Gas boiler + water cylinder/ immersion heater

FreeBear

Jeepers_Creepers said: Most systems have their CH and DHW controlled completely separately, so there should be no need to turn off any rads - unless there's some flow easing through?

I get a bit of thermosyphonic circulation in my antiquated system - No zone valves.. Shutting off the upstairs radiators saves 10-15 minutes of boiler run time, so worth doing in the summer.

greatcrested

FreeBear said:

greatcrested said: In summer when the heating is off, I use the immersion heater to heat the cylinder water.

You might want to rethink that strategy - Heating a tank full of water takes around the same amount of energy for gas or electricity. Gas is a quarter the cost of electricity.

I'd suggest turning off all the upstairs radiators and then see how long a tank takes to heat with gas. Then compare that to the time it takes with the immersion heater. Monitor the gas & electricity consumption and then do the sums.

I've tried both over the years - though not very scientifically!

Boiler is oil, not gas (and oil is currently cheap though).

I tend to heat the tank once every 2 (or in hot weather 3!) days. So at least I'm not wasting the water I've heated. Day one mixed with cold I get a hot shower. Day 2 hot tap only shower is comfortable. Day 3 hot only and water is luke warm which is fine in hot weather....!

It'll also keep your system's pump and some valves active over the summer,

Yes learned that the hard way. Frozen 3 port valve. I now run the heating 2-3 times over the summer.....

pinkpiglit

We have just (two weeks ago) replaced the hot water cylinder in our 2 bed/2 bathroom flat. 

The main reason for doing this is that I'm a BIG fan of baths in winter (ideally accompanied with a nice glass of red...)  My experience of relying on gas boilers to heat sufficient water has been woful and I always ended up with lukewarm water.

princeofpounds

As others have said, nothing at all unusual about your set-up.

Combi systems are a more common choice for smaller properties in modern builds. They are more efficient, not because the boilers are any better, but because they only heat water you are going to use. They potentially have great flow, if well-specified enough. They can be cheaper to install, because it's only one large piece of kit (and I think this has as much to do with their common adoption as any actual advantage in operation).

On the other hand, they can suffer problems regulating temperature and flow with multiple water sources being used (e.g. the infamous partner turning on the tap or washing machine when you're in the shower moment!). Reliability is a complicated subject - combis are pressured and a bit complex, so can be a bit less reliable in terms of critical problems, but cylinder systems contain a few more simple components that can fail (such as valves and pumps). But often it's cheaper to repair problems that pop up in a cylinder system, as you are less likely to need to replace the expensive boiler itself. Combis can also be noisier (ok, small issue in most cases, but not always depending on where they sit).

I'd pick a combi if I was building a new 2 bed, but if you have a good functional cylinder system, I wouldn't see any need to change it outside of a full house renovation. You'd probably need decades and decades to make back the cost on the difference in efficiency, and otherwise the advantages are not that clear. If the cylinder isn't very high, then as others have mentioned upstairs shower pressure can be a bit weak in a cylinder system - you'll figure that out on day 1 if it's an issue. But the easiest way to solve that by far is to replace the shower with a pumped version - I did that at my last place and it's the best shower I've ever used. Nothing like those nasty little electric showers people tend to think of (which themselves have got a lot better).

greatcrested

princeofpounds said:

 If the cylinder isn't very high, then as others have mentioned upstairs shower pressure can be a bit weak in a cylinder system - you'll figure that out on day 1 if it's an issue.

It's not the height of the cylinder that determines the water pressure, it's the height of the cold tank in the attic above that feeds the cylinder.....

princeofpounds

greatcrested said:

princeofpounds said:

 If the cylinder isn't very high, then as others have mentioned upstairs shower pressure can be a bit weak in a cylinder system - you'll figure that out on day 1 if it's an issue.

It's not the height of the cylinder that determines the water pressure, it's the height of the cold tank in the attic above that feeds the cylinder.....

Thanks, yes.

kayen

thanks everyone for your comments, much to think about! 

There's only one bathroom and it's upstairs so there wont be 2 showers going at once.    As far as I know the water pressure is ok in the bathroom but there's only a bath, no shower facility (the current people use a bucket in the bath...I couldnt cope!).

Maybe I'm thinking about it wrong but I just assumed that because I'll be installing a walk in shower (and probably replace bath as bathroom is fairly large  2.3 x3.5 metres), if I was likely to change the heating at some stage anyway it would need to be done at the same time?? 

If I kept the existing boiler/cylinder set up and do a full bathroom refurb (walk in shower + bath + relocate toilet/ basin), would they need to be 'dug up' or interfered with much if I later wanted to switch to combi?  (not sure how all the pipes and plumbing fits into this picture!)

FreeBear

kayen said: f I kept the existing boiler/cylinder set up and do a full bathroom refurb (walk in shower + bath + relocate toilet/ basin), would they need to be 'dug up' or interfered with much if I later wanted to switch to combi?  (not sure how all the pipes and plumbing fits into this picture!)

Depending on where the bathroom is located in relation to the boiler and hot water tank, putting a combi in at a later date need not be too disruptive. If you are planning on doing a bathroom refurbishment *now*, it makes sense to plan the plumbing so that connecting a combi at a later date doesn't involve digging everything up again.

kayen

thanks @FreeBear I havent yet decided whether to change boiler set up *now* or at a later stage, at this stage just trying to get a better handle on the options/implications to minimise unnecessary rework/ expense

Upstairs bathroom with water cylinder is pretty much above the kitchen where the boiler is. Surveyor also said theres water stored in a polyprop tank in loft space (not sure if this is part of the set up)

...planning the plumbing to accommodate potential future combi -  does this mean leaving pipes exposed or positioning things differently etc?

Jeepers_Creepers

kayen said:

thanks @FreeBear I havent yet decided whether to change boiler set up *now* or at a later stage, at this stage just trying to get a better handle on the options/implications to minimise unnecessary rework/ expense

Upstairs bathroom with water cylinder is pretty much above the kitchen where the boiler is. Surveyor also said theres water stored in a polyprop tank in loft space (not sure if this is part of the set up)

...planning the plumbing to accommodate potential future combi -  does this mean leaving pipes exposed or positioning things differently etc?

Yes, that plastic tank in the loft will be your cold water storage tank (CWS). It's the height of that which controls the hot and cold water flow to your bath taps - ie how successful a shower would be without assistance - ie adding a pump (yuck...)

You can test how well a shower should work by getting a tap-nozzle push-on shower hose and holding it up over your head - is there still decent water flow? If yes, then you can stick with the system you have if you like. If 'no', then you need to either improve your current system (raise that CWS higher or else add a shower pump) or else swap to a mains-pressure-driven one such as a combi.

(Again, a combi will only be as good as your mains supply - you need decent flow and pressure at upstairs height; pressure drops off at something like 0.1 bar per metre height? (Don't quote me - that's plucked out of the air)

A reason why you might want to go combi sooner is if the freed-up cupboard with cylinder might become part of your new bathroom layout? Would you want to clear the whole room out and start afresh with a larger space, or are you happy to keep that cylinder cupboard as it is, as a separate cupboard?