Connecting 2 oil boilers

[honestbob]

Hi all,
hoping for a bit of advice, I have a customer who has a non-condensing oil combi boiler and would like me to connect another ordinary boiler with a vegetable oil burner to the heating circuit, to cut down on his oil bill in the winter. I've used a dunsley neutraliser before to connect oil and solid fuel, and when I researched different ideas I found something that I'm sure would have done this job, but can't find exactly what it was anywhere. I think it may have been a low loss header, or a primary-secondary loop. I've no experience of either of these systems and wondered if anyone can point me in the best direction? Cheers.

 

[SimonJohns]

Few options

Just a couple off the cuff

1. Low loss header
2. Thermal store


More info would be better.
Which boiler would you like to use?
Would you like to use the pair together?
What type of system are they serving?

 

[Dotty]

You want a low loss header, individual pumps and back end valves.

 

[honestbob]

Cheers, thats what I hoped. The boilers are already there, a potterton combi, and I think the veg oil boiler is an Ideal, looks a few years old, fitted in an out building. My thoughts were combi boiler to low loss header using its own internal pump, veg boiler in outhouse with separate PRV and expansion vessel and pump feeding second circuit to low loss header, heating circuit taken from other side of low loss header. Valves on everything at the header for repairs without draining whole system (is that what you meant by valves on the back end?). If there was room for a thermal store, that is what I would have suggested, but I just have a small cupboard beside the combi to work in. The idea is for the boilers to work independantly, so if the veg oil runs out, or the boiler breaks down, the potterton can be turned back on for regular priced oil heating. As its a Potterton combi, the system is sealed, only feeding a single heating circuit. I seem to remember that you can make a header from 1 1/4" copper, so long as the T's are taken off in the right places. Has anyone any experience of doing this? I've never gotten involved in commercial/industrial plumbing, but get the impression that this is the system used for using 2 smaller boilers (cascade?) instead of one big one? Next is the question of wiring the three pumps and 2 boilers together. Never found an electrician who would even attempt something like this unless I did a wiring diagram and supplied any strange parts!

 

[Dickie]

Though the terminalagy is Yanky, a Primary/Secondary loop is the easiest thing to do with an installation of that nature. Plenty on Google about it, and a simple 'lead/lag' control system also works well.
HTH

 

[honestbob]

Thanks all, what's the advantage/disadvantage of using a losses header over a primary/secondary loop? I don't quite get the loop idea, seems like a lossless header in a circuit with a pump. I really appreciate all the advice on this, having no experience of these set ups.

 

[Dotty]

No. The back end valves are essential and automatic. If you're on 22/28mm pipework then a domestic 2 port valve will do the trick, wired to bring the boiler and pump on once opened.

They are there to prevent short circuiting through the non functioning boiler.