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Checking Gas Rates and Heat Inputs – Natural Gas

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).

25 thoughts on “Checking Gas Rates and Heat Inputs – Natural Gas”

    1. 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

    1. 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/

  1. 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

  2. Magnificent goods from you, man. I have understand your stuff previous to and you’re just extremely wonderful. I actually like what you’ve acquired here, certainly like what you are saying and the way in which you say it. You make it enjoyable and you still care for to keep it wise. I can not wait to read much more from you. This is actually a terrific site.

  3. 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..

  4. 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!

  5. 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

  6. 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

  7. 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 🙂

  8. 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 ?

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