Installing Tankless Hot Water System - Amp Questions & Using AWG 6 Wire with Current Tank

Question

I'm looking into researching about installing a Hot Water Tankless system.

Specifically I want to install the following:

Rheem Tankless Water Heater 2.14 GPM 13 kW Self-Modulating Electric Wall Mount

It has the following power requirements: (RTE 13)

I had a few questions:

Lets start with the obvious, I'm not 100% my service is adequate. I have 100Amp service in a 1 Bedroom trailer that utilizes Electric Heat. I have 2 20Amp breakers dedicated to two different Electric Baseboards as well as the usual appliances. As it is a one bedroom it isn't often that many appliances are being used simulataniously, but I do want to be not tripping anything just by using hot water + heating the home.

• Can my setup handle this hot water tank?

Here is an image of my breaker and the panel breakdown:

If so, perhaps this should be a seperate thread, but I'm just putting it all ine one for now....

• Can I upgrade the current wire to AWG 6 and the breaker to 60Amp and hook that up to my current hot water tank system. The reason being I'd like to get the wiring/breaker setup so that when I go to install the tankless system it's "plug and play". I'm not sure if the different thickness of wire and size of breaker will matter if I am using a higher rated wire/breaker than needed. I'm guessing people just don't go higher because it costs more, but I'm not sure.

Answer 1

Can you install 6 AWG Cu wire?

Or 4 AWG Al wire? You bet, that'll be fine. Upgrade away. You are always allowed to oversize wire.

Further, at these large sizes, the new aluminum AA-8000 alloy is perfectly accepted. It's legal all the way down to 15A circuits, but home inspectors will start writing nasty-grams in your buyer's report if they see it below about #4 size.

Can you upsize the breaker on the existing appliance?

No No No No No.

Breakers don't just protect wires. They also protect appliances.

You need to follow the appliance's instructions and labeling and fit the breaker they tell you to. Or find its actual watts/VA/amps, convert to amps, derate by 125% and use the next breaker size up, and wire appropriate for that breaker. 4 AWG Al is appropriate for a 20A or 30A breaker (way too big, but as said, bigger is fine.)

Is your panel ready for this heater?

Do you have the physical breaker space? Yes, because you'll pull the existing water heater breaker.

Does your panel have the capacity? That is a sobering question given your panel's present loads. I don't have the expertise to answer that.

AFCI outlet

A GFCI outlet is alright. An AFCI outlet is worthless. AFCIs protect the wiring in the walls not appliances (except they are rather useful for electric blankets).

There are only two places AFCI protection makes sense: at the breaker itself (and QO certainly makes that). Or just past the breaker at a receptacle or deadfront, which may be cheaper by enough to justify a short stick of EMT conduit to a metal junction box.

Answer 2

Being a small home and only seeing 2 circuits (240v baseboard 20 amp heaters) you would be pushing the service, but it might work, you would be removing the double pole 20 in 1-3 and installing the 60 amp or going from 5kw to the new 13kw or April 8 kw higher draw or approx +33 amps while in use compared to the old one. We don’t actually add the breakers to figure out the total load on the service, where I could see a problem in the winter when you need full power on the water heater with the 2 base board circuits running the actual draw there could be right around 80 amps having the dryer or oven going along with some lights and you may trip the main. So it is very close. I would want to monitor the power usage with the above turned on and see what the actual draw is before saying yes or no.