BTUs radiators (winter is coming...)

[JonathanRyan]

I have a large living room. It's 6m X 3.5 and has 80s double glazed sliding doors along one of the short sides. It has one radiator on the long wall near the sliding doors and for reasons I can't add another radiator. So thermally it's pretty poor.

I want to replace the rad because the room never gets warm and I think it's partly because the rad is old and newer rads are a lot more efficient.

The rad is 1900l X 700h double panel with 1 set of fins. It's probably 20 - 30 years old but in modern terms it's like a type 21. An online calculator suggests I need about 8,000 BTU for a room that size. The only rads I can find that are roughly the right size (close enough to make plumbing easy) are Type 21 at 10,000BTU and type 22 at 13,000

Questions.....

1. Are new rads really that much more efficient? Given that the room is cold, I suspect the current rad is producing quite a bit less than 8000 BTU but an equivalent size would be 10K. Does that seem plausible or have I got my sums wrong?
2. If there's a TRV on it, then apart from initial cost of buying it, is there any problem fitting a massively overpowered rad? My inclination is to get the Type 22 so it will heat the room faster but will this somehow make the rest of the house colder?

 

[boogie man]

Yes newer rads are more efficient, I’ve gradually replaced old style Barlow rads in my 1980s built place with the equivalent sized ones from Screwfix and the new ones are much quicker to heat up. Mostly because the steel is thinner I suspect, but I also think they’re a bit better designed too.

Dont go hugely oversized with the replacement or your boiler might struggle if it’s already running close to its maximum output. I’d go for the 10 k model out of the two you listed. You’d need to fit a TRV to comply with modern plumbing regs anyway.

Just a thought though, does the existing rad ever get hot? Presumably it was sized correctly for the room when it was put in, so it may well just be full of sludge now if it’s an old system and has never had the inhibitor topped up regularly or a filter fitted. It could be worth valving it off, taking it off the wall and running a hosepipe through it to see what comes out. If it runs black it might be more economic to have a power flush done on the whole system and a Magnaclean filter installed afterwards.

 

[Box Brownie]

Yes newer rads are more efficient, I’ve gradually replaced old style Barlow rads in my 1980s built place with the equivalent sized ones from Screwfix and the new ones are much quicker to heat up. Mostly because the steel is thinner I suspect, but I also think they’re a bit better designed too.

Dont go hugely oversized with the replacement or your boiler might struggle if it’s already running close to its maximum output. I’d go for the 10 k model out of the two you listed. You’d need to fit a TRV to comply with modern plumbing regs anyway.

Just a thought though, does the existing rad ever get hot? Presumably it was sized correctly for the room when it was put in, so it may well just be full of sludge now if it’s an old system and has never had the inhibitor topped up regularly or a filter fitted. It could be worth valving it off, taking it off the wall and running a hosepipe through it to see what comes out. If it runs black it might be more economic to have a power flush done on the whole system and a Magnaclean filter installed afterwards.

AFAIK a guide as to sludging in a radiator is if when the HC is running & up to heat and on the surmise that you have bled any air out of the system, is if the sides (entry & exits) and the top area is hot but the lower area is cold ........= sludge in that radiator.

 

[boogie man]

AFAIK a guide as to sludging in a radiator is if when the HC is running & up to heat and on the surmise that you have bled any air out of the system, is if the sides (entry & exits) and the top area is hot but the lower area is cold ........= sludge in that radiator.

Depends on how bad the sludge is really. If the bottom of the rad is badly blocked it’ll reduce the flow radically and the rad will never heat up properly. The pipes can also get partially blocked.

 

[mj4456]

I remove the radiators when decorating* and always flush them out with a hose-both directions-in summer I usually open the system drain cock-it’s outside-and let it run a bit watching mucky water disappear, fresh inhibitor get added every year not long after when the annual service gets done, all happens before hopefully heating is needed as a safety check.
*Wife likes at least one room done every year on a rotation, she imaginings I like decorating.

 

[admirable]

A few years ago a mate had a very similar issue, large room with concrete floor, we sourced two 800mm wide vertical 'designer' radiators in a sale and fitted them in the same position in series using the same original connections with a joining pipe between them. Made a huge difference to the room temp but not much difference to the heating bill.

 

[boogie man]

I remove the radiators when decorating* and always flush them out with a hose-both directions-in summer I usually open the system drain cock-it’s outside-and let it run a bit watching mucky water disappear, fresh inhibitor get added every year not long after when the annual service gets done, all happens before hopefully heating is needed as a safety check.
*Wife likes at least one room done every year on a rotation, she imaginings I like decorating.

