CCN1.....ACS...

[Gastel]

Ive just passed my theory for CCN1 & passed most of my practical bar safety control devices which I must say was the hardest part of the course, I now have to re-sit it next week along with my Appliances & Im bloody petrified as theirs alot riding on this for me.....not least im paying for it meself, when I came to the rig (S.Controls) I managed to identify most of the controls but when it came to Identifying faults,correcting them & checking pressures/FSD I fell to pieces.....arrggh, has anyone got any tips,diagrams or anything for me to study which would help me confidence?

Cheers in advance,

PS How did people find the Appliances assesments, Im down for Cen1,CKR1,HTR1 & Wat1

 

[ChrisR]

Which "body" are you using - CITB, BPEC, ...?
You presumably have a book with all the stuff in about how the devices work?
Do you understand it?
When you say "find faults" do you mean on the Controls? Usually it would be fairly obvious, like a sensing electrode with a bit of wire tied across it.

I think it's all very simple but then I would - I teach and assess ACS! A lot of people are scared by it, and panic. The solution is to think how each device works (it's Open Book, you can look it up), and think what would STOP it working.

If they ask how you would test a device, the answer is always the same - simulate the fault. For an air pressure switch for example, you don't go pulling pipes off it, you STOP THE FAN!

SOme centres are more strict than others. Had a guy who had been working on Keston boilers for 10 years, thought he was god's gift. But he hadn't a clue how a thermocouple worked, he never sees them day to day. Sent him back to his books, with his tail between his legs! AFter he'd read it up he understood, and all was ok.

 

[Gastel]

Thanks for replying chris, its CITB......I do have the books & ive read & read, the problem is part panic which I can't help.......And I must admit I cant seem to remember how they friggin work in sequence come assessment time, I was hoping somebody could send me some more detailed diagrams of how these FSD/safety controls work.......so as I could really drum it in this weekend, I wouldn't like to go thru this again as ive found it pretty stressful!

 

[gas4you]

I wouldn't like to go thru this again as ive found it pretty stressful!

What are you going to do in 5 years time then

 

[Gastel]

This is initial i'm doing, re-assessment is alot less......& 5 yrs is a bit off anyway)

 

[ChrisR]

Are you looking too deeply?
Nobody will expect you to know what all the springs and bits of rubber in a MFC are for.
Do you know, though, how to test for working pressure and burner pressure , and adjust bp, and adjust the pilot, and which bit the solenoid is?

What happens if a precision pilot gets vitiated - and what does that mean?How could that happen anyway - 2 ways...

How is a thermocouple used? How would you test it? How could you test a new one if you'd just taken it out of tthe packet, before fitting it?

One you need to be sure about is the controls used on an oven. What's the bypass for...

What does a zero governor do - again, no need to draw the internals of the thing.

What might a liquid expansion device do?


Well that's most of it covered!

This is initial i'm doing, re-assessment is alot less

Oh no it isn't. Same stuff, less time, and you're expected to get it straight away!

 

[pannierstan]

I always used to love asking engineers to explain the difference between Vapour pressure and a Liquid Expansion and how to identify each.

Bring back Bi-mettalic strips that what I say. Serviced a Minerva the other day. Flippin great....took me 2 hrs almost.

Stan

 

[Gastel]

Are you looking too deeply?

Dont think so

Do you know, though, how to test for working pressure and burner pressure , and adjust bp, and adjust the pilot, and which bit the solenoid is?

Yes, the main functions on an MFC are main gas cock,solenoid,governor and FSD.......working pressure is taken from meter, burner pressure & gas (working) inlet pressure is taken from P1 P2 test points on gas valve,pilot is adjusted with small screw on gas valve??

What happens if a precision pilot gets vitiated - and what does that mean?How could that happen anyway - 2 ways...

Isn't that the ODS device......which causes the flame to lift of if theres a problem, therefore cooling the thermocouple which then closes gas valve, lack of oxygen or blockage of aireation tube would cause this wouldn't it?

A thermocouple basically sends a small voltage thru 2 dissimalar metals which then hold open a electro magnet valve,right?

