Rad calc websites

[larkim]

Radiator sizing isn't something I do every day, so when I wanted to get one for the small bathroom ensuite I thought I'd find a straightforward online calculator which would help.

Well, I did. Several in fact. But they all seem to give wildly different results!!

e.g.

gives 1572 to 1966 e.g. give s 1361

Dimensons are 3m x 1.4m x 2.4m(h) room, double glazed, south facing, no fre nch windows (it's an ensuite!!!), 1 outside wall. On the radcalcs site I'v e used "lounge/dining room" as they don't include bathrooms in their calcs, and to be consistent done the same for the B&Q one (answer is the same if I choose bathroom anyway). The range on the radcalcs one is due to specify ing either wooden floor (which the room has) or solid floor (lower BTU), wh ich aren't specified fields on the B&Q one.

Of course, for the difference between a £25 rad and a £32 rad, its not a problem to over-specify, but just curious as to why they might be so wild ly different.

Matt

[Roger Mills]

Most of the on-line calculators make a lot of assumptions about things which you need to specify explicitly if you want an accurate result. They get different results because they make different assumptions!

There used to be one or two programs floating around from the likes of Barlo and Myson which enabled all the relevant parameters to be specified. I have used both in the past, put haven't needed to do any calcs for several years, and haven't got a copy on my current computer.

Maybe someone has?

[Dave Liquorice]

460 W or 576 W not that "wildly different". 500 W ball park and unless you really know the full construction of all the walls, floor and ceiling, windows, doors etc you are going to be making assumptions about the heat loss through them.

I'd go for somthing towards the top end of the range on the basis that if it's a bit oversize the room will just warm quicker before the TRV shut's it down. Rather than being undersize and stuggling to make the set temperature.

[Andrew Gabriel]

I still use a Myson one I downloaded over 10 years ago. It was in beta and seems to significantly over-estimate the power required, but better the devil you know. Also, it needs Java 1.3 and has to run on a case-insensitive filesystem, and is very flaky trying to run it on current systems.