Get a magnaflow filter put into the system, it cleans up all the magnetite (black sludge) in the rads and pipework and you should find any water you drain out will be clear after it’s been in for a while. It will get rid of the need to back flush the rads every time. It’s a pretty simple job to fit, or a c/h guy can put one in, but it sounds like you can already do straightforward plumbing jobs. Easy job to clean out the filter once a year as you can isolate the filter with the fitted valves, I can do mine in about 20 minutes. It also gives you an easy access point to add your inhibitor.

 

[JonathanRyan]

Thanks for all the replies - I think I'll go with @boogie man 's advice not to oversize too much in case I start to need a new boiler to keep up

We have an Inta Klean filter which is very similar to a Magnaflow so it should keep things clean. But we have microbore so the flow will never be great ;(

The rad heats up after a while but never really manages to heat the room. For reasons to do with the microbore and some very expensive flooring we can't really add any more radiators to the room.

One related question....I'm replacing some rads upstairs and want to fit smart TRVs (we have a Honeywell Ecohome system). It looks like I'll need to buy TRVs for each rad, throw the cap away and replace with the smart cap. With this in mind, does the quality of the TRV matter much? More money gets you a nicer cap but since I'm throwing them away am I OK with whatever's cheap in Screwfix?

 

[mj4456]

Have recently fitted a magnetic filter, possibly a magnaflow, label facing the wrong way to see, will see how it goes.

 

[boogie man]

Thanks for all the replies - I think I'll go with @boogie man 's advice not to oversize too much in case I start to need a new boiler to keep up

We have an Inta Klean filter which is very similar to a Magnaflow so it should keep things clean. But we have microbore so the flow will never be great ;(

The rad heats up after a while but never really manages to heat the room. For reasons to do with the microbore and some very expensive flooring we can't really add any more radiators to the room.

One related question....I'm replacing some rads upstairs and want to fit smart TRVs (we have a Honeywell Ecohome system). It looks like I'll need to buy TRVs for each rad, throw the cap away and replace with the smart cap. With this in mind, does the quality of the TRV matter much? More money gets you a nicer cap but since I'm throwing them away am I OK with whatever's cheap in Screwfix?

I’d just go for the cheapest TRV if you’re chucking the heads away. The plating might be a bit thinner but they’ll still work fine for what you want. I usually go for Pegler as a decent compromise between quality and price but I don’t think there’s much point in your case.

Dont forget you’ll have to adjust the system balance after you’ve changed that living room rad. Tbh I’d tweak the balance anyway so you get a little bit more flow going to that room ( eg shut all the upstairs rad valves down a fraction).

 

[stumac]

What's you cavity wall and loft insulation like ? No point fitting anything for the heat to go straight out the walls .

 

[Bobsyeruncle]

I have a large living room. It's 6m X 3.5 and has 80s double glazed sliding doors along one of the short sides. It has one radiator on the long wall near the sliding doors and for reasons I can't add another radiator. So thermally it's pretty poor.

I want to replace the rad because the room never gets warm and I think it's partly because the rad is old and newer rads are a lot more efficient.

The rad is 1900l X 700h double panel with 1 set of fins. It's probably 20 - 30 years old but in modern terms it's like a type 21. An online calculator suggests I need about 8,000 BTU for a room that size. The only rads I can find that are roughly the right size (close enough to make plumbing easy) are Type 21 at 10,000BTU and type 22 at 13,000

Questions.....

1. Are new rads really that much more efficient? Given that the room is cold, I suspect the current rad is producing quite a bit less than 8000 BTU but an equivalent size would be 10K. Does that seem plausible or have I got my sums wrong?
2. If there's a TRV on it, then apart from initial cost of buying it, is there any problem fitting a massively overpowered rad? My inclination is to get the Type 22 so it will heat the room faster but will this somehow make the rest of the house colder?

Give me the ceiling height, room width and length, external walls total length, window area, floor type (solid or floorboards, room above type (bedroom?) and wall type (stone, insulated/uninsulated and I'll tell you the correct heat loss for the room.
A new K2 radiator will produce and radiate better heat than the current radiator. You can now get K3 radiators which have 3 panels and 3 sets of fins.

