Problems with Maximum Demand figure

[markythesparky]

Who installed the sub main and the lighting then? Where has he gone? The on site guide gives diversity calcs on heating appliance's. client may be ppaying for it but it will be you who is being sued when the system keeps overloading. If you are going to stand by your loading calcs you should make sure you have professional indemnity insurance. this is why engineers get involved.

 

[Jon Hodgson]

They Landlord had their own electrician carcass out the high lighting and install the submain which isn't connected or tested from what I have seen. Only reason I know the loading fotr the lights is that I counted and Calculated it first and its all one bank as well.

Not sure why there was no consultation about the requirements for the supply though its rather odd in my opinion

I have the OSG out in front of me water heater diversity is only applied once there are 3 instantaneous heaters in the installation there are only going to be two and the third is an undersink unit with storage so all are 100% of f.l. regardless of being domestic or commercial from the way I read it.

 

[Guest55]

you dont need a chartered engineer for a modest commercial extension mark.
this is straightforward load assesments and planning that any competent designer \ installer could undertake.
as for getting sued from overload ? (if it ever happened )
i'd blame the owner as it was he whom specified the dno supply ;-)

 

[markythesparky]

I have the OSG out in front of me water heater diversity is only applied once there are 3 instantaneous heaters in the installation there are only going to be two and the third is an undersink unit with storage so all are 100% of f.l. regardless of being domestic or commercial from the way I read it.

Agreed. It wasn't the water heating I was concerned about, I thought your cooking appliances calcs were wrong.

 

[markythesparky]

you dont need a chartered engineer for a modest commercial extension mark.
this is straightforward load assesments and planning that any competent designer \ installer could undertake.
as for getting sued from overload ? (if it ever happened )
i'd blame the owner as it was he whom specified the dno supply ;-)

Biff, I totally agree. But Jon has said he is not confident with his calcs and therefore could consider whether he wants to stand by them. And I agree with both of you, it seems very strange that someone has installed circuits already but has not had consultation and has now vacated the site. Who is going to sign this work off and connect it?

 

[Jon Hodgson]

Domestic cooker installation says 10A +30% f.l. of connected cooking appliances in excess of 10A gives 18A if i got it right.

Commerical says 100% of f.l. of largest appliance and 75% of f.l of remaining appliances which is where the 30A comes from

 

[markythesparky]

I stand corrected. I don't have OSG to hand and I didn't know that Commercial was different.

 

[Jon Hodgson]

Its not that I'm uncertain of my calcs as such its just that I wanted to make sure that I was on the same page as everyone else and that I hadn't ballsed up my interpretation of the OSG if you get where I am going with this.

First time doing any commercial work under my own steam I've done plenty before thats been worked out before hand by someone else.

Rest assured it will not be me testing what has gone in already I will not put my name to it period, I am not putting my name to the installation of the board either only going on the circuits I put into place!

 

[Engineer54]

Oh dear god, are you really trying to make those max demand and diversity formulas quoted in the BGB work?? Best of luck to you if you are!! They are totally useless (except for the domestic cooker formula) except maybe for make believe C&G questions!! Unfortunately for you, it's takes many years of experience to assess by calculation only, accurate results...

 

[markythesparky]

Oh dear god, are you really trying to make those max demand and diversity formulas quoted in the BGB work?? Best of luck to you if you are!! They are totally useless (except for the domestic cooker formula) except maybe for make believe C&G questions!! Unfortunately for you, it's takes many years of experience to assess by calculation only, accurate results...

Which is why I said, 'this is why engineers get involved'