2365 Design Project - May need some advice.

[RDB85]

Circuit 1 & 2 - Cafe Lights

• Ib = 0.27A
• In = 6A Type B breaker
• Installation Method = 4B
• RF = Ca 1.03 Cg = 0.80
• Iz = 7.28A
• csa = 1mm² 13.5A VD 44
• Actual VD = 0.35v
• Max Vd = 6.9v
• Max Disconnection Time: 0.4 seconds
• Earth Fault Loop Impedance = 7.28Ω
• Maximum Earth Fault Loop Impedance BS7671: 7.28Ω
• Zs-Ze = R1+R2 = 7.28 - 0.11 = 7.17Ω
• Calculated Zs = 18.10 + 18.10 x 30 x 1.20/1000 = 0.67 +0.11 = 0.78Ω

 

[RDB85]

Kitchen Lights

• Ib = 3.91A
• In = 6A Type B breaker
• Installation Method = 4B
• RF = Ca 0.94 Cg = 0.80
• Iz = 7.97A
• csa = 1mm² 13.5A VD 44
• Actual VD = 5.16v
• Max Vd = 6.9v
• Max Disconnection Time: 0.4 seconds
• Earth Fault Loop Impedance = 7.28Ω
• Maximum Earth Fault Loop Impedance BS7671: 7.28Ω
• Zs-Ze = R1+R2 = 7.28 - 0.11 = 7.17Ω
• Calculated Zs = 18.10 + 18.10 x 30 x 1.20/1000 = 0.67 +0.11 = 0.78Ω

 

[RDB85]

Pool Power PVC Conduit 90°C thermosetting singles

Circuits 1 - Changing Room Sockets - not sure whether to do a 20A radial.


Pump Room Equipment ( 32A 400v 5-core 90°C SWA Clipped Direct)

• Ib = 32A
• In = 32A Type B breaker
• Installation Method = 20C
• RF = Ca 0.91 Cg = 0.73
• Iz = 48.17A
• csa = 6mm² 53A VD 6.8
• Actual VD = 6.528v
• Max Vd = 6.9v
• Max Disconnection Time: 0.4 seconds
• Earth Fault Loop Impedance = 1.36Ω
• Maximum Earth Fault Loop Impedance BS7671: 1.37Ω
• Zs-Ze = R1+R2 = 1.37 - 0.11 = 1.26Ω
• Calculated Zs = 3.08 + 3.08 x 30 x 1.28/1000 = 1.18 +0.11 = 1.29Ω

 

[RDB85]

If those circuits could be checked that would be much appreciated. I will upload the others once I’ve checked them and wrote them out. I may need some advice on maximum demand and diversity. Thanks.

 

[Richard Burns]

It takes a long time to go through multiple questions and it can be hard to identify what numbers you have used and correlating the information that you have used with the results is another difficulty.
Note that when using 90°C cables that all the cable terminations and enclosures should be rated to 90°C as well, I am sure this is covered in your training and is taken account of for this project, but it is important to note that if it is not taken into account the cables should be downrated to 70°C.
Also note that 70°C cables are thermoplastic not thermosetting (probably just a typing error there)

Based on your current circuits I notice that every Zs calculation shows the circuit length as 30m, but then the results do not match with your answers.
For the lighting circuits not knowing the circuit length makes it impossible to calculate Volt drop, however you have three lighting circuits with different design currents and presumably different lengths and yet the calculated volt drop is the same in each case. The values also seem high unless you have very long circuits perhaps you could show your working there.
The pump room equipment appears to be a single circuit and presumably not grouped as it is clipped direct SWA yet you have a grouping factor of 0.73, I cannot work out where this is derived or why but you may have more information about it.
Check your maximum permitted volt drop for this circuit as well.
For installation method it is common convention just to use the letter e.g. C rather than including the installation method number e.g.20, however including the number does give more information so could well be useful.