 

[Bobsyeruncle]

Get a magnaflow filter put into the system, it cleans up all the magnetite (black sludge) in the rads and pipework and you should find any water you drain out will be clear after it’s been in for a while. It will get rid of the need to back flush the rads every time. It’s a pretty simple job to fit, or a c/h guy can put one in, but it sounds like you can already do straightforward plumbing jobs. Easy job to clean out the filter once a year as you can isolate the filter with the fitted valves, I can do mine in about 20 minutes. It also gives you an easy access point to add your inhibitor.

Filter only removes dirt from the water, it won't remove sludge from the radiators or pipes if they are sludged up....only a proper power flush will do that, but on a microbore system it might make things worse.....

 

[boogie man]

Filter only removes dirt from the water, it won't remove sludge from the radiators or pipes if they are sludged up....only a proper power flush will do that, but on a microbire system it might make things worse.....

The post I was replying to said that particular user’s rads were regularly getting flushed through with a hose but the drain out water was still showing signs of corrosion. Hence my suggestion of installing a filter. I did say in an earlier post that a badly sludged system might need a power flush. I wasn’t aware that power flushing could cause issues in microbore systems though?

A Magnaclean filter certainly picks up magnetite in the system water as well as dirt, hence the name at a guess. I can’t speak for other makes of filter.

 

[Bobsyeruncle]

The post I was replying to said that particular user’s rads were regularly getting flushed through with a hose but the drain out water was still showing signs of corrosion. Hence my suggestion of installing a filter. I did say in an earlier post that a badly sludged system might need a power flush. I wasn’t aware that power flushing could cause issues in microbore systems though?

A Magnaclean filter certainly picks up magnetite in the system water as well as dirt, hence the name at a guess. I can’t speak for other makes of filter.

Power flushing a micro bore system will remove sludge from the radiators but it can then get stuck in the manifolds....

 

[boogie man]

Power flushing a micro bore system will remove sludge from the radiators but it can then get stuck in the manifolds....

Ah yes, makes sense. Must admit I haven’t had any dealings with microbore systems.

 

[JonathanRyan]

Give me the ceiling height, room width and length, external walls total length, window area, floor type (solid or floorboards, room above type (bedroom?) and wall type (stone, insulated/uninsulated and I'll tell you the correct heat loss for the room.
A new K2 radiator will produce and radiate better heat than the current radiator. You can now get K3 radiators which have 3 panels and 3 sets of fins.

Thank you

Room is 3.7m wide by 6.3m long and 2.3 high. One of each of those walls is external. One entire wall (3.7 X 2.3) is a sliding door. It's double glazed but to 80s standard not 21stC. There's another small window about 1.4 X 1m Floor is concrete with oak flooring. We have plenty of loft insulation and cavity wall insulation.

Room above it is a similar sized room with carpet.

 

[Bobsyeruncle]

Thank you

Room is 3.7m wide by 6.3m long and 2.3 high. One of each of those walls is external. One entire wall (3.7 X 2.3) is a sliding door. It's double glazed but to 80s standard not 21stC. There's another small window about 1.4 X 1m Floor is concrete with oak flooring. We have plenty of loft insulation and cavity wall insulation.

Room above it is a similar sized room with carpet.

Hi Jonathan
I calculate the heat loss for the room at approx 3.5kw which is just under 12,000 BTU's.
A Stelrad K2 radiator 700h x 1800 wide provides a heat output of 3.53kw.
I'd suggest a room that size may get a more balanced heat if you were able to use 2 smaller radiators at each side of the room unless the larger one is fairly central.

 

[Box Brownie]

Hi Jonathan
I calculate the heat loss for the room at approx 3.5kw which is just under 12,000 BTU's.
A Stelrad K2 radiator 700h x 1800 wide provides a heat output of 3.53kw.
I'd suggest a room that size may get a more balanced heat if you were able to use 2 smaller radiators at each side of the room unless the larger one is fairly central.

I think Jonathan mentioned new plumbing is not practical or possible.

I think I read somewhere that the current generation of electric storage radiators are (very?) energy efficient. So perhaps one of them added at the opposite end of the room might take up the slack???

 

[mj4456]

Anyone else tried the small fans that fit on top a radiator to move the air from the bottom up the rad to encourage convection?

 

[JonathanRyan]

Hi Jonathan
I calculate the heat loss for the room at approx 3.5kw which is just under 12,000 BTU's.
A Stelrad K2 radiator 700h x 1800 wide provides a heat output of 3.53kw.
I'd suggest a room that size may get a more balanced heat if you were able to use 2 smaller radiators at each side of the room unless the larger one is fairly central.

