Updating Radiators – help with BTU's

bpk101

I’m looking to update my radiator system, replacing the current panel style rads with traditional column style rads in all rooms except the bathroom and kitchen.
I wont really have a plumber on site until the rads are ready to install so I’d like to start shopping around now for best makes/models/prices and need advice on what size rads to look for and where to put them.

Here’s a site sketch of each room we’re updating, the pink areas mark where the current panel rads are situated:

http://bpkersey.com/images/Radiator.jpg

The house is a Victorian Mid-terrace in london with standard double glazing. Lounge is north facing, Dining Room south.
I’ve tried a few online BTU calculators but I’m not sure how accurate they are?? Any experts out there with some advice would be great.


ps: we currently have one very long rad in the hallway but none on the 1st floor landing… is this right?

pps: we're looking to have a log burning stove installed in the lounge later in the year. I've been advised though not to factor this into the radiator system as we still need a system that's fully efficient on it's own (for when stove is not in use). Is this right?

jhs14

I think they're generally accurate, but there's no harm in having more BTUs than you need, so I would oversize by at least 1000 BTU (for an average sized living room etc) just to be sure, it won't make a difference other than heat the room quicker. It won't make the room 'too hot' - that's what TRVs are for.

Furts

bpk101 wrote: »

The house is a Victorian Mid-terrace in london with standard double glazing. Lounge is north facing, Dining Room south.
I’ve tried a few online BTU calculators but I’m not sure how accurate they are?? Any experts out there with some advice would be great.

I am not an expert but will add three observations.Your mid terrace will receive shelter, and lack of exposure, from those each side. You may have shelter with the back garden, fence, out buildings and trees. You are in London where the climate is mild with the highest temperatures in the UK. I do not know if these points would be taken into account with a btu calculator.

Then there is the dual points of insulation and draught sealing. I say this because I have sealed my rooms and put in high levels of insulation. My btu requirement is around 33-50% of the calculations.

Plus my home is in an exposed location with minimal shelter. Hence one would expect my heat requirement to be greater than the btu calculation.

teneighty

I had to do some BTU calculations recently and the various free online calculators gave wildly varying results.

However this one gave results almost identical to the calculation the plumber did. http://www.diydoctor.org.uk/calculators/btu-calculator.htm

bpk101

teneighty wrote: »

http://www.diydoctor.org.uk/calculators/btu-calculator.htm

I'ved notice all these calculators say something like 'The calculator below is meant only as a guide'...

If the calculators are a guide, and the plumbers probably use the same calculators who do we turn to for accurate measurements i can use to base actual radiator purchases on?

jhs14

bpk101 wrote: »

I'ved notice all these calculators say something like 'The calculator below is meant only as a guide'...

If the calculators are a guide, and the plumbers probably use the same calculators who do we turn to for accurate measurements i can use to base actual radiator purchases on?

I suspect plumbers don't use them at all, and rely on experience to size radiators.

Just don't worry about getting it precise. Go to a few online calculators, stick your roomsize in. If they give wildly different results then tend towards the larger figures.

Some calcualtors let you put it lots of additional information - how many outside walls, wall construction, window sizes, whats above, whats below, how exposed the house is, etc etc.

Those calculators will be more accurate. The simpler ones will assume a lot of those considerations, giving a less accurate result.

But like I said, in any case, all it will give you is a figure of how many BTUs are required to heat the room. There's no harm at all in having more BTUs, so if you're worried, add a thousand or two BTUs to the result. It doesn't need to be accurate.

jhs14

Too few BTUs = the radiator will not heat the room

Too many BTUs = the room will heat up quicker

No downside to having too many BTUs!

bpk101

And does anyone know how to calculate the hallway, staircase and 1st floor landing? As one room or two?

The 2 x spaces interconnect (via staircase) meaning height is double in some areas. i can do that math to work out the overall volume of the 2 x spaces combined but should i be calculating this as one space?

There's currently no radiator on the 1st floor landing. But the largest radiator in the house is currently in the hallway... is this serving the landing too??

jhs14

bpk101 wrote: »

And does anyone know how to calculate the hallway, staircase and 1st floor landing? As one room or two?

The 2 x spaces interconnect (via staircase) meaning height is double in some areas. i can do that math to work out the overall volume of the 2 x spaces combined but should i be calculating this as one space?

Some BTU calculators let you vary the hight of the room - you could model it as a 5 metre high space. Try that, comapre it to the two rooms added together, and go with the higher figure.

There's currently no radiator on the 1st floor landing. But the largest radiator in the house is currently in the hallway... is this serving the landing too??

Yes. Heat rises.

jhs14

Are the current radiators sufficient? If so, then just replicate the BTUs - add a bit more to be on the safe side.

bpk101

jhs14 wrote: »

Are the current radiators sufficient? If so, then just replicate the BTUs - add a bit more to be on the safe side.

No idea... we've recently bought the place, have no record of the current radiator BTU's and don't currently live there (awaiting refurb) so haven't tested the system.