CHECKING GAS RATES AND HEAT INPUTS (M3)
NATURAL GAS
Where the gas meter records the gas consumption in cubic metres the following procedure should be used.
Gas Rate Procedure Meter Measuring in m3
The following procedure is just one method of calculating gas rate: –
- Turn all the appliances OFF.
- Record the meter reading. (example shows a reading of 00048.104m3)
- Turn the appliance under test to FULL ON.
- At the same time as turning the appliance on start recording the time
- When exactly two minutes have elapsed record the meter reading. (example shows a reading of 00048.188m3)
- Subtract the first reading from the second reading. This will give you the volume of gas passed in m3.
Gas rate over two minutes: –
| = | 48.188 |
| -48.104 | |
| = | 00.084 m3 |
Therefore the Gas Rate over 1 minute
| = | 00.084 m3 ÷ 2 |
| = | 0.042m3 |
So to calculate the hourly consumption, the gas rate for 1 minute is multiplied by the number of minutes in an hour.
Therefore Gas Rate/hour
| = | 0.042 x 60 |
| = | 2.52m3/hr |
We can convert this figure to cubic feet by multiplying the figure by 35.37.
Therefore 2.52 x 35.37 = 89.1324ft3/hr
Gross Heat Input = 89.1324 x 1040 = 92697 Btu/hr (27.16 KW)
To assist in the process, the chart below has been configured to provide an easy reference. It is based on a GROSS CV of 38.79MJ/m3 (1040 Btu/ft3). So in our example over a two minute period 0.084m3 is used, look at the table below for 0.080 = 2.40 m3/hr (25.8KW) and 0.004 = 0.12m3/hr (1.3KW). Add the two together 2.40 + 0.12 = 2.52m3/hr and a gross input of
25.8 + 1.3 = 27.1KW
|
GAS USED in 2 Minutes |
HOURLY RATE EQUIVALENT |
EQUIVALENT HEAT INPUT |
||
|
M3 |
M3 |
Ft3 |
kW |
Btu/hr |
|
0.001 |
0.03 |
1.06 |
0.3 |
1100 |
|
0.002 |
0.06 |
2.12 |
0.6 |
2200 |
|
0.003 |
0.09 |
3.18 |
1.0 |
3300 |
|
0.004 |
0.12 |
4.24 |
1.3 |
4400 |
|
0.005 |
0.15 |
5.31 |
1.6 |
5500 |
|
0.006 |
0.18 |
6.37 |
1.9 |
6600 |
|
0.007 |
0.21 |
7.43 |
2.3 |
7700 |
|
0.008 |
0.24 |
8.49 |
2.6 |
8800 |
|
0.009 |
0.27 |
9.55 |
2.9 |
9900 |
|
0.010 |
0.30 |
10.61 |
3.2 |
11000 |
|
0.020 |
0.60 |
21.22 |
6.4 |
22000 |
|
0.030 |
0.90 |
31.83 |
9.7 |
33000 |
|
0.040 |
1.20 |
42.44 |
12.9 |
44000 |
|
0.050 |
1.50 |
53.06 |
16.1 |
55000 |
|
0.060 |
1.80 |
63.67 |
19.3 |
65900 |
|
0.070 |
2.10 |
74.28 |
22.5 |
76900 |
|
0.080 |
2.40 |
84.89 |
25.8 |
87900 |
|
0.090 |
2.70 |
95.50 |
29.0 |
98900 |
|
0.100 |
3.00 |
106.11 |
32.3 |
109800 |
|
0.200 |
6.00 |
212.22 |
64.4 |
219700 |
Note: – Essex Heating Services accepts no liability for the accuracy of this table and the figures that it contains. You should check the data before using it to carry out any adjustments. (Please refer to the Gas Regulations before implementation – this is your responsibility).
nice explanation and its very detailed with graphs on it.. thank you, i like your post!
Thank you for your comment. I have been away for a little while due to the volume of work etc. I will be making a few more posts.
Regards
Well done Essex Heating on your technical data.
Regards
Alan Thomas Corgi registered commercial gas engineer ( RETIRED)
Hi Alan,
Thank you for your comment. Are there any other subjects that you feel could be added to the Blog for discussion?
How would you do it with other meters i.e the U6 or the E6,
The easiest way to Gas Rate would be to turn on the boiler and either run the hot water or central heating. Go to the Gas Meter and note the reading. Time the gas usage for 2 mins and then take a note of the reading. Take the first reading from the second and look this number up on a Gas Rating Table (these are easily available from most plumbers merchants). Just be careful to make sure that you apply the correct size to the table you are using – Cubic Metres to the Cubic Metres table – I hope this helps/
I enjoyed your comments and I thought your description were helpful
Take the first reading then after 2 min at full rate take second reading. Take the first reading from the second and then multiply by 321 gives you kw
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Thanks. Shortly coming up for my re-assessment. Have always had problems remembering the correct calculation procedure. The chart always comes in very handy,as generally the tutors don,t mind an open book,then I keep the chart beside me. thanks again. hopefully only 2 more re-assessments before i can give it up,that Is unless I win the lottery..
how do you gas rate a old u6 meter anybody
Please forward your questions to
essexheatingservices@gmail.com
Regards
Thanks for free tips. Very helpfull to me. Great work.
Just wanted to add my thoughts on the calculation and ease of remembering.
Gross Heat Input = 89.1324 x 1040 = 92697 Btu/hr
divide by 3412 gives you kW from Btu
=92697/3412 =27.168kW
“jasone on September 17th, 2011 8:00 pm”
Take the first reading then after 2 min at full rate take second reading. Take the first reading from the second and then multiply by 321 gives you kw
Gives a value of 26.96kW
This is a difference of 0.208kW from the Btu to kW conversion; which as a percentage error is 0.208/27.168 8100 = 0.76% less than 1% error of the actual conversion which in the scheme of things is negligible.
Jasone has the simplest method to remember for heat input conversion with a less than 1% error.
BTW, it is kW not KW 🙂 great article, thank you!
Thanks Julian, very interesting.
it is funny how we all have different methods. I time for 2 minutes then multiply the result be 30. I then times that figure by 10.65 to get the gross heat input. If I want the net I divide the gross figure by 1.11
I got more easy way to do gas rating check this out:
•Turn all the appliances OFF.
•Record the meter reading. (example shows a reading of 00048.104m3)
•Turn the appliance under test to FULL ON.
•At the same time as turning the appliance on start recording the time
•When exactly two minutes have elapsed record the meter reading. (example shows a reading of 00048.188m3)
•Subtract the first reading from the second reading. This will give you the volume of gas passed in m3.
Gas rate over two minutes: –
= 48.188
-48.104
= 00.084 m3
gas rate formula for metric meter with digital display:
=2 minute reading*30*10.76
=2*00.084*30*10.76
=27.125
Thank you Sanjiv. Its interesting to see the different ways to check Gas Rates and Heat Inputs.
don’t forget kW
Could you kindly ask the forum if anyone has a definitive means of gas rating where a “liberty ” gas meter is installed.
Well done man your very good
I use this method
A = first reading
B = reading after 2 minutes.
B-A
X 30 = m3/hrs
X 10.71 = Gross
÷1.11 = nett
Hope this helps someone 🙂
Thanks I think it’s best way to explains thank you very much
Hi all not sure if this blog is still up and running but I’ve got my first gas safe inspection coming up and would like to know what I might be in for !! Any comments that might be of use ?