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-   -   Help Needed Choosing 220v or 120v Tankless Water Heater and Proper Amperage (http://www.diychatroom.com/f18/help-needed-choosing-220v-120v-tankless-water-heater-proper-amperage-162624/)

wonderworm 11-08-2012 04:38 PM

Help Needed Choosing 220v or 120v Tankless Water Heater and Proper Amperage
 
The water heater that feeds a clothes washer and a kitchen sink went out and I'm going to replace it with a tankless.

I have both a dedicated 120v line with a 30amp breaker to use or I can have the electrician tap into the 220v line that powers the living room airhandler.

My question is this: The current breaker on the 220v line is 30amps. The 220v tankless needs up to a 60 amp breaker. If an electrician taps into that 220v wire and adds the 220v tankless on it, can he then just upgrade the total amps on the breakers to 90amps to ensure that both can run at the same time without tripping the breaker?

jbfan 11-08-2012 04:51 PM

You are going to have to run a new circuit for the water heater.

wonderworm 11-08-2012 05:06 PM

So when you mean run a new circuit you mean I need to buy about 60ft of 240v copper line and run it behind all the sheetrock to the breaker box to create a dedicated line to the breaker box??

Isn't there another way to use a 240v tankless? The room it will be in is a utility room that has 240v line going to a dryer, the furnace, and small air handler for just the living room. Per the breaker box, I have dual pole 40amp breakers for the furnace and dual pole 30amp breakers for the air handler.

If I can't do that then my other option is to use the dedicated 120v line which currently powers the 40g water heater. This line is on a 30amp dual pole breaker so it will work if I buy a 110-120v tankless but from what I have read, i'm worried that the 120v tankless will only push warm water (not hot) when washing clothes since clothes washers use 2-2.5 gpm usually.

Anyone know the GPM flow for those new energy efficient front loading washers? Maybe a 120v tankless will be enough for one of those front loading washers.

Dave632 11-08-2012 05:08 PM

I'm confused. (Not a rare occurrence :))

How can a tankless heater be OK on a 30Amp 120V circuit, yet need 60A @ 240V?

Jim Port 11-08-2012 05:12 PM

You may need to upgrade your entire service to allow the tankless to work.

The current water heater is not 120 if fed from a 2 pole 30 amp breaker.

wonderworm 11-08-2012 05:17 PM

Quote:

Originally Posted by Dave632 (Post 1047549)
I'm confused. (Not a rare occurrence :))
How can a tankless heater be OK on a 30Amp 120V circuit, yet need 60A @ 240V?

I haven't bought the tankless yet.

My choices are to buy a 240v tankless that requires 50-60amps

Or to buy a 120v tankless that requires 30amps.

There is already a 120v wire going right to the spot and this would be the easiest install but I'm worried that it will be too weak to provide hot water to a clothes washer. It would provide heat to a washing machine and 1 sink.

If I buy the 240v tankless, I would tap into the furnaces 220v line (about 4 feet away) and then upgrade the breakers to something alot higher than dual pole 40amp. (I'm asking if it's feasable to go the 240v route or if a 120v may be sufficient).

wonderworm 11-08-2012 05:21 PM

Quote:

Originally Posted by Jim Port (Post 1047550)
The current water heater is not 120 if fed from a 2 pole 30 amp breaker.

Thanks, I think it is 2 pole because it says 30amp and it takes up 2 full spaces in the electrical panel where as other 20 amp breakers are only taking up 1 slot. Is that 2 pole?
For the water heater, the label on it says 120v so I'm assuming it is a 120v 40 gallon water tank. Are most water heaters 220v??

ddawg16 11-08-2012 05:28 PM

I have a feeling that you do not understand ckt amperage and associated wiring.

The 240Vac tankless is going to use about 14,000 watts and would need #6 AWG wire.

The 120Vac unit would use about 3600 Watts and could get by with #10 AWG wire.

If you attempt to install a 50 or 60A breaker for the 240Vac using your existing wiring...you are going to melt the wire and likely start a fire.

Instead or looking at tankless units based on voltage and current, sit down and figure out the potential hot water GPM the washer needs.....then find a tankless unit that will supply that amount....

Once you have that figured out....hire an electrician to hook it up. Not that you can't do it, but it's my understanding that most warranties for those tankless units stipulate that they are installed by a qualified person.

jbfan 11-08-2012 05:29 PM

Most water heaters are 240, but small 6 to 10 gallon one can be 120.
You can not tap into any line and just upgrade the breaker.
The breaker is sized to match the wire and the load.

Canucker 11-08-2012 05:46 PM

Why does it need to be tankless for a washing machine and kitchen sink?

wonderworm 11-08-2012 05:55 PM

Quote:

Originally Posted by Canucker (Post 1047574)
Why does it need to be tankless for a washing machine and kitchen sink?

Long story, but this is just 1 of 5 water heaters in the home and since it is only used sparingly, it seems tankless would make the perfect replacement and not wasteful. It looks like I will just order the 120v tankless. I am in a southern state with warm ground water so hopefully the 120v tankless will work.

wonderworm 11-08-2012 06:01 PM

Quote:

Originally Posted by jbfan (Post 1047565)
Most water heaters are 240, but small 6 to 10 gallon one can be 120. You can not tap into any line and just upgrade the breaker.
The breaker is sized to match the wire and the load.

Looks like the current tank is only 19gallons, not 40 as I thought. It has a single element and that's why it is only 120v.

ddawg16 11-08-2012 06:09 PM

Quote:

Originally Posted by wonderworm (Post 1047580)
Long story, but this is just 1 of 5 water heaters in the home and since it is only used sparingly, it seems tankless would make the perfect replacement and not wasteful. It looks like I will just order the 120v tankless. I am in a southern state with warm ground water so hopefully the 120v tankless will work.

In that situation, tankless makes sense....but you need to determine what your real GPM requirement is...then go from there.

md2lgyk 11-09-2012 08:36 AM

Does your area have natural gas? Gas tankless heaters (I have one) are easier to deal with.


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