LARGE house boiler sizing

[voivod]

Hi
Just started with a new firm...and they have decided that I am to size the boilers for the properties. Was not told this before I started and the old guy left.
I have boiler sized for years with mears then stars ...then the whole house method.BUT the next 2 properties are 50 kw and 150kw (original boiler sizes)
Question....how do you boiler size on OLD stone built properties of that size?
Have tried looking it up ...but seems whole house only goes upto 35kw? And most calculators dont do old houses?
thanks in advance
steve

 

[SafeGasInstall]

did you use this ?

Replacement Boiler Size Calculator

 

[voivod]

did you use this ?

Replacement Boiler Size Calculator

Hi Yup used that before but is only ment to be used upto 35kw?...or so I was told. And also doesnt have parameters for old type construction builds.

 

[DirksPlumbing]

Fairly easy, check the total output of the existing radiators, add a bit for the coil and and that is all the system can put out anyway. No need to fit 50kW if you only can loose 20odd kW.

Mind, you are wanting to calculate the boiler output. Do not compare the input values when you are going for a like for like replacement.

 

[SafeGasInstall]

here is a suggestion :

which boiler are you likely to install ? Call local rep and get them to do all the calculations . I know some one that has done many times , and keeps doing it this way for a light commercial and commercial, where boilers are over 100kw

 

[Reg Man]

Part L B Building Regulations, formulas.

 

[SafeGasInstall]

Do you have a link ?

 

[Gas]

You size it to meet the maximum load expected, what is there now is irrelevant as you can not do a size for size replacement anyway, so you need to employ a full design heat loss method.

 

[voivod]

have started working it out ...am on room 27 ....another 13 to go. (am also on tools so awkward to do it )
But seems its going for rhi or fits tarrif (not been officially told which yet ). so need whole house calculations for it .
Grr why didnt I just stay a plumber heating engineer and not specify stuff lol

 

[happyflyer]

Set yourself a spreadsheet up in Excel and have all the relevant "U" values down the side for cut and past
you can use the sheet over and over again, just change the values, it only takes minutes
to do a 20 rad job, different ACRs for each room can be set too, work out at the end of line
Watt/m2 for comparisons, this is what Excel is best at. Don't give up on it, this is another
string to your bow.

 

[voivod]

not going to give up lol....am doing it on the stars software just now.
Hoped there was an easier method ...like whole house method ...but for BIG houses . Cant find the relevant rhi or fits calculator for whole house. (guy who left got rid of anything I could reference of,,,grr)
Why do people live in huge mansions and estates...sure they would prefer a nice wee 3 bed semi detached

 

[AWheating]

just stick in a combi.

 

[stevetheplumber]

just stick in a combi.

not as mad as it sounds we did an arabs house in hampsted with 4 combis one for each bath room heating to surrounding rooms not my idea i hasten to add

 

[AWheating]

not as mad as it sounds we did an arabs house in hampsted with 4 combis one for each bath room heating to surrounding rooms not my idea i hasten to add

It usually goes like.......... "you have 3 bathrooms, a combi wont cope, you need an unvented cylinder"............... "what about 2 combis?"

 

[Ermintrude]

Some gas meter and carcas? Did an bloke from east and he had multi point heater!!

 

[voivod]

combis on a 151kw system....might need 1 or 2 lol

 

[WHPES]

Use this version:

www.energysavingtrust.org.uk/content/download/2654/62295/version/

 

[doitmyself]

Use this version:

www.energysavingtrust.org.uk/content/download/2654/62295/version/

But it says, on the first page:

"This method should not be used for a typical, very large, or unusually shaped dwellings, where more detailed methods should be used."

 

[voivod]

aarrgggh....think will just tell him am only doing wee hooses frae now on

 

[Wet dream]

Measure square meter of each floor add them together and for a older property allow 50 watts per square meter. You want be far off.

 

[happyflyer]

Measure square meter of each floor add them together and for a older property allow 50 watts per square meter. You want be far off.

WD, are you sure 50w/m/2 sounds a bit on the low side to me for an old house???

 

[Ermintrude]

Work on ufh producing 125 w/m2 for anything before 1980

 

[albatross]

I use 40 watts per CUBIC meter, more accurate if you have high ceilings.

 

[Ermintrude]

Got an excel sheet to do it properly, taking into account internal external walls internal external ceilings. 40w per cube is no good in north facing room with 26m2 of single glazing!