Replacing Radiators - column or convection, double, single, BTUs!?

delmonta

Leethos said:

Hi, the one point which has been raised above that needs consideration is that of the expansion vessel. A column radiator even the modern steel type will have a greater water content than a steel panel radiator of the same size. You need to factor in the volume of water in the system and ensure that the vessel in the boiler has spare capacity to take up the additional expansion required if you opt for a number of column radiators.

Thanks I didnt even know what an expansion vessel was before today! How would I go about checking if it was big enough, as I planned to replace three single panel convection rads with column rads

Jeepers_Creepers

delmonta said:

thanks, the type 21 radiators of the same size (meaning I won't have to move pipes) are about double the BTU rating that I supposedly need, and twice the price. So I'm not sure this is necessary considering the room will also be insulated soon. 

As for hanging on an internal wall, it would mean taking up floorboards and moving all the pipework, seems like a lot more work. You are right they are currently under the windows, but to be honest in both rooms it sort of makes sense and looks quite neat being under the windows. I cant see much of a better place without moving them to the other side of the room! which would be a hassle

Thats why I wanted to work this out now, so I can get the people doing the insulation to put some stud work in exactly where I need to fix the rads

Any idea how thick the internal insulation will be? If up to, say, 35-40mm, then you should get away with just using longer coach bolts to secure them - no need for battens. And I know it might seem daft, but once the brackets have been correctly located, if you apply a thin coat of an adhesive such as StixAll or Grippfill to the mating surfaces before screwing them down, that'll really help stop any future movement.

Sizes; going slightly 'oversized' is generally a good thing as it means you'll get the same heat output but with a slightly lower water temp = more efficiency with modern condensing boilers.

You can't go 'too' big, but it would usually be silly as most folk want their rads as compact as possible. If, say, your boiler is currently running flat out supplying the house and can only provide 2kW to a particular rad, then replacing that rad with a 4kW jobbie will still only give you 2kW output. If, however, your boiler is heating your house with ease and has surplus capacity, then the new 4kW rad will give you - yes - 4kW. Unless you tweak down the lockshield to limit it to ~2kW...

So, if your current boiler can currently heat your home using your current rads, it'll still heat your home using double-sized rads. But the double-sized rads won't give out double unless the boiler can find double too.

With modern rads which convect well, it really doesn't matter too much where you position them, so keep them under your window if that's where you like them. Failing that, I tend to place them where they are out of sight, so behind sofas provided there's enough room to allow a good air flow around them. If it's a large room, then you might want to position them so's they're at opposing ends.

Rads are designed to heat a room, and not just what's sitting close to them. Having said that, they are obviously 'hot', so the immediate area will tend to be warmer.

Insulating the external (solid?) walls is a great move, and I think will make a very noticeable difference (along with draughtproofing the floorboards...). So, if your current single-panel rad did a reasonable job of heating the room, a similar-size replacement should manage it with relative ease. I personally wouldn't go 'double' unless there's a very good reason.

delmonta

Jeepers_Creepers said:

delmonta said:

thanks, the type 21 radiators of the same size (meaning I won't have to move pipes) are about double the BTU rating that I supposedly need, and twice the price. So I'm not sure this is necessary considering the room will also be insulated soon. 

As for hanging on an internal wall, it would mean taking up floorboards and moving all the pipework, seems like a lot more work. You are right they are currently under the windows, but to be honest in both rooms it sort of makes sense and looks quite neat being under the windows. I cant see much of a better place without moving them to the other side of the room! which would be a hassle

Thats why I wanted to work this out now, so I can get the people doing the insulation to put some stud work in exactly where I need to fix the rads

Any idea how thick the internal insulation will be? If up to, say, 35-40mm, then you should get away with just using longer coach bolts to secure them - no need for battens. And I know it might seem daft, but once the brackets have been correctly located, if you apply a thin coat of an adhesive such as StixAll or Grippfill to the mating surfaces before screwing them down, that'll really help stop any future movement.

Sizes; going slightly 'oversized' is generally a good thing as it means you'll get the same heat output but with a slightly lower water temp = more efficiency with modern condensing boilers.

You can't go 'too' big, but it would usually be silly as most folk want their rads as compact as possible. If, say, your boiler is currently running flat out supplying the house and can only provide 2kW to a particular rad, then replacing that rad with a 4kW jobbie will still only give you 2kW output. If, however, your boiler is heating your house with ease and has surplus capacity, then the new 4kW rad will give you - yes - 4kW. Unless you tweak down the lockshield to limit it to ~2kW...

So, if your current boiler can currently heat your home using your current rads, it'll still heat your home using double-sized rads. But the double-sized rads won't give out double unless the boiler can find double too.

With modern rads which convect well, it really doesn't matter too much where you position them, so keep them under your window if that's where you like them. Failing that, I tend to place them where they are out of sight, so behind sofas provided there's enough room to allow a good air flow around them. If it's a large room, then you might want to position them so's they're at opposing ends.

Rads are designed to heat a room, and not just what's sitting close to them. Having said that, they are obviously 'hot', so the immediate area will tend to be warmer.

Insulating the external (solid?) walls is a great move, and I think will make a very noticeable difference (along with draughtproofing the floorboards...). So, if your current single-panel rad did a reasonable job of heating the room, a similar-size replacement should manage it with relative ease. I personally wouldn't go 'double' unless there's a very good reason.

Thanks for the detailed reply. I think the insulation is 100mm internal and external. So it should make a big difference. They did say you'd need studs/battens etc to change heavy things like rads. But thats fine, they can account for that when doing it, its not problem to add a few studs. 

In the winter when it was below freezing was the only time the house struggled a bit to get warm, it was ok if you closed the doors to rooms, but the hallways are quite big and only have a small rad for the whole downstairs and upstairs. But thats ok, I dont need the halls to be extremely warm, it would waste a lot of energy. At some point I should replace the hallways rad with something larger. 

But once the insulation is in, I think replacing the radiators like for like should be fine, and the new ones will be more efficient hopefully

Jeepers_Creepers

100mm insulation?! Wow.

And - yup - you'll need battens!

delmonta

Jeepers_Creepers said:

100mm insulation?! Wow.

And - yup - you'll need battens!

Definitely 100mm external. I'm almost certain they said 90 or 100mm internal too. yeah its a lot!