Household power circuits and current ratings

[verysupple]

Hi all,
I'm designing a new rig at the moment, although it probably won't get built for a fair while. It's going to be pretty much the same as QldKev's recirculating 1V system which is detailed in threads here if you seach for it (and I thought I was so clever and original until I started resarching it... ).

Anyhoos, I've already got a Tobins 2400 W over the side immersion element which I plan to use, at least to start with. I might add a 2200 W fixed element later if I think I need it and just use the OTS for a boost during ramps to strike temp and boil. Either way, at least one of the elements will be PID controlled during the mash. I'm planning to use a Kaixin pump for the recirculation.

So, my first query is if it's going to be a problem having the PID and the 2400 W element running off a single 10 A GPO? It'd only be 10.02 - 10.05 A max. so I'm guessing that's fine? The pump and whatever other devices would be running off a second GPO.

My second query is if it's necessary to get a heavy duty extension lead (15 A, 1.5 mm2, but with 10 A plugs so they fit in the GPOs)? Part of me thinks if it needs to carry 10 A and it's rated for 10 A it'll be fine, but I've read comments in other threads suggesting it might not be. The part I don't really understand is what's the point in having cable rated for 15 A if the plugs and GPO are only rated for 10?

My third query is to do with the photo below of my fuse box. I've figured out which circuits have power outlets near to my soon-ish to be brewing area (the balcony of our apartment, I currently brew in the kitchen on the stove) and I'm just wondering how trustworthy the current rating labels are on the fuses, as the most convenient setup would be to use two different GPOs on the one 28 (?) A circuit.

And lastly, I'm not sure if that's a circuit breaker on the far left (sorry I cut it off a bit). It says "AC 250 V, 80 A". Even if it is, 80 A seems like a lot. Is it worth incorporating a 10 A RCBO into my PID? Everything will be earthed properly but you can never be too careful when electricty and liquids are involved, right?

Sorry for the long-winded, many questioned post. All advice is greatly appreciated.

 

[mombius hibachi]

Hi mate,

The 80A one is your main switch, it doesn't trip at 80A or mean you have 80A at your disposal, it is there to turn off everything in one switch. A main isolator for your apartment essentially.
Wow, I'm a sparky in WA and haven't ever seen 28A domestic power circuits before...
I'm guessing that's 4 or 6mm2 cable. Lucky you, though it looks like you could use a board upgrade to breakers and some RCD's, especially as that fuse won't blow until your drawing well over 28A, which if you're standing in a puddle of water/wort will be the end of your brewing career.
You should get a sparky to check it first, but you should be able to run your 2 elements and pump and pid controller off one (28A) circuit, though prob not much else, e.g. toaster, kettle.
You can draw 10A continuously or even more through a 10A lead/plug, though this will lead to melting and failure, hence why people recommend using a 15A lead and plugs. Its always better to over engineer with electricity. Fuses are there to protect cables, not appliances. So a 10A socket outlet can provide you with 28A by the looks, which will melt and cause destruction should it happen, and fuses take longer to trip than breakers...
Hope that helps a bit.
Cheers

 

[Ducatiboy stu]

I would be looking at replacing those ceramic fuses with moderm CCT breakers. Fuses dont offer the protection you realy need. Not all GPO's are rated at 10A, but the ones you commonly see are. A 15A GPO can only be bought as a singlem and you can have only one on a CCT.

The problem you might have is that whatever GPO youre using to power your rig might also be part of a the cct for the rest of the house, this is when you run into trouble as your Kettle is sucking 10A, but then when someone turns another aplliance on in the house it will either blow the fuse/breaker or the internal wiring will heat up due to the extra current draw

Your querry about the fuses and rating has more to do with the fuse wire size used. Lots of people use the wrong fuse wire ( ie to big )and end up burning the house down, You can plug in cct breakers that replace the fuse holder, cheap and much better and safer

 

[spog]

The wrong size fuse wire,yep seen that many times and the scorching on them is amazing!
Never catch me doing that and I'm a dumb chippie!

 

[Ducatiboy stu]

 

[Pogierob]

Ok, just to be clear...

consult an electrician,

I personally don't think that a brew forum is the place to get advice about "life or death" choices, if you are not qualified to touch it, don't.. if you are not sure what it draws, then confirm with someone who is..

Is your life honestly worth a couple of beers?

your life, your beer, I double dare you to put that in the hands of a stranger on a forum that tells you it's ok to "load it up and brew"..

 

[MitchD]

As an electrician who did his apprenticeship in melb i would strongly recommend you get a professional to have a look. From first view of that fuse board you almost certainly have black rubber insulation. I spent time than i want to remember under houses and in roof spaces replacing this stuff, it has broken down over time and cant be trusted. a rewire and new switchboard is the answer.

After you get the house checked then you should be fine with one 10a (2400w element) but you will need a different/new circuit for the other 2200w element.

 

[verysupple]

Thanks for the replies everyone.

It sounds like I was right when I thought the best option would be to use two different circuits. That's no big deal.

As for ye olde fuse board, if anything is done to it like changing to breakers and RCDs, it'll be done by a professional. I'm renting, so is this unsafe enough (for regular purposes, not brewing) to try to get the landlord to replace the fuse board with modern gear? I don't think they'll do anything to it if it's fine for every day use.

