Adding to CH system & boiler size query

Hi,

I need to add to our existing CH system in order to heat an intergral garage conversion.

First query; Our boiler is a Glow worm 40-50 RF model currently running 10 rads total BTU output 34500 and I want to add 2 more rads(12000 BTU) in the garage conversion.

Is the existing boiler big enough for this new total (rads) 47000BTU??

Also, upstairs at the moment theres 15mm CH pipework with 10mm microbore running off it to the various rads. I want to come off this existing 10mm microbore near another upstairs rad and use this to feed the new rads in the "garage". by going into the "garage" loft and dropping down to the 2 new rads.

Can I come off the microbore to do this or must I come off the 15mm?

Can I run 2 new rads (12000BTU total) from this new pipework or does each of the new rads need a seperate feed?

PS I need to run the pipework approx 25ft inside the "garage" loft in order to connect to one of the rads which is at the far end.

Hope I've explained ok! Thanks in advance..........

any chance of anything on this I'm in the middle of it and can't work out whether I'm doing the right thing doing a 7.5metre run using 10mm microbore or whether I should be continuing the 15mm for this 7.5m and dropping down to the rads using the microbore.

I've done quite a bit with 15mm copper in the past but never used microbore before

Gonna be tight, you need approx 8000btu's for your hot water so with 47,000btu's needed for rads +20% margin = 56400 +8000 =64400btu's
boilers gonna work hard, if you have a cylinder stat, time hot water to come on an hour before heating so all boiler output goes to rads and T/valves set correct so as they shut down more oompff left for other rads which may struggle.
Dont tee off the 10mm pipe, it will be a miracle if it copes, if you allready have more than 4 rads off the 15mm run, that will most likely be a dissapointment as well, you need to upgrade the 15mm's to 22mm's and then tee off in 10mm's to the new rads, keep the 10mm runs as short as possible, all in all if you follow that lot you should have a good chance, dont forget to put some cleanser through and an inhibitor when all finished.

Thanks for replying Pedanticman I was hoping that was going to be the advice on the boiler and had a sneaking suspicion that it had to be 15mm not microbore so great to be confirmed.

I'm assuming the only reason the upsatirs has 15mm and the downstairs has microbore is that the downstairs rads can be fed by the 10mm pipework dropped down behind the drylining????????

If this is the case, would it be better to run 15mm striaght to the new rads as in the conversion I have a fair space behind the new studwall??

Thanks again....................

YOu can only supply about 14000 Btu/hr from 15mm, & would guesstimate 5000 from 10mm. ie one medium sized rad if more than a couple of metres!

Will be fine to run 15mm pipes all the way to the rads if you want and can only helpmatters.