exam question

[ambrosia]

just doing an online mock exam for my gas safe exams, one of the questions was

You attend a property where the appliance shows only the heat input in btu's / hr. You have a metric meter. What formual will you use to confirm the correct heat input and is the reading on the data plate likely to be gross or net?

it then went on to say 1.3 m3 of gas was burnt in 2 min test

anybody know the formula to calculate kw/h to btu's

i tried;
30 x 1.3 x 10.7 / by 3412 to get btu's/hr, but it wasnt close to any of the answers

 

[psk]

hello ambrosia,

i came up with 47727 btu's

is that in any of ur answers

 

[kirkgas]

3412btu = 1kw,
so divide the HI from the data badge by 3412 to give you kw, then divide by 1.1 to give you kw net, tho old data badge will be gross if it doesnt say net, recheck the question cause it would be a big appliance that burns 1.3m3 in 2 mins, (more likely 1.3m3 in 1hr)
a quick calc for gas rate is gas used in 2mins x 321 = HI in Kw's
here is a link to a spreadsheet i have made up which gives you gas rate and HI by inputting either gas used in 2mins or time taken to burm 1ft3
https://spreadsheets.google.com/ccc...ZlNqSXB2QVdxb2RNa2t5VkE&hl=en&authkey=CI256Ww

 

[kirkgas]

just doing an online mock exam for my gas safe exams, one of the questions was



it then went on to say 1.3 m3 of gas was burnt in 2 min test

anybody know the formula to calculate kw/h to btu's

i tried;
30 x 1.3 x 10.7 / by 3412 to get btu's/hr, but it wasnt close to any of the answers

from your calculations you have a metric calculation then you have divided by 3412 to try to get BTU's. surely if you have a Kw answer you need to MULTIPLY by 3412 to get it to btu's
from your example i would say you have 419.64kw (or 1,431,811 btu's) so have a wee look at the question again!!!!!!!

 

[kirkgas]

hello ambrosia,

i came up with 47727 btu's

is that in any of ur answers

how did you get 47,727 btu's from 1.3m3 gas in 2 mins

 

[kirkgas]

just doing an online mock exam for my gas safe exams, one of the questions was



it then went on to say 1.3 m3 of gas was burnt in 2 min test

anybody know the formula to calculate kw/h to btu's

i tried;
30 x 1.3 x 10.7 / by 3412 to get btu's/hr, but it wasnt close to any of the answers

i have a few training tutorials that i have made up, PM me with youe email address and i will send them to you

 

[ranger1]

test drum capacity per revolution x 3600 = whatever divided by the seconds for 1 revolution of the test drum, gives you m3/h. m3/h x cv of gas divided by 3.6 gives you KW. btu/h = kw x 3412.
3600 seconds per 1 hr, 3412 is number of btu/h per 1 KW, CV of gas is 38.6 mj/m3, 3.6 is number of mj/h per 1 KW , hope that helps

 

[psk]

hi kirk,

i assumed the 1.3m3 per hr just as u said.

so i turned that into kws by multiplying by 10.76

i got 13.98kw gross as 10.76 is gross figure and i multiplied that by 3412 to get 47,727 btu

i just followed the logic manual on page b3 to get the conversion rates.

i might be wrong kirk so that was just my calc.

any suggestions on this calc?

thx

 

[kirkgas]

ah right, if you have assumed 1.3m3 per hr we are on the same wave length,everyone has their own way, and TBH im listening to the footy on the radio so i cant work yours out, haha
however even if we take gas used as 1.3m3 per hr
the rule of thumb method i have is gas used in 2mins x 321
so 1.3/30x321= 13.91kw, 13.91 seems a "real" answer, (to get this to btu's 13.91 x 3412 = 47,460) so close enough to yours due to slight variations in calculations

 

[ambrosia]

thanks guys i wasnt expecting so many answers so quickly

more likely 1.3m3 in 1hr

it probably was that makes more sense, i wrote it from memory

 

[safc]

Thought i would add my method:

1.3 divide by 0.0283 = 45.94 ft 3ph

45.94 x 1035 = 47,547.9 BTUs