You can draw 10A continuously or even more through a 10A lead/plug, though this will lead to melting and failure, hence why people recommend using a 15A lead and plugs. Its always better to over engineer with electricity.

This is exactly what I thought. Hence my confusion about using extension leads that have cables rated for 15 A but 10 A plugs (you can get them at Bunnings). I figured what's the point of using a cable that won't fail if the plugs and GPO still will?

 

[bazfletch3]

Important to point out too that the type of cheese in the foil wrapper has a big influence on the current rating of the foil; I think you can get close to 20A out of parmesan.......

 

[verysupple]

This is exactly what I thought. Hence my confusion about using extension leads that have cables rated for 15 A but 10 A plugs (you can get them at Bunnings). I figured what's the point of using a cable that won't fail if the plugs and GPO still will?

So, I went back and found the thread where I'd read that people got better performance using heavier duty extension leads. The claims were that the elements performed better when using an extension lead with higher gauge wire.

So I investigated the benefit of using a 10 m lead with 1.5 mm2 conductors compared to 1.0 mm2 conductors.

Resistivity of copper at 60 C, p60 = 2.14 x 10-8 ohms.m (I used 60 C because I figured you wouldn't want to get much hotter than that given standard duty leads are usually rated for 75 C)
l = 10 m
A = 1.0 or 1.5 mm2

R = pl / A

So for 1.0 mm2 conductors R = 2.14 x 10-1 ohms and for 1.5 mm2 conductors R = 1.42 x 10-1 ohms

So the maximum voltage drops due to the leads conducting 10 A would be 2.14 V and 1.42 V respectively using 240 V AC.

That's pretty small and I doubt you would notice the difference in element performance if the voltage to it only dropped that much.


Anyway, getting back to the question, is there some other reason not to use a standard duty extension lead with a 2400 W element?

 

[Ducatiboy stu]

Its not the voltage drop, its the current carrying capability

 

[verysupple]

That still doesn't make sense to me. What's the point of using cable that can carry 15 A if the plugs are only rated for 10 A?

What I want to know is what's wrong with a cheap light/standard duty extension lead if it's rated for 10 A and you only draw 10 A through it?

 

[Ducatiboy stu]

Nothing

 

[wobbly]

Its not the voltage drop, its the current carrying capability

As implied in Verysupple's post above the issue is the heat generated in the extension cable (Ohms Law Watts = Current squared times resistance)

The 15 amp cable will only have to dissipate 14.2 watts of energy where as the 10 amp cable will have to dissipate 21.4 watts of energy

Wobbly

 

[dave81]

I know as an electrician in WA and also someone who has had investment properties , that power/lighting circuits need to be protetced by rcd's.this maybe something worth looking into to get a board upgrade rolling from your property owner.as has already been said a fuse is extremely slow to blow and especiall dangerous if the wrong size fuze wire has been put in in the past by someone untrained.maybe conatct your office of energy in your state(I know its probably not called that in your state or here any more I havent worked in the domestic sector for years) to see what the electrical requirements are for rental properties and then back to the property owner with youe findings.

 

[verysupple]

Hey dave81,
I know QLD has similar laws (regulations?) about having more modern safety gear installed in rental properties so I did some searching around for the Victorian regulations and didn't really find much other than something really vague like "It has to be safe", or something to that effect.

I did find a pck of replacement fuse wire in the cupboard that must've been left by previous tenants. Luckily it only has 8 and 16 A wire and seeing as my circuits appear to be 16 and 28 A it's unlikely that any of the fuses have too high a gauge wire in them. But I still want it all replaced with modern gear anyway.

On Wednesday I sent the agent an email about some other outstanding maintenance work and also outlined my concerns over the electrics. I haven't heard back yet but a nice sparky from this forum has offered to swing by and check it out and maybe write a letter I can give the agent if they're not willing to play along. They should at least listen to a professional.

 

[Eagleburger]

I would be more concerned about old switches and power points than extension leads. That said, I use 1.5mm leads.

 

[Eagleburger]

Expanding on my previous post. where there is the most resistance in a line you will get the most heat. Old switches and power points can be bad if the contacts are corroded or loose. The first timed I brewed electric I melted the extension plug socket with only a 2000w heater. I immediately got a leccy to upgrade that complete circuit to 20a and installed a second 20a circuit. Both have RCBO's on them. Now the only thing that gets hot is the element.

 

[Nath151]

Also most domestic leads eg. White ones you buy from bunnings are 0.75mm2 so are more prone to heating up melting the insulation and shorting out under continuous heavy loads
Cheers Nath

 

[verysupple]

Thanks for all the help everyone. As I kind of expected the heat dissipation seems to be the biggest issue in terms of extension leads.

Also most domestic leads eg. White ones you buy from bunnings are 0.75mm2 so are more prone to heating up melting the insulation and shorting out under continuous heavy loads
Cheers Nath

It might depend on where you are, but the cheapest leads at my Bunnings are the Arlec ones which are 1.0 mm2 per core. When I actually get around to (have enough funds for) building this rig I might do a test run with the lead I have and keep a really good eye on temps and discolouration of plugs etc. If it's not A-OK I'll upgrade.