I'm about to get central heating installed in a house in West London which only had electric radiators. It's a 3 bed semi which is a bit larger than normal and we would like enough capacity should we decide to do a loft conversion which may rule out having a traditional system (or is it possible to have the tank under the eaves?). I've had a few plumbers who have quoted for vaillant turbomax plus 837 (15 ltrs/min of hot water + 9 rads + 2 towel rails) but I'm worried the pressure in the showers won't be adequate especially if we do loft conversion and have 2 going at the same time. The mains pressure is 2.5 bar and we will be installing all new pipework. With a conventional system, I know I could have a pump but I'm worried about the noise factor as the hot water tank and bathroom are in the middle and very close to all bedrooms. I haven't had a quote for megaflow but been led to believe that it's hideously expensive, is this true? I've been told that condensing combis will save on the energy bills but they are very unreliable as the technology is still developing, and that repairs are expensive. Any advice gratefully appreciated?
Depending on your loft it may be possible to squeeze a cold cistern in there somewhere. So you may be able to keep the current traditional system - you will probably find it simpler to go for a sealed CH system however so you can loose the CH header tank (many conventional systems can be converted to sealed as well at a later date if required).
With a combi the pressure of the hot water will be at mains pressure. The more significant issue is what flow rate the boiler can sustain of water at a usable temperature. How much you need will depend a bit on the type of shower you have/want. Many will work well on 6 l/min, so two from the boiler mentioned should be possible. If you however want a shower panel or some other shower head that requires a very high flow rate then you may be disappointed.
depends on your definition of "hideously" ;-) Will be quite pricey though.
You adviser was perhaps 15 years out of date... You will pay a little more for the boiler but should get that back in reduced bills. The reliability of a modern condensing boiler should no worse than conventional types.
As you are stuck for space there are two approaches:
View two combi boilers. One doing one zone of heating the other doing another (up and downstairs). Each boiler will have two 2-port zone valves operated by a programmer/stat for each zone, preferably a Honeywell CM67, or equiv. Combine the DHW outlets using non-return valves, which will fill a bath pronto and give good power showers for two showers.
With combi's the most important figure is the flowrate. 11 litres/min is fine for showes and the odd slow filling bath. Here is a recent post of mine...
For an even better flow rate and cheap too for what you get, assess using two Worcester-Bosch Junior combi's.
For high flowrates it is cost effective to use two Juniors and combine the DHW outlets. Worcester-Bosch will supply a drawing on how to do it, or ask me here. Two Juniors are available for around £1000 to £1100 depending on what sized units you buy. They have 24 and 28 kW models, you could one 24kW and one 28 kW. That is cheaper than the Worcester HighFlow 18 litres/min floor mounted combi and can deliver about 21.5 litres/min and never run out of hot water. The highest flowrates of any infinitely continuous combi is
22 litres/min, which is the ECO-Hometec which costs near £2K.
Have one combi do the downstairs heating on its own programmer/timer (Honeywell CM67 or equiv) and one do upstairs. Natural zoning, so you don't have to heat upstairs when you are not up there saving fuel. The running cost will be approx the same as a condensing boiler heating the whole house. No external zone valves either, and simple wiring up too. The Juniors are simple and don't even have internal 3-way valves.
Also if one goes down you will have another combi to give some heat in the house and DHW too. Combine the outlets for the DHW bath pipes and all the baths you want very quickly and no waiting. Best have the showers on separate combi's. They will do two showers no problem at all.
Do not exceed the gas meter flowrate of 212 cu foot per hour. To calulate, e.g., a boiler is 100,000 BTU/hr. Divide by 1000 giving 100 cu foot per hour. Add up all the appliances.
The Juniors are not condensing combi's, yet overall heating costs will be equivalent to a one condensing boiler as the upstairs will not be heated most of the time.
A win, win, situation.
Its advantages are:
- space saving (releases an airing cupboard). Both can go in the loft, or at the back of the existing airing cupboard.
- never without heat in the house,
- high flowrates (will do two showers and fill a bath in few minutes,
- No waiting for a cylinder to re-heat
- Natural zoning, one does upstairs and one does down
- hardly any electrical control work (running a wire to a programmers/stat and power to each,
- simple no brainer installation,
- minimal components used.
- less piping used
- cheap to run overall as upstairs would be off most of the time
- etc.
