Radiator size calculator easy calculations

[wetdrip]

If you're looking for an easy rad size calculator.
Here's to links which do the calculations for you.
Hope this helps.

Heated Chrome Towel Rails, Designer Radiators, Bathroom, Cast Iron, Electric, Traditional


Or this:

http://www.homesupply.co.uk/radiator...calculator.php

 

[Worcester]

Neither link takes account of location parameters or flow temperature, might just as well use a finger in the air... So not compliant with CIBSE Guide A

If both companies continue to promote such practices, they will just compound the problem of poor design.

 

[Worcester]

It makes it worse that so many forum members tell clients not to cut corners, get a proper person in , and then those same people continue to use a tool like those above. Just shot themselves in the foot...

 

[SimonG]

It makes it worse that so many forum members tell clients not to cut corners, get a proper person in , and then those same people continue to use a tool like those above. Just shot themselves in the foot...

It's alright though as most forum members aren't mcs or linked to a quality management system and only have to answer to themselves and the ones paying the bill.

 

[Worcester]

It's alright though as most forum members aren't mcs or linked to a quality management system and only have to answer to themselves and the ones paying the bill.

LOL, That's precisely why it isn't alright ... I wonder how they sleep at night ? Do they actually understand the impact of their actions on the clients fuel bill?

 

[SimonG]

LOL, That's precisely why it isn't alright ... I wonder how they sleep at night ? Do they actually understand the impact of their actions on the clients fuel bill?

I do, that's why I keep it tight.

 

[SimonG]

and I sleep like a baby everynight

 

[AWheating]

It makes it worse that so many forum members tell clients not to cut corners, get a proper person in , and then those same people continue to use a tool like those above. Just shot themselves in the foot...

i think what alot of guys do is use such calculators for pricing up work and then will correctly calculate requirements if the job is won. As you know yourself it can take alot of time to design correctly, not worth spending a day in the books if you have not got the money coming in to pay for the time/labour.

also these calculators do normally state that they are a guide only.

 

[happyflyer]

Not sure this thread is going anywhere but look at it this way.


1) Put a radiator in a space that is too small and your dead.

2) Your under-size radiator may be OK when the OAT is say 5 deg C (5 is arbitrary) I just picked 5

2) Put a radiator in a space that is too big without proper control on it and you are definitely going to waste energy

3) If you size a radiator perfectly for an outside condition of say -2 Deg C when the OAT is 10 Deg C the radiator is oversize.

So what do you do???

You put proper control on each radiator and I don't mean bog standard TRV and you use a boiler with weather compensation.

Are you going to do all this, no.

And BTW, when you installed your system, new or retrofit did you make sure that the roof space has more than 50 mm of insulation and the house is properly draft proof, etc etc it's the whole package if you are going to start banging on about wasting energy, its not just radiators sizing, it's the big picture.

The problem is your plumbers, not environmentalists or members of Greenpeace

 

[wetdrip]

Neither link takes account of location parameters or flow temperature, might just as well use a finger in the air... So not compliant with CIBSE Guide A

If both companies continue to promote such practices, they will just compound the problem of poor design.

The links above are I.M.O. great little helpers for those wishing to do a quick estimate.
Plus I've factored in "Plumbers commonsense" an often overlooked attribute.
There's no such thing as the perfect calculation; that's why we have temperature controls/thermostats.

A little sprinkle of Plumbers Commonsense or +C:

• Outdoor temperature. The amount of heat lost from a building can depend on its location. During a typical winter in Poland, temperatures can range from -16°C on the coast to -24°C in the mountains. The lower the outdoor air temperature, the higher the heat loss is.
• Building location and wind conditions. Buildings situated in open space and in windy regions lose heat at a higher rate than identical buildings located in a settlement protected from extreme weather.
• Age of building. Modern buildings are usually better insulated than old, leaky buildings. They have a low rate of heat transfer and therefore need less heating to maintain a comfortable temperature.
• Windows and glazing. High quality windows reduced the rate of heat transfer and cut the costs of heating for the homeowner.
• Position of external walls. Rooms without any external walls will have a lower rate of heat transfer.
• Indoor temperature. The purposes for which the room is used should be considered – the higher the required temperature is, the larger the radiator should be.
• Heating parameters. In most cases heat loss figures are stated according to the industry standard EN442, i.e. water temperature, flow and return and the indoor temperature are calculated at the level of 75/65/20°C. If the installation operates within different parameters from the ones given or the indoor temperature is lower or higher than 20°C, correction factors must be used.

