What BTU/Wattage for a vertical rad?

andybookie

I am looking to purchase a vertical rad for my kitchen (measurements and details below).

I have had differing options in terms of necessary output.
Every online calculator is suggesting a BTU of around 2500.
A plumber friend said similar 2500 to 3000 (you'd want to go more than go less, so closer to 3000)
Brooks suggested 7000.
Our plumber suggested around 2000 watts which is around 6800 BTU.
But also he suggested a particular Quinn radiator which I looked up was only 1180 watts or 4000 BTU.

So my recommendations vary from 2500, 3000, 4000 and up to 7000 BTU.
I'm totally confused.

What are your guys' thoughts?

Thanks

Kitchen: 3.8m x 3.1m x 2.4m
Above: Heated room
Below: Concrete
Windows: Double glazed (new)
Windown area: 2.65m2 (window and french doors)
Outside walls: 2

andybookie

Just now my plumber has said, take the cubic metres of the room and give it 100 watts per m2.
So that's 28m2 which is 2800 watts or 9500 BTU.

So now my plumber has separately recommended 4000, 7000 and now 9500.
My plumber friend 3000.

I am in a bind and have no idea what to do.

metricspaces

I've recently looked at this myself and I feel your pain. It doesn't seem like the "experts" have any universally agreed calculation for BTU.

You can think about it another way though if you are replacing a radiator. Are you happy with the current output of your existing radiator? If yes, then find out the BTU of this radiator and just get a new radiator that can match this BTU.

Keep in mind too that different manufacturers display BTU values at different temperatures - so make sure you are comparing like with like. See here https://www.onlyradiators.co.uk/blog/radiator-delta-ratings-explained/

Your plumber who said "100 watts per m2" is basically picking an number out of the air in fairness. It is really dependent on your heating system and your house. The online calculators you see try to take into account the latter - they factor in windows, insulation etc.

andybookie

That's actually really useful.
Thanks.

andybookie

metricspaces wrote: »

You can think about it another way though if you are replacing a radiator. Are you happy with the current output of your existing radiator? If yes, then find out the BTU of this radiator and just get a new radiator that can match this BTU.

This is a great suggestion.
It is probably something like this. The look and the measurements are similar.
https://www.wickes.co.uk/Wickes-Type-22-Double-Panel-Premium-Universal-Radiator---White-600-x-1200-mm/p/201486

metricspaces

One other thing. It would be wise to err on the side of caution i.e. it will do no harm to go higher in BTU. You can always put a TRV on it to reduce down the heat output. Personally I would put a TRV on it anyhow.

If you ended up with a rad where the BTU was too low then you are out a massive amount of money to address the problem - two radiators and two plumber fees. Compare that cost to going for a slightly higher BTU.

andybookie

The site does state it conforms with EN-442 EEC legislation, but doesn't mention the year of 2013, it's bestheating.co.uk

Should I be fine with these guys?

Andy

andybookie

I see they have separate BTU's for each level.
Their default is T65, so thanks for the heads up.
I would have been over-estimating the BTU by about 25%.

Thanks again.

andybookie

This is my old boiler. Does anyone know whether this is T30, T50 or T65 as I know this would then make a difference in what output I need to align to.
Thanks.

metricspaces

If you find out the BTU of current radiator at specified T value, then you don't need to know the T value of boiler. You can simply buy your new rad to match the spec of the old rad.

The BTU values in relation to T values are all relative as I understand. So if your old rad says 1000 BTU at T30 and your new rad as same, then they will both have same BTU at every T value.

andybookie

metricspaces wrote: »

If you find out the BTU of current radiator at specified T value, then you don't need to know the T value of boiler. You can simply buy your new rad to match the spec of the old rad.

The BTU values in relation to T values are all relative as I understand. So if your old rad says 1000 BTU at T30 and your new rad as same, then they will both have same BTU at every T value.

But I don't know the BTU of my old rad, that's the point.

metricspaces

andybookie wrote: »

But I don't know the BTU of my old rad, that's the point.

