Radiator advice

The main radiator in my living room needs replacing (rusty under the paint and small drip), I figure I may as well replace the other radiators at the same time (as they’re the same age).

I quite like the idea of switching to aluminum radiators (always had cheap steel ones previously) but are there any recommendations for online suppliers. When I started looking it there seemed quite a few places with some nightmarish Trust Pilot reviews. Also any recommendations on quality brands/ranges for both the radiators and TRVs (I don’t want/need Tado’s though, just normal TRVs that will last a while. Although are auto-balancing TRVs worth it to?), happy to pay extra for quality. I’m not looking for designer radiators either really, just simple, plain ones with a good BTU rating.

I won’t be fitting them myself but I take it most plumbers are OK fitting stuff supplied by the customer?

Can’t help with suppliers but why aluminium?

For std rads (well nice looking high output uprights as desired by mrs) We used and were very happy with Radiator outlet. So was our fitter, as one rad was dinged , they told us to chuck it and sent a replacement.

We just chose by size, btu, warranty and looks.

I **think** the most efficient are type 22 panel (*other opinions are avavilable)

Can’t help with suppliers but why aluminium?

Mostly as I’m hoping they’ll last longer but I also like the quicker warm-up time (the quicker cool down I can live with), and I don’t really want to pay stainless steel money. I’ll be factoring in a power-flush and a decent amount of inhibitor to.

I think you’re overthinking it

Mostly as I’m hoping they’ll last longer

But decent quality standard steel rads, with the correct inhibitor in the system, last for years and years and years and years anyway

the quicker warm-up time

I guess, technically, they may heat up quicker, but will it really make that much difference? Steel rads become hot within minutes of the heating coming on, even the furthest ones from the boiler.

For TRVs, Danfoss (at least that’s what every plumber I’ve ever used has used)

I’m by no means an expert but isn’t aluminium more reactive than steel? I don’t know what boiler you have so don’t know what material you’re heat exchanger is. But surely you’re asking your inhibitor to do more work to avoid galvonic corrosion?

But decent quality standard steel rads, with the correct inhibitor in the system, last for years and years and years and years anyway

This is what I was thinking.  I’m sat next to a rad that’s been here since 1985 and there’s no issues.
I think the inhibitor is more important.  I had a MagnaClean fitted a few years ago and it seems good at picking up crap as it floats around the system as well as making it easy to add inhibitor.

 I’m not looking for designer radiators either really, just simple, plain ones with a good BTU rating.

I’d go along the same lines as everyone else, just keep it simple, get whatever Stelrad suits your fancy and put a branded trv with it (eg Honeywell, danfoss, Drayton).

You just need to make sure the radiator size/output is appropriate for the room, which is where your heating engineer comes in.

I got the horizontal line which I think is worth the bit extra in looks over traditional standard looking rads and used Drayton rt212 (we just needed the body of the trv for a tado type system).

You could be right, maybe I should just go with decent quality steel radiators. I’m currently on my 3rd set of radiators in my 30 year old house though, the last two sets supplied by the plumber so likely as cheap and basic as they come. Had my boiler replaced 6 or 7 years ago (Vaillant combi), it had a flush + inhibitor + small inline magnetic filter thing at the time.

Maybe I just get that filter device changed with a better model and flush + inhibitor + change to better quality mild steel radiators… Any recommendation on quality steel brands?

Stelrad

Size them for low flow temp, then you will be heat pump ready and you will be more efficient with your gas boiler too.

Stelrad would be a safe bet.

What’s happening to the radiators that they need replacing every 10 years?

Pin hole leaks as they rust through

We have a few steel radiators in our house that were fitted in 1995 which are still fine, although most were replaced with stelrad type 22 when we had the work done on the house in 2018, as recommended by our plumber.

Most of my radiators date from 87

I did buy a couple of new ones from B&Q as they were known brands at good prices and easy to get.

I thought aluminium radiators were supposed to be more efficient?  Can’t remember where I heard that tho and could be cobblers

I thought aluminium radiators were supposed to be more efficient?  Can’t remember where I heard that tho and could be cobblers

It’s cobblers. A radiator has one job – to lose heat. You put hot water in it, it absorbs the heat from the water and loses that heat into the room. There’s nowhere for any energy to be lost. And energy that is lost die to inefficiency is generally lost to, er, heat.