Thank you that's very helpful. The old rad is about 700 X 2000 which suggests 700 x 1800 k2 is the modern equivalent. Should heat a lot faster.

You'd absolutely right that a better option would be to also hear the wall opposite the french doors. However we have beautiful oak flooring throughout the ground floor and no rad to patch in to anywhere near. It would be messy or very expensive.

I think I read somewhere that the current generation of electric storage radiators are (very?) energy efficient. So perhaps one of them added at the opposite end of the room might take up the slack???

I keep seeing adverts for these with similar claims. However, I've checked with people who own them and say they are just as frustrating as the old ones. Also, we tend to use this room in the evening which is the wrong use case for storage - we'd have to store the heat from cheap rate electricity all day and use it in the evening. Although the new ones claim that do that people tell me they don't ;(

 

[Box Brownie]

You do seem to be between a rock & a hard place.......

Poorly positioned and hence inefficient (to heat the whole room) radiator.

Costly options to add another radiator into the system

Possible to use a 'space heater' but even the most most efficient would be expensive to run for anything other than task/localised heating.
NB would one of those Dyson space heaters be suitable(?) for such on demand needs

 

[JonathanRyan]

You do seem to be between a rock & a hard place.......

Poorly positioned and hence inefficient (to heat the whole room) radiator.

Costly options to add another radiator into the system

Yeah - it's a lovely house but the heating is annoying We looked at an ASHP. For various reasons I don't think it's suitable for the house but the cost was incredibly reasonable - until we mentioned microbore. Replumbing the house would actually cost more than the ASHP - and that's with running pipes at the surface.

Meanwhile, we have electric blankets Incredibly cosy and cheap to run while watching the telly

 

[gerry s]

You will not get more than 7500btus from 10mm so I'm afraid just putting a larger radiator will not work. Obviously if it's 8mm it won't heat the existing rad to full output.
Your limited by the size of pipe not radiator.

 

[Box Brownie]

You will not get more than 7500btus from 10mm so I'm afraid just putting a larger radiator will work. Obviously if it's 8mm it won't heat the existing rad to full output.
Your limited by the size of pipe not radiator.

So much for the wisdom of the builders using Microbore in the first place

 

[Nod]

Microbore is easy and cheap to install. Fine for smaller installations too.

 

[JonathanRyan]

You will not get more than 7500btus from 10mm so I'm afraid just putting a larger radiator will work. Obviously if it's 8mm it won't heat the existing rad to full output.
Your limited by the size of pipe not radiator.

Interesting. We have 10mm but I hadn't thought of it restricting maximum output. It's 15 under the floor but 10mm to the rads.

So much for the wisdom of the builders using Microbore in the first place

I mean it was quicker to install so.....

Even more fun, we have single ended valves. So there are two 10mm microbore pipes at one end of the rad and none at the other - apparently there's a pipe inside the rad to feed water to the opposite end. Even quicker / cheaper to install. Until 40 years later.

 

[mj4456]

Could you feed another rad using surface mounted piping installed behind false skirting boarding?

 

[Nod]

Interesting. We have 10mm but I hadn't thought of it restricting maximum output. It's 15 under the floor but 10mm to the rads.



I mean it was quicker to install so.....

Even more fun, we have single ended valves. So there are two 10mm microbore pipes at one end of the rad and none at the other - apparently there's a pipe inside the rad to feed water to the opposite end. Even quicker / cheaper to install. Until 40 years later.

Should be easy enough to extend one of the pipes to get to the far end of the new rad.

 

[JonathanRyan]

Could you feed another rad using surface mounted piping installed behind false skirting boarding?

For this room no ;( It's a long run and one direction crosses the door and the other the fire place.

Should be easy enough to extend one of the pipes to get to the far end of the new rad.

Easy, yes. Also, ugly

 

[Nod]

Not necessarily. The new pipe can be hidden behind the lower part of the rad.

 

[Bobsyeruncle]

The old rad is about 700 X 2000

If that's the exact size, you'll be able to get a 700 x 2000 K2

 

[boogie man]

We looked at an ASHP. For various reasons I don't think it's suitable for the house but the cost was incredibly reasonable - until we mentioned microbore. Replumbing the house would actually cost more than the ASHP - and that's with running pipes at the surface.

We looked at it briefly too but I don’t think it’s the best solution for our place either. I believe you have to upsize the radiators by something like 40% for a heat pump system? So that’s more added expense. Apparently the circulating water temp is a lot lower than a conventional c/h system, so needs a bigger rad surface to achieve the same result.