Electrical question, Water heater in out building

[WobblyElvis]

I have an out building [shed] I plan on putting a shower in. I can bury and underground cable from the main building out to the shed. This line would be powered by a 30 amp 240V breaker and this main building has a newer panel with two grounding rods. I'd like to run this line to a small 4 breaker panel and put in some outlets and a water heater for a shower.
Two "experts" have given me differing advice.
First one said to stick a grounding rod in the ground and make sure the panel and the water heater are grounded using this rod.
Second "expert" says that's nonsense and to simply power the small water heater using a GFI outlet.
Buildings are 40 feet apart and both buildings just sit on blocks on the ground.

 

[Al]

A grounding rod can't hurt. I would be careful of a GFI,,you will get nuisance trips.
I am not an electrician. But I have done my share of wiring.

 

[Kawiguy454]

If the water heater has its own properly sized breaker in the out bldg sub panel and the heaters element blows it will short enough current to pop the breaker.

I used to fix commercial cooking equipment and dealt with elements up to 25KW x 4 in 480v 3 phase configurations in steam boiler. They always had breakers.

 

[eljefino]

You need the ground rod(s) for the outbuilding.

The only loophole is if you run one small 120V, 20 amp circuit. Then you can GFI it inside the main house. But your circuit is too big.

 

[i_hate_autofraud]

Don't use a GFI outlet for a water heater, even a small water heater. Reason is that the trip current for a GFI is intentionally very small and will false trip:

The water heater and it's element may have enough capacitance to ground + the water to false trip a GFI outlet. "Capacitive Reactance" - [Xc]" in combination with 60 Hz and 120 VAC will cause a tiny current to flow from the heater element thru the water to the grounded heater body to the ground wire that can unbalance the GFI detector - GFIs must 'see' all current from the hot (black) wire return via the neutral (white) wire, if not, a trip occurs.

If you really want to use a GFI, get a GFI breaker intended for large equipment with a slightly higher trip current to stop false trips.

Only GFI a single dedicated circuit with a single load, otherwise the [Xc] of multiple loads and circuits will false trip a GFI all day long!

A grounded heater will also ground the water and the copper pipes, so you are safe.

Extra ground spikes? Sure no prob!

 

[WobblyElvis]

Just read on the net that electric heating elements often break down over time and lose their ability to electrically insulate themselves from the water. This leads to nuisance trips of a GFI.

The electric water heater is my home is grounded the usual way with a bare copper wire as part of the 240V 14/2 that powers it. This is the same way the water heater in the shed would be grounded. Why does this out building need it's own ground spike?

I'm really confused here. If the heating element leaks current into the water, will current not try to flow through the person in the shower and down the drain to ground?

 

[Anduril]

An outbuilding requires its own grounding rods if it is powered by more than one circuit. I'm assuming the water heater is on a 30 amp breaker, I'd give myself 50 amps for the subpanel to make sure you have some headroom.

EDIT: Never mind, I see you are in Canada. I know the CEC is similar to the NEC but I don't know if what I said about ground rods applies.

 

[SHOZ]

What kind of water pipe will deliver the water? But when in doubt this forum will have the answers.

http://forums.mikeholt.com/

 

[exranger06]

The water heater has nothing to do with the ground rod. The outbuilding with subpanel does. Anytime you have a subpanel located in a separate building, that building needs its own ground rods. You also need four separate conductors running from the main panel to the subpanel (2 hots, 1 neutral, and 1 ground) and make sure the neutral is NOT bonded to the ground in the subpanel.

 

[WobblyElvis]

There will be 4 conductors from the main building to the sub panel. If I put in ground rods and attach this ground rod to the panel, that panel will also have the ground wire from the main building attached to it? So in fact all ground rods and all panels/ electrical boxes are connected in both buildings. Is this correct?

 

[exranger06]

Originally Posted By: WobblyElvis
There will be 4 conductors from the main building to the sub panel. If I put in ground rods and attach this ground rod to the panel, that panel will also have the ground wire from the main building attached to it? So in fact all ground rods and all panels/ electrical boxes are connected in both buildings. Is this correct?

Yes.

 

[WobblyElvis]

That be what I do then.

 

[i_hate_autofraud]

Originally Posted By: WobblyElvis


I'm really confused here. If the heating element leaks current into the water, will current not try to flow through the person in the shower and down the drain to ground?



The heating element seldom leaks current directly to the water, since the energized nichrome heater wire is encased in compressed insulating sand inside a thick compressed alloy copper sheath that is grounded. If there is a low resistive path inside the element it grounds out to the copper sheath which is grounded as well as the heater vessel and outer case.

(Years ago I contracted at a factory that made "Pyroil brand" block heaters that made their own heater elements in-house! saw the machines and the whole process - photocopied some of their cool ideas for myself - lol!)

Since most water systems have copper pipes to the taps they're grounded too. If you use plastic pipes the water is grounded inside the heater.

We're actually a lot safer then we realize, UL, ULC and CSA for the last 50 yrs have built in safety to product design / test requirements for Certification then the public will ever realize! Electrical fires and deaths can usually be traced back to causes of negligence /lack of maintenance of the end user or owner, but not the Standards used to certify a product or the testing for Certification!

 

[WobblyElvis]

As I see it now, the water tank will be grounded by a bare wire that runs to the sub panel. The sub panel will be grounded in two ways. To it's own ground rod at the out building and through a ground wire back to the main building that has it's own ground rods. The neutral bus bar is not grounded at the out building. I don't think the neutral bus bar is grounded at the main panel either.

 

[Anduril]

The neutral and ground are connected at the main panel, but that is the only place they are connected.