Is there any markings on it to tell what make it is? Mine have the make on the plastic cap that is on the valve. If you find the make then hopefully you can find the rad online.

If you can't find the make just get the dimensions. Get the type (https://www.victorianplumbing.co.uk/bathroom-ideas-and-inspiration/difference-between-type-21-and-type-22-radiators). Then find as many rads online that match this spec. Get all the BTU values. Then you could take the max to be safe? Or take the average and add some % for safety.

andybookie

metricspaces wrote: »

Is there any markings on it to tell what make it is? Mine have the make on the plastic cap that is on the valve. If you find the make then hopefully you can find the rad online.

If you can't find the make just get the dimensions. Get the type (https://www.victorianplumbing.co.uk/bathroom-ideas-and-inspiration/difference-between-type-21-and-type-22-radiators). Then find as many rads online that match this spec. Get all the BTU values. Then you could take the max to be safe? Or take the average and add some % for safety.

No, no markings.
I would have thought that it might be possible to see from the attachments that T number (which I believe is the max temperature the boiler can get to)

Can anyone deduce what it is?

Thanks

metricspaces

andybookie wrote: »

No, no markings.
I would have thought that it might be possible to see from the attachments that T number (which I believe is the max temperature the boiler can get to)

Can anyone deduce what it is?

Thanks

If you look at my thread I think someone mentions how it's not that easy to know what the T value is.

Have you looked at various rads that match your size and what BTU they have? There might not be that much variance.

andybookie

metricspaces wrote: »

If you look at my thread I think someone mentions how it's not that easy to know what the T value is.

Have you looked at various rads that match your size and what BTU they have? There might not be that much variance.

Hi
I read your thread and no one mentions about how to figure if T50 or T60.
The reason I don't want to go by my current radiator is that I am not confident it is the correct BTU for the room.
The only piece of the jigsaw I am missing is knowing what T my boiler is.

Wearb

andybookie wrote: »

Hi
I read your thread and no one mentions about how to figure if T50 or T60.
The reason I don't want to go by my current radiator is that I am not confident it is the correct BTU for the room.
The only piece of the jigsaw I am missing is knowing what T my boiler is.

The Delta T is decided at the design time of the installation and its a complicated procedure involving flow rates, pipe sizes, heat source, heat loss etc.. I know a lot use a rule of thumb, but that wouldn't help you to decide.

The best way -as I think has already been said- for you is to do a heat loss calculation on a room that you find is being heated satisfactorily and compare that rad to some rad charts. Simpler ways have also been suggested.

andybookie

Wearb wrote: »

The Delta T is decided at the design time of the installation and its a complicated procedure involving flow rates, pipe sizes, heat source, heat loss etc.. I know a lot use a rule of thumb, but that wouldn't help you to decide.

The best way -as I think has already been said- for you is to do a heat loss calculation on a room that you find is being heated satisfactorily and compare that rad to some rad charts. Simpler ways have also been suggested.

When you say a heat loss calculation, do you mean a BTU calculation as I have performed those, but when it comes to buying a rad they have different BTU's per radiator depending on the Delta T rating. Hence, I'm in the same predicament.

Wearb

andybookie wrote: »

When you say a heat loss calculation, do you mean a BTU calculation as I have performed those, but when it comes to buying a rad they have different BTU's per radiator depending on the Delta T rating. Hence, I'm in the same predicament.

For the room heating satisfactorily; supposing the heat loss calculator suggested 3kw. Check what delta t would be required from that existing rad to give 3kw output. Note: if any insulation improvements have been made, they will throw that calculation off unless adjusted.

metricspaces

andybookie wrote: »

Hi
The reason I don't want to go by my current radiator is that I am not confident it is the correct BTU for the room.

What makes you think this?

andybookie

Heat lost calculator show BTU's 2279 Watts 668
I don't know how to calculate what delta t would be required from that existing rad to give 3kw output?