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Author Topic: Gas meters, KW or MJ supply rating  (Read 3697 times)

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Offline newguy

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Gas meters, KW or MJ supply rating
« on: November 08, 2012, 11:09:58 AM »
For some this might be a silly question but I have come across meters that don't display the KW or MJ rating. I know there is an equation to work out the KW from Cubic meters, can anyone help?   

Linkback: https://www.plumbers.co.nz/forum/gas-regulators-meters/69/gas-meters-kw-or-mj-supply-rating/1292/

Offline robbo

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Re: Gas meters, KW or MJ supply rating
« Reply #1 on: November 08, 2012, 05:10:48 PM »
hi guys, As far as i am aware a kWh is a unit of energy and a cubic meter is a unit of volume. They cannot be converted,but i could be wrong, cheers

Offline robbo

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Re: Gas meters, KW or MJ supply rating
« Reply #2 on: November 08, 2012, 05:37:00 PM »
hi guys, don`t know if this conversion chart will help,cheers

Offline newguy

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Re: Gas meters, KW or MJ supply rating
« Reply #3 on: November 08, 2012, 05:47:57 PM »
Thank you Robbo, very cool chart.

Am I reading it right

Capacity of 750 NZ meter @ 3 kPa gauge = 800 MJ/hr
Capacity ofAL 425 meter @ 3 kPa gauge - 1,500 MJ/hr

Is this what I should be looking at? I'm confused.

Offline peasea

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Re: Gas meters, KW or MJ supply rating
« Reply #4 on: November 08, 2012, 09:17:42 PM »
42 mj per cub metre ( nat gas ) , to get actual value thru meter multiply 101.5 (atmospheric pressure ) plus regulator pressure x 101.5   this is called meter factor , the retailer mutiplies the cubic meters consumed times the meter factor to get the true amount of gas used ,

Hope this makes sense ,

Going to be interesting how the retailer will charge when they dont have access to gas certificates showing working pressure , I believe they accessed these to determine the meter factor for their customers . It appears all the domestic regulators are standard set at 2.5kpa around wellington area now .

Had an installation recently with 7.5 kpa , bit of a cockup from the meter installer , it was only discovered because we installed a new gas heater , the neigbours were wondering if I was there to look for a gas leak , they had two rinnai infinities discharging towards there backyard , they never complained to anyone though , when we had the reg changed the gas smell went away.and the pilot light on the gas fire in the place stopped flaring like the Maui burn off chimney , this was operating like this for 2 years , I was able to check back online to see who had done the install , that option will soon be gone , I dont understand why they want to remove the online certs , in my opinion it will be a bad move , will have to wait and see   

Offline peasea

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Re: Gas meters, KW or MJ supply rating
« Reply #5 on: November 08, 2012, 09:45:08 PM »
just checked the chart ,  must be a misprint standard residential meter supplies 400mj an hour when you look at the numbers they dont add up

8 cubic meters   = 8x42 =336 mj or 93.3 kw

Offline peasea

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Re: Gas meters, KW or MJ supply rating
« Reply #6 on: November 08, 2012, 09:49:54 PM »
In my previous post I assumed we were talking natural gas , the chart does make sense with lpg

96 mj per cubic metre

its getting late I should be asleep

Offline Plumber

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Re: Gas meters, KW or MJ supply rating
« Reply #7 on: November 08, 2012, 11:20:45 PM »
Not sure if this is what you are after..

If you know what you KW rating your appliance has you can work out the gas usage like this:

V x H /T

V= Volume m3 (in Cubic/meters) H= 3600 in one hour (seconds) T= time of one revolution (in seconds) To be more accurate you can also multiply by pressure. Then you convert from cubic meters per hour to MJ/h by multiplying the answer by the heat value of that particular gas. You get MJ/h

Hope this helps.  :-\
 

Please note that the advice I am giving is only my opinion and not necessarily a fact.  Please refer to our terms and conditions.

Offline newguy

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Re: Gas meters, KW or MJ supply rating
« Reply #8 on: November 09, 2012, 08:33:38 AM »
Thanks for your help guys, great place to go to with things like this! Cheers

Offline newguy

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Re: Gas meters, KW or MJ supply rating
« Reply #9 on: November 16, 2012, 11:13:53 AM »
ha.. So easy 10m3/h = 100mj/h on Natural Gas  ;D


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