Water Heaters.

[doorpro]

Hello all,

It's been a year or two since replacing the 20-gallon water heater aboard the boat so I know that next year or the year after that I'll be doing it again.

So, here's a thought. I have 5 A/C units aboard the boat but only use 4 and I have replaced the ones that get used the most. However, all these A/C units are 220v so I have a spare breaker and direct power feed should I use the A/C circuit that isn't used.

My question is does anyone think that the 220v circuit would handle an On Demand water heater because in the home they're problem free and this would fix my water heater problems that occur every three to four years and of course they're about $1,000 every time I need to buy one. I have replaced the heater myself four times now.

Just to add that a few years ago I pulled one of the water heaters apart to see just where the problem lies and it is basically the aluminum tank inside the heater that has three welded seams in them and it's the weld that fails. I even had a welder look at one and he basically said that these units are built to fail and repairing it wouldn't help as the other welds were also about to fail.

So, I'm sorry if I dragged on but I am really hoping that someone would know if the 22v breaker and circuit would run and on demand water heater Which is much smaller and manageable than the size of the 20 gallon one used aboard these boats.

I hope that I have covered everything, and it looks like the "Amps" needed are the issue. I guess that I should look into the amps pulled on the A/C units and the amps needed to run an on-demand water heater.

Thanks to all.
Regards,
Doug.

 

[alldodge]

It will work, the issue is sizing. Will need most likely need 30 amp breaker for even the smallest unit

 

[doorpro]

Damn that's great news. I have a 50 amp circuit.

 

[cyclops222]

Why not buy a different brand hot water heater the same physical size ? With a better construction and warranty? A normal plumber can help you select a unit to fit. Will check if the USCG has a safety code for Hot Water heaters.

 

[doorpro]

Hello, I had the same idea 5 years ago so did that two heaters ago and the issue was the same. It lasted a tad over three years just as the Attwood HF2000 did. Attwood actually had a three year warrantee until a couple of years ago and lowered it to two years. Coincidence? I doubt that.
Thank you for the suggestion though.

 

[alldodge]

Good thing with boats is the low flow rate, so finding one that can produce the right GPM rate should be easier to find

 

[alldodge]

Moved it to electrical to get more eyes on the question

 

[cyclops222]

We are missing some facts ?
Is this a fresh / drinking water system ?
River water ? Ocean water ? Showers only ?

 

[alldodge]

We are missing some facts ?
Is this a fresh / drinking water system ?
River water ? Ocean water ? Showers only ?

It's a hot water heater

 

[KD4UPL]

On demand water heaters use a LOT of amps. I'd guess your 50 amp circuit is probably minimal but may work. On demand heaters are rated in Kw. The 50 amp circuit is good for 9.6 kw when loaded to 80%. This would be the max in a residential situation. Boat "codes" may be different.

 

[ESGWheel]

Some addition thoughts and a caution, of which you may be aware, but just in case….

With the On Demand Water Heater (ODWH) you will no longer have the advantage of using engine coolant to heat the water as the Attwood HF2000 allows. Perhaps you did not use that feature and always depended on AC to run it.

You will need to be sensitive to the rating (kW and thus current) of the selected heater as highlighted by KD. It’s easy to go large on ODWHs that will be 18 to 20kW which will well exceed 50A draw. Using the 50A breaker you will be limited to a max of about 10kW (Power = Volt * Current > P/V = A or 10,000W/220V = 45A). So, keep this in mind and see if you can determine it will meet your needs.

Also using an ODWH is different. With a typical tank type WH when taking a shower, you turn on both the hot and cold and adjust as needed. Doing this with a ODWH will frustrate the person showing. There are lots of reviews on RV sites about folks installing ODWH only to take them out again because they did not understand how to use it. See this link for a video that explains this.

Caution: do not assume you can reuse the exiting water heater wiring and simply move those wires over to the 50A breaker. The breakers in the panel are to protect the wiring and not the device and by using wiring not appropriately sized for the 50A breaker is dangerous and not to code. So, make using the appropriately sized wiring (it’s a function of both current and length) and the proper type of wire (stranded not solid wire) a priority. If there is any doubt about how to do this best to contract with an ABYC certified electrician.

Lastly, it occurs to me that using stainless steel tank (vs aluminum) would solve the frequent replacement issue. While they are about 2x cost, seems worth it. Interestingly I did not find and “marine stainless-steel tank” water heaters in my goofing around on web. While they have stainless, it was the outside box and not the tank; the tank was always aluminum or coated aluminum. Seems odd to me.

Please post how it goes and the final outcome of what you did and why so others may benefit. Thanks.