Upgrading radiators

[perky416]

Hi guys,

The current radiators in my house are old single panel ones all of them measuring approximately 150cm x 70cm.

According to the chart on the following page this rad should have an output of less than 1450 watts:
http://www.simplifydiy.com/plumbing-and-heating/radiators/power

I have used many of the online BTU calculators, I took the highest reading (the calculator took into account glazing size, type, type or room or floor above and below, number of external walls, type of external walls etc) and added 20% to be safe, that gave me a required output of 843 watts. As you can see that is a lot less than the current radiator if the chart is to be believed. The radiator gets hot but the room is still cold so I need a bigger radiator.

What do you guys recon, is the chart no good or is it the online calculators?

 

[endecotp]

The heat output from a radiator also depends on the temperature of the water from the boiler.
Does the calculator you've used allow for that? Probably not; it's probably assuming that the water is 75 C.
If it's less than that (and modern boilers work most efficiently at lower temperatures) then the heat output will be less.

 

[Hot&Cold]

Myson heat loss calculator.have a look at the tutorial before entering your requirements

http://www.myson.co.uk/hlm/index.htm

They also do some imperial sized radiators

 

[motorbiking]

Check the temp of the return pipe that goes back in to the boiler. if your boiler is working hard when the heating is on, then bigger rads wont make a difference.

 

[alan999]

To remove a few variables you could turn the boiler up to max and turn off all the radiators except for just one room. Close the door. If after a couple of hours the room is still cool then it can only mean a bigger radiator required (unless the pipes are blocked or the radiator is blocked or the boiler is struggling or its draughty etc but you get the idea)
As a rough guide I have also used a fan heater in the past ie if a 1kw fan heater cannot heat a room then its doubtful a 1kw radiator can either.

 

[John D v2.0]

To remove a few variables you could turn the boiler up to max and turn off all the radiators except for just one room. .

There's a good chance the boiler will get the water up to temperature, overshoot, then turn off the gas and pump for a while. This means that wouldn't be the quickest way to heat the room. You'll need at least enough radiators on top dissipate the minimum load of the boiler, or you can work out how to turn off the eco pump mode and switch to continuous pump. But even then the burner would be off for a while.