Here’s a brain tickler for trainees

[MFS Electrical]

Sintra chap of course while you are here fancy changing the title on my EICR coding thread to EICR coding challenge for trainees?

 

[Sintra]

Sintra chap of course while you are here fancy changing the title on my EICR coding thread to EICR coding challenge for trainees?

All done mate.

 

[MFS Electrical]

All done mate.

I see that.... very fancy

 

[GMES]

Sintra, while you're here do you mind sticking the kettle on.

 

[Richard Burns]

Ok first post on here so be gentle.

An excellent response there with thought and planning.
I won't say more yet, to allow others a chance to give their ideas.

 

[MFS Electrical]

Sintra, while you're here do you mind sticking the kettle on.

A cuppa would be nice actually just milk please

 

[TJ Anderson]

Ok first post on here so be gentle. Cable calcs would be as follows;

Ib - 10000/230 = 43.5 amps so a 45 amp mcb in one of the spare ways

It - 45/1.03 = 46.35 amps made some assumptions that the ambient temperature would be 20C and the cables would be by them selves not grouped together. Using reference method c this would size the cable at 10mm.

Checking volt drop on the cable would be 4.4 x 43.5 x 3 / 1000 = 0.57v and 4.4 x 43.5 x 18 / 1000 = 3.4v these both come within the allowed 6%.

Might as well check Zs by calculation while I'm at it which would be R1+R2 per meter for 10mm is 6.44 milli ohms so 6.44 x 18 / 1000 = 0.11 ohms. Ze for tncs would be a maximum of 0.35 ohms so worst case would be 0.46 ohms. On a 45 amp mcb the max Zs would be 0.78 so again all good.

Isolators could be vertical 2 gang 50 amp double pole switches mounted out side the bathroom door.

As for making sure about not going over the max demand I can think of two ways of doing it. The simplest and cheapest way would be a subtable rated change over switch mounted some where accessible by the CU so only one shower can be used at a time. The other way that I can think of but maybe wrong (educate me) would be the use of two suitably rated contactors wired as you would for forward reverse motors (few less wires as not swapping two phases just switching the line from one contractor to another). Each contractor would then power one shower. Momentary switches could then be wired by each bathroom to turn on each shower, but not the other.

Really good.....nice work.

Couple of things you may wish to consider

What table and column did you use for (Iz)?

You have used (In) in your (It) calc. Do you think these particular loads can exceed (Ib) under normal operation?


Look at VD% allowable again too....


Also, I see you have gone with 10/4mm 6242 cable from your calc values. I'm sure you do know ......but how do you know it is suitable to carry earth fault current as cpc is smaller than line conductor? How did you determine this?

 

[MFS Electrical]

No one else going to have a bash?

 

[curly]

Rubbish there is always a way especially if the customer says no matter the cost,

I'm installing this and she can get her heating done at the same time

Elnur Connected MAC15 3-15kW Mattira Electric Combi Boiler (Heating & Hot Water) - https://www.heatershop.co.uk/elnur-connected-mac15-3-15kw-mattira-electric-combi-boiler-heating-hot-water?gclid=CjwKCAiAo8jgBRAVEiwAJUXKqKq8tAXhctf1PXP2syq1wDODom-4tTjavVXqL_sGLnxpgP0Hoz1tVhoCGs8QAvD_BwE

 

[MFS Electrical]

Rubbish there is always a way especially if the customer says no matter the cost,

I'm installing this and she can get her heating done at the same time

Elnur Connected MAC15 3-15kW Mattira Electric Combi Boiler (Heating & Hot Water) - https://www.heatershop.co.uk/elnur-connected-mac15-3-15kw-mattira-electric-combi-boiler-heating-hot-water?gclid=CjwKCAiAo8jgBRAVEiwAJUXKqKq8tAXhctf1PXP2syq1wDODom-4tTjavVXqL_sGLnxpgP0Hoz1tVhoCGs8QAvD_BwE

The point is the customer wants two electric showers and how would you do it? This would be a feasible alternative but the spec is two electric showers. Absolutely no deviation at all from the spec is allowed.