Help understanding radiator measurements

[Milleniumaire]

I'm looking to replace a 27 year old single panel radiator with a double panel version in a room that always feels cold regardless of the radiator having a fully open TRV and the radiator being hot to the touch. While decorating the room, now seems to be the right time to do what I've been thinking about doing for years!

The big issue will be doing this without altering the pipes to avoid having to cut into the chipboard flooring and having to drain down the system to move the pipes. Currently, the pipe centres are 970mm apart and the distance from the wall is around 31mm (29mm for right side and 33mm for left side). This is wall to pipe centre. The current radiator dimensions are 890mm wide by 620mm high.

Looking at the Stelrad catalogue I don't see any single radiator (Type K1) that match mine. I'm looking to replace it with a Type K2. Many of the dimensions shown for the brackets and radiator width have two measurements, with the second shown in brackets with an asterisk alongside it. What are these two measurements as nothing explains them?

For example, for the Type K2 bracket, for the narrow bracket side I see 14 (*17) and for the wider side of the bracket I see 25 (*32). For the K2 radiator pipe centers to wall measurements I see 73 (*76). These radiator measurements appear to include the bracket width, but as there are two ways of fitting the bracket, why aren't there two lots of measurements!!!! Totalling confusing to me at the moment!!

I'm trying to determine the minimum pipe centres to the wall for the K2 when the bracket is fitted using the narrow side.

Here's a link to the Stelrad instructions showing these measurements: Stelrad-Horizontal-Panel-installation-instructions

I would appreciate any help in understanding these measurements. Also, why don't they provide measurements for the pipe centres for the flow and return pipes?

Thanks.

 

[Milleniumaire]

Thinking about it, I guess the radiator tails can be fitted to determine the pipe centres, but I would assume there is a minimum size when the tail is screwed into both sides of the radiator as far as it will go? Likewise, to accommodate pipes that are further apart, it could be screwed less, but there will be a limit to provide this maximum pipe centres measurement?

My current pipe centres are 970mm, so a 900mm radiator width allows 35mm on either side and the valves will take some of this. How long is a standard radiator tail?

 

[ETAF]

you can buy extension tails and cut them down , from screwfix or toolstation - i have done this a few times when replacing old imperial radiators

i also downloaded the install info off the screwfix site and worked out how far out the rad centre would be - and on 2 rads i added some wood to the bracket to match the existing pipework

Also have you checked the BTU of the room , I purchased various different types of radiator and as one was under a window it was just higher for BTU and the others just on a wall so height was not an issue

the link to screwfix often does not work here
BUT for example
Essentials 1/2" BSP Male x 15mm Compression 65mm Chrome Radiator Telescopic Valve Extender 2 Pack (10954) - this is telescopic - which i would not use - but i just cut them down - very easy with a mulittool - but juist for illustration , search toolstation and screwfix for radiator tails
toolstation have them to and different lengths available

You may want to buy some caps just to go onto each side of the valves when you lock both valves - just in case they dont complety turn off
SOMETHING like these Flomasta Brass Compression Blanking Nut 15mm (55441)

 

[Milleniumaire]

You may want to buy some caps just to go onto each side of the valves when you lock both valves - just in case they dont complety turn off
SOMETHING like these Flomasta Brass Compression Blanking Nut 15mm (55441)

I have some plastic blanking nuts that came with the original TRV's, but I always wonder just how strong they are, since the pin is probably putting a lot of force on the plastic. Still, you would think the manufacturers would consider that and ensure they are strong enough.

I'm planning to remove the radiator this weekend so will need to dig out the blanking nuts. We have a number of different types of TRV's around the house and all use different sized blanking nuts.

I suspect the main issue I'm going to face with replacing this radiator is getting a K2 style that is close enough to the wall to fit the existing pipework. It may not be possible as the existing radiator was fitted using the narrow side of the brackets to accommodate the pipes being very close to the skirting board. It's a shame it wasn't fitted with the wider side of the brackets as that would have given more space.

 

[ETAF]

i was talking about the caps that go onto the valve where the radiator tails fit on

have you checked the BTU on what size you need ?

i have fitted all 3 types in the house , based on size , BTU and matching existing pipework

look at the screwfix rads and download the instruction PDF - that provides all the dimensions of the different rad types T11, T21 & T22 - which i used when i fitted
T21 and T22 replacements

in fact i purchased from toolstation - trying to find the same info i used from their site

Also dont forget to wrap a lot of PTFE tape onto the radiator tail that goes into the radiator - first one i fitted i did not know this and it leaked and needed a lot of ptfe tape turns

 

[denso13]

My current pipe centres are 970mm, so a 900mm radiator width allows 35mm on either side and the valves will take some of this. How long is a standard radiator tail?

