warming-up-water-and-rooms-the-junkers-combi-boiler/

and look to the future


http://www.heatingandventilating.net/metering-solutions-end-of-the-combi-boiler



Jeezo, Ian is correct, you do like to google. I don’t really need or want a history lesson in how combi boilers were developed.

Those links aren’t even relevant to the statement you’ve highlighted. It’s not hot news that the government want to ban gas boilers from new builds and distric heating is a great method for heating housing developments, blocks of flats etc. Sign me up for cheaper and more environmentally friendly
heating.
Combis aren’t going anywhere any time soon. Ill take a stab in the dark, there’s probably 7-10 million combis fitted in the UK? They have their place in the market and its not just in one bed flats.

The trick is to try and keep an open mind.
 
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A combi will more than satisfy your needs, the choice is all about your HW demands and as there are only 2 of you in the house you will manage it no problem
 
H

Hot&Cold

My Johnson and Starley Reno is 16 kW ( heat only ) and fits into a small space.

J&S are coming up to a 100 years of supplying uk heating/ventilation goods. Bernard have you been invited to their bash :?: As a swedish owned company the food will be nice :LOL:
 

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