Gas rating

[Henchman76]

I am sorry as this has undoubtedly been asked before but can someone explain to me the quickest and most efficient means of gas rating an appliance when filling in the benchmark book at the end of an installation. I want to nail every aspect of this industry and do things properly. Sorry again if this sort of things annoys the verterans

 

[AllyBongo]

iPhone app

 

[GasmanxxxR1]

Set appliance into maximum operation

Time the dial on the gas meter for 2 mins
Make a note of how much gas was used in two mins, Times this figure by 3600, then divide by time passed in seconds (120) This will give you the meters cubed per hour figure. Toget the KW input gross figure times it by 10.76

 

[GasmanxxxR1]

eg
Gas meter at start is 1234.300
Gas meter after two mins is 1234.356
Gas passed equals 0.056

0.056 X 3600 = 201.6
201.6 divided by 120 seconds = 1.68m cubed/hr
1.68 X 10.76 = 18.07 KW heat input gross

 

[GasmanxxxR1]

This is for a metric meter
When my head stops spinning i will post an imperial one unless someone beats me to it

 

[BLOD]

Version I use is,
Gas passed through meter in 2 mins (eg 0.056) multiplied by 30 to get m3/h

 

[GQuigley67]

once you get your 2 minutes gas rate(0.056) times it by 321 to get KW(17.976) then times it again by 0.09 to get m3/hr(1.61)

although different answers it is still within tolerance and is a much quicker calcuation.

imperial you would divide 1098 by how long it took for 1 complete revolution(i.e 1098/56 = 19kw)

 

[baronwills]

Metric meter - Note amount of gas passed in 2 mins X 30 to give amount in m3/hr X 10.77 to give KW Gross. Divide by 1.11 to give KW Net.

Imperial meter - Time one revolution of the dial. 3600 (secs in an hour) divided by time of a revolution. Divide by 35.37 to convert to m3/hr. Multiply by 10.77 to give KW Gross. Divide by 1.11 to give KW Net.

 

[tamz]

There are many ways to calculate it and how accurate your answer will depend on the calorific value of the gas

For imperial, time the meter for one complete revolution of the dial then
3600÷time = ft³/hr x 0.0283 = m³/hr
eg
32 secs for 1 rev
3600÷32 = 112.5 ft³/hr x 0.0283 = 3.184 m³/hr

You may find these usefull too if you can't remember the sums

 

[royston]

Get a corgi slide rule from corgi direct.

 

[kirkgas]

eg
Gas meter at start is 1234.300
Gas meter after two mins is 1234.356
Gas passed equals 0.056

0.056 X 3600 = 201.6
201.6 divided by 120 seconds = 1.68m cubed/hr
1.68 X 10.76 = 18.07 KW heat input gross

using the above measured gas used in 2 mins multiply 0.056 x 321 to give you HI in Kw gives you 17.98Kw, which is close enough, unless you use the ACTUAL calorific value of the gas from the gas bill, this rule of thumb method id fine, if you need to do it on a U6 meter, time how many seconds it takes to burn 1ft3 of gas, then divide 1097 by the time taken, this will also give you the HI in Kw, eg it takes 64 secs to burn 1ft3, 1097/64=17.14Kw

 

[Henchman76]

Thanks chaps your help is greatly appreciated ! I am really graeful for your trusted opinions. Ill have a go at working it out now

 

[Deano202]

Hi sorry to but in but does anyone know the allowable tollerences when gas rating an appliance from what it should be to what it is doing surely you can't be expected to hit the mark all the time there must be a 5% or so diffrence I can't find it in my bpec gas book .

 

[kozak1968]

On vaillants the tolerance is + 5% or - 10%.