Multipoint as CH boiler & kettling

[Doctor Evil]

Because you read regulation and don't think. You have not come up with one reason why it is technically not safe. Nor one. Even the reg you stated was meaningless.

That is why he is uprating the pumping. The keeting I'm pretty sure is scale left over from mains pressure operation.

Quoting regs again, and using no brains. BTW, men made the regs, they never came down with Moses.

Not in engineering. I don't see a reasoning engineering mind here, just a reg quoter.

Yep.

The mans said it was a temporary measure until money is available for a condensing boiler. He doesn't want to touch the gas part, so only worked on the water. The condenser he says will be installed by professionals.

He originally asked question re: condenser, and then thought about keeping the multi-point for a while, as that is what they do in the USA, and asked relevant questions. He was intelligent enough to see there was no safety risk whatsoever, so went ahead. No one thought he would but he did, and it works. Once he de-scales the kettling will go away.

[Doctor Evil]

The electric caber tosser comes in again. It only heats a thermal store, in one go, in a few minutes. Its length of operation is not a negative point.

[Doctor Evil]

No it doesn't.

Appears none.

Ed hasn't come across it before, so it must be unsafe. They do this in the USA, but not here, and I may be wrong on this point, but I can't recall any reg that says you can't use fresh water in a non-ferrous CH circuit, as they do in the USA in soft water areas.

I know of a copper tubed boiler, the FuelSaver, that was used with fresh water in a soft water area of the UK without any problems. The makers said no, no fresh water because of scale, because some dumbo somewhere would put one in a hard water area and then they have kickback problems.

I have seen an Ascot multi-point used a boiler, similar to this Thorn, except it had a pipe stat to maintain the boiler temp and was on a normal; two 2-port system. A fried of mine did this when he was broke after buying an old house. The Ascot was being ripped out of council flats and it was about 1 year old. BTW, it never kettled and was descaled before use. It was in still in use the last time I heard.

Ed is typical of the British mentality, of "we always do it this way", and blind to all engineering reasoning. That is why we still have cavity walls (on one else does), have tanks in lofts (the UK and Ireland are alone in this), and put washing machines and boilers in kitchens. The Swedes think we are mad. But we have always do this so it must the right way. Duh!!!!

Regs are there so the idiots can follow them and a decent safe job results. Intelligent engineers can go outside regs without compromising safety.

[Doctor Evil]

How dramatic. Must have taken a course at RADA.

The above was sensible.

Acting on the gas valve diaphragm, if there is one.

The scale is probably the cause.

I doubt that is the case, if the flow adnreturn pipes are clear.

And any qualified gas/heating engineers would give a report saying the appliance was safe, as it is.

It is not unusual. In other countries on-demand water heaters are used for this application.

Described as so it is safe. It is a water heater and lo-and-behold! It is heating water as intended. Working well within the makers safety framework.

I don't think he is at all. He didn't want to touch the gas side , so installed a thermal store and re-piped the water side. I have read nothing he has written that indicates naivety. He came up with and ideas, asked questions, assessed, and went ahead, knowing safety was not compromised.

You are guessing. Ask him, he might tell you.

Said with a heavy Scottish accent. How 1930s corny Hitchcock.

[Egremont]

... but a waste of time, I said in the OP that the boiler could do with a descale to help out the problem. It is one of, but not the only, variable - boiler used to run reasonably well under original conditions (though it should have been descaled before).

It is.on the cool flow to the boiler from the store.

The flow rate I've estimated is 10L/min, co-incidentally the same as is was before with my (crocked) mains pressure. Obviously other variables have now changed, such as the input water temperatre (for which there is no defined maximum that I am aware of). The documented minimum head is 2.29m, which (correct me if I'm wrong) would result in a fraction of this flow. In fact so much so I would have thought even stone cold water would boil vigourously - perhaps in this situation internal settings are used to reduce gas pressure?.

How dare you- I'll have you know I've got a GCSE in Home Economics!.

There is no point is asking me about problems that I'm not yet aware of (:.>). The only other issue, which I again reported in the OP, is that the boiler case seems (I'm not sure) to get hotter than I remember. If so this would be another symptom of the water getting too hot too soon, another reason I was thinking about a 'bigger' pump to improve boiler cooling.

And please remember - I'm only evaluating this solution!.

