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GeorgeBainbridge
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Two smaller combies instead of a larger one?
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But you can get a reasonable heat only boiler and an unvented for about £1400.
I admire your lateral thinking! Go for it!
You have found, as many have before you, that many of the 'plumbers' who frequent this site can't think out of the box....that's why they are plumbers! Sorry guys, it's true.
G
GeorgeBainbridge
Two 24kW Integas combis are got for less than £2K I have seen the 24kW for around £900 inc outside sensor
They will deliver about 22 litres/minute for ever, that is 660 litres in half an hour. The cost of a 600 litre unvented cylinder and all the zone valves to zone the CH and all the rest is far more than the two highly reliable, better performing two Intergas 24kW combis. Fiting the two combis is far less labour as well, again making it cheaper.
Do the sums and count properly.
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Oh dear I fear I might be right.
I think you have misread the specification!
A 24 kW combi will only heat about 8 li/min to 44 C at this time of year!
You should go and play with a combi to see how they work. You would learn a lot more than just reading spec sheets!
G
GeorgeBainbridge
The only one who can't read spec sheets is you. The 25kW is 9 litre per min at 35C temp rise. As the main water temp is around 8 to 10C that gives about 9 litres a min at 45C. A shower a is around 40C so it will give around 10 litre a minute. The rest of the year it will belt it out at a higher flowrates.
9 litres per minute for a high pressure shower is fine. One combi does a shower each. Get a higher kW com,bi and even better, if you want that of course, which most will not be bothered with.
You can't read or count. You have never seen two combis in action. I have have many times.
Hi and thank you for all your comments regardless of direction. Just from this thread I have learned so much and so glad to read both sides of the argument.
Gas meter is in the porch and the outlet from meter is the old iron pipe which I believe is just under 22mm if I am correct. As with all semis the pipe runs under hallway and goes up to airing cupboard under the stairs. Altogether the run is under 10 meters (5.5 meters from meter to staircase and up another 4 meters to airing C).
Upstairs there are 5 rads (4 for bedrooms and one for the shower room), so I was thinking a combi for this setup does not have to be very powerful. I figured that the sink in the shower room is never on at the same time as the shower.
So what size combi do I need?
Downstairs zone would feed kitchen tap, main bathroom shower and bath and 5 rads (rads being a bit bigger for lounge, hallway, dining room etc).
What size combi do I need for this zone?
As mentioned above, bath can be connected to both but we hardly ever use the bath. We are a family of 4 but both girls at the moment are at uni.
I was thinking that each combi with lower KW would cost around £850 and with the zoning system I might actually save money in the long run. What would be the point of having the rads on downstairs at night when sleeping in the bedroom. These days with freezing temps many set their heating to come on in the middle of the night for bedrooms but no need to have them on downstairs and vice versa.
On the other hand as mentioned in another point, combis tend to break down quicker but would it compensate for the costs since each combi would be working half as much?
So far the answer seems to be either an unvented system or two combis.
On a side note: The biggest problem I have had is to actually find a plumber who would “WANT TO” think about these things. As one plumber told me 3 weeks ago “Look mate, we go to a house and tell them they need a combi of this KW or a different system. They say OK and we get the job done. No one before has questioned what we do. You are asking too many questions. I have a combi in my own house and its working fine so if it is ok for me then you should be happy with this”.
I asked him as to costs of running his own heating per month. He didn’t know. His wife pays the bills.
I asked him if an oversized boiler would be less efficient (I had read this on this forum). He didn’t reply.
In the end he phoned back saying he doesn’t want the job because I seem to know too much and might question his job later. He has been in the trade for over 20 years and is a heating engineer for Wise…….
Gas meter is in the porch and the outlet from meter is the old iron pipe which I believe is just under 22mm if I am correct. As with all semis the pipe runs under hallway and goes up to airing cupboard under the stairs. Altogether the run is under 10 meters (5.5 meters from meter to staircase and up another 4 meters to airing C).
Upstairs there are 5 rads (4 for bedrooms and one for the shower room), so I was thinking a combi for this setup does not have to be very powerful. I figured that the sink in the shower room is never on at the same time as the shower.
So what size combi do I need?
Downstairs zone would feed kitchen tap, main bathroom shower and bath and 5 rads (rads being a bit bigger for lounge, hallway, dining room etc).
What size combi do I need for this zone?
As mentioned above, bath can be connected to both but we hardly ever use the bath. We are a family of 4 but both girls at the moment are at uni.
I was thinking that each combi with lower KW would cost around £850 and with the zoning system I might actually save money in the long run. What would be the point of having the rads on downstairs at night when sleeping in the bedroom. These days with freezing temps many set their heating to come on in the middle of the night for bedrooms but no need to have them on downstairs and vice versa.
On the other hand as mentioned in another point, combis tend to break down quicker but would it compensate for the costs since each combi would be working half as much?
So far the answer seems to be either an unvented system or two combis.
