Replace double radiators for type 21 or 21?

jamjar92

I am having some work done in the master bedroom, which means the draining down the heating system, and replacing the radiators for smaller type 22 from double radiators no fins. I will running some cleaner and add inhibitor.

While I am doing this I wondered should I replace some of the other radiators is it worth doing?

They are all double radiators with no fins, so would replace like for like in size, and the TRV, lockshield, with a type 22 rad.
1 x Living Room
1 x downstairs hall
1 x daughter's bedroom

2x master bedroom will be replaced anyway. The 3rd bedroom I use for an office, radiators new, along with kitchen, conservatory, upstairs hall.

I read that oversizing and reducing the flow, could save money by burning less gas, love to be people's/trade person views on this.

Also the TRV's are over 15 years old. I will replace with Drayton TRV4's like I done with the others, when I replaced for assorted reasons.

FreeBear

Double panel, no fins would be Type 20 (not sure if such a thing was ever made). Type 21 is a double panel with a single set of fins between the two. Type 22, again, double panel, but with two sets of fins, so quite a bit thicker than a Type 21.

Going from a Type 21 (or even Type 20) to a Type 22 will give you more heating surface (i.e. greater output), so the room will heat up faster. Dropping the flow temperature will reduce the speed the room heats up, but will push the boiler further in to condensing mode and thus improve efficiency. Whether you will save on overall gas consumption will depend very much on how you run the system in terms of timings & thermostat settings. There is potential to save.

I've gone from vintage Type 10 (single panel, no fins) to Type 11 and Type 21, and it has been well worth it - Also been fitting new windows/door and insulating which helps to keep the heat in.

jamjar92

@FreeBead all the radiators in the house were type 20 (double no fins) then we moved in 2005, never seen type 20 every referred to or type 10 you had, only type 11,21,22 and type 23.

So the only advantage would be room heating quicker?

Might just do the downstairs hall, as I want to add to drain point here there, and daughter's bedroom, she always says its cold.

BUFF

Type 22s will give you more output at the same flow temperature as similar sized type 21s. If you have (or are planning) a condensing boiler or heat pump it might make a slight difference in terms of efficiency or speed the room heats (depending upon how you choose to run the system).

Type 22s are slightly deeper than 21s.

FreeBear

jamjar92 said:

@FreeBead all the radiators in the house were type 20 (double no fins) then we moved in 2005, never seen type 20 every referred to or type 10 you had, only type 11,21,22 and type 23.

So the only advantage would be room heating quicker?

Might just do the downstairs hall, as I want to add to drain point here there, and daughter's bedroom, she always says its cold.

The room heating up quicker is one advantage, the other is being able to run at a lower flow temperature.

If daughter is complaining that her room is always cold, it would be worth running the numbers to see what size radiator is recommended - https://starsapp.co.uk/basic-heat-loss-calculator/ - Go ~25% larger, and you'll future proof yourself for the day a heat pump is installed. I'd also check for cold draughts coming in around the window frame up there and possibly consider insulating the walls. But insulating walls is disruptive & messy as well as expensive unless you can do the work yourself.

ThisIsWeird

Hi JJ.

I think to clarify what FreeBear said - "Going from a Type 21 (or even Type 20) to a Type 22 will give you more heating surface (i.e. greater output), so the room will heat up faster. Dropping the flow temperature will reduce the speed the room heats up, but will push the boiler further in to condensing mode and thus improve efficiency", yes, the room will heat up faster if you run the larger rad at the same (hot) water temp as now, but the new rad will heat up the room at the 'same' speed if the boiler's flow temp is reduced.

Ie, you can equally heat a room using 'hot' water via a 'small' rad, or 'cooler' water via a 'large' rad. What difference does this make? Only that a boiler running 'cooler' will be running further into its 'condensing' mode, so will be able to extract more heat from the burner, and send less waste heat out t'flue = more efficiency.

If your bedroom is going to be used as a bedroom - ie only needs, say, one hour's heat last thing at night, and ditto in the morning - the savings will be small. So, the 'sums' should be considered - is it worth spending £100-£200 on replacing a perfectly ok radiator, if it's going to add a tiny %-age of extra savings? The answer is usually, "Only worth doing if you have to replace it anyway".

There is another future factor, tho' - if you change to an ASHP or other energy alternative, then these do tend to only provide the 'cooler' water, so current rad sizes may struggle.

What to do?! I think what I'd do is to certainly consider replacing (upsizing) rads in 'living' areas - the sitting room, kitchen, dining, etc. - as these will likely be running for many hours per day, so the savings should be noticeable. Once fitted, turn down the boiler's CH flow temp a good 5 or 10oC and see if that still heats the rooms properly. (Ie, don't leave the boiler running as hot as now, and just bask in the new super-fast heating of these rooms!)

Of course, the single biggest improvement you can usually do is to the insulation levels of your house. Try and factor that in even more so.

jamjar92

@BUFF The boiler maybe done later this when we are done with the current cold spell. Heatpump would be way into the future.

@FreeBear  Thanks I will check the link, I used bestheating calc. The room as two outside walls both with cavity wall insulation and loft insulation with a depth of what was minimum in 2005. 

jamjar92

@ThisIsWeird regarding replacing rads, I think I will do downstairs hall, and daughter's room.
The others will do when the boiler is replaced this year.

Loft insulation below current regs as it was done in 2005, think 100mm, I am sure it 150mm minimum now.
Planning having the loft partially boarded so it can be used for storage, will putting more down then,

ThisIsWeird

jamjar92 said:

@BUFF The boiler maybe done later this when we are done with the current cold spell. Heatpump would be way into the future.

@FreeBear  Thanks I will check the link, I used bestheating calc. The room as two outside walls both with cavity wall insulation and loft insulation with a depth of what was minimum in 2005. 

Ideally, any rad calculator should be now done based on the new, lower, boiler flow temp. Delta whatsit (plumbers will advise).

ComicGeek

FreeBear said:

jamjar92 said:

@FreeBead all the radiators in the house were type 20 (double no fins) then we moved in 2005, never seen type 20 every referred to or type 10 you had, only type 11,21,22 and type 23.

So the only advantage would be room heating quicker?

Might just do the downstairs hall, as I want to add to drain point here there, and daughter's bedroom, she always says its cold.

The room heating up quicker is one advantage, the other is being able to run at a lower flow temperature.

If daughter is complaining that her room is always cold, it would be worth running the numbers to see what size radiator is recommended - https://starsapp.co.uk/basic-heat-loss-calculator/ - Go ~25% larger, and you'll future proof yourself for the day a heat pump is installed. I'd also check for cold draughts coming in around the window frame up there and possibly consider insulating the walls. But insulating walls is disruptive & messy as well as expensive unless you can do the work yourself.

Stelrad's factor for converting from 50 Delta T to 20 Delta T for optimum heat pump use is 0.304 - that's a massive 329% size increase, so 25% larger isn't probably going to do anything for future heat pump use.

locky123

Flow temp of 50degC, which would mean a deltaT of 30 for 20degC room temp, will reduce radiator output by roughly 50%. Air source heat pumps operate at max efficiency at lower temp range of 30-40degC, so there will be further reduction in heat output.
https://www.clyderadiators.co.uk/delta-t-conversion
Try calculating the heat output in BTU or kW required for the room using online calculators, most radiator suppliers have them.