You are talking about taking almost 40AH from your house bank to take a 15 minute shower. If your bank is 200AH that’s a 20%. Not sure if you have flooded lead acids or AGMs, but they are around 300-500 cycles. So it’s a safe bet that after 300-500 showers you need to buy new batteries. If your bank is 400AH like mine, you could potentially double the amount of showers. Also 400AH agm bank is more than 1000$.
As Josh said, inverters are very lossy abut 30-40% of energy is lost. In addition sinusoid produced is hardly that of a 120V residential AC supply. Granted heater is just a resistor but its unclear what kind of control mechanism and electronics they are using to monitor heating and overheating etc. If things don’t seem to work as expected that would be my first point to check. On the other hand, 12V heating elements are not powerfull enough for instant water. You need about 2000W hating element at 12V. I don’t believe that exists. Few years ago I searched for 12V heating element replacement for 6 gal seward products water heater. I was able to buy 450W 12V element on ebay that I fitted into the tank instead of the AC element. It never heated any water but I was not expecting it. I am using to dump access wind generator power on sunny days when solars have already filled the house bank. Petar Horvatic Sundowner 76 C&C 38MkII Newport, RI From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Josh Muckley via CnC-List Sent: Wednesday, September 02, 2015 10:38 AM To: C&C List Cc: Josh Muckley Subject: Re: Stus-List Hot water tank I did some rough math and it looks like you'll need ~38Ahrs of power for a 15 minute shower. Your inverter will be drawing 150amps through the supply wires and your alternator would have to recharge that amount. With the stock alternator (35amps) it would take over and hour. I do think I remember you having an upgraded alternator. Of course the assumption was that the hot water was at full flow for the 15 minute duration. The instant waterheater is just a resistive load. It would be more efficient and possibly safer to eliminate the inverter from the picture. It would take some electrical and electronics skills to re-engineer the unit to run on 12v instead of 120v. That new water heater really is shockingly smaller. You'll have to let us know how it turns out. Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Aug 31, 2015 10:15 AM, "Edd Schillay via CnC-List" <cnc-list@cnc-list.com> wrote: My hot water tank was failing as well and I’m in the middle of putting in a replacement — the hard part was getting the old one out of the tight space under the galley. I decided to go with an on-demand water heater which will either be powered by shore power or an inverter (2000W) while the engine is running. Here’s the one I picked: http://m.rakuten.com/product/263816304?listingid=337903396 <http://m.rakuten.com/product/263816304?listingid=337903396&adid=29963&sclid=pla_google_Zoro> &adid=29963&sclid=pla_google_Zoro And here is old and new side-by-side: https://dl.dropboxusercontent.com/u/15162917/ENTERPRISE/heaters.jpg I’ll try to finish it up over the next couple of weeks, but if not, it’ll be a quick winter project. All the best, Edd Edd M. Schillay Starship Enterprise C&C 37+ | Sail No: NCC-1701-B City Island, NY Starship Enterprise's Captain's Log <http://enterpriseb.blogspot.com/> On Aug 30, 2015, at 11:13 AM, Josh Muckley via CnC-List <cnc-list@cnc-list.com> wrote: In most of the little hot water tanks the anode is part of the hot water outlet nipple. Follow the link for pictures of the tank rebuild I did. https://drive.google.com/folder/d/0B8pEh5lnvP1ydEpoMU1MWmx6Qms/edit Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Aug 30, 2015 10:26 AM, "phorvati . via CnC-List" <cnc-list@cnc-list.com> wrote: And make sure you have zinc anodes. Electrolysis will eat something. On Aug 29, 2015 8:51 PM, "Jim Watts via CnC-List" <cnc-list@cnc-list.com> wrote: Put a meter on it and read what kind of voltage you are getting. 110V AC does not generally give little shocks. Jim Watts Paradigm Shift C&C 35 Mk III Victoria, BC On 29 August 2015 at 16:15, Michael Crombie via CnC-List <cnc-list@cnc-list.com> wrote: I'm working my way down my project list and finally got to my hot water tank. The PO just told me that it didn't work. I was getting 120V at the heating element so I checked the element and it was fried. I installed a new element and turned it on for a test. Got hot water after about 10 min, so I went to close everything up. But when I was doing that I touched the pressure relief valve and got a small shock. The green ground wire runs to one of the mouting bolts on the heating element and also to the water tank frame. So that seems ok. I also checked for continuity between the hot and neutral wires and the relief valve or frame and got none. So i'm puzzled. The shock wasn't big, but i definitely felt something. Any ideas??? Thanks, Mike Atacama 33 mk ii Toronto Sent wirelessly from my BlackBerry device on the Bell network. Envoyé sans fil par mon terminal mobile BlackBerry sur le réseau de Bell. _______________________________________________ _______________________________________________ Email address: CnC-List@cnc-list.com To change your list preferences, including unsubscribing -- go to the bottom of page at: http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
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