Egremont.

[Andrew Gabriel]

Let's suppose that when achieving a 40C rise, the temperature at the pipe wall where the heat input is actually increases by 60C and then mixes with the water in the centre of the pipe which had no rise. Now, when you start feeding in water at, say, 45C, the temperature at the pipe wall will rise to 105C -- and there's your kettling.

To avoid this, you would need a higher flowrate to limit the temperature rise, or higher static pressure to raise the boiling point (which your hot water cylinder may not withstand).

The non-thermostatic ones have a static flow restrictor to adjust for different water pressures.

The casing of mine gets hot if you draw water continuously.

Does your unit have the over temperature cutout fixed near the top of the heat exchanger, or does it predate that (which would be scarey with what you're doing in particular)?

If the water boiled, what is the escape route for the high pressure steam?

[Egremont]

The Thorn may be inefficient (75%?), but it has always given trouble-free service. It costs about 40 quid a year to look after, much simpler & cheaper than fancy modern boilers with their pcbs and the like. As the new CH won't be heavily used, I reckon overall running costs (including maintenance) would be lower than modern condenser, excluding the £1.5-2K or so the CORGIs will want for putting one in. And I'm personally not even convinced a modern boiler would outlast my current one.

Incidentally, I think a new boiler would involve a location change as the (room-sealed) Thorn is in a bedroom. And someone would have to do some ariel brickwork to block up the 12" vent.

So, any safety issues apart, there isn't much argument for putting in a condenser today [unless it's going to put the house price up by more than the boiler cost]. As my usage will be low the 'planet' argument is weak, and at least I've been able to get the gas fires taken out. I don't want to sound like Victor Meldrew but there would also, I confess, be a quiet satisfacton in defeating the system - a very expensive system at that.

Unfortunately the 'controversial' nature of the proposed installation is a concern that may yet push me into line and get a condenser put in. Even if it's truely safe (I'm not yet fully convined it's not) I just don't think the 'system' will tolerate this installation, and this problem (rather than the boiler) will blow up at some later date.

Sad but true - but will reflect on this in next few days.

Egremont.

[Dave Plowman (News)]

Sort of my thoughts. Next door have one, and I was surprised just how hot the case got after running a bath. I suppose it might have maxed out, but the idea of running one all day for house heating strikes me as dangerous.

As a matter of interest, are domestic multi-points rated for commercial use where this might happen? My gut feeling says no.

[Doctor Evil]

More like 25C

I pretty sure this multi-point has temperature regulation that modulates the burner to some degree. Over the past 30 years multi-points have had some temperature control. The old Ascots had none and were left to go wild.

If it doesn't, a high temp limit pipe stat on the hot flow would be needed to cut out the pump. The pumps operation activates the gas valve.

Up the flow pipe, which has "no" restrictions, into the the store and up the open vent to the header tank. Just like any other boiler connected to a direct thermal store.

[Egremont]

Yes this back up my suggestions in the OP. FE tank is at 6M and could be raised to 7.5M, cylinder will take working head of 10M so all OK.

OK thanks

Sadly predates a cutout, agree that this is a problem but it's just an unfortunate attribute of the existing boiler - whatever it's application. With the new setup I was at least going to put in some sort of (not currently existing) safety control, like the pipe stat Dr Evil mentions and perhaps a temperature alarm. Steam would escape to the vented cylinder.

Thanks for the input. Regarding a previous post, when you used to descale the h. ex on your old multipoint in the bath (hope this was you and I'm not sure I phrased that right!), did you do anything in particluar to get the solvent to flow through the pipes - did you just pour it through or just chuck it in a bath of the stuff?. I'd like to get a continuous how flow running through to attack the scale but haven't worked out a good way yet.

Egremont

[Doctor Evil]

You have been told before. It is connected to a thermal store. Repeat that to yourself 10 times. The boiler reheats the store all in one go, in a matter of minutes, then switches off and stays off until a re-heat is required.

Yep.

Go to the doctor and get your guts seen to.

[Egremont]

My boiler may be inefficent, but the CH circuit isn't - there are upstairs & downstairs zones with TRVs in every room. At any given time all but 2 or 3 of the rooms will have CH switched off anyway. This hopefully means that, in the winter, the boiler will run intermittantly to heat up the Thermal Store, not continuously all day. But maybe something to review if/before I sell up & move...