Aluminium might have a lower specific heat capacity than steel, which would make it absorb the heat more quickly from the water and lose it more quickly into the room, but for all practical purposes the difference would be minimal (especially as the greatest amount of mass in the system is the water, which is the same in either radiator)

There is something strange with your system for it to be rusting through radiators at that rate. I know you said you had it flushed and inhibitor put in, but I’d be making sure that side of things is sorted on the next set.

And the advice to go for a low flow temperature is a very good one. You’ll be futureproofing your house for when you want to get a heat pump, and you’ll be able to run a condensing gas boiler more efficently.

A radiator has one job – to lose heat. You put hot water in it, it absorbs the heat from the water and loses that heat into the room. There’s nowhere for any energy to be lost.

Well, aluminium has higher conductivity than steel so it can put more heat into the room for the same size of rad.  That allows you to run your rads slightly lower temperature and hence your condensing boiler will run slightly more efficiently.

I looked for alu rads for this reason but they were all terribly expensive compared to the boggo steel ones. And the effective difference in heat output wasn’t great, 10% ish from memory.  I was able to double the heat output for the whole house by fitting rads that were 10cm wider on each end and double rather than single.

A few points:

If you’re replacing every rad then a power flush might be a waste

A proper power flush will be £500+ with chemicals and most of the crud tends to accumulate in the ground floor rads before flushing. A dose of either Sentinel X400 or X800 will begin the cleaning process https://sentinelprotects.com/uk-en/catalog/cleaners/x400-high-performance-cleaner/x400-high-performance-cleaner/x400-high-performance-cleaner/groups/g+c+p+a+view

Change the rads and there’s only the boiler, pump and pipework left. Fit a filter, e.g.  Magnaclean or similar, but there are better and worse pipes to use, so don’t just stick it where convenient.

On commissioning the new rads the system should be cleaned to remove manufacturing crud, flux etc. There are chemicals for that, e.g. Sentinel X300

…layers of grease or oil will be present on new components such as on the internal faces of radiators. The presence of this debris and these residues inside the system can lead to rapid pin-hole corrosion of the radiators.” https://sentinelprotects.com/uk-en/catalog/cleaners/x300-cleaner-for-new-systems/x300-cleaner-for-new-systems/x300-cleaner-for-new-systems/x300l-1l/groups/g+c+p+a+nr+view

Follow that up later with an inhibitor, e.g. Sentinel X100, and steel rads will last for decades.

Job done

Well, aluminium has higher conductivity than steel so it can put more heat into the room for the same size of rad

I’m struggling to understand this point. Surely the high conductivity just means it reacts quicker?

I’m struggling to understand this point. Surely the high conductivity just means it reacts quicker?

Well, the water is flowing through the rad and it takes a certain amount of time to do that.  The higher the conductivity the quicker the heat leaves the rad i.e. the more heat can leave in that time; so the cooler the water is as it leaves.  This is the same as having a larger steel rad.  This means your room will heat up quicker for a lower flow temperature i.e. input temperature to the radiator.

Lower flow temperatures mean a more efficient gas boiler, at most about 20%.  But running a heat pump at low temperatures could make it 2-2.5x more efficient.  Given the price difference between electricity and gas, this is the difference between paying a lot more than gas or a lot less.

But decent quality standard steel rads, with the correct inhibitor in the system, last for years and years and years and years anyway

The rads at my old place were on their last legs. But I think my grandparents had them fitted new when they moved in so would be pushing 50 years old today and I wouldn’t exactly call them “quality.” I’m not wholly certain that they aren’t older than that, even.

Lower flow temperatures mean a more efficient gas boiler, at most about 20%.  But running a heat pump at low temperatures could make it 2-2.5x more efficient.

I understand that, but the output of the radiator surely contributes the most to that, rather than what it’s made of. I can see aluminium maybe has a factor in making the BTU rating higher, but adds cost where perhaps you’d be better just sizing up a steel radiator?

Maybe the fact that it reacts quicker to heat means the return temperature is lower, so increases effeciency? I cannot see how it’ll have an effect with a heat pump though, other than the general system is slower to react?

The energy is stored in the water not the metal, the metal transmits it, whatever material it is made off is not going to increase efficiency by a significant amount. They are also convectors more than radiators.
The most important thing is to get the output correct given the designed flow and return temperature and the desired room temperature.
If speed of transfer of heat is so important why is underfloor heating so good coupled with heat pumps? You aren’t looking to diatribe heat quickly with a heat pump but to keep trickling it in matching the heat loss with the energy input