Adiobatic

[scotsparky]

ok doing the adiobatic its a 5.21A fridge on a 10A mcb. selected 2.5mm cable4metre run in conduit on wal,l (method B)

Ze (DB0 is 0.103ohms and calculated Zs is 0.173ohms. Disconnection time on a BS60898 type c is 0.1 with this fault current.
after i have done the calk i am getting a size of 2.9mm so uprate to 4mm. this seems to big as its a 2.5 supply. am i missing something?

 

[Sintra]

With those figures i get the same result.

Using 143 as a value for k.

 

[Guest123]

If you cant get it to comply using If = Uo/Zs then use manufacturers I2T values. What make of MCB is it???


Just as an example for a 10A B type MEM manufacturers I2T = 21000A.

Using this figure gives a minimum CPC size of 1.26mm.

 

[WayneL]

Why are you doing this? - or am I missing something

 

[scotsparky]

It for the 2391-20 project so no manufacturer. they ask you to work out the minimum CPC size for 4 circuits in a kitchen (you choose all wiring details) its to check you can use the adiobatic. I just found it odd that its higher than tha live cable.

 

[Guest123]

A little tip for you on that particular question if you're using singles......you wont get it to work unless you use the manufacturers data. One of the lads is doing this now and he got proper stuck on this one.

Basically if you increase the cpc to allow for the result of the adiabatic then it throws your Zs out again so you have to recalculate it and it just keeps on going on and on. It's because the Ze is so low.

Also you can select a manufacturer as I'm sure one of the q's asks for the design and spec of all the main intake switchgear so just note that you've used manufacturers data

 

[WayneL]

Got it now

 

[scotsparky]

A little tip for you on that particular question if you're using singles......you wont get it to work unless you use the manufacturers data. One of the lads is doing this now and he got proper stuck on this one.

Basically if you increase the cpc to allow for the result of the adiabatic then it throws your Zs out again so you have to recalculate it and it just keeps on going on and on. It's because the Ze is so low.

Also you can select a manufacturer as I'm sure one of the q's asks for the design and spec of all the main intake switchgear so just note that you've used manufacturers data

I am using merlin Multi 9 and emails been sent to there tech squad

 

[mogga]

sparky when i di the Select Sqa the adeobatic equation was a bassa specialy when the turor said If you had uses Micc you wouldnt need to do the equation

 

[scotsparky]

Mogga i am doing the City and Guilds. The theory is straighforwrd but i was continnually getting an od result so asked here to double check. see the probs now and now know solution Simples!

 

[mogga]

where you doing it ? im looking at funding the chit side of things

 

[scotsparky]

Did the course at Stow college in Glasgow. Passed the written and just finnishing project. Thwe writen exam is a beuty! it you struggled on 2391-10 the you will love the 2391-20.
I have just had a look at the select courses and they dont seem to go into much detail.

 

[mogga]

yea the select course i did was the 16th edd one through the firm I worked for at the time seemed like an Easier option than CnG and firms dont seem to recognise it specialy english based firms its the fundings a bummer looked at cost of 500-750 for 2391 10 havent dared look at 2391 20 yet Good luck with it tho

 

[Guest123]

Try your local technical college.....my mate paid £270. I dont think it was much more than that when I did it.

 

[ringer]

If you cant get it to comply using If = Uo/Zs then use manufacturers I2T values. What make of MCB is it???


Just as an example for a 10A B type MEM manufacturers I2T = 21000A.

Using this figure gives a minimum CPC size of 1.26mm.

Where did you get the manufacturer's data from for this example Lenny?

I have downloaded the 'Eaton Modular Protection and Control Devices' pdf from their website,
Miniature Circuit Breakers - Product Guide (3.5 Mb) and can see a table in that, but do not see where you got the 21000A figure from. Can you describe where you get the figures from, or am I looking in the wrong document?

Am trying to calculate CPC size required for singles in conduit from a Eaton MBH120 with Zs of 0.24ohms on 230V nominal supply using k=143