Which boiler do heating engineers have in their own house?

Paul Barker · 21 Dec 2006

Bigburn said:
Why simpler and better

Because you would have a true dual system like the dual ignition on a Rols Royce, all functions would remain available to the user if one combi broke down. This is he main benefit of the two boiler option. Simpler because In your method you would need a hell of an array of diverter gear to switch the duties of one or the other combi to perfrom the role of the other while it was on shutdown.

I didn't really think this needed any thought.

Water Systems · 21 Dec 2006

Paul Barker said:
Bigburn said:

Why simpler and better

Click to expand...

Because you would have a true dual system like the dual ignition on a Rolls Royce, all functions would remain available to the user if one combi broke down. This is the main benefit of the two boiler option. Simpler because In your method you would need a hell of an array of diverter gear to switch the duties of one or the other combi to perfrom the role of the other while it was on shutdown.

I didn't really think this needed any thought.

Paul, you got it wrong. It was one combi doing downstairs CH only one doing upstairs CH. Two separate systems. Easy to do. Both can be side by side or split. No diverter valve, etc.

The DHW is split, one combi doing one bathroom, one the other, The outlets only combine for baths using check valves.

If one goes down then there will be DHW and heat somewhere in the house. No diverter valves or complex control wiring at all. Just two white boxes on the wall and a clock programmer for each. Make sure the two combis do not exceed the gas meter rating. A gas meter can take approx 62 kW. Two 24 kW combi will do fine.

This a is highly cost effective route to get a cheap to run zoned CH system, mains power showers and quick bath fills. And backup too. Price up two boilers, cylinder and all the zone valves - no contest. I have seen a number of these installations and they work very well and no tanks or cylinders either. One had the combis on top of each other under the stairs. Another had them in the garage, another in the loft. Another had them split, one in the loft and one in the kitchen. The one in the loft did upstairs CH.

The same with washing machine, Have two £300 jobs in the garage (can be stacked) rather than one £1,000 Meile - people only buy a Meile because it is reliable and attempt to reduce down time. With two the washing is done all in one day and the load is spead between the two so they last longer. If one is down one works. Easy, cheaper and no down time.

Paul Barker · 21 Dec 2006

Water you got it wrong. When one of your combis breaks down you will only have heating and hot water in half the house. Where's the beauty in that?

Water Systems · 21 Dec 2006

Paul Barker said:
Water you got it wrong. When one of your combis breaks down you will only have heating and hot water in half the house. Where's the beauty in that?

You will have heat and DHW somewhere in the hosue. That is a great advantage over none at all. The two combi system as I described is cheap and very effective. It delivers on all points.

It can be easily DIYed it is so simple.

Bigburn · 21 Dec 2006

Paul Barker wrote

I have an Ideal mexico (aged at a guess 30), a Buderus 500 24c (aged 1), a Glowworm Hideaway (aged >10), and an Ariston Eurofighter a23 mffi (aged 9).

Must be a very large home to warrant four boilers .

JohnD · 21 Dec 2006

Paul has a London home; a country house in Berkshire; a shooting lodge near Balmoral, and a place in Cowes where he keeps his yacht.

Water Systems · 22 Dec 2006

Paul Barker said:
Water Systems said:

Two combis is good. One doing upstairs CH one down - naturally zoning. Separate showers and join outlets for baths only using check valves. Very cost effective.

Click to expand...

Simpler and better to put them in tandem with balancing gate valves on ch and dhw so that there are no hydraulics to change when one goes down, with the proviso that they may not fire on low hot water demand, so it may be necessary to connect the dhw in series. Therefore careful selection of boiler by enquiry with manufacturer.

I doubt if any maker would approve coupling two combis with the DHW in series. I approached Ferolli about joining the outlets of two combis. They got back and said no. I asked why as technically there is no reason why two cannot be joined using check valves. They said back pressure on the heat exchnagers. I told them this can't happed as check valves are being used and a check valve can also be on the cold feed to each combi so giving belt and braces and suitable shock arrestors fitted. They still said no.

Technically they were wrong and could not give a decent technical reason not to. I think they don't want to set a trend and all the cowboys and DIYers just connect up the DHW oulets with check valves and their tech deptartment is then overrun.

Worcester-Bosch said fine and sent a diagram.

It would certainly make more sense to me to buy two 24kw combis of known reliability than one 40kw combi.

That is true and a higher DHW flowrate too.

You have though to consider gas pipe/meter sizing, fluing and space issues. Probably most practical if customer has a garage or utility area which also houses the gas meter.

