How many showers??

[NozSpark]

Been doing a PIR in a B&B today.

The main supply is 3 phase TNC-S with each phase supplying individual single phase CU's (on each floor) via 100A BS88 switch fuses and SWA feeds.

Now on the top floor aswell as having 3 x 32A socket circuits and 3 x 6A lighting circuits,,, they have 4 x 8.5kW showers.

With diversity this is about a 155A load, just for this board!

So what code would you give it bearing in mind that there are only 4 bedrooms on this floor each with only 2 double sockets??

To me it should be a code 2

 

[Andy™]

Been doing a PIR in a B&B today.The main supply is 3 phase TNC-S with each phase supplying individual single phase CU's (on each floor) via 100A BS88 switch fuses and SWA feeds.

Now on the top floor aswell as having 3 x 32A socket circuits and 3 x 6A lighting circuits,,, they have 4 x 8.5kW showers.

With diversity this is about a 155A load, just for this board!

So what code would you give it bearing in mind that there are only 4 bedrooms on this floor each with only 2 double sockets??

To me it should be a code 2

id go with code 2 aswell - there is a good chance of overload when everyone gets up and goes in the shower

 

[ianmacd]

[quote name='Andy

 

[binky]

argument 1/ But it never has tripped, therefore no overload????? Think I would go with code 3 or 4, provided that supply cables etc etc are suitably protected so that given an overload situation something trips/blows somewhere.

argument 2/ Main switch for DB is only 100A so 155A represents possible situatution that main switch couldn't cope if required too so showers should be spread over 2 CUs.

Think I would look for thermal damage of terminals/ cables within DB and decide accordingly.

 

[Voltimax]

Strike everything up and clamp test it. Then make your decision.

 

[a1spark]

argument 1/ But it never has tripped, therefore no overload????? Think I would go with code 3 or 4, provided that supply cables etc etc are suitably protected so that given an overload situation something trips/blows somewhere.argument 2/ Main switch for DB is only 100A so 155A represents possible situatution that main switch couldn't cope if required too so showers should be spread over 2 CUs.

Think I would look for thermal damage of terminals/ cables within DB and decide accordingly.

Think I would go along these lines too Binky.........In an ideal situation It would be a Code 2 but that would neccesitate an Unsatisfactory on the Report, A lot depends on the likelyhood of them all being on at the same time

...Code 3.. Requires further investigation is tempting me on this one.

 

[NozSpark]

argument 1/ But it never has tripped, therefore no overload????? Think I would go with code 3 or 4, provided that supply cables etc etc are suitably protected so that given an overload situation something trips/blows somewhere. 100A BS88 switch fuse at supply for each phase... this is a single phase DB!argument 2/ Main switch for DB is only 100A so 155A represents possible situatution that main switch couldn't cope if required too so showers should be spread over 2 CUs.This DB's main switch is a BS4293 100A / 100mA RCD... the floor below which is on a different phase has 2 x 8.5kW showers on it!

Think I would look for thermal damage of terminals/ cables within DB and decide accordingly.TBH there are no signs of thermal damage at all

I quoted a Max Demand for this DBas 155A, but TBH lets say that all the showers were on and each room had a kettle going and TV on (lets ignore the lights),,, this then comes out at 175A.

My main concern is if this place is fully occupied with a group of people, they all go for an evening meal and then back to the B&B for a S,S&S before going out for the night.

bad day explode

But saying that, they say it's been ok for the last 10 years?

 

[PC Electrics]

According to the time/current curves in the BRB, a 100A BS88 will rupture in approx 8 seconds when 142A flows. 4x 8.5kW showers on at the same time = 142A.

So, if they've never had a blown main fuse in 10 years, you can say with 99% certainty that all four showers have never been on at once.

Seems to me, that the chances of having all four showers in four guest rooms running at the same time are vanishingly small. There almost certainly wouldn't be the water flow available to support four electric showers either.

I don't believe a code is required on your PIR, but you could bring it to the clients attention as a possibility.

You could change the BS88 to a 1361, then you get 12 seconds! Arf, arf!

 

[bengie]

isn't the maximum demand the rating of the main breaker not the total of the loads, thats what the man in charge of our electrical QA informed me.

 

[bengie]

oh i agree there, it was more of a test sheet thing.

 

[Evans Electric]

I quoted a Max Demand for this DBas 155A, but TBH lets say that all the showers were on and each room had a kettle going and TV on (lets ignore the lights),,, this then comes out at 175A.My main concern is if this place is fully occupied with a group of people, they all go for an evening meal and then back to the B&B for a S,S&S before going out for the night.

bad day explode

But saying that, they say it's been ok for the last 10 years?

Noz you are doing the classic sparky thing, you have non existant people going out for non existant meals ,then coming home at the same time and having non existant $hits , Shaves and showers. But then you note that in 10 years there has not been a problem. Therin lies the answer.