Radiators - where and size?

Deedoodee

Any particular good places to get a radiator? I was just going to get one from Screwfix, simple double 22. 

Also, if upsizing, do you upsize based on BTU? So if I used an online calculator which said my room needs 11,000ish BTU, There’s another radiator in there (but I can’t find it’s BTU output) would going for 9,000ish BTUs be enough? 

NSG666

Screwfix rads are ok and often come with TRV/lockshield deal. Well packaged and you can get foc delivery (my experience anyway although some on here will disagree).

Online calculators are ok but you can get different results from e.g. B&Qs or City Plumbing etc - use BTUs or Watts but don't mix them. If you are upsizing your rads that's presumably because you are not happy with the temperature the current rads can achieve so you don't want to go for an output less than calculated. If you get a big rad the room will heat up quicker and the TRV will do it's job but if you undersize you might never get to the temperature you'd like.

Bendy_House

And with most future house heating energy sources likely to be operating at much lower temps than what we are currently used to with gas boilers - we are probably talking at around 40oC - then sizing the new rad(s) for this would likely make sense. Ie, you may also consider replacing the other one for a bigger fellow too.

Even before the transition to a greener energy source, if you can turn your existing gas boiler's flow temp down to, say, 50oC because you've fitted larger rads in your main living area, you should have immediate energy savings as it'll be running in near full condensing mode most of the time.

Deedoodee

Do I need to replace all the radiators to be able to run the boiler at lower temps? 

The other one is a ‘designer’ rad (it’s really ugly) but I’m not keen to replace it because it’s not in the best location and if replacing, I’ll probably want to move it too depending on how we live in the space. 

Im considering replacing the ones in two of the three bedrooms (the larger ones) IF the current ones aren’t double panel 22.

I’m mostly confused about oversizing, do I look at the dimensions and choose the biggest one I can get in the space, or choose based on output (ie higher BTU than required because Screwfix only give BTU at delta 50)

Bendy_House

Improved insulation is the second (and bigger) part of this equation, of course!

As you suspect, the remaining rads will obviously run a lot cooler with the boiler turned down, so won't give out nearly as much heat as they currently do. So, yes, they'd 'need' oversizing too.

The way I see it, though, is that bedrooms really do not need to be 'warm'. Jumping out of bed and running around in the alltogether without fear of goose pimples is a luxury that many of us will find hard to justify as energy prices increase; after all, it's why gawd gave us duvets and warm bodies to cuddle.

Instead, having the 'chill removed' might be a compromise worth having.

So, personally, I wouldn't immediately over-size the bedroom rads, as the cost of doing so would be counter-productive. But, when the time comes to replace them, then reconsider the size.

If the rad you are replacing is in the main living area - sitting room, that sort of stuff - then that's surely the biggie, and where most of the heating will be required, and for the longer periods. All other rads should be shut off until needed.

And, this is your call. But it's what makes sense, I believe; get your current boiler working as efficiently as possible for as long as it lasts, and also get ready for a transfer to a greener alternative in the future.

Deedoodee

Bendy_House said:

Improved insulation is the second (and bigger) part of this equation, of course!

As you suspect, the remaining rads will obviously run a lot cooler with the boiler turned down, so won't give out nearly as much heat as they currently do. So, yes, they'd 'need' oversizing too.

The way I see it, though, is that bedrooms really do not need to be 'warm'. Jumping out of bed and running around in the alltogether without fear of goose pimples is a luxury that many of us will find hard to justify as energy prices increase; after all, it's why gawd gave us duvets and warm bodies to cuddle.

Instead, having the 'chill removed' might be a compromise worth having.

So, personally, I wouldn't immediately over-size the bedroom rads, as the cost of doing so would be counter-productive. But, when the time comes to replace them, then reconsider the size.

If the rad you are replacing is in the main living area - sitting room, that sort of stuff - then that's surely the biggie, and where most of the heating will be required, and for the longer periods. All other rads should be shut off until needed.

And, this is your call. But it's what makes sense, I believe; get your current boiler working as efficiently as possible for as long as it lasts, and also get ready for a transfer to a greener alternative in the future.

Thanks. The second bedroom is also my partner’s home office, and is north facing, and he doesn’t like to be cold, hence considering replacing and oversizing. Though WFH might become a luxury given energy prices and we might just both cycle into the office instead.

So for the replacement rad, oversizing would just be to ‘future proof’ as I wouldn’t be able to run the boiler at a lower temperature if the other rads will be too cold? Have I understood that correctly? 

How do I ‘oversize’? Do I choose one with a bigger output? 

Bendy_House

Deedoodee said:

Thanks. The second bedroom is also my partner’s home office, and is north facing, and he doesn’t like to be cold, hence considering replacing and oversizing. Though WFH might become a luxury given energy prices and we might just both cycle into the office instead.

So for the replacement rad, oversizing would just be to ‘future proof’ as I wouldn’t be able to run the boiler at a lower temperature if the other rads will be too cold? Have I understood that correctly? 