 

[RDB85]

Based on your current circuits I notice that every Zs calculation shows the circuit length as 30m, but then the results do not match wit

How we are to do the length of the circuit, is by measuring each circuit, we have a scale drawing 1:50, on A4, however that has been submitted for critique marking, As that was Q2 were we needed to draw the lighting circuits for each room, as I am only allowed to take certain questions home. I thought it best to use the maximum allowed which was 30M As we have to fill in a table at the very end in pencil, I can just change some of the calculations once Q2 which is the drawings has been marked and given back to me for any changes.

 

[RDB85]

For the lighting circuits not knowing the circuit length makes it impossible to calculate Volt drop, however, you have three lighting circuits with different design currents and presumably different lengths and yet the calculated volt drop is the same in each case. The values also seem high unless you have very long circuits perhaps you could show your working there.
The pump room equipment appears to be a single circuit and presumably not grouped as it is clipped direct SWA yet you have a grouping factor of 0.73, I cannot work out where this is derived or why but you may have more information about it.
Check your maximum permitted volt drop for this circuit as well.
For installation method it is common convention just to use the letter e.g. C rather than including the installation method number e.g.20, however including the number does give more information so could well be useful.

I will show you my workings for the Pool, Kitchen and Cafe Lighting, my apologies. My mistake with the SWA, I will adjust that accordingly. As its a single cable, there would be no grouping. I will also check the maximum permitted volt drop for the circuit also.

For the sockets in the changing rooms, I was thinking of putting a 20A radial socket as it seems that it would not require a 32A ring circuit, as it would only have items such as hair dryers etc being plugged in.

I will add my circuits now with corrections and also the workings out.

 

[RDB85]

I have printed the drawings out, I can from memory remember the number of lights. The scale on the drawing is 1:50, so would it be safe to say 1cm is 1m I never done scale drawings so I am unsure of what scale to use.

 

[westward10]

The scale of 1:50 means for every 1 it is 50 full scale. So 1cm on your plan equates to 50cm in reality.

 

[RDB85]

The scale of 1:50 means for every 1 it is 50 full scale. So 1cm on your plan equates to 50cm in reality.

Okay, I am just trying to work out what I could use as the maximum circuit length is 30m. As the spec states All circuits lengths to be estimated from drawing scales. For the purpose of the project, it no circuit should not exceed 30m.

 

[RDB85]

I may just use 2cm is 1m as I don't have a Metric Triangular Scale Ruler and we were not told to get one.

 

[Pete999]

How we are to do the length of the circuit, is by measuring each circuit, we have a scale drawing 1:50, on A4, however that has been submitted for critique marking, As that was Q2 were we needed to draw the lighting circuits for each room, as I am only allowed to take certain questions home. I thought it best to use the maximum allowed which was 30M As we have to fill in a table at the very end in pencil, I can just change some of the calculations once Q2 which is the drawings has been marked and given back to me for any changes.

Are we taking this course or are you?

 

[RDB85]

Are we taking this course or are you?

I am just explaining where the 30M comes from. But I need a Triangle Ruler in order to measure the circuits, as you can't do it with a ruler. Sorry if I caused offence.

 

[Richard Burns]

2 cm is 100 mm is a workable way of doing it.
Westward10 has explained how to use a normal ruler to get your measurements.
If you have printed the diagrams at full size on A3 paper then they will be scaled 1:50 so if you measure 9 cm as the width of a room on the page then in reality the room will be 50 x 9 cm i.e. 450 cm or 4500 mm.
The picture is 50 times smaller than the real thing.
To get you started I have drawn out approximate dimensions on what I believe is the diagram you are using for the pool. If you can measure on your printed versions values to give similar results you should be able to work on from there for the rest of the building.
Because my measurements are manual on rough copies they could be a few mm out in measurement, for instance the front to back of the pool building is about 230 mm, but on measuring again it might be 231 mm this would change the size from the given 11500 mm to 11550 mm.
The purpose of the project is allow you the chance to learn how to do things like scale measurements and accurate circuits so that you can use this confidently in work at a later date; so it is good to practice now and get things correct, much better than getting things wrong on a real installation!

 

[RDB85]

That's brilliant, thanks very much. I've ordered one of those rulers to also do it. As it would be actually beneficial as you say to learn how to do it now.