On a side note: The biggest problem I have had is to actually find a plumber who would “WANT TO” think about these things. As one plumber told me 3 weeks ago “Look mate, we go to a house and tell them they need a combi of this KW or a different system. They say OK and we get the job done. No one before has questioned what we do. You are asking too many questions. I have a combi in my own house and its working fine so if it is ok for me then you should be happy with this”.
I asked him as to costs of running his own heating per month. He didn’t know. His wife pays the bills.
I asked him if an oversized boiler would be less efficient (I had read this on this forum). He didn’t reply.
In the end he phoned back saying he doesn’t want the job because I seem to know too much and might question his job later. He has been in the trade for over 20 years and is a heating engineer for Wise…….
J
joinerjohn
I see Walter Systems has changed his name again. 
With HW demand and only 5 rads per floor you are effectively providing a combi boiler for each of two flats, if you see what I mean.
A combi suitable for one shower would probably be the smallest you can reasonably get which is say 24kW, perhaps a Vaillant Ecotec Plus 824 or similar, which will have more than enough capability for the 5 rads on it's floor. So 2 x 24kW combis.
BTW you might like to consider making emergency cross connections available to cover for a single boiler failure during a cold spell?
I recently had my boiler moved and a storage-combi installed combined with my whole system heating flow reversed. Several plumbers were not interested, too much thinking involved! Only one relished the challenge of the project which actually was very straightforward as I had done all the investigation work up front. He did a great job and has since done the same for a neighbour's house.
A combi suitable for one shower would probably be the smallest you can reasonably get which is say 24kW, perhaps a Vaillant Ecotec Plus 824 or similar, which will have more than enough capability for the 5 rads on it's floor. So 2 x 24kW combis.
BTW you might like to consider making emergency cross connections available to cover for a single boiler failure during a cold spell?
I recently had my boiler moved and a storage-combi installed combined with my whole system heating flow reversed. Several plumbers were not interested, too much thinking involved! Only one relished the challenge of the project which actually was very straightforward as I had done all the investigation work up front. He did a great job and has since done the same for a neighbour's house.
G
GeorgeBainbridge
I see Walter Systems has changed his name again.
Who is he?
For someone who claims to "know" people on here I am surprised that you dont admit to knowing all your other names:-
Dr Drivel ( my favourite )
Water Systems
Walter Systems ( or was that someone making fun of you? )
Big Burner
George Bainbridge
And a few others which were banned before I could remember them!
Interesting how your 11 li/min showers have now reduced to 9 li/min.
Nor do they take account of loss of temperature between boiler and shower.
I realise that you dont actually do any practical work or measurements but I have seen one that lost 18 C but that was routed in iron pipe throught the loft.
Tony
Dr Drivel ( my favourite )
Water Systems
Walter Systems ( or was that someone making fun of you? )
Big Burner
George Bainbridge
And a few others which were banned before I could remember them!
Interesting how your 11 li/min showers have now reduced to 9 li/min.
Nor do they take account of loss of temperature between boiler and shower.
I realise that you dont actually do any practical work or measurements but I have seen one that lost 18 C but that was routed in iron pipe throught the loft.
Tony
G
GeorgeBainbridge
Each combi will need a 22mm gas supply right back to the meter. So another 22 pipe to accompany the iron pipe. Size up the gas pipes.
24kW will do.
Do you have a gas hob? What other gas appliances do you have? A 24kW will do but if you go for it, up the kW on this one, in case the kitchen tap is turned on. Put a flow regulator on the kitchen tap. You do not need firehose flows.
Joining the two DHW outlets is easy. Two check valves and a shock arrestor. A great selling point for the house.
Compare like with like. A large unvented cylinder and system boiler and the zone valves and all the rest. The two combi is cheaper. The Intergas has been mentioned and these are highly reliable and simple with integrated Weather compensation, saving fuel money. The zoning will save on energy bills.
Two combis does that great.
They do not work as hard for sure. But quality combi do not break down a lot. That is an old wives tale. In a combi all is inside the case. If the ballcock sticks in an F&E tank no one blames the system boiler. You have to compare system vs system in faults, not open vented boiler vs combi boiler. The Intergas combi has only 4 moving parts and will be more reliable than most open vented boilers.
The man is a con-man prat. A heating engineer would give you all the figures. He is probably a plumber who picked it up and moved over to boilers because they are good earners. he may have no qualifications except a Career change CORGI course to get the gas certificate. The salesman in a car showroom doesn't tell you which car to buy and what engine size you need.
Go to an installer and tell him say, I want two Integas 24kW combis fitted here serving this and this. Do not take any notice of their suggestions. They want to push you into what they make more money on. You see that on these forums.
G
GeorgeBainbridge
I am flattered you think I am with all these people.
Are you the Tony Agile they say is a useless prat over on the Screwfix forum? Its too much of a coincidence with the names.
I would check this with the makers before embarking on this fit. Some do not recomend this type of setup.
Have used two combis same house but HW delivery was not commoned. Alsao, UV cylinder fitted for bathrooms hot water.
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