Spirotrap mb3 and flow restriction advice.

[Paulrsm]

Hi.

I recently bought a spirotrap mb3 22mm to install in my central heating.
The flow and return pipes into and out of the top of my boiler (prima profile 60e) are 22mm, these go into tees which tee off straight into plasterboard.

Unfortunately when I chopped out the plasterboard below the boiler where the trap was due to be fitted I found that the flow and returns were 28mm. Checking the manual for this boiler it says 22mm is all that was required.

So now I have a trap that's the wrong size. My question is would it be ok to install the 22mm trap into the 28mm return pipework, using reducers? What would this do to the flow back to the boiler based on the fact that it reduces to 22mm at the tee on top of the boiler anyway?

Or should I just buy a 28mm trap? In fact if I did buy a 28mm trap is there a difference in the traps themselves or are just the fittings larger?

Any help/advice appreciated.

Paul.

 

[ScottishGasMan]

If the boiler is running at its full power (which I believe is about 21Kw) then 28mm pipes are the correct size and 22mm would be undersized, in either way it would be better to just get the 28mm filter if you can return the current one

 

[Paulrsm]

Thanks for the reply.

I don't think the boiler is that powerful, this page http://www.homeheatingguide.co.uk/efficiency-tables.php?model=001966 states about 17.5kW which I think equates to 60,000 BTU which, I presume is what the 60 in 60e stands for. The installation manual also states 22mm pipework with only the 80e and 100e requiring 28mm.

Yes I agree I would rather fit the correct size filter but the ebay seller is refusing a return and the 28mm costs about £25 more, hence I'm enquiring if I could get away with using this smaller one.

 

[ScottishGasMan]

Going by the book. 22mm pipe work running with an 11*c change in temp (which is what your boiler will be aiming for) running at a typical water flow rate would allow a maximum of 13kw to be utilised from the boiler, older installations generally they knew this and used 28mm for larger boilers.

That being said, your house probably wouldnt draw the full load for most/all of the year as that should be when its -1*c/-3*c outside.

If your not getting a replacement then you may as well try it, if it operates ok with no noise then will probably be fine. You can always remove it and reinstate 28mm if theres a problem

 

[Paulrsm]

Thanks again for the reply.

I was hoping for a more definative yes it would be ok or no you'll cause 'this' problem. The hassle of maybe having to restore the pipework if it doesn't work is putting me off just trying it. Also then it would be a 'used' spirotrap. It least just now I can sell it as new.

Also you mention 13kW. I've added up, roughly, the BTU's of my currrent radiators and the house full comes to 56,000 BTU about 16.5kW is this why 28mm was used do you think? Or is my boiler undersized for the radiator system?

Regards.