Linking Boilers.

[slizer82]

Can two system of combi boilers be linked to give a greater heat output to the central heating??, or would can you link two heat only boilers and use external pumps?
The reason I ask is that I need to heat a space which needs 20kw of heat in its own right and is 12meters away from the boiler at its furthest point, and am thinking of pipe heat loss ect,total building requirement is 40kw including other areas.
Any advice greatly appreciated.

Thanks.

 

[kevindgas]

linking two system boilers is straight forward. I have the instructions for Vaillant Ecotecs in series PM me if you need them.

 

[bengasman]

Do I get this right?
You want to link 2 boilers to increase heat ouput and when you have achieved that, you want to zone the building to separate the areas.
3 timers, 3 zone valves, 3 thermostats, long wires, long pipes loosing heat........

Would it not be simpler to just use the 2 boilers separate?

 

[Norcon]

12 meters is no great distance to justify installing two boilers.
Another fuel supply and flue needed and extra servicing costs.
As far as pipe losses are concerned this can be addressed by using appropiate insulation or piping system and in any case the losses may well be within the fabric of the building and contribute (though minimal) to the space heating.

 

[mickyg]

are you saying you've calculated 20kw of heat loss ??
anyway, whats wrong with a 40kw boiler?

 

[kevindgas]

are you saying you've calculated 20kw of heat loss ??
anyway, whats wrong with a 40kw boiler?

summer time heat requirements? boiler breakdown? just a couple of reasons to use 2 rather than 1

and on an install we have done Ecotec 418 and 428 linked together they jointly supply, 1 underfloor, 1 heating and 1 cylinder circuit via 2 pumps and 3 zone valves

in the summer only the 418 is switched on

 

[D_Hailsham]

I need to heat a space which needs 20kw of heat in its own right and is 12meters away from the boiler at its furthest point, and am thinking of pipe heat loss etc.

Provided the 12m of pipes is within the building, the heat lost from them is still contributing to heating the building. A 22mm pipe will loose about 56 watts per meter from uninsulated copper pipe, i.e 2688 watts. If well insulated it will loose about 8w/m, or 192 watts.

 

[doitall]

Agree with Kevingas two boilers are fare better and cheaper.

 

[Norcon]

That's just an opinion Doitall.
One quality boiler regularly serviced knocks spots of a two boiler set up IMO.
In any case your larger gas boiler will modulate down anyway.
And I don't see how its cheaper.
With regard to your image I don't see two boilers nor understand what relation this has with two boilers being fare better and cheaper.

 

[slizer82]

The area to be heated is a village hall , plus admin offices, all on gound level (no upstairs) my plan is to zone by three areas using room stats, the areas being the main hall admin area of two rooms and kitchen corridor office and w.c in the other area.The reason for the two boiler enquiry was I was worried wether one boiler, (thinking of a Worcester 42 cdi) , even though its got a good heat output would cope with the runs ect, was planning on using 28mm copper on flow and return for furthest runs.Also wanted good response, especially for main hall.
I was going to use fanned convectors in hall to speed up heating, but they want lst rads so need as much heat as poss.
Sorry to harp on thanks for your advice/input.

 

[doitall]

slizer82, if you look closely you will see the pic is a village hall.

The main hall 4 x fan heaters are on 35mm then splits 22mm to each heater.

The 4 other zones, Bowls, Snooker, changing rooms, and the green room for private meeting etc all 22mm each.

There are several very valid reasons for more than one boiler, the hall above we used 3 boilers and a separate time control for each zone.

The heat requirements in the building are around 65Kw and around 3Kw if just the snooker room is being used.

2-3 boilers connected to a reverse return, and set as a lead and lag, so for the most part just one boiler is ticking over, will save loads of money.

You cannot afford the heating to be off or broke down, 2 or more boilers give you that piece of mind.

 

[bengasman]

Zoning by using 3 thermostats?
No zonevalves? No timers?
What would you think is the difference in capacity between 2 x 20 kw and one 40 kw?

Would the rgi who is going to install this not be the best one to judge what would work as he will be the one correcting things under warrantee if they don't work?

Don't you think he would possibly not be best pleased if a layman were to tell him how he should do his job?

And if he did follow your design and it does not work accurately, would you pay him to redo it or expect him to absorb the cost and alter it free and for nothing?

 

[doitall]

That's just an opinion Doitall.
One quality boiler regularly serviced knocks spots of a two boiler set up IMO.
In any case your larger gas boiler will modulate down anyway.
And I don't see how its cheaper.
With regard to your image I don't see two boilers nor understand what relation this has with two boilers being fare better and cheaper.

A large commercial boiler for the maximum output will not modulate down to the lowest, see my last post, heating requirement is 3Kw to 65Kw.

I posted the pics to show the zoning, which just happens to be perfect for the poster, giving each area it's own control depending on occupancy.

The green room is used as a play group, 10:00 to 12:00 ish, and anytime for meeting etc, a general purpose room in other words.

The main hall is used most day 17:00 ish for activity groups, and again some evenings for entertainment and bar activities

Bowls is used most mornings, and some afternoons.

Snooker is every evening from 18:00 to 23:00.

Every area is independent and can be programmed separately or together.

 

[doitall]

Zoning by using 3 thermostats?
No zonevalves? No timers?
What would you think is the difference in capacity between 2 x 20 kw and one 40 kw?

Would the rgi who is going to install this not be the best one to judge what would work as he will be the one correcting things under warranty if they don't work?

No I don't, 90% of domestic heating engineers wouldn't know where to start.

Don't you think he would possibly not be best pleased if a layman were to tell him how he should do his job?

That's what design engineers and consultants are for.

And if he did follow your design and it does not work accurately, would you pay him to redo it or expect him to absorb the cost and alter it free and for nothing?

If the installer is unhappy with any part of the design he should say so and get a variation order, Drawings are indicative, not a Bible.

 

[kevindgas]

That's just an opinion Doitall.
One quality boiler regularly serviced knocks spots off a two boiler set up IMO.
In any case your larger gas boiler will modulate down anyway.
And I don't see how its cheaper.

again its down to your opinion vs someone else, but in my opinion there is a lot to be said for a 2 boiler set up
when set up right you can run which ever boiler you need or both at times to suit the useage

the set up we installed as I said, runs the 418 in the summer, the 428 in the spring / autumn and both in the winter as that is how the customer wants to use the heat.

summer water only, Spr/Aut water and underfloor and in the winter the rads are also on.
it won't suit all though