MCB type ratings (b,c,d)

[DanBrown]

Hi Guys,

I have just been on a call out to a ventillation fan within a kitchen sometime tripping out on startup.

Basically the fan runs at about 9 amp full on-load current, but the start-up it in the region of 100 amp. Could anyone tell me what rating the fan should be on, and what is if any the theory behind selecting the correct rating type of the mcb. It was on a type ''C'' 20amp that i thaught was adequate for that type of startup.

What is the theory behind selecting the correct rating....


Thanks

 

[alex]

if its tripping a "c" type try a "d" type thats for high start up current.

 

[Shakey]

Hi Guys,

I have just been on a call out to a ventillation fan within a kitchen sometime tripping out on startup.

Basically the fan runs at about 9 amp full on-load current, but the start-up it in the region of 100 amp. Could anyone tell me what rating the fan should be on, and what is if any the theory behind selecting the correct rating type of the mcb. It was on a type ''C'' 20amp that i thaught was adequate for that type of startup.

What is the theory behind selecting the correct rating....


Thanks

ok "In" is the MCB nominal rating (say it has a In of 10A)

Type B's have an instanteneous trip current of 3 to 5 times In (so 30-50A)

Type C's are 10 to 20 times (so 100-200 amps)

Type D's are 20-50 times (so 200-500amps)

think those are the values, dont have the OSG in front of me

 

[danzor]

think those are the values, dont have the OSG in front of me

you are the OSG Shakey!

 

[Spudmiester]

If it was on a type C already and has only started tripping it recently, sounds like the fan or cable could be faulty.

 

[ian.settle1]

ok "In" is the MCB nominal rating (say it has a In of 10A)

Type B's have an instanteneous trip current of 3 to 5 times In (so 30-50A)

Type C's are 10 to 20 times (so 100-200 amps)

Type D's are 20-50 times (so 200-500amps)

think those are the values, dont have the OSG in front of me

I thought it was

Type 'B' 3 to 5 times

Type 'C' 5 to 10 times

Type 'D' 10 to 20 times

Have just checked in OSG Page 51 and it is as I have posted.

 

[Shakey]

I thought it was

Type 'B' 3 to 5 times

Type 'C' 5 to 10 times

Type 'D' 10 to 20 times

Have just checked in OSG Page 51 and it is as I have posted.

I am not even going to check Ian, and the book is in front of me

I was 'off the cuff' when i wrote the figures down

thanks for the correction

 

[LukeScotty]

so whats your theory guys on the fan? faulty fan, or wrong mcb ?

 

[rumrunner]

hi
i would suspect the fan ,or at least where its air is coming from ,or going to ,i check everything else first ie ,loose connections,then"megger the motor", check the fan on the motor as well ,its probably clogged with grease,
good luck

 

[ian.settle1]

Check the trunking that the fan is in as if it has not been cleaned for ages it counld be that blades are jamming on the congealed grease which will be in the trunking with it being in the kitchen.