Cascading boilers.

[spikewt]

Just looking to see people's opinions on linking 2 system boilers.
To keep it short an sweet, the existing system has about 28 very large rads, in an old building used as a children's nursery. Its had a 40 kw heat only boiler running it but it's not coped very well. The hot water is heated by immersion heaters.

They want the hot water heated by the boilers now.

My idea is to cascade 2 x 32kw ideal vogue system boilers through a 80kw plate heat exchanger that connects onto the vented heating side but take the cylinder flow and return from the sealed side using motorised valves.

Ill add a drawing in the morning.

- 2 domestic boilers to keep any commercial side of things out the way. U16 meter 2 meters away with no other gas appliances.

Im just wandering if anyone has done this.

Iv tried to talk to vaillant but they can be so hard work and I'm not a big fan of Worcester but I know they have this set up available.

 

[lame plumber]

Best Practice: Low Loss Headers - CIBSE Journal February 2014

not an expert on cascading but is this what your on about, worked on a couple and when set up right they work really well on bigger systems.

 

[IDCHAPPY]

Sounds reasonable enough mate, the Vogues should cope fine 🙂

 

[lame plumber]

helps if you read it more carefully, if your putting all the work in, why not go sealed all round and llh, might even make the system work better overall.

 

[spikewt]

I was thinking of trying to keep each side separate as the existing system is quite old. Although there may be some pressure there anyway with the header tank being quite high, I just didn't fancy pressuring such a big system. A bonus to a heat exchanger is there's only a low amount of system water running through the new boilers so easy to keep clean.

This is what I thought anyway.

Im onto ideal about what they think but their being very black and white, which I can understand but its not very helpful when they tell me they don't how to do the wiring as they've not been asked this before. Which I find strange.

 

[tolly]

helps if you read it more carefully, if your putting all the work in, why not go sealed all round and llh, might even make the system work better overall.

I presume he's concerned with pressurising existing rads and pipework so wants to keeps existing rad circuit vented and use plate hex to keep boilers clean aswell?

How old are the existing radiators and pipework then?

 

[tolly]

I presume he's concerned with pressurising existing rads and pipework so wants to keeps existing rad circuit vented and use plate hex to keep boilers clean aswell?

How old are the existing radiators and pipework then?

I think I was a bit late there lol

 

[spikewt]

id say about 30+ years on some of the pipework and the rads are either from then or slightly newer. Were not talking really old rads but the system has been added on a few times by the looks of it and chopped about abit.

I does all work ok though. Just really struggles with only 40kw.

 

[tolly]

I know you said your not a big fan of Worcester but maybe speak to them and consider the Buderus GB162

 

[Dotty]

I do like the GB162. Quite possibly my favourite boiler.

 

[spikewt]

I'll take a look. Does that come under domestic?

 

[Dotty]

The lower end of the range would.

 

[spikewt]

Should have looked first. That would be a brilliant way to go but its a commercial boiler so I can't install it on a domestic ticket.

 

[ShaunCorbs]

Should have looked first. That would be a brilliant way to go but its a commercial boiler so I can't install it on a domestic ticket.

the GB162 65kW you should be able to, as well it used to be upto 70kw input then above is commercial,

but i would be looking to put a commercial boiler in a place like that, as i have seen alot of domestic boilers in cascade formate and fail very early/ not being upto the job

also have you worked the room sizes/ heat losses out, and whats in at the mo convector heaters or rads/lst?