Are there any quality boilers/manufacturers, at any price?

[Tony Bryer]

No, that was my mum's. Heat exchanger replaced after four years (service missed so Keston wouldn't replace under 5-year warranty) - as said elsewhere this didn't come cheap (£700 inc labour IIRC). Due to continuing unreliability (internal exchanger leak losing pressure and locking out?) she got it replaced by a W-B last summer. This wouldn't keep running for more than a week or two at a time before locking out. Tracked down to the 'professional' installer not realising that this model didn't have an internal bypass and on a S-plan system you need to have an external one (which was there for the Keston but he took it out). Haven't heard any more for a couple of months so hopefully now all OK. If not, at least it's not down to me any more.

[charles]

[Snip]

the Kestons at our theatre are 13 years old.

[Doctor Drivel]

They can last for ever if fitted properly in a "clean" system and maintained properly. Ignorant jobbing, bathroom changing "plumbers" rip them out because they do not know how to put them right, which would cost a fraction of a new boiler.

Intergas are making great inroads in the UK. They have been here for decades under the Atmos rebadge. Parts are easily available in all major parts outlets. ATAG are easy for parts. The boilers are just as simple as any other. ATAG and Intergas rarely go wrong. ATAG have service agents. You don't want a dumb plumber looking at it, as he would say rip it out and put in PoxiBatterton as he makes a good mark-up on it. Merc cars are best serviced by Merc agents, same with quality boilers.

Fitters do not want to learn another setup procedure from the LCD display. Hence they use one they can understand because they pretty thick.

[Doctor Drivel]

5-7 years is rather exaggerated. Condensing boilers are no different to regular boilers. All they have extra is a condensate drain.

[Dave Plowman (News)]

Bikes and boats don't have to meet the same emissions as cars. The orbital engine isn't used on cars - despite all the hype when it came out, and millions spend on development. Most will see a parallel there...

[Doctor Drivel]

To what?

[Tim Streater]

2) Not if their website is anything to go by. Four or five browsers here suggest that their web designer needs a good smack.

[Dave Plowman (News)]

If I add a condensate drain to an old boiler it becomes a condensing one?

Excellent - will save a lot of money.

[Dave Plowman (News)]

Image? You think the average car driver cares what type of engine is in use?

It's not possible to make a two stroke meet emissions regs in practice. Their fuel consumption is also poor. This is why they're only used for purposes where their low production costs outweigh this. In countries where it doesn't matter.

Just why do you think every car maker in the world sticks to four stokes, given the paper advantages of some other configurations? It's simple - those advantages are only on paper.

[John Williamson]

Almost all large diesels as used in ships are two stroke. They also have the highest fuel efficiencies of all internal combustion engines, currently over 50%. Two stroke engines scale up better than four stroke engines.

Two stroke engines as used in motorcycles and cars are built as cheaply as possible, so they need to use a fuel/ oil mix. They could be designed not to, but that adds complexity, cost and weight.

At the sizes used in motor vehicles. At other sizes, other cycles work better.

People don't generally use four stroke engines either for very small or very large applications.

[Fredxx]

Dribble will haplessly ignore hydrocarbon emissions if it gets in the way of his argument.

[Dave Plowman (News)]

Large diesels used for this sort of application aren't comparable to what is suitable for road use. For a start, they run at or near a constant speed. 2 stoke supercharged diesels were once used on road trucks by Commer - but not now. Just about all common trucks and cars are four stroke.

As much as all the complicated valve gear used on a modern two stroke?

Not only size.

Efficiency and emissions don't much matter for very small engines. Weight may be crucial, though. And of course cost. Most very large engines run at a near constant speed.

[John Williamson]

Assuming you mis-typed two for four there, yes, as not using the crankcase to compress the charge leads to things like blowers to get the charge into the cylinders to start with. That's why the Commer two-strokes you mentioned had to use a supercharger. The penalty is less if you're already using a turbocharger, though.

Fuel efficiency isn't vital, no, nor is emmission control, though power per gramme can be very important. As for constant speed, marine diesels work over about a three to one speed range (60 - 200 rpm) at pretty constant efficiency levels, which is wider than most automotive engines nowadays. Most of the ones I use day to day have a useful power band from 1250 to 1800 rpm, with maximum fuel efficiency being in a quite narrow band centred on 1500rpm.

[Dave Plowman (News)]

A decent car diesel will have a useful power band from about 1500 - 4500 rpm.

I'd love to see the efficiency figures for a large ship diesel. Surely most of the time it will run at a near constant speed once on the open sea?

[Tim]

Actually, that's the first combi that I might be prepared to let through my front door, IF its construction & quality are up to scratch. The design is way more sensible than the usual combi design and should in theory make it much more reliable. (it has two separate heat exchanging coils, one for CH, one for HW. No diverted valves needed).

Tim

[Dave Plowman (News)]

The diverter valve on my old system was still working fine when I replaced the boiler for a system one which has its own. It was over 25 years old.

[John Williamson]

I'll admit that the ones I use are a tad larger than that. Look for the Volvo DH12C engine specifications, although the Scania equivalent isn't too different. The narrow power band is a by-product of the emmissions control requirements. Valve and injection timing are both critical, and the former can't easily be varied while the engine is running, despite the attempts at VVT by certain makers in the past.

The cars we have will indeed rev up to 4000, but aren't happy doing it. Again, the most economical cruising speed is at about 1700 rpm, which has been optimised by the makers to be at 80mph in top, 56mph in fourth and 30 in third, to get the best figures for the EU consumption tests.

Yes, and also at constant power, given the direct coupling to the propellers. The makers all state 60 - 200 rpm as the operating speeds, though, without mentioning efficiency at the lower speeds. Even in the

1950s, they were doing over 40% thermal efficiency at best speed/ power, and are now up to 54% for the best of them. Train diesels aren't all that far behind, which leads to the interesting thought that unless you're generating your electricity by nuclear power, a diesel locomotive may well generate less pollution overall than an electric one.

[gremlin_95]

ATAG boilers seem to be held in high esteem by a lot of installers.

[Andy Champ]

Starting an engine that relies on a turbocharger must be interesting... more so than a supercharged one. Though I suppose you could have both, or a compressed air tank.

Small boat engines are all going 4-stroke BTW, the emissions regulations are being applied to smaller engines. I've heard people cursing the extra weight of an outboard you have to hand carry.

Andy

[John Williamson]

The big ones are all compressed air start. I've not played with anything smaller that didn't use crankcase compression or a reed valve.