Boiler options and installation advice for Type B23 Flue

[RDS]

I've been asked to carry out a boiler replacement for a customer but haven't come across this type of set up before, i'm looking for a bit of advice from some of you more knowledgable chaps!

Boiler is in the kitchen cupboard on top floor of flat, its a Halstead CBX 24, and the flue terminates up on the flat roof - a Type B23 I believe with the appliance drawing air for combustion from the room - open flued! First time i've come across this set up and wondered:

• What boiler manufacturers are reccomended and are able to provide a replacement option.
• How tricky is it to drop flue liner down void to connect to boiler.
• Any other advice regarding replacing one of these!

I've attached some pics for your veiwing pleasure, and any advice is much appreciated!

 

[Last Plumber]

Looks similar to a vertex flue idea. Although that type were normally installed to use combustion air from a ventilated loft.
Not seen one quite like yours before to be honest. Don't know if they are still made like that, maybe others will know?

Be careful to ensure the ventilation is correct. The boiler is not an open flue'd appliance so don't make the mistake of thinking it is. The termination positions on vertex were always treated the same as open flue's.

Sorry, that's all I can offer in the way of help, don't know if it is any use? Maybe ring Halstead and ask if they still manufacture those? The ventilation requirements should be available.

 

[RDS]

Looks similar to a vertex flue idea. Although that type were normally installed to use combustion air from a ventilated loft.
Not seen one quite like yours before to be honest. Don't know if they are still made like that, maybe others will know?

Be careful to ensure the ventilation is correct. The boiler is not an open flue'd appliance so don't make the mistake of thinking it is. The termination positions on vertex were always treated the same as open flue's.

Sorry, that's all I can offer in the way of help, don't know if it is any use? Maybe ring Halstead and ask if they still manufacture those? The ventilation requirements should be available.

Glad to know it's not just me then!

I've tried phoning halstead - dont think they exist anymore, i was just getting redirected to a 80p/min dimplex technical line. In the CBX manual it does say the Type B23 flue option is open flued however, and does state the ventilation requirements too.

I had considered changing boiler location so a standard horizontal flue could be used on an external wall but customer has just had the kitchen done and it would pretty much involve ripping the lot out to run/access pipework!

 

[ShaunCorbs]

Viessmann make a chimney kit that takes air from the room or if the stack is vented there

 

[Last Plumber]

Glad to know it's not just me then!

I've tried phoning halstead - dont think they exist anymore, i was just getting redirected to a 80p/min dimplex technical line. In the CBX manual it does say the Type B23 flue option is open flued however, and does state the ventilation requirements too.

I had considered changing boiler location so a standard horizontal flue could be used on an external wall but customer has just had the kitchen done and it would pretty much involve ripping the lot out to run/access pipework!

Sorry, I will re-word that. The appliance is designed as room sealed but there are various flueing options.

One of those is Type B23 which means the flue/intake is open to atmosphere in the room in this case but there is no requirement for a draught diverter and the appliance has a fan upstream of the heat exchanger.

So yes, technically if it has that flue, you would rightly class the appliance as being open flued.

When talking open flue, I always initially think of natural draught with a draught diverter, real open flue in other words! I would personally refer to this one as forced draught!

Must be getting old, lol.

If Shaun is right with what he says, it might be your only option unless others do it too?
On the Domestic side I tend to stick with Vaillant and I can't say I have seen anything like that with them but sometimes if you aren't looking for something you don't know it exists.

 

[RDS]

I had a brief look at Viessmann flueing and saw that option, wasn't sure if was just for commercial though so will definitely look into that further - thanks Shaun.

I get so used to only seeing room sealed boilers that when i saw it completeley spun me. My first thoughts were that it had been cobbled together - espicially as the air intake part of the flue is a bit on the Sod! Its kind of nice to have something a bit different though to make you think and learn something new.

 

[RDS]

Looks like the Viessmann Vitodens 100 it is along with their flexible chimney liner. Expensive flue though coming in at nearly 700£ for 12.5m! I'm struggling to get clarification on whether air for combustion can be taken from the duct creating a room sealed appliance rather than taking air for combustion from the room and needing to provide ventilation? The duct is ventilated top and bottom as required but also services 2 other boilers in other flats with their flexible liners for combustion gases. My obvious concern is that if one of the other flats flues is compromised the air supply in the duct will be contaminated. Just wondering if anybody can clarify this or point me in the right direction to check.

 

[ShaunCorbs]

Flexible Pipe Chimney Kit

Flexible Pipe Chimney Kit

viessmanndirect.co.uk

yes you can take from the duct pg18

https://viessmanndirect.co.uk/files//8f659b57-753d-4191-976c-aac9000e8bdd/1905%205414641VPA00011_1%20Vitodens%20Flue%20Guide.PDF

But I would be concerned if there’s other appliances in the and how tight they are guess you could do a o2 test but they would need to be operating etc

 

[RDS]

Thanks for your help Shaun, it's much appreciated. My thoughts exactly on doing O2 test - but as you say would need other flats appliances operating too.