Two small cased combis don't take up that much room. A gas meter can cope with 62 kW input of the combis.

nickso · 22 Dec 2006

its technically simpler to have two combis on two floors....i have many customers with large houses with this setup. works well and like water systems said it leaves ch/hw in at least one part of the house. ive swapped bits over from one to the other to suit the customer before.

i always hate working on the houses/hotels with several boilers connected in series....usually ends up in nightmares.

theres one house with three boilers in series with zone valves everywhere and a massive panel of relays on it.......i dread calls from that guy

Water Systems · 22 Dec 2006

nickso said:
its technically simpler to have two combis on two floors....i have many customers with large houses with this setup. works well and like water systems said it leaves ch/hw in at least one part of the house. ive swapped bits over from one to the other to suit the customer before.

The points is they can both be together or split for convenience. Technically simpler depends on the house layout.

When I suggest this route to many they look at me as if I am mad. I then give the the prices to acheive a zoned system using tanks and cylinders and zone valves, pumps etc - which is always cheaper, and then the two combis is faster to fit too. They still don't see it.

When using body jet showers the two combis never run out of hot water. How many people have spent a fortune installing larger cylinders?

Most installers go on what they have been doing for 20 years and are not prepared to think.

i always hate working on the houses/hotels with several boilers connected in series....usually ends up in nightmares.

theres one house with three boilers in series with zone valves everywhere and a massive panel of relays on it.......i dread calls from that guy

In series? Return into Boiler 1, flow out of boiler 1 into return of boiler 2, and on. Phased boilers are in parrallel and are switched in to demand.

Not good at controls eh. Modern sequencing contyrols are small and very good.

kevplumb · 22 Dec 2006

Two small cased combis don't take up that much room. A gas meter can cope with 62 kW input of the combis.

really please explain how a U6 passes enough gas without being overloaded

Water Systems · 22 Dec 2006

kevplumb said:
Two small cased combis don't take up that much room. A gas meter can cope with 62 kW input of the combis.

Click to expand...

really please explain how a U6 passes enough gas without being overloaded

A U6 passes 6 cu meters of gas . Keep it below and it is not past its rating. Can't you figure that out?

Although they do have an overload.

nickso · 22 Dec 2006

Water Systems said:
.

i always hate working on the houses/hotels with several boilers connected in series....usually ends up in nightmares.

theres one house with three boilers in series with zone valves everywhere and a massive panel of relays on it.......i dread calls from that guy

Click to expand...

In series? Return into Boiler 1, flow out of boiler 1 into return of boiler 2, and on. Phased boilers are in parrallel and are switched in to demand.

Not good at controls eh. Modern sequencing contyrols are small and very good.

er yeh sorry parallel

i didnt mention modern controls

....that old relay board is a pain, but i worked it all out thanks.....maybe makes me good at controls, old or not

Paul Barker · 22 Dec 2006

You can still buy International Octal Relay Bases and suitable plug in relays at RS components, but actually I even noticed that Edward Edmunson electrical factors keep stock and they are inexpensive.

I have been calling for boiler manufacturers to use plug in relays, as many times we could fix the boiler by pluging in a new pump or fan relay. Though sometimes I have found it is not the relay itself but a dry joint where it is soldered to the board.

I have made up two pump heating systems using relays, but it's better on the whole to go S plan, because you sometimes have to use a zone valve aswell on one or the other channel to prevent the return of the other backflowing and heating it partially. If the pipework layout is good this doesn't happen. Mainly I just use a second pump on an existing gravity hot water system when fitting a bs1566 cylinder to bring the controls up to current standards economically.

nickso · 22 Dec 2006

i quite liked the grundfos 2 pump system......cant remember if it had a fancy name or not.....only seen it twice though.

it does seem a shame sometimes to throw away a whole board for one relay

Water Systems · 22 Dec 2006

Paul Barker said:
You can still buy International Octal Relay Bases and suitable plug in relays at RS components, but actually I even noticed that Edward Edmunson electrical factors keep stock and they are inexpensive.

I have been calling for boiler manufacturers to use plug in relays, as many times we could fix the boiler by pluging in a new pump or fan relay. Though sometimes I have found it is not the relay itself but a dry joint where it is soldered to the board.

I have made up two pump heating systems using relays, but it's better on the whole to go S plan, because you sometimes have to use a zone valve aswell on one or the other channel to prevent the return of the other backflowing and heating it partially.

You install non-return valves just after each pump.

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