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Well I managed to get a distinction in the C&G 8202 level 3 written final exam, despite C&G's odd questions! So thanks to all the people on here who chipped in with answers to my questions!

Is there a source for the 1.8 factor used for picking a breaker for discharge lighting circuits? Is it in BS7671?

Just wanted to confirm my understanding here. Ignoring power factor for the moment, I know that the formula used to get current from total power is total power/(root 3 x phase voltage) This is the phase current, so we use this for each line cable and fuse, of which there'll be 3. The root 3...

Todays class ended in a bit of a fiasco trying to work out how to check compliance for measured Zs, when given various protective devices. For example: A circuit is protected by a 20A BS88-2 fuse and measured Zs is 2.08 ohms. Ambient temp is 20 degrees C. I approached this question using the...

Just run through a past exam paper June 2022. The last question is, as usual, a cable calc. I was pretty close to the right answers on most of it. However two things threw me, when I checked the anwer sheet. We've been taught that for a basic radial power circuit, You find the Ib (design...

C&G seem to think an electric fire heats a room by conduction? Surely it only heats by convection and radiation? They ask for three ways an electric fire heats a room. Electric underfloor heating would certainly use conduction but an electric fire? Maybe there is conduction after the radiated...

Our level 3 lecturer seems to be confused on how to use the tables in appendix I, for calculating Zs. They said that you look up the resistance in Table I1 and if the ambient temp is below 25°C, use the factors in Table I2. If over 25°c, use table I3. I don't think this is right. Table I2 is a...

I assume that a main RCD tripping while working on an isolated (at the breaker) circuit, means neutral to earth current. Is it a sign of a fault somewhere else?

A friend of mine has an electric hob which, they tell me, is plugged into a 13A socket! I didn't think that would be possible... Anyway I had a look at a typical ceramic hob online and the specs seem to show 3x rings at 2.8kW and 1x rings at 2.4kW. Further down the specs list it says total...

Just looking to find out where to select 't' the disconnection time for the Adiabatic formula. (This is for college not an actual install.) Using an EN60898 breaker, 16A. Type B. Do I look up a datasheet for the breaker? Do I use table 41.1 in the regs book? Part of regulation 411.3.2.2 (0.4...

Was in class today and googled 3 phase transformer. These 2 images came up and I can't see that they would do much ? The C&G handout on transformers image is also shown.

Just started Level 3 C&G and we're doing cable sizing calcs. Using a previous years exam question. We ran through a few examples of radial circuits, all well and good. Following this proceedure: Work out total load on circuit from plan. Work out design current. Ib. Ib<In<It Find suitable...

We have some big, heavy double glazed bi folds made from accoya. They are 5 years old and due for some paint but I've noticed the joints have opened up on the frames a little so the door is no longer square. Not sure the technical term for this, but before I paint them, is there a way to get...

OK, I think there are two right answers here... Again, nothnig in the actual course notes on this... You have to pick one, no option to write an essay on how they are all prone to issues after x years... I'd argue that an ASHP and Solar Thermal have similar maintenance requirements. Only...

Any thoughts on this question: Which one of the following devices will disconnect in the fastest time if a short circuit current of approximately 300A occurred on a circuit? a) 32A/30mA Type C RCBO b) 32A Type B circuit breaker c) 32A Type C circuit breaker d) 32A Type D circuit...

In the system boiler I have, there's an integrated circulation pump. Just wondering what benefit this has over and external pump or if there's a specific reason for one needing to be integrated due to being a pressurised non-vented system? Does it just make installation easier?

Just out of curiosity, I assume a system boiler has to work with an unvented system and a system boiler cannot be put into a vented system? (due to the lack of pressure)

We have an old Potterton Profile 80e. Now that the cold nights have started, I've just set the programmer to run the CH. I've just noticed that the CH pump stops when the boiler cycles to off. Rads take forever to warm up! The selector switch in the boiler is set to Fully Pumped, so the pump...

Putting new undercloaking back after replacing sofits. The undercloak boards are butted and not overlapped right? The top of the fascia board is about 30mm above the top of the rafter, so the last bit of undercloak needs to kick up and rest on top of the fascia, right? Do I just fill the gap...

I've serviced the o-rings on the main cartridge to stop a dripping shower head but the temp control tap is still almost impossible to set to max cold. The end stop is set correctly, the tap is just really hard to move. It moves in very slight increments. The machanical tap moves fine. Is this...