Wherever possible, radiators should be installed on the external wall under the window. This way, the cold air flowing in through the window is heated by the radiator and distributed evenly around the room. Also, using several small radiators in a large room rather than one bulky radiator will ensure better heat distribution. The physical size of a radiator is also important, so that the room looks well balanced. There is nothing worse than having a small but high output radiator placed against a large blank wall. In terms of room aesthetics, it is better to pick a larger dimensioned radiator with a lower output per square metre. If a radiator is to be covered; for example, by curtains, the radiator should be significantly bigger to account for reduced heat transfer.
In rooms with high air humidity, such as bathrooms and saunas, panel and decorative radiators should not be used unless adequate ventilation is present.

 

[happyflyer]

The links above are I.M.O. great little helpers for those wishing to do a quick estimate.
Plus I've factored in "Plumbers commonsense" an often overlooked attribute.
There's no such thing as the perfect calculation; that's why we have temperature controls/thermostats.

A little sprinkle of Plumbers Commonsense or +C:

• Outdoor temperature. The amount of heat lost from a building can depend on its location. During a typical winter in Poland, temperatures can range from -16°C on the coast to -24°C in the mountains. The lower the outdoor air temperature, the higher the heat loss is.
• Building location and wind conditions. Buildings situated in open space and in windy regions lose heat at a higher rate than identical buildings located in a settlement protected from extreme weather.
• Age of building. Modern buildings are usually better insulated than old, leaky buildings. They have a low rate of heat transfer and therefore need less heating to maintain a comfortable temperature.
• Windows and glazing. High quality windows reduced the rate of heat transfer and cut the costs of heating for the homeowner.
• Position of external walls. Rooms without any external walls will have a lower rate of heat transfer.
• Indoor temperature. The purposes for which the room is used should be considered – the higher the required temperature is, the larger the radiator should be.
• Heating parameters. In most cases heat loss figures are stated according to the industry standard EN442, i.e. water temperature, flow and return and the indoor temperature are calculated at the level of 75/65/20°C. If the installation operates within different parameters from the ones given or the indoor temperature is lower or higher than 20°C, correction factors must be used.

Wherever possible, radiators should be installed on the external wall under the window. This way, the cold air flowing in through the window is heated by the radiator and distributed evenly around the room. Also, using several small radiators in a large room rather than one bulky radiator will ensure better heat distribution. The physical size of a radiator is also important, so that the room looks well balanced. There is nothing worse than having a small but high output radiator placed against a large blank wall. In terms of room aesthetics, it is better to pick a larger dimensioned radiator with a lower output per square metre. If a radiator is to be covered; for example, by curtains, the radiator should be significantly bigger to account for reduced heat transfer.
In rooms with high air humidity, such as bathrooms and saunas, panel and decorative radiators should not be used unless adequate ventilation is present.

There's no such thing as the perfect calculation; that's why we have temperature controls/thermostats.

This line clears it all up

 

[Ray Stafford]

There's no such thing as the perfect calculation; that's why we have temperature controls/thermostats.

This line clears it all up

The controls and stats can help you get less out of an oversized emitter, but won't let you get more out of an undersized one.

Also, if occupants are too cold, they blame the installer.

If their energy bills are higher than they might be, they blame the energy company or the government.

Since steel panel radiators are so cheap, and oversizing carries only a tiny financial cost, almost all the incentives lead the installer towards oversizing.

 

[Masood]

The controls and stats can help you get less out of an oversized emitter, but won't let you get more out of an undersized one.

Also, if occupants are too cold, they blame the installer.

If their energy bills are higher than they might be, they blame the energy company or the government.

Since steel panel radiators are so cheap, and oversizing carries only a tiny financial cost, almost all the incentives lead the installer towards oversizing.

Spot on, Ray - I always err on the generous side when sizing rads and boilers. The customers can turn it down, but if it's on full and not warm enough it's me they'll be moaning to (and about!)

 

[Gas]

What i find funny is the people who are most vocal about always doing the calcs, are normally just desk jockey's with no real world experience at all, they fail to to see the irony that they are using someone else's calculations which themselves are based on averages, not on irrefutable fact.

 

[Ermintrude]

Every calculation and mathematical relationship mapping physical properties is an approximation and has a few conditions. The butterfly effect is the start , chaos theory.

 

[happyflyer]

What i find funny is the people who are most vocal about always doing the calcs, are normally just desk jockey's with no real world experience at all, they fail to to see the irony that they are using someone else's calculations which themselves are based on averages, not on irrefutable fact.

