Boiler change

[Meady]

Went to look at a boiler yesterday as it doesn't heat all the radiators up properly. At the moment there is a 24kw boiler fitted, I measured up all the radiators in the house (16 of them and the majority of them are big ones) how would you figure out the combined output of all the radiators, some of them are old with no Finns on the back and some are new. Ive compared the sizes to modern purmo, Quinn and heatline rads and the outputs from these are from 25kw to 35kw.

Also the flow and return from boiler to cylinder is only 22mm, if the total output needed is between 25-35kw would it be best to up that to 28mm or is 22mm enough?

cheers

 

[Neil K]

Is their Hw ok? If answer is yes then 22mm is fine. Is there a gate valve on the Hw primary return so you could balance it down and push more heat to the rads?

 

[lame plumber]

if its a short run to the cyl, 15mm would be ok, doesnt mean the radiator circuit is sized correctly

 

[Meady]

This is when it's on heating only.

 

[lame plumber]

best thing to do would be to start with balancing the whole system having proved the rads arent full of sludge.

 

[Meady]

if its a short run to the cyl, 15mm would be ok, doesnt mean the radiator circuit is sized correctly

Really, it's probably about 5-6 metres to the cylinder both on the same floor. You can see a separate 22mm F/R going upstairs and downstairs, but that means nothing for what's under the floor really.

 

[scorps]

Do you mean from boiler to cyl cupboard were I presume the divertor valves are,then yes the F&R would be better in 28mm,hope it's an 'S' plan and not a 'Y' plan

 

[Meady]

Do you mean from boiler to cyl cupboard were I presume the divertor valves are,then yes the F&R would be better in 28mm,hope it's an 'S' plan and not a 'Y' plan

Yeh boiler to cylinder where the 2 port valve is for the heating.

 

[scorps]

Then yes if your calcs on the heating are right 22mm will struggle,it should be 28mm to cyl cupboard. Check with this Replacement Boiler Size Calculator

 

[Nostrum]

How do you know the radiators aren't oversized?

You should carry out a heat loss calculation,preferably room by room, not add up all the radiators.

22mm may be fine, but without knowing the heat load it's impossible to say.

 

[Ermintrude]

That app must be a bit off said I need 50kw!!