New houses - no combi boiler!?

[Jon]

Hi,

Before I start, I'm not trolling, but trying to satify my curiosity:

I've been reading up on heating systems on here for a while and the pro's/cons of combi boilers etc. We've got a 4 bed, seven year old house with a conventional non-condensing boiler and a gravity fed DHW system with storage tank. We had the HW tank replaced last year just after we moved in which cost ~=A3400 in all. The plumber sugegsted we get rid of the storage tank and get a combi boiler. We said no because if the boiler went we have no electric showers installed, but the immersion heater would provide hot water in the event of boiler failure so we could still wash etc and therefore take the panic off getting the boiler fixed.

My g/f and I went to look at some local show homes (Barret I think they were) on Sunday as something to do. All of them were three story semi/terraces of either 3 or 4 bed. Upon inspection of the heating systems they had installed, all of the houses had a conventional condensing boiler and what I believe to be pressurised hot water storage systems (with the two smaller tanks!) with a single heating zone, in an S-plan system.

I find it bizarre why seeing as they've done it on the cheap by not seperating the S-plan system into an S-plan+ so the heating was more efficient and controllable, why didn't they save further money and put a combi boiler in and save the expense of the pressurised DHW system?

As it is, all of the heat from the CH (due to the open stairways) would simply rise to the top floor which would be sweltering I would have thought. With the heating still running, trying to keep the lower floors at temperature.

Would anyone like to share their thoughts on this?

Thanks,

Jon

[Dave Plowman (News)]

Because most know that a sensible priced combi is less than ideal for a family home. And would be a minus point for sales.

I'm less convinced about zoning the average house, though, unless parts are totally unoccupied. The idea of central heating is to have the whole house at equitable temperature. I suppose if you only ever use a bedroom to sleep in and never visit it at other parts of the day it might make some sense. But few do.

[Tony Bryer]

Yes, but if you use a couple of programmable stats for the two zones and

*know how to program them* (which probably cuts out many occupants of average houses), you can keep the bedroom zone at a lower, but not unheated, temperature until near bedtime, likewise in the morning the living area can come on a bit later. Split zoning my place was very definitely worth the extra cost, £100 or so.

[Dave Plowman (News)]

I'm happy with one programmable stat altering the temp for various times throughout the whole house. In practice the heating hardly ever comes on during the daytime setback period anyway except on the coldest days. So zoning off the bedrooms would make little difference. I also like a warm bedroom to get up in.

[Man at B&Q]

expense of the pressurised DHW system?

Because it is very easy to end up with a very poor system. A combi would be a negative selling point for me, based on experience. I'd rather have a stored hot water system and a decent pumped shower.

MBQ

[Doctor Drivel]

Before I start, I'm not trolling, but trying to satify my curiosity:

I've been reading up on heating systems on here for a while and the pro's/cons of combi boilers etc. We've got a 4 bed, seven year old house with a conventional non-condensing boiler and a gravity fed DHW system with storage tank. We had the HW tank replaced last year just after we moved in which cost ~£400 in all. The plumber sugegsted we get rid of the storage tank and get a combi boiler. We said no because if the boiler went we have no electric showers installed, but the immersion heater would provide hot water in the event of boiler failure so we could still wash etc and therefore take the panic off getting the boiler fixed.

My g/f and I went to look at some local show homes (Barret I think they were) on Sunday as something to do. All of them were three story semi/terraces of either 3 or 4 bed. Upon inspection of the heating systems they had installed, all of the houses had a conventional condensing boiler and what I believe to be pressurised hot water storage systems (with the two smaller tanks!) with a single heating zone, in an S-plan system.

I find it bizarre why seeing as they've done it on the cheap by not seperating the S-plan system into an S-plan+ so the heating was more efficient and controllable, why didn't they save further money and put a combi boiler in and save the expense of the pressurised DHW system?

As it is, all of the heat from the CH (due to the open stairways) would simply rise to the top floor which would be sweltering I would have thought. With the heating still running, trying to keep the lower floors at temperature.

