Tankless Water Heater

9 Responses to “How Can I Tell If I Have 200 Amp Electrical Service?”

1. Electrical Inspector
   January 8th, 2010 @ 11:29 am

   The size of your service is determined by two things; the Main Disconnect (Breaker) ampacity, and the size of your service entrance conductors. For example; you could have a 200 amp panel and main breaker, but have only #6 AWG Service Entrance Conductors left over from an old 60 amp service. No matter what size panel you install, those number 6 conductors will burn up before they give you anything close to 200 amps. This is why it is important to know the actual electrical “load” required by your home.
   I have never, ever seen a residential appliance that requires 200 amps. Somehow, I think you have miss-stated or misunderstood something in the installation instructions.
   Most tankless water heaters I’ve seen require no more than a 60 amp, 240 volt feeder circuit. I’ve seen some as low as 40 amps.
   If the Manufacturer specifically states a 200 amp service is required to the dwelling, NEC 110.3(B) requires that a minimum 200 amp service be installed. If it is a recommendation, a 100 amp service may be okay, if you have a small house with no other electrical heating appliances (stove, furnace, cook top, oven) and no other large loads like a pool pump or spa.
   The only way to be sure is to hire a QUALIFIED, licensed electrician to do a load calculation for your home. Have him use the “Standard” load calculation from NEC Article 220, parts II & III; rather than the “Optional” method from part IV. The “Optional” method will often give you a lower figure for your required load, but the “Standard” gives a little more “room” for future additions to your electrical system.
   If you have a very large home, or, in your specific case, an “all electric” home [with lots of "add-ons" already (pool, spa, steam-room, etc.)], you may find a 400 amp service is required. This can be done with a “poor-man’s 400″, which is actually a 320 amp meter and two 200 amp panels. If you live somewhere that has adopted the 2008 NEC, you can install one of the newly allowed “super-panels” that will give you a true 400 amp service (with 84 breaker spaces).
   Incidentally, “Alvarz” is wrong; the smallest size service allowed on a new home (or installed as an up-grade) is 100 amp. I have seen residences that have 800 amp services (& nearly got lost trying to find my way out).

2. Charles C
   January 8th, 2010 @ 12:50 pm

   Yes you have 200 amp service. Actually two 100amp panels. Tankless water heaters for a house as opposed to a single use like a kitchen sink can draw 200 amps or more.
   but to use the 200 amps for the tankless means you will have no capacity for anything else. this is why tankless are not more popular for replacements, most houses require an upgrade to the electrical service which can be expensive.
   Edit: Jayktee, I went to the UK site and could not find this question under DIY. Perhaps you are lost?

3. Irv S
   January 8th, 2010 @ 4:11 pm

   If the house is all electric, you almost certainly have
   a 200 Amp. Service.
   Those columns of breakers are branch circuits.
   The main will either be in the center at the top of the panel or elsewhere.
   Follow the incoming line from your meter to find the Main(s).
   Note: That tank-less water heater needing 200A.,
   (Are you sure of that?, Sounds excessive.),
   might mean a new service.
   It doesn’t use that 200A. for long, but it might be long enough to trip
   out a 200 Amp service with other loads imposed.
   Get the system evaluated before you pop for that heater.
   Any wiring changes should be part of the installation contract.

4. alvarz
   January 8th, 2010 @ 4:52 pm

   you have a standard electrical service. It is 100 amps at 240 vots.
   the voltage is Split into two hot wires. each is 120 volts at 100 amps
   the power company does not supply houses with any more than that.
   I dont know where you got all those figures from but you are good to go for a tankless hot water heater.
   Get it installed by a liscensed electrician/ and a liscensed plumber. you will need to get a permit for the changeover and it will have to be inspected.

5. brndnh72
   January 8th, 2010 @ 9:32 pm

   it looks like you have a 100 amp panel and most likely a 100 amp subpanel which is fine even though that seems a little funny, you would have to upgrade everything for a 200 , a new panel , meter socket outdoor wiring and grounding system, you are looking at around $2500 for the whole thing , i dont recommand changing your panel just for the hot water it isnt worth it we have done this for people and they end up regreting it

6. Bill P
   January 8th, 2010 @ 10:06 pm

   I really don’t know why you have two 100 amp breakers in the panel, usually there is on double breaker which says 100 or 200 on the double breaker.
   I would go outside where the meter feeds the house there should be a breaker box or a fuse box there. That should have a correct size on it.
   Hope this helps

7. Jim W
   January 9th, 2010 @ 4:13 am

   Call a qualified professional electrician, only an on site inspection can verify the type of service you have. Even if your panel is a 200 amp panel, you may not have a 200 amp service.

8. lost soul
   January 9th, 2010 @ 6:36 am

   not necessarily, read the buss bar.

9. jayktee9
   January 9th, 2010 @ 12:47 pm

   Ask this on Answers US site- this is UK and Ireland.

Leave a Reply