Manhole Size

[Sajid khan]

I am working on a project in which i have to run 4 MV feeders
4X( 3X1C-240 sq mm) unarmoured Aluminum cable in 6 Inch Dia conduit.
The overall dia of one aluminum cable as i get from cable table is 35 mm dia.
The conduits will b burried 2ft Below grade.

How would i calculate the manhole size..

If some one can show the calculation work, it will really be helpful.

Regards.

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[Sajid khan]

I am working on a project in which i have to run 4 MV feeders
4X( 3X1C-240 sq mm) unarmoured Aluminum cable in 6 Inch Dia conduit.
The overall dia of one aluminum cable as i get from cable table is 35 mm dia.
The conduits will b burried 2ft Below grade.

How would i calculate the manhole size..

If some one can show the calculation work, it will really be helpful.

Regards.

Sent from my GT-I9300I using Tapatalk

4 MV feeder ( 12 Nos 240 Sq
mm Al conductor) in 4 Nos 6 inch Dia conduit.

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[Julius Right]

If you need the duct bank size it is one question. However, the manhole dimensions depend less on the duct bank size but more on the ergometric arrangement.

 

[RumRunner]

4 MV feeder ( 12 Nos 240 Sq
mm Al conductor) in 4 Nos 6 inch Dia conduit.

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Since this pertains mostly to poco, the info you need is beyond the scope of this site.


Try this, you might find this helpful:


https://www.scribd.com/document/224484020/Electrical-Manhole-and-Handhole-Design-Guide

 

[Sajid khan]

I need manhole size..

If you need the duct bank size it is one question. However, the manhole dimensions depend less on the duct bank size but more on the ergometric arrangement.

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[Julius Right]

One duct of 6" can accommodate 2 feeders so you'll need 2 ducts.
The minimum ductbank dimensions will be 550 *300 mm. and
the dimensions of the manhole will be 1.5m at the input of the cables and 1m in front of the entrance.The height 6 ft.1.83 m according to NESC 2007 RULE 323. Manholes, handholes, and vaults

 

[Julius Right]

If you intend to run each feeder in a separate conduit [duct] the ductbank cross section will be 550*550 mm. However, the height of the manhole has to be the same 1.83 as per NESC.
These are the minimum inside dimensions.

 

[Sajid khan]

The height is too much... Can we reduce it to 1.2 Meters.

If you intend to run each feeder in a separate conduit [duct] the ductbank cross section will be 550*550 mm. However, the height of the manhole has to be the same 1.83 as per NESC. View attachment 20472
These are the minimum inside dimensions.

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[Sajid khan]

I cannot open this.. is it abailable in PDF??

Since this pertains mostly to poco, the info you need is beyond the scope of this site.


Try this, you might find this helpful:


https://www.scribd.com/document/224484020/Electrical-Manhole-and-Handhole-Design-Guide

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[Bill4477]

Check out this site:

http://precast.org/wp-content/uploads/2011/05/Manhole_sizing_recommendations.pdf

 

[Julius Right]

It is very interesting Bill4477. However, it is about pipe line visiting manhole and not for electrical cable ducts.

 

[Sajid khan]

It is very interesting Bill4477. However, it is about pipe line visiting manhole and not for electrical cable ducts.

Same openion

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[Dale001289]

I am working on a project in which i have to run 4 MV feeders
4X( 3X1C-240 sq mm) unarmoured Aluminum cable in 6 Inch Dia conduit.
The overall dia of one aluminum cable as i get from cable table is 35 mm dia.
The conduits will b burried 2ft Below grade.

How would i calculate the manhole size..

If some one can show the calculation work, it will really be helpful.

Regards.

Sent from my GT-I9300I using Tapatalk

Since you're using 240 sq mm I assume this is an IEC project vs NEC? For domestic US projects NEC Art 110.70 in addition to the NESC would be a helpful resource.
With only 4, 150mm diameter conduits, your manhole wont have to be excessively large. But there are a few basic parameters you need to consider. Will there be a fixed ladder? Will there be a sump pump? Will there be future cables/conduit? Are you in a Classified area, i.e. Zone 2 (Div 2)? And last but most important - have you determined cable bend radius requirements?

 

[RumRunner]

I cannot open this.. is it abailable in PDF??

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The above url is a proprietary document file for manhole designers.

You can use the address: www.scribd.com to gain access to the document.

If the link is not hyper, just type it on the prompt. Keep in mind that most documents are for design engineers and may require registration.

All the best.

 

[Sajid khan]

Thanks for the information
I am also a Design Electrical engr.

The above url is a proprietary document file for manhole designers.

You can use the address: www.scribd.com to gain access to the document.

If the link is not hyper, just type it on the prompt. Keep in mind that most documents are for design engineers and may require registration.

All the best.

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[Sajid khan]

Yes this is an IES project.
I would refer to NEC also for reference as u mentioned.

I have much concerned about the depth of the manhole. Considering the bending radius of the cable, it would not be much, Generally 12 times Overall Dia of the cable which in this case would be 35x12=420 mm So if we consider the depth of the manhole to be 900 mm i think would be pretty enough.

Since you're using 240 sq mm I assume this is an IEC project vs NEC? For domestic US projects NEC Art 110.70 in addition to the NESC would be a helpful resource.
With only 4, 150mm diameter conduits, your manhole wont have to be excessively large. But there are a few basic parameters you need to consider. Will there be a fixed ladder? Will there be a sump pump? Will there be future cables/conduit? Are you in a Classified area, i.e. Zone 2 (Div 2)? And last but most important - have you determined cable bend radius requirements?

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[Dale001289]

Yes this is an IES project.
I would refer to NEC also for reference as u mentioned.

I have much concerned about the depth of the manhole. Considering the bending radius of the cable, it would not be much, Generally 12 times Overall Dia of the cable which in this case would be 35x12=420 mm So if we consider the depth of the manhole to be 900 mm i think would be pretty enough.

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Yes, 12 times OD is about right - and is consistent with NEC Article 300.34, by the way. The manhole is really more of a 'hand hole' since your proposing only a 3'-0" depth. This would put your conduit duct at about 24" depth when it enters the hand hole - depth is also consistent with NEC Table 300.50, btw. It should be wide enough to pull cable out - then make a loop in order to reenter the hole without damage to cable.

 

[Sajid khan]

Yes, 12 times OD is about right - and is consistent with NEC Article 300.34, by the way. The manhole is really more of a 'hand hole' since your proposing only a 3'-0" depth. This would put your conduit duct at about 24" depth when it enters the hand hole - depth is also consistent with NEC Table 300.50, btw. It should be wide enough to pull cable out - then make a loop in order to reenter the hole without damage to cable.

Thanks will check the mentioned NEC Articles

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