Replacing immersion cylinder with Condensing boiler, is it possible?
- Thread starter Fionageko
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I don't know how you arrived at such a low efficiency figure, perhaps you could explain?
I have a 17 year old combi, it has been regularly serviced, has never broken down, has never required spare parts.
Yes, it may take longer to run a bath, but it gives a damn good shower, through a thermostatic mixer.
It suits my family of three, I like the idea of only heating the water when necessary.
Whatever system we lean towards, we will get used to it; taking it's flaws and benefits for granted. Having a combi with such good showers, I naturally have more showers than baths, if my partner is having a shower, I won't run the water for washing up.
Yes, I may have been lucky with my combi; but it takes up little space, heats water when I want it, hasn't got a complicated wiring centre and zone valves etc.
How many zone valves/actuator heads have you changed in the last 17 years Harry?
Some discussion of the pros and cons of the systems are fine, but going on and on can be so off-putting.
Sometimes, all it comes down to is personal preference - and we should be willing to accept that.
Lots, but mostly due to a failure of the design of the valve actuators, none changed at all, since changing to a different design.
I would suggest, you have been very lucky with the reliability of your combi, most are not so lucky. Combis are an all-in-one package, much more complex internally than a heat-only, very much more to go wrong, more difficult to fix, and nothing inside that the DIYer can fix.
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Yep you're quite right. I thought this was a normal forum but it has degenerated into the usual ****ing contest by the usual type of knowalls that you usually find on the Internet.
It is what is known as an ongoing discussion. If it offends, then use the 'unwatch' button..
@Fionageko as you are no doubt aware by now, you have opened a bit of a can of worms with your original question. Fundamentally there are 2 camps, the combi camp and the storage camp. It always raises the same to'ing and fro'ing when this question comes up. There can be limitations when it comes to a combi supplying HW, hence the animated discussions that always deem to follow.
As far as your original question is concerned though, it is relatively straightforward to change your regular/system boiler over to a combi.
1 clear question need to be answered, is your cold mains water pressure and flow good enough to support a fully mains hot and cold water system. An experienced (recommended) plumber should be able to find that out for you. The other main upgrade point you may have to consider are - the gas supply may have to be increased to supply enough gas for the combi as they tend to use more gas than 'regular' boilers do.
Everything else being equal then is would be pretty straightforward for most experienced installers.
As far as your original question is concerned though, it is relatively straightforward to change your regular/system boiler over to a combi.
1 clear question need to be answered, is your cold mains water pressure and flow good enough to support a fully mains hot and cold water system. An experienced (recommended) plumber should be able to find that out for you. The other main upgrade point you may have to consider are - the gas supply may have to be increased to supply enough gas for the combi as they tend to use more gas than 'regular' boilers do.
Everything else being equal then is would be pretty straightforward for most experienced installers.
If you want to have a discussion open a discussion thread...
I'm not a fan of combis, but just to be clear for the OP, combis don't use more gas overall than regular boilers, but usually rated higher for HW demand, so instantaneous gas flow is higher.
I would suggest that is dependent on how they are installed, pipe runs etc., and how they are used.
An heat only boiler, can be a much lower Kw output, and can therefore modulate much lower than a combi. Every single time a hot tap is turned on, the combi boiler needs to fire up, lots of heat and gas wasted, heating the heat-exchanger, often much of it wasted, for a pint of hot water.
For the OP's needs, it would suit just fine, but they already have a much more expensive open-vented system installed, which could easily be adapted to their needs, is cheaper more convenient to have repaired, when it becomes necessary, plus a much less complex boiler, with much less to go wrong.
Add in the almost certain need for a new, larger gas supply pipe, which might involve an ugly new pipe run a long way, along the outside of the building.
I know, I was keeping it simple. Combi advocates might base their HW efficiency on all the daily HW in one hit. I suspect in practice there's very little difference.
Probably, until it comes to the efficiency of the central heating use, where you might have a combi boiler, some 2 or 3 times the Kw output, needed, to provide the heat input needed.
Viessmann make a combi up to 36kw that can still modulate to < 2kw in CH mode but probably a bit on the expensive side, most only modulate to ~ 5kw, too high.
I think level of ability to modulate, will be the next big advertising battle, if it's not already?
I’ve noticed in several recent threads references to need for a large turndown ratio, even to the extent of implying the system won’t work properly without. I’m sceptical and don’t think it makes more than a marginal improvement. The heat has to go somewhere, and generally things are most efficient at rated power - electric motors, IC engines etc. I haven't seen any figures for boiler efficiency vs turndown.
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