Standard are 40mm centres from the radiator to the pipe and 70mm out from the wall for a K2.

 

[terryplumb]

Your pipes are too close to the wall to allow any double panel radiator to be fitted without altering the pipework.

 

[Milleniumaire]

I have no idea what make the existing radiator is, probably a cheap trade model purchased by the builder/plumber, but based on the BTU ratings of a single panel radiator, anything would be better! I may not be able to be too selective as I'm probably limited to what will fit!

A couple of years ago I replaced a small toilet radiator, similar to the one I want to replace now, but much smaller. It took me a while to find something that would fit and in the end I installed a MHS Decoral aluminium radiator, which on paper had much higher BTU output. For a small downstairs toilet, it didn't really matter and it was likely that anything would be better than the original. Being aluminium, it does heat up very quickly, but also cools quickly!

I'm not really interested in "calculating" the BTU for the room. It's an office that I spend 8 hours a day working in, and has always been a cold room during the Winter months, so I also have a Dyson fan heater! Shouldn't be necessary if the original installer had sized the radiators correctly! Any gain in BTU is an advantage and if it end's up being too warm, which is unlikely, I can always turn the TRV down.

Most of the radiators in the house have TRV's and all are set on max and always have been!

 

[Milleniumaire]

Your pipes are too close to the wall to allow any double panel radiator to be fitted without altering the pipework.

Yes, I'm coming to that realisation (again). Thanks

 

[Milleniumaire]

i was talking about the caps that go onto the valve where the radiator tails fit on

have you checked the BTU on what size you need ?

i have fitted all 3 types in the house , based on size , BTU and matching existing pipework

look at the screwfix rads and download the instruction PDF - that provides all the dimensions of the different rad types T11, T21 & T22 - which i used when i fitted
T21 and T22 replacements

in fact i purchased from toolstation - trying to find the same info i used from their site

Also dont forget to wrap a lot of PTFE tape onto the radiator tail that goes into the radiator - first one i fitted i did not know this and it leaked and needed a lot of ptfe tape turns

Thanks for the feedback. I have replaced a few radiators around the house over the years so I'm familiar with fitting tails. For the last radiator I replaced, a couple of years ago, I used Loctite 55 thread wrap, which is much thicker than PTFE tape. Initially, I put too much on and couldn't tighten up the tails as much as I wanted to get the pipe centres correct! I prefer it because it doesn't compress/chew up as easily as PTFE tape.

 

[ericmark]

One would assume the system was designed rather than thrown together 27 years ago, so why is there now a problem? I had the same, and was considering a larger pair of radiators, but simply putting a thermostat in the cold room, so the boiler ran a little longer, cured the problem.

I will guess in my case, the increase in loft insulation, and upgrading of double glazing resulted in the room with thermostat cooling slower, so the boiler simply not running for long enough.

 

[Milleniumaire]

One would assume the system was designed rather than thrown together 27 years ago, so why is there now a problem? I had the same, and was considering a larger pair of radiators, but simply putting a thermostat in the cold room, so the boiler ran a little longer, cured the problem.

I will guess in my case, the increase in loft insulation, and upgrading of double glazing resulted in the room with thermostat cooling slower, so the boiler simply not running for long enough.

One would hope so, but I'm not so sure

The original Saunier Duval combi boiler was replaced around 15 years ago with a Vaillant system boiler and a large unvented cylinder. This system operates very differently to the old one and the Vaillant system does allow a heat curve to be defined and uses an outdoor thermostat for weather compensation. We've also added UFL in an extension and in the bathroom and a Low Loss Header, so yet more changes, but these have been in place for years now. I can't say any particular change has had an impact on certain rooms feeling colder in Winter.

It's very possible the heat curve setting was reduced at some time in an attempt to cut heating bills, but even in the evening when the house is toasty and the radiators are very hot, my office is still noticeably cooler than the rest of the house.

Maybe as I age I'm also feeling the cold more so it is becoming more noticeable.

The warmest room in the house, by far, is the kitchen/sitting/dining area, which has a solid floor with underfloor heating. The slab warms up in the morning and stays warm throughout the day.

There's a thermostat controlling the downstairs radiators in the hallway and this is the coldest part of the house, so is always the last area to get to the required temperature before the heat supply to the radiators is reduced.

A few years after we bought the house we extended into the loft, so the hall and landing became a much larger area, with the same single, but large radiator in the hall heating it. That's another radiator I keep thinking needs to be changed to heat the larger area.