Biomass boiler with gas/oil back up

[Chalmers7]

Hi folks,

Got a client who wants a biomass boiler added to there property which has two plant rooms, would you use the biomass boiler which comes as a container pre plumbed, would you connect to the plant rooms via a low loss header or would you use a heat exchanger to transfer heat keeping separation ?

 

[Nostrum]

Not quite sure what you mean, I take it you mean LPG rather than mains gas?

It's very site specific, you need to determine what fuel your using pellet/chip/log etc then decide where your fuel store will be and weigh up the costs compared to dropping a cabin down and running heat main into the property. Then theres the flue etc

I would use a low loss for the link up though unless your using a store or accumulator which will act as the same thing.

 

[Chalmers7]

Hi, what I mean is there will be two plant rooms, they currently have oil boilers which are ancient, the client want to add a pellet boiler but have it as a external heat module. Within the module is a accumulator, I'm wondering from the accumulator would I be best having a plate heat exchanger keeping the separate circuits or would it be better having a low loss header with boiler and accumulator feeding it? If there is two plant rooms I would need two plate heat exchangers with pumps running back to the heat module?

 

[Nostrum]

Not sure why you would use an accumulator with a pellet boiler, you could fit a buffer into the plant room, run heat main into plant room and couple the 2 into a buffer, personally I wouldn't use heat exchangers unless you wanted to avoid connecting directly onto existing system for whatever reason, less efficient form of heat transfer, more expense and another component to go wrong?

Are you looking to use the oil boiler(s) as back up?

 

[Chalmers7]

Yeah oil working as a back up.

So with a buffer I would have both heat sources feed the buffer then draw off the buffer to the rads etc? I'm not too worried about keeping the systems Independant I'm more worried about the pellet boiler overheating as many jobs I've been on where clients have pellet boilers fitted they have little usage because off overheating and melting the heat meters.

These are multi national company's fitting these in schools which is more worrying.

 

[Nostrum]

your best bet is to work with a manufacturer who will design a system for you for free and supply schematics. I'm just progressing into biomass myself, but I can only presume the reason for above problems being either oversized boilers without suitable modulation or poor control design.

They can get quite complicated which is why some manufacturers are offering design service. Have you got a manufacturer in mind>?

From what you've said, yes I would use a buffer which means you can under size the boiler slightly if needs be as the buffer will also store additional heat for peak demand and also act a hydraulic separation between the 2 boilers.

 

[peteheat]

The pellet boiler shouldn't overheat, they are almost as accurate as oil or gas give them a set temperature to work to and they modulate back or switch off when they reach set temperature plus 5 > 10% depending on the make, model and size.

A lot does depend on the boiler output, I have seen less controls on the very big pellet boilers than on the small domestic units, a 500 Kw one was "Always On" but it did modulate back to just enough heat generated to keep it lit as the pipe work in the building was big enough to use as a heat dump.

I would avoid using the existing system into the buffer, it is a back up that could be taken out in time and has worked for years in its present set up so why change it?

 

[Nostrum]

How would you connect the existing system in peteheat?

 

[peteheat]

How would you connect the existing system in peteheat?

See you in the pub tomorrow :wink_smile: