Two Boilers Wiring Together

[Steve3948]

Could be to do with the existing pipework, one big boiler could heat to quickly and lock-out.

Schools and Hotels often have 2 boilers through an Optimiser Controller.

 

[SLIPSHOD & SLAPDASH]

Well what do i know. All i can say is for at least the last 7 to 8 years all large houses i have worked on have 2 boilers.

I asked around the other day and the various plumbers all said about the same thing, that boilers are most efficient when running at their max, but this may only be  needed 15% of the time, so running 2 smaller boilers with the stat turned down lower on one will work out much more efficient than one large one. Also the backup  facility if one breaks down.

 

[Sidewinder]

The backup thing I can relate to.

I suspect however, an underlying cause is that they are only approved on domestic, not commercial!

 

[SLIPSHOD & SLAPDASH]

Commercial systems have been using multiple boilers for longer, i remember wiring some up as an apprentice. Usually they have more space to fit a big unit though.

 

[Sharpend]

Please don't be misled they are both NEW boilers??

Been and had a look today as told it was ready for wiring.

Seems there's been a bit of a bodge as gas two heating zones, water, UFH, so four zones three valves and not a pump in sight. :

 

[batty]

System boilers?

 

[Sharpend]

Standard boilers, not combi's.

Ok I'm not too familiar with wet UFH set ups. So the UFH has a controller which has terminations for the hot water pump and cylinder stat, and one radiator stat and pump, trouble is the hot water is to be circulating all the time therefore pump permanently running, the boilers just bring the tank up too temp as needed, apparently it ensures instant hot water at each tap!

So can I just wire up the zones separately to the UFH, negating the need for the UFH controller on these zones? Or does the controller have some overriding necessity for these zones?

Looking on the boiler mfr site they show just a LNE and SwL to the underfloor heating controller, I'm guessing a generic schematic?

UFH is manufactured by pipelife if that helps anybody? I shall be contacting them in the coming days, but if you guys have feedback much appreciated.

 

[steptoe]

UFH normally has a valve that closes once the water is up to temp and then the UFH pump keeps circulating to get the room temp up,

remember, UFH runs at a LOT lower temp than rads, probably only 30-40 degrees or something like that, too hot and the pipes will blow,

UFH has a seperate stat and pump at the manifold, and possibly seperate valves on each zone as well as the valve on the manifold,

you really need a bit more info on it tbh.

 

[Sharpend]

Well the manifold has four actuators? which are electrically switched via the controller, there is only one floor zone one stat. I'm guessing that the controller will balance heat through pipes as required and operate pump?

 

[steptoe]

yep, that sounds about right,

do you know what sort of controller it is yet?

you need to be careful, some controllers work with cat5e [etc] and NOT normal 3c&E to the stats.

 

[Sharpend]

Doesn't bode well can't find any info from mfrs website?

 

[MeFil]

Have a look on the worcester bosch website.  If you dig about they a page showing a low-loss header that is used to connect the 2 boilers together.  They also have a page to a cascade sequence controller, which controls which boiler fires when, but that looks a bit commercial.  

 

[Sharpend]

Thanks mefil, I've already grabbed them hence the relay.

I'm just not 100% on the UFH controller in respect to what the plumb has put in with the DHW and other rads.

Still it'll all come clear soon!