Egremont.

[Doctor Evil]

A good quality boiler would, cheap ones probably not. Generally, you get what you pay for. On a thermal store I would advise a simple non-modulating condensing boiler. Quantum Boilers do a high quality boiler with a stainless heat exchanger and a 10 year guarantee on the exchanger. Also have two stats on the thermal store to ensure no boiler cycling. The boiler will then probably outlast you.

The great point about thermal stores is that simple non-modulating boiler can be used.

The Heatsaver is the basic bioler.

[Egremont]

can be used...

...and as discussed last March, the interface to the (now tested & working*) new CH system (excluding boiler) is also simple, so all in all getting the thermal store was worthwhile even if I end up.putting a condenser in. Will bear in mind your boiler selection, but would CORGI have his/her own ideas?.

Egremont.

[Doctor Evil]

The working head is only from the level of the header tank, vertically down to the bottom connection of the water heater/boiler.

[Doctor Evil]

Also, once your mains pressure is upgraded the DHW can go on this and powerful showers and no tanks. Al there and prepared. The CH system is simple too, and easy to zone off using only simple pumps.

No. The Quantum is a condensing boiler, and coupling it to a store directly is all within the regs.

Corgi have to go by the regs, they are NOT the regs. They don't make them, although their members seem to think so.

[Dave Plowman (News)]

So a matter of minutes is all that's needed to heat the house all day? Think you've started on the sauce rather early.

[Aidan]

Drivel has omitted most of the relevant facts.

In the US, the most usual domestic installation is heating by a warm air 'furnace' and the hot water supply by a direct-fired gas water storage heater, similar to the ones sold by Andrews here. Hot water 'hydronic' heating is fairly unusual. The economies of scale mean that gas-fired water storage heaters are relatively cheap.

A certain US company has marketed DIY underfloor heating kits. They recommend connecting the UFH to the existing domestic water heater. They publish diagrams on their web site showing these installations. The water in the UFH will be at a low temperature and will be stagnant in the UFH tubes for the entire summer. Legionella and other organisms will proliferate in the water. This same water then goes into the domestic hot water system.

Many competent US heating contractors strongly advise against the use of these systems. They are indignant that there are no federal laws prohibiting the installation of these systems. Such systems are prohibited in some states. They are only sold to DIY installers who are not aware of the hazards.

Only an incompetent idiot would install or specify one of these systems. I am not surprised to find that Drivel thinks; " They don't have any problems."

They have huge problems. The UK NHS prohibited the use of DHWS for heating some 20 years ago, at least. Drivel also thinks that there are no problems with your "unusual" installation.

You need to think about the origin of the technical advice that you choose to heed.

[Andrew Gabriel]

Just to be clear -- I'm talking theoriticals here. I'm not suggesting you do this -- I don't want to be stood in the dock next to you, or even in your absence ;-)

The cutout in later models also guards against the diaphragm valve sticking and keeping the burner on when the flow stops. It's a standard electrical self-resetting temperature sensor mounted on the outlet pipe at the top of the heat exchanger, which is connected in series with the flame sensor thermocouple. If it opens, the gas solenoid will drop out and cut the gas supply to the main burner and pilot. Although the sensor is self resetting, the unit won't operate again until the pilot is relit. I don't know what the temperature it opens at, but I would have thought something around 85-90C would have been good enough.

I didn't do anything as fancy. Just stood the heat exchanger upside down in the bath, and poured in kettle descaler with a funnel. Don't try and completely fill it, as it will bubble and girgle as CO2 is given off, and beware of it spitting out the acid. When it finished, I poured it out and poured in some fresh, repeating until it finished bubbling. BTW, this was an old bath scheduled for replacement anyway. Don't let kettle descaler anywhere near an enamelled bath -- it will wreck the enamel surface (and the metal heat exchanger will likely scratch it). ISTR the descaler went bright blue or green (can't remember which it was now), which may mean it wasn't the right chemical for use in that heat exchanger (it was sulphamic acid).

My newer one has teflon coated pipework, and has not shown any signs of scaling up in the 5 years since it was fitted.

[Egremont]

regs. They don't make them,

OK it wasn't so much a regs thing but an installer might have his/her own preference, and may want to choose.