15mm from boiler or 22mm

M

marsaday

I am renovating a house at the moment and i have a combi heating system with 6 rads and a towel rail on the loop. It is a small 3 bed semi.

The heating is all in 15mm and because i have rejigged some walls and moved some rads about the pipework going into the boiler is all exposed and has been cut at the moment.

So do i just reinstate everything back to 15mm or should i put the flow and return into 22mm ? It would mean taking the pipework up stairs in 22mm until the hall way, where it will branch off to 15mm and the same on the ground floor.

OR is everything ok as it is in 15mm ?
 
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Your system is probably right on the limit of the heat that 15mm main F and R pipes can carry. Maybe the system worked OK like this in the past. However, if you ever need to add extra rads, increase the size of existing ones or maybe extend your house, you may find 15mm insufficient.

As above have said, if you have the opportunity to replace the main pipes with 22 where it branches, will make sense.
 
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M

marsaday

Ok will do. I think the house had heating put in on the cheap in the past.
 
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Ok will do. I think the house had heating put in on the cheap in the past.

Maybe it was put in decades ago when people had smaller rads and less of them. Kitchens and box rooms often didn't have rads. People were made of sterner stuff but houses seem to be getting warmer these days.

Some people just had a few rads for what was called 'background heating' and other heat sources were used in addition. Older properties could have originally had a coal back burner, and a handfull of rads is all it could manage.

Just a guess.
 
M

marsaday

Yes maybe. The rads are all singles with fins, so i think they were put in in the last 10 yrs. I have swapped one for a double fin and changed a smaller single for the bigger single which i had left over. So i have added to the system in a small way.
 

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