3 phase submain showers

[Johnconnor]

Hi, I'm working in a building which has a three phase supply. There is two electric showers, sockets, water heater and lights going in a toilet block/seating area. For this I'm looking to take a 10mm 4core cable to a submain near the toilet block and running everything from here. The run is about 20m. Would this be sufficient for two showers being used in the morning and evening regularly. Should I be looking at 7.5kw to keep to loads down?

Thanks.

 

[buzzlightyear]

What type of system is it, are you taking
Single phase, are your calulations correct.

 

[Johnconnor]

Tns 80a 3ph. From the submain i will be installing rcbos and putting each shower on a separate phase. I know 32a a phase is more than sufficient on a 10mm 4core swa feeding the sub dB then 10mm T+E to the iso/shower. Just wanted to know thoughts as showers could be used alot throughout the day. Which is why I'm opting for 7.5kw and not 10kw showers

 

[Jock from the north]

Tns 80a 3ph. From the submain i will be installing rcbos and putting each shower on a separate phase. I know 32a a phase is more than sufficient on a 10mm 4core swa feeding the sub dB then 10mm T+E to the iso/shower. Just wanted to know thoughts as showers could be used alot throughout the day. Which is why I'm opting for 7.5kw and not 10kw showers

Hi do you mean your ocpd for your 10mm 4 core will be 80 amps or the supply to instalation is 80 amps

 

[Johnconnor]

The supply installation is 80a per phase rather, the ocpd for the 10mm would probably end up on a 50a

 

[Jock from the north]

The supply installation is 80a per phase rather, the ocpd for the 10mm would probably end up on a 50a

Is there much else in building using load

 

[buzzlightyear]

How did you calculate your loading,
Show your loading calculations..

 

[Jock from the north]

The supply installation is 80a per phase rather, the ocpd for the 10mm would probably end up on a 50a

Is there electric heaters in toilet block /seating area ,is it a single immersion ,hand dryers etc .what type of building is it that they require regular showers morning and night

 

[Johnconnor]

Just sockets and lights in the building. Sub main will have 2 showers, 3.5kw water heater, 3 x panel heaters( not sure of loads just yet on those) all plug top i do know, sockets, lights, fans etc. Its a shared office space where people cycle too hence the showers in the morning. There's also a gym near which people will come back and use the showers after or on lunch.

 

[westward10]

You need to work out your design current before you can be confident in selecting a supply cable.

 

[Johnconnor]

No worries. I will work out the design current. Cheers for the replys. Last question, would 7.5kw showers be better for alot of daily use over a 9.5kw one? Assuming the design of the installation was sufficient for both.

 

[Jock from the north]

Just sockets and lights in the building. Sub main will have 2 showers, 3.5kw water heater, 3 x panel heaters( not sure of loads just yet on those) all plug top i do know, sockets, lights, fans etc. Its a shared office space where people cycle too hence the showers in the morning. There's also a gym near which people will come back and use the showers after or on lunch.

Your panel heaters are likely to be 2 kw or less if using something like rionte .I would possible meusure what there using just now in there existing office then work out your own loadings checking bonding conductors etc

No worries. I will work out the design current. Cheers for the replys. Last question, would 7.5kw showers be better for alot of daily use over a 9.5kw one? Assuming the design of the installation was sufficient for both.

If its just for modern office workers to hose them self down after taking the cycle lane to work I'd give them a 7.5 kw

 

[baldelectrician]

I would suggest a water cylinder (possibly unvented) and an immerser.
You can get 3 phase immersers which are better for the supply, they will have a quick recovery time.

If you design it well then the cylinders will do all the showers plus the wash hand basin water as well.

This will make the load lower as you will be able to have hot water storage

 

[Johnconnor]

I would suggest a water cylinder (possibly unvented) and an immerser.
You can get 3 phase immersers which are better for the supply, they will have a quick recovery time.

If you design it well then the cylinders will do all the showers plus the wash hand basin water as well.

This will make the load lower as you will be able to have hot water storage

Yes good point. I did mention this to them, but the builder and the plumber were not interested

 

[Jock from the north]

Yeh m

Yes good point. I did mention this to them, but the builder and the plumber were not interested

Yeh more work for them.a cold water feed to an electric shower suits them better.also they tend to stick with what they know

 

[brianmoooore]

Don't forget that a lot of what you are proposing has no diversity allowance when calculating currents. You have to assume that all the electric showers nd water heaters are in continuous use, unless you include devices to ensure that they all can't be used together.

 

[baldelectrician]

Hi, I'm working in a building which has a three phase supply. There is two electric showers, sockets, water heater and lights going in a toilet block/seating area. For this I'm looking to take a 10mm 4core cable to a submain near the toilet block and running everything from here. The run is about 20m. Would this be sufficient for two showers being used in the morning and evening regularly. Should I be looking at 7.5kw to keep to loads down?

Thanks.

If you are the designer YOU tell them what can be done (using max demand guidance / site specific info)
If they over rule you have THEM specify what they would like YOU to do and make them aware that they will take responsability for any failings in design

I would walk away of someone told me to do a job that could bite me in the rear

Make sure you cover your back. Have a email / paper trail to back you up.

Are you an employee or self employed?