How to measure 220?

Discussion in 'General Electronics Chat' started by mcpeck, Feb 10, 2008.

  1. mcpeck

    Thread Starter New Member

    Feb 10, 2008
    Hey guys, I'm not a professional electrician, but have worked with electrical quite a bit and have a pretty good understanding of regular household 110v.

    I have a friend with a hot tub and he is in the process of replacing all of the pumps and heating elements and basically re-doing everything on it. Anyway, there are both 110 and 220 options when buying new systems. He's pretty sure that he's got 220 running to at least part of the tub, but also thinks there is 110 going to part of it.

    I thought these things ran purely on 220, but the guy who owned the house before him was kind of a Jerry rig type of guy, so who knows.

    I need to go over and see if and where the 220 is on this thing, but I have never done anything with 220 and am not really sure how to go about measuring for it with my multi meter.

    Is it the same as measuring any 110 curcuit? Is there anything I should watch out for especially? I asked if there was a separate breaker for what he thinks is the 220, and he said there is a separate breaker there, so I'm assuming there's 220 in the house then, just need to know how to measure with the meter.

  2. thingmaker3

    Retired Moderator

    May 16, 2005
    The breaker for a 220 circuit will be a "ganged" breaker - two breaker switches with a strong mechanical connection between them. Ideally, there will be a red "hot" wire from one of them and a black "hot" wire from the other. The white wire goes to the neutral bus and the bare or green wire goes to the ground bus.

    On the tub end, anything requiring 110 will go between one of the hot wires and the neutral (white) wire. Ideally, one should balance current between these - almost never 100% practical, though. Anything requiring 220 will go between the red and black wires.

    Here's why:

    If there is ANY doubt whether the work can be performed SAFELY, please hire a licensed electrician. We're a heck of a lot less expensive than funeral costs or hospital burn unit co-pay.
  3. SgtWookie


    Jul 17, 2007
    If the guy who had the place before ran his own wiring, he may have "cheaped out" on it and used undersized wire, or 2-conductor w/ground instead of 3-conductor wire w/ground for 220. If you measure voltage between the white (neutral) wire and ground, I suggest that you have an unsafe situation.

    Since you're talking pool/spa wiring, shouldn't the breaker be a GFCI type? That protects the spa users in the event that there is current in the ground wire.

    What's the current rating of the breakers, and the wire gauge that was used? It should be marked on the insulation jacket.
  4. mcpeck

    Thread Starter New Member

    Feb 10, 2008
    Yeah I just got back from over there, and the first thing I noticed was the double breaker in the separate breaker box, I knew that was 220 from having it in my house for electric heaters.

    I traced it out from there and found exactly what you guys are saying, a red hot wire, a black hot wire, a white neutral and a green ground, they are all black wires with different color electric tape wrapped around each end to show the above mentioned colors. They run from the breaker on real thick gauge wire, and then into a splice box where the splice down into slightly smaller gauge color coded wire, 2 black, 1 white and 2 green.

    Then they go into the controller/timer box, and I pulled the cover off that controller and see where the 2 black cables hook up and a sticker saying 220V, so obviously he didn't look in there, and obviously 220 service is present. This box looked to be about 20 years old and had what looked to be 4 relays or some type of solenoids in there.

    The 220 runs directly from that controller/timer into the "heat stick", but the water pump for the filter and air pump for the jets, have plugs on them that look like regular extension cord 3 prong plugs and they plug into thsi box and then inside the box they are hardwired back into the service. I traced them back into the controller and the green goes to ground the white ties directly into the white (neutral) of the 220 circuit and the black wire(hot) goes up into the relay/solenoids.

    I can see on the pump it's rated for 115V, so it must be running on 110, as well as the air pump. These wires with the 3 prong plug on them are standard gauge, like you would find with any extension cord, so I can only assume they are not running 220, also since the pump label specified 115V.

    I can see a transformer inside this box as well, and figured it was what was stepping down the 220 to 110, but now that you say it, it looks like both 220 hot's are running into the heat stick and the pump and air pump are getting only 1 hot wire, meaning they would only get around 110 right?

    Anyway, he did mention that somebody told him about a GFI, but isn't the breaker basically a GFI in and of itself or is there a separate GFI that needs to go in somewhere?

    I didn't notice anything in the circuit anywhere, other than the main breaker, unless I either missed it or it's in that controller/timer box and maybe what I thought were relays were GFI's??

    Thanks for the info guys, any more help would be greatly appreciated.
  5. SgtWookie


    Jul 17, 2007
    I'm NOT an electrician! I just want to make that clear.

    GFCI breakers are different from conventional circuit breakers, and considerably more expensive.

    Conventional breakers generally "trip" in one of two ways:
    1) In response to a moderate overload over a period of time.
    2) In response to a high overload over a very short period of time.

    A conventional circuit breaker might sell for between $3 and $10, depending on the current and voltage rating.

    A GFCI breaker, in addition to the trip modes above, will also trip if current in the ground circuit above a certain level is detected, usually a few milliamps. Such breakers are considerably more expensive; more in the range of $30-$100.

    What is the amp rating of the 220v breakers in the separate panel?
    How was the separate panel supplied; from the main bus in the main panel, or does it have it's own drop/feed?

    Were there any individual breakers where the pump and air pump plug in?

    If the 220 breakers are rated 15A, then there wouldn't need to be additional breakers where the pump and air pump plug in; however that should at least have a GFCI outlet (much cheaper than buying GFCI breakers). But the GFCI outlet needs to have at least as high rating as the 220 breakers do.

    If the 220 breakers are rated in excess of 20A and there are no breakers where the outlets for the pump/air pump plug in, you need an electrician to come over and look at it.

    Everything that is in a circuit must be rated to carry the current that's specified on the breaker that is between the device being powered and the bus. For example, you can't use an outlet rated for 15A on a 20A breaker; you would have to use a 20A rated outlet.