help with diversity

[getwiredin]

I have a job to install a new 3 phase DB to supply 9 showers in a care home, it is an old installation and the main switch is only rated at 100a. how do i apply diversity to this to see if the existing mains would be adequate, thanks

 

[Specialist]

Hi mate: Take a look at table A2 in the OSG.

 

[needasparks]

Finding out how many care staff they have working in the morning might give you an idea on how many showers will get used together as i don't think in care homes they can shower alone,
just a bit of info i picked up from homes i work in.

 

[trev]

Is a shower not classed as an instantaneous water heater now?
Yes I know no one will ever run them at max demand

 

[Specialist]

Yep trev, as far as i know.
So would be 100% of the largest, 100% of the next largest & 25% of all others.

 

[trev]

Sorry to be a total pain in the rear but if you have to ask how to apply diversity........

 

[SirKit Breaker]

I have a job to install a new 3 phase DB to supply 9 showers in a care home, it is an old installation and the main switch is only rated at 100a. how do i apply diversity to this to see if the existing mains would be adequate, thanks

Do the same calculation as for single phase and times it by three. The most important part of this job is keeping the phases as near balanced as possible. You are very unlikely to pull all 300a at anyone time anyway. I have an HMO with 4 x 8kW showers and it has not had a problem since rewired 6 years ago. If yours does tip it over the edge with 9, then you may have to install some sort of relay set up so only so many showers can be on at a time.

Calculation,

Add all breaker values up, i.e 6+6+16+16+32+40 and so on, then multiply the the total by 0.4.

Cheers.........Howard

 

[ruston]

Another point to consider ; although prbably not your responsibility , is can the water pressure respond to their demand .

 

[Inteificio]

I only use the OSG diversity calc when I do not know what the use will be.

As you know intended use, I would explain that with the current set up you can run X at once, is that enough or would you like me to up the wires for X cost.

The water pressure idea is a good one too.