Trainee gas questions in this thread ONLY please

[bassmonster]

what are you opinions about the flame picture here? is the orange caused by dust/dirt?

 

[Ermintrude]

Flame looks blue and radiants hot. On my phone. Normally dust results in soot. What was the bp ?

 

[bassmonster]

BP was 19mb. data badge states 19.25.

 

[erpkid]

Looks fine to me. If burning incorrectly the radiants get sooty.

 

[Ermintrude]

Just a wild card tip here lads and lasses. Keep your Facebook profile sensible. We just sacked a lad off( didn't even start his first day) as his Facebook was all about smoking weed and getting up to mischief. Sorry .

 

[kirkgas]

Just a wild card tip here lads and lasses. Keep your Facebook profile sensible. We just sacked a lad off( didn't even start his first day) as his Facebook was all about smoking weed and getting up to mischief. Sorry .

Have to say, schoolboy error in this day and age

 

[bassmonster]

another quick question.

just need some clarification please.

When pipe sizing, i know that you are allowed 1mb drop in pressure. Does this mean the drop is allowed per appliance. for example, 1mb drop on boiler, then another 1mb drop on hob or is the 1mb drop permissible as a whole? hope that makes sense....

 

[Ermintrude]

1mb across whole system. With every appliance running at full chugg.

 

[bassmonster]

1mb across whole system. With every appliance running at full chugg.

Thanks Ermintrude....

 

[Ch4 plumbing]

1mb across whole system. With every appliance running at full chugg.

That's including the misses too!!

 

[bassmonster]

hi all,
I've not logged in for a while..been really busy completing my portfolio which has now been finally signed off.

I'm just revising to sit my exams.

I've come across few questions on gas rate and heat input which has got my stumped...i just cannot seem get the correct answers. by using the method i've been taught to calculate.

any help in showing the calculations would be much appreciated so i know where i'm going wrong:

Assume the following specification for the questions which follow:Metric CVgross (nat.gas) = 38.76 MJ/m3
Imperial CVgross (nat.gas) = 1040 btu/ft3



The Index of a U16 meter is showing a reading of 60.00 then 2 minutes and 24 seconds later it is showing 60.18 during which time a large domestic boiler was operating. What is the heat Input of the boiler?


I. 4.85 kWnet.
II. 28.06 kW net.
ii. 43.65 kW net.
iv. 48.45 kW net.


A natural gas fire is operating at full rate and timed for a period of 2 minutes ans 3 seconds. The G4 meter index starts at 00001.230 and ends at 00001.249 during this period. What is the heat input of this appliance?



i. 3.268 kWnet
ii. 3.628 kWnet
iii. 5.394 kWnet
iv. 5.987 kWnet

The index of an E6 meter is showing a reading of 26942.987 and again 2 minutes and 5 seconds later during it's showing 26943.053 which time a combi boiler was operating on hot water. What is the heat input of the boiler?



i. 11.24 kW net.
ii. 12.48 kW net.
iii. 18.44 kW net.
iv. 20.4 7 kW net

 

[tamz]

Some combi that can burn 15.6384m²/hr ¿

 

[bassmonster]

ok, i've figured out the first 2...if anyone is interested, here's what i did:

0.18 x 3600 = 648
648 / 144 seconds = 4.5
4.5 x 38.76 = 174.42
174.42 / 3.6 = 48.45kw

0.019 x 3600 = 68.4
68.4 / 123 = 0.55
0.55 x 38.76 = 21.55
21.55 / 3.6 = 5.98kw


i'm still struggling with the last one through..........

 

[bassmonster]

Hey all,
I've got my exams in 2 weeks time.

i would appreciate any pointers as to what I can expect for the practical exam. what will i be expected to know and which tasks to carry out?

 

[Chris F]

Hey all,
I've got my exams in 2 weeks time.

i would appreciate any pointers as to what I can expect for the practical exam. what will i be expected to know and which tasks to carry out?

Tightness test, gas rating appliances, service a fire, fault find a cooker, fault find a section of pipework, vents and flues, name a load of controls on a board. Service a water heater errrrrrrr mm I'll think of some more

 

[Chris F]

The last question is 20.47 I think. I just work it out to 2 minutes and go a fraction higher courtesy of the mr combi gas rate app

 

[Ermintrude]

Read bs5440 and just know where to find stuff. Few questions of flues

 

[Ermintrude]

Will post some questions

 

[bassmonster]

Thank you Chris and Ermintrude.

Chris, i worked out the calculations for the last question:

The index of an E6 meter is showing a reading of 26942.987 and again 2 minutes and 5 seconds later during it's showing 26943.053 which time a combi boiler was operating on hot water. What is the heat input of the boiler?

26943.053 - 26942.987 = 0.066
0.066 x 3600 = 237.6

237.6 / 125 seconds = 1.9008

1.9008 x 38.76 = 73.675008

73.675008 / 3.6 = 20.46528

For any other trainees who are reading this, the values in red at constant...

 

[Chris F]

Thank you Chris and Ermintrude.

Chris, i worked out the calculations for the last question:

The index of an E6 meter is showing a reading of 26942.987 and again 2 minutes and 5 seconds later during it's showing 26943.053 which time a combi boiler was operating on hot water. What is the heat input of the boiler?

26943.053 - 26942.987 = 0.066
0.066 x 3600 = 237.6

237.6 / 125 seconds = 1.9008

1.9008 x 38.76 = 73.675008

73.675008 / 3.6 = 20.46528

For any other trainees who are reading this, the values in red at constant...

Well done mate

 

[Ermintrude]

 

[bassmonster]

Hello All,
another quickie..

I'm struggling a little with understanding downstream and upstream when it comes to placement of fans on boilers.

can someone please explain to a complete idiot which one if downstream/upstream from the image and why...






Also, when it comes to upstream of gas meter, does it this mean flow of gas before the meter or after..... :thinking:

 

[newcastle phill]

See it as the way a river flows.

Its the travel direction of the gas or gasses in this case
Up is where it's coming from.
Down is where its going.


Fans upstream of the heat exchanger will be positive pressure.
And downstream negative pressure.

Ultimately see upstream (oil/gas exploration) and downstream as consumer/end user

 

[newcastle phill]

In this order

Natural draught
Downstream
Upstream
Downstrean


In the diagram instances the reference is in relation to the position fan to the burner

 

[bassmonster]

Thanks Phill. I completely get this now. Cheers.