Hey Gas,

I don't think "U" values and thermal resistivity values that we use every day to work up heat loss calculations are derived from averages, they are derived from empirical calculation and actual tests, some now rather complex, we don't all use Fears Mear (not saying anything wrong with Fears Mear) I know most plumbers work to the nearest brick :chillpill: but you do need to try and get your heat loss calculation right and then the control of the emitter output to room temperature right also.

 

[Ermintrude]

Hey Gas,

I don't think "U" values and thermal resistivity values that we use every day to work up heat loss calculations are derived from averages, they are derived from empirical calculation and actual tests, some now rather complex, we don't all use Fears Mear (not saying anything wrong with Fears Mear) I know most plumbers work to the nearest brick :chillpill: but you do need to try and get your heat loss calculation right and then the control of the emitter output to room temperature right also.

U values are averages. Thermal resistance is a function of temperature. Conduction is normally used to calculate heat transfer, the boundary layer dynamics and inter median convection and radiant heat are ignored / amalgamated into u value. I thought that the Values were measured by BRE.

 

[happyflyer]

U values are averages. Thermal resistance is a function of temperature. Conduction is normally used to calculate heat transfer, the boundary layer dynamics and inter median convection and radiant heat are ignored / amalgamated into u value. I thought that the Values were measured by BRE.

What are "U" values of materials or structures or elements of structures an "average" of can you explain in more depth, tell us all how you think the "U" valve of a single skin of plain brickwork is derived, I am intrigued.

 

[SimonG]

U values are created by the r values, not forgetting the inner and outer layers of air. Long time since I looked at all this.

I'm sat in the living room at looking at the walls, to the front it's stone, don't know how thick, don't know if there's a cavity and don't know the material of the inner leaf in fact not even sure if the bay window has an inner leaf. Back wall is brick outside, cavity?, inner construction? Now other than cut a core through the wall to be able to measure and see what's what I would be 'approximating' the construction and therefore the heatlosses.

Even if you know the structure there will be varying densities to the stone, brick etc. I would imagine bricks densities would vary by batch and the stone being a natural product will vary greatly.

Yes you have to do some work on heat losses, but you also have to use common sense.

Another couple of months and this whole debate will rage again, it's one of those topics, just like to paste or not to paste.

 

[Ermintrude]

[DLMURL]http://eu.wiley.com/WileyCDA/WileyTitle/productCd-EHEP001604.html[/DLMURL]

It's a good book. Will upload an extract,

 

[happyflyer]

U values are created by the r values, not forgetting the inner and outer layers of air. Long time since I looked at all this.

I'm sat in the living room at looking at the walls, to the front it's stone, don't know how thick, don't know if there's a cavity and don't know the material of the inner leaf in fact not even sure if the bay window has an inner leaf. Back wall is brick outside, cavity?, inner construction? Now other than cut a core through the wall to be able to measure and see what's what I would be 'approximating' the construction and therefore the heatlosses.

Even if you know the structure there will be varying densities to the stone, brick etc. I would imagine bricks densities would vary by batch and the stone being a natural product will vary greatly.

Yes you have to do some work on heat losses, but you also have to use common sense.

Another couple of months and this whole debate will rage again, it's one of those topics, just like to paste or not to paste.

Simon,

It matter not, most of the heat losses in a building are via the ACR and not the structure, so 20% either way on the structural losses won't let you freeze to death and air is a known fixed value, unless someone knows different.

 

[happyflyer]

[DLMURL="http://eu.wiley.com/WileyCDA/WileyTitle/productCd-EHEP001604.html"]Wiley: Fundamentals of Heat and Mass Transfer, Sixth Edition - Frank P. Incropera, David P. DeWitt, Theodore L. Bergman, et al[/DLMURL]

It's a good book. Will upload an extract,

How much ££££ these are poor plumbers you are addressing not rich builders, 6th edition, hell must have been some mistakes in the first 5

 

[Ermintrude]

Think it's about £60 ish. Way past level of builders! This book is for taper and jointer and some high level fire stoppers.

 

[happyflyer]

Think it's about £60 ish. Way past level of builders! This book is for taper and jointer and some high level fire stoppers.

Erm,

If its now £60.00 it wasn't a best seller ever, not for us pond life, bottom feeders.

 

[Ermintrude]

It was a spesified book on my course, I paid £60 10 or so years ago

 

[wetdrip]

If off to my allotment to gather this mornings eggs and the last of this season's runner beans.

 

[happyflyer]

Nice one wetdrip, hope that's put an end to this thread, you haven't got a hen called Ermintrude have you

 

[Worcester]

Thanks for all the comments and replies. My initial comments were made deliberately to stimulate the debate and to try to make people aware of the limitations of each of their different approaches . - And each one has its problems, and not a single one is perfect.