There are 2 bypasses on an oven, one on the thermostatic exp valve & 1 on the FSD, once the thermostat has heated sufficiently the gas is passed thru to burner on bypass rate which basically is the lowest rate to maintain flame/burner,when stat cools full gas rate is passed thru burner again & then so on....

A zero governor - fan comes on,solenoid opens gas valve....air blast draws diaphram down causing valve to lift of seating.....gas flows thru,fan switched off, tension spring pulls valve closed.

What do you think of my answers chris, would you pass them?

My assessors told me the initial is longer than the re-assesments??

 

[chrishutt]

Gastel, your post would be clearer if you used the Quote function. Go back to the post, click on the edit tab (top right corner), then you will see a series of blue boxes along the top, starting with B , then i, etc. There is a Quote box. Highlight (left click on mouse) the sections of your post which are quotes from ChrisR, then click on the Quote tab,

so you get something like this

 

[Gastel]

Sorted now

 

[ChrisR]

Nearly there - this isn't quite right, have another go:

There are 2 bypasses on an oven, one on the thermostatic exp valve & 1 on the FSD, once the thermostat has heated sufficiently the gas is passed thru to burner on bypass rate which basically is the lowest rate to maintain flame/burner,when stat cools full gas rate is passed thru burner again & then so on....

How do you adjust bp on a typical mfc?
What might a liquid expansion device do?
And Stan's question?


From the Standards (no MI):
A room has two 7kW radiant gas fires in it. Do you need a vent?

A room has two DFE's in it. What vent does that need?

Have you done the flues bit of the practical yet?
Tightness & gas rates?

The reassessment has fewer multi choice, but a lot less time to do the rest in.

 

[Gastel]

How do you adjust bp on a typical mfc?
What might a liquid expansion device do?
And Stan's question?

Bp is adjusted by the screw on the regulator?
Liquid exp device works on the principle of heat & expansion of liquid to open/close bellows on a safety device?
Vapour differs from liquid exp in that when the liquid reaches boiling point in the phial it vapourises causing rapid volume increase pressure?

Can you enlighten me on the works of the oven thermostats/fsd & bypass from your point of view.......I don't want to look at books just now, i'd rather get my own perception of how they work.

A room has two 7kW radiant gas fires in it. Do you need a vent?

Yes, 7kw = adventitious air for 1 vent.......7x5=35cm for the other

A room has two DFE's in it. What vent does that need?

235cm?

Done the flues & Tightness

Cheers again chris.

 

[EliteHeat]

235cm?

Two radiant fires plus two DFEs? - that room clearly has no ceiling or roof, therefore no ventilation required

 

[ChrisR]

Bp is adjusted by the screw on the regulator?

Which screw?

Liquid exp device works on the principle of heat & expansion of liquid to open/close bellows on a safety device?

Bellows for what? What else might it do?

Vapour differs from liquid exp in that when the liquid reaches boiling point in the phial it vapourises causing rapid volume increase pressure?

So, why would that be used instead of the Liquid one?

Can you enlighten me on the works of the oven thermostats/fsd & bypass from your point of view.......I don't want to look at books just now, i'd rather get my own perception of how they work.

It isn't MY perception, matey, you got it wrong! If I tell you the answer it's tha same as you having it in a book. As you say, get it clear in your head.
Every day we get several conversations like:
Assessor "Not really right, think about it and explain it again, step by step"
Assessee changes it a bit, thinks a bit , and we go round the loop a few times.
Assessee says "That's what I said!"
Me "no you didn't"
A "Well it's what I meant"
Me "Oh I thought you meant what you said..."!

Some centres, I gather, just say "Wrong", and are a bit quick to show you the door.

Yes you got the vents ok. I was probing a bit because when I was first taught, there was a load of doubt about knocked through lounges, and whether they should have 2 x 7kW adventitious allowed. It seems that has gone. Just as well with all the sealed rooms we live in now!

 

[Gastel]

Which screw?

Take screw cap of first,then adjust BP screw accordingly.

Bellows for what? What else might it do?

For controlling gas flow......they also work for controlling thermostat temp.

So, why would that be used instead of the Liquid one?

It works alot quicker,also vapour can be used to open & close electrical contacts using a microswitch.

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