Extension cords for new e-Brew setup

ryan_george said:

I'm looking for some feedback for a new electric rig I've got planned. I've done a lot of research on this site (and others) but I'd just like to hear some comments/suggestions from here.

I've been brewing 10 gallons with an electric kettle (5 kW) for about a year now with no problems, but I'm moving out of my apartment into a house and I'm planning to upgrade the system.

I'm going to make an e-HERMS with another 5 kW heater and keep my existing 5 kW kettle. Maybe down the road I'll add a separate 5 kW HLT (I'm going to use the HERMS tank as the HLT for now).

The one big issue is power accessibility. I want to brew in the garage to minimize spill damage and to have an area permanently setup for brewing. My nearest power outlet is the stove (50A receptacle) but it is ~75' away. I'd like to be able to run both elements at the same time (~42 A) and also run a pump and other auxiliary components (another ~2-3 A or so).

My calculations say that I'll need 6 gauge wire. I've found some 30' 6/3 + 8/1 RV extension cables with 50A ends for $82.
Question: Is there any reason why I couldn't buy three of these (to get 90') to power my rig? This will all be GFI protected (50A GFI breaker at the stove outlet).

Also a question for the electricians on the board: Do I need to derate the current capacity of the wire due to the 90' length for purely resistive loads? If so, please explain why. Although code might dictate that I need to, I don't understand how it would apply for the load I'm putting on it.

Thanks for the help!

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lschiavo said:

I don't see why you could not use the cables. You could also make your own custom cable and maybe save some money. It will be heavy and not much fun to roll out for a brewday.

Wire has some resistance. The longer the run the more resistance. The higher the current the more loss in the wire = heating. #6 copper at 50A and 90-ft, you should have about a 4.5V drop on the wire and dissipate about 220W in the cable. You should be ok.

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bigljd said:

I'm using a 100' of 10/3 with ground UF cable 'extension cord' to power my spa panel and control panel out in my brewshed. I may eventually bury it but for the winter it's just laying across my backyard along a fence. It plugs into a receptacle that I tied to a 30 amp breaker in the home's main panel. The wire is ornery as hell to unravel - I'm sure 6 gauge would be more difficult yet, but it is doable. The extension cords you mention would likely be more flexible than my UF cable, but it would be heavy.

In the post linked below you can see the distance from the shed to the house - it's about 75':
https://www.homebrewtalk.com/f170/m...-pid-ssr-build-281085/index3.html#post3500624

Here's the cable I bought - it was a bit cheaper than HD or Lowes. It ships from VA and shipping is very cheap (a couple dollars to NC I think). I don't know if they have 6g or not, but you can check the interwebs and ebay for a good deal.

100' 10/3 w ground UF cable

Hope that helps.

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ryan_george said:

Thanks for the feedback. I understand the voltage drop and the self heating of the wire. As we add more length we get a larger total dissipation, however, we are also adding a proportional amount of extra surface area for the wire to lose heat by conduction/radiation to the surroundings. I'm not trying to get into an argument with you, I'm just trying to challenge the common beliefs. For these resistive loads, every foot of wire will be the same temperature whether it's 5' or 500', it's just the total heat loss that is different. Again, please don't take this as a stab at you.

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lschiavo said:

I agree with you.

It is really less about heating and more about voltage drop in a cable. If the same wires were in a conduit with other heavily loaded circuits, the combined heating effect could be significant. This is when wire is derated and is based on conductor fill.

The voltage drop is about 2%. That is acceptable for most any load. You could drop half the voltage in the cable and a resistive load will still function just at a decreased output. A few hundred Watt loss in your case is insignificant.

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ryan_george said:

Is that UF cable meant to be constantly handled? Or once it's in place you're supposed to leave it alone? I will have to coil/uncoil my wiring every time I want to brew, so I need something that is meant for that (ie, not solid core wire). Also, looks like that place doesn't carry much 6 gauge. Thanks anyways!

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