Would anyone like to share their thoughts on this?

[Doctor Drivel]

Because it is very easy to end up with a very poor system. A combi would be a negative selling point for me, based on experience.

[Andrew Gabriel]

Not sure I'd quite agree with your idea of central heating, but zoning provides for that. If my upstairs gets up to temperature first, it gets switched off whilst the downstairs can continue getting up to temperature.

Don't need zoning for that. Just turn off the relevant radiators.

[John Rumm]

A pressurised hot water system will be seen by many purchasers as a positive benefit since it gives the impression of the best of both worlds - mains pressure hot water and hence decent showers, and high flow rates at high temperature so good bath filling performance.

The zoning issue is going to be less visible to most customers, so they can cut costs here.

[sm_jamieson]

With the reported dangers and required maintenance, it may put some people off. Mind you, its immersion heaters with vent to header tank that people are worrying about at present. Simon.

[John Rumm]

Very few I would have thought. Correctly designed and installed pressurised systems seem to give little cause for concern.

(No doubt dribble will be along shortly to post his video of what happens when you defeat all the safety interlocks and thermostats on a pressurised tank and leave the immersion on)

Indeed. Old systems that people think are in need of no maintenance are more of a danger.

[Dave Plowman (News)]

Same with mine - but with individual control over each room, not a zone.

Then it would never be warm?

[Dave Plowman (News)]

Do you ever read a post before replying with one of your adverts?

[Ian_m]

My mate once went to great effort to zone his house with different upstairs and downstairs zones with separate thermostats, but in the end he admitted not really worth it.

Issues were:-

- Add yet more to go wrong in the plumbing, another 3 port valve in his case.

- Both upstair and downstairs basically tended to run in sync anyway and both be on or both off as both settled to "house temperature".

- Yet more devices to programme with temperature and time settings.

- Yet more devices to forget to change when the clocks change.

[Rob]

Why? My experience is the opposite - no hot water once some cleanliness-obsessed person has drained the tank. Or, heating water that isn't used.

And would be a minus point for sales.

Again - I prefer them, and it would affect my buying decision. Unless you insist on power(ful) showers I really don't see the point of the extra pipes and space of a conventional system.

Rob

[whitely525]

It's the incorrectly installed systems that people worry about

[<me9]

That's ok in theory, and is how I set mine up. 'Management' thinks otherwise, and both zones are on almost continuously. Upstairs at 19.5C, downstairs is permitted to be as low as 19C for some small part of the day.

Anything less than 19C 'is absolutely perrishing'.

I keep it all turned off during the time she is out. It rarely has time to drop below 18C.

[David Hansen]

On Fri, 11 Jan 2008 16:28:22 +0000 someone who may be Rob wrote this:-

The only way they are likely to draw off a whole cylinder rapidly is if they have a deep bath. A modern rapid recovery cylinder should be up to temperature again within 20 minutes, roughly when they emerge from the bathroom.

If they have a long power shower then the boiler will be heating the cylinder while they are showering and it is unlikely they will manage to empty the cylinder completely if it is properly sized.

It stays nice and warm in a properly insulated cylinder, which means at least double the standard thickness.

[Rob]

As opposed to instantly available hot water all the time? Of course, it's nothing like the flow, and combis are not up to multitasking (flush the toilet and hot water? Nope), but I've grown used to that. My experience of conventional systems is nothing like yours. A good hour to heat up the tank.

Mind you, 20 minutes is pretty good, things have changed since my day ;-)

Yes, but there must be some heat loss, plus the space/cost for a tank (and header presumably) and additional pipework.

I don't think there's a compelling universal reason for either. I prefer a combi.

Rob

[Dave Plowman (News)]

Assuming you haven't turned the water heating off, a fast recovery cylinder will have the water hot again in no time.

How often do you never need hot water over a longish period? With good insulation a storage cylinder will keep it hot for a long time.

Seems not in this case. As was said a combi is *much* cheaper on a new install so the developers must know something you don't...

Strangely a combi can provide a reasonable shower. It's filling a bath quickly that is their problem.