An integrated heat bank (this supplies DHW and the CH zones) with a Glow Worm "heating" boiler heating it. Glow Worm make excellent condensing boilers.
See
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and also see
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will custom make, or adapt a model nearest to your needs, as will DPS.
As you are stuck for space there are two approaches:
View two combi boilers. One doing one zone of heating the other doing another (up and downstairs). Each boiler will have a programmer/stat for each zone, preferably a Honeywell CM67, or equiv. Combine the DHW outlets using non-return valves, which will fill a bath pronto and give good power showers for two showers.
With combi's the most important figure is the flowrate. 11 litres/min is fine for showes and the odd slow filling bath. Here is a recent post of mine...
For an even better flow rate and cheap too for what you get, assess using two Worcester-Bosch Junior combi's.
For high flowrates it is cost effective to use two Juniors and combine the DHW outlets. Worcester-Bosch will supply a drawing on how to do it, or ask me here. Two Juniors are available for around £1000 to £1100 depending on what sized units you buy. They have 24 and 28 kW models, you could one 24kW and one 28 kW. That is cheaper than the Worcester HighFlow 18 litres/min floor mounted combi and can deliver about 21.5 litres/min and never run out of hot water. The highest flowrates of any infinitely continuous combi is
22 litres/min, which is the ECO-Hometec which costs near £2K.
Have one combi do the downstairs heating on its own programmer/timer (Honeywell CM67 or equiv) and one do upstairs. Natural zoning, so you don't have to heat upstairs when you are not up there saving fuel. The running cost will be approx the same as a condensing boiler heating the whole house. No external zone valves either, and simple wiring up too. The Juniors are simple and don't even have internal 3-way valves.
Also if one goes down you will have another combi to give some heat in the house and DHW too. Combine the outlets for the DHW bath pipes and all the baths you want very quickly and no waiting. Best have the showers on separate combi's. They will do two showers no problem at all.
Do not exceed the gas meter flowrate of 212 cu foot per hour. To calulate, e.g., a boiler is 100,000 BTU/hr. Divide by 1000 giving 100 cu foot per hour. Add up all the appliances.
The Juniors are not condensing combi's, yet overall heating costs will be equivalent to a one condensing boiler as the upstairs will not be heated most of the time.
A win, win, situation.
Its advantages are:
- space saving (releases an airing cupboard). Both can go in the loft, or at the back of the existing airing cupboard.
- never without heat in the house,
- high flowrates (will do two showers and fill a bath in few minutes,
- No waiting for a cylinder to re-heat
- Natural zoning, one does upstairs and one does down
- hardly any electrical control work (running a wire to a programmers/stat and power to each,
- simple no brainer installation,
- minimal components used.
- less piping used
- cheap to run overall as upstairs would be off most of the time
- etc.
An integrated heat bank (this supplies DHW and the CH zones) with a Glow Worm "heating" boiler heating it. Glow Worm make excellent condensing boilers.
See
formatting link
and also see
formatting link
They will custom make, or adapt a model nearest to your needs, as will DPS.
If you can fit a hot water tank somewhere, that takes care of the shower problems - oodles of hot water and high flow rates. But do run the thing off mains pressure. It costs a little more than a combi system, but you can site the hot water tank anywhere.
Combis are great for piddly little bachelor flats with no room for a hot water tank or header tank. Otherwise I think they are the worst of all possible worlds. Mains presure system boiler and pressurised HW tank is the luxury solution to fast baths and powerful hot showers.
IMM will differ and blind you with bullshit about efficiency, saving the whales and why tory land grabbing toffs ought to be hunted with foxes etc. Ignore him, apart from amusement.
Exactly. It's May now, and you forgot to post your solution for this month to central heating, world hunger and the economic ills of the 3rd world. You posted the April one - try to keep up.
a million combis can probably supply a million bathrooms. A hot water tank suitably insulated and situated inside the house will supply three or 4 showers off a muich smaller bioler.l
But will need a much larger cylinder, NOT TANK. The terminology gives away your amateurism. In fact a very large and expensive cylinder too. Having a small boiler does not mean economy in installation or running costs
It is best to use all the gas you can use from your supply (having a boiler(s) of approx 200,000 BTU/hr) to heat water faster and store far les; better if storing none at all. No large spaces taken up by large cylinders.
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