How do I ‘oversize’? Do I choose one with a bigger output? 

Oversizing would be good future-proofing, yes, but if you cannot really turn the boiler's output down to take full advantage at the moment - because other rads still need the heat - then the solution is simple; turn down the control valve on the oversized rad so it behaves like a 'normal' one!

So, if you fitted a half-size-up rad in the living room, you can make it provide the same output as your previous rad, and with the same 'high' water delivery temp, by simply tweaking its lockshield valve down to reduce the flow to it. Or, if it has a TRV fitted, this will do the job anyway when the room reaches the desired temp - it'll shut the rad down.

(It can be slightly more tricky if the room it's in is also the Room Stat room, as how fast this room gets to temp will affect the rest of the house. So, if you find the sitting room (the room with the oversized rad) is heating up far too quickly at the expense of the rest of the house, you close down its Lockshield to effectively 'reduce its size'. I hope that makes sense?)

In essence, if you are replacing rads in any event, you'd be silly to not take advantage and go 'oversized' - the added cost is minimal. You can then - if needed - make any 'oversized' rads work like 'normal'-sized ones by tweaking their L/Ss down. When the future arrives (oxy?), your rads will be ready and waiting.

How to select the right size? I am hoping that there are good radiator size calculators out there that'll help, and they'll have the feature of being able to add the heat source's flow temp to the equation, as well as the usual - room size, no. of windows, age, etc.

ANYONE KNOW OF A GOOD ONE?

BUFF

Bendy_House said:

Even before the transition to a greener energy source, if you can turn your existing gas boiler's flow temp down to, say, 50oC because you've fitted larger rads in your main living area, you should have immediate energy savings as it'll be running in near full condensing mode most of the time.

Assuming that you do have a condensing boiler ...
If it's an old non-condensing boiler it won't make much difference to boiler efficiency (& your rooms will take longer to heat up until you install larger output rads)

Deedoodee said:

How do I ‘oversize’? Do I choose one with a bigger output? 

Yes

FreeBear

Deedoodee said: How do I ‘oversize’? Do I choose one with a bigger output? 

Once you have worked out the output of the radiator for a particular room based on a ∆T50, you need to apply a correction factor to get the rating for a lower temperature.

• ∆T20 0.304
• ∆T30 0.515
• ∆T40 0.748
• ∆T50 1.000

So... If you have a calculation that says you need a 6,000BTU radiator at ∆T50, but you want to run at a ∆T30, the calculation would be - 6,000/0.515 = 11,650BTU

A word of warning with type 22 (and even more so with type 33) - They stick out a long way from the wall, so if you were hoping for a slim fit, you will be disappointed. Another thing to be aware of - Aluminium radiators will perform a little better at lower temperatures compared to steel ones. More expensive though, and I'm not convinced the extra cost is warranted.

If you are buying Kudox radiators from Screwfix, the manufacturer has a handy table you can consult to see which one you need to order - https://www.kudox.com/wp-content/uploads/2017/08/2014-04-09-Kudox-Steel-Panel-Radiators-Technical-Data.pdf

Deedoodee

FreeBear said:

Deedoodee said: How do I ‘oversize’? Do I choose one with a bigger output? 

Once you have worked out the output of the radiator for a particular room based on a ∆T50, you need to apply a correction factor to get the rating for a lower temperature.

• ∆T20 0.304
• ∆T30 0.515
• ∆T40 0.748
• ∆T50 1.000

So... If you have a calculation that says you need a 6,000BTU radiator at ∆T50, but you want to run at a ∆T30, the calculation would be - 6,000/0.515 = 11,650BTU

A word of warning with type 22 (and even more so with type 33) - They stick out a long way from the wall, so if you were hoping for a slim fit, you will be disappointed. Another thing to be aware of - Aluminium radiators will perform a little better at lower temperatures compared to steel ones. More expensive though, and I'm not convinced the extra cost is warranted.

If you are buying Kudox radiators from Screwfix, the manufacturer has a handy table you can consult to see which one you need to order - https://www.kudox.com/wp-content/uploads/2017/08/2014-04-09-Kudox-Steel-Panel-Radiators-Technical-Data.pdf

Yes, the Kudox ones are the ones I’m looking at

Deedoodee

BUFF said:

Bendy_House said:

Even before the transition to a greener energy source, if you can turn your existing gas boiler's flow temp down to, say, 50oC because you've fitted larger rads in your main living area, you should have immediate energy savings as it'll be running in near full condensing mode most of the time.

Assuming that you do have a condensing boiler ...
If it's an old non-condensing boiler it won't make much difference to boiler efficiency (& your rooms will take longer to heat up until you install larger output rads)

Deedoodee said:

How do I ‘oversize’? Do I choose one with a bigger output? 

Yes

The vendor put on the PIF that it’s from 2019 (though it’s come to light that they incorrectly filled in/ lied in other parts of the PIF… ). Both the plumber and electrician have said ‘oh this is a new one!’ when they saw the boiler so I assume it’s relatively new.