Storage hot water system


Bryce Procter
 

I was recently watching a random YouTube where the boat owner was replacing his storage hot water system with an on demand electric heater. I dont like changing Henry's well thought out systems though this did get me thinking. The swap was simple, worked well, saves considerable weight, significant increase in engine room space, low maintenance and easily replaced if and when needed. No doubt some deal breaker downsides I haven't thought of? Any thoughts or advice appreciated.

Cheers 

Bryce Procter 
SV Seamaster ll
SM 2000 #467


Courtney Gorman
 

You won’t get the benefit of free hot water while you’re running the engine or running the generator because you don’t have storage for the hot water


On Jul 22, 2022, at 9:57 AM, Bryce Procter via groups.io <Balibryce@...> wrote:

I was recently watching a random YouTube where the boat owner was replacing his storage hot water system with an on demand electric heater. I dont like changing Henry's well thought out systems though this did get me thinking. The swap was simple, worked well, saves considerable weight, significant increase in engine room space, low maintenance and easily replaced if and when needed. No doubt some deal breaker downsides I haven't thought of? Any thoughts or advice appreciated.

Cheers 

Bryce Procter 
SV Seamaster ll
SM 2000 #467


Chris Paul
 

HI Bryce,

Bryce, I like your idea but, according to my research, it is not practical on a yacht, even dockside. 
You need lots of electrical power to make a fast enough flow of hot water to have a decent shower. 
I did a quick google and found specs for what I think is the type of heater you saw on youtube. 
(Small single phase 240V instantaneous water heater)




This heater requires 7.1KW of power, heats water to 50C and supplies only 1.5 L/min hot water flow (12L/min is normal household shower flow rate). To get a better flow rate requires significantly more power. 

 Problem 1: (Where will you get 7.1KW of power?)
I don't think the ONAN generator could supply that much output power.
If you tried to use the power outlet on the dock it would trip the 16A circuit breaker (About 3KW) . 
Maybe a large inverter could handle 7Kw power surge for a 5 minute shower but 600Ah batteries would suffer.

 Problem 2: (Flow rate)
Even if you find the electrical power, 1.5L/min at 50C is not much water. 


I have been thinking for some time about another system that may work.

I lived in house with a solar hot water system connected to a 300L storage tank that provided hot water, even mid-winter unless the sun did not shine for about 3 days. 
When the water became a bit cold (maybe 30C) I would boost electrically for about 10 mins and the water was hot again.
This system was not cheap to buy, but was cheap to run. I had so much hot water I never felt guilty having long showers.

 

The system below is a marinised version of the house system and also has solar photovoltaic cells. 
If this was installed & connected to the existing HWS I believe it would provide much of the hot water without needing much generator or engine time. 
Anyone cruising summers in temperate latitudes and winters in the tropics, would probably have constant hot water. If the water temperature droped below shower comfort level then probably a short burst on 220V water heater would resolve the issue. 

I am not sure where or how to install such a system (solar arch, railings or above bimini??) but I would be most interested in any thoughts or ideas from others. 



Chris Paul
SV GLAZIG
SM352
NZ








On Saturday, 23 July 2022 at 01:57:13 am NZST, Bryce Procter via groups.io <balibryce@...> wrote:


I was recently watching a random YouTube where the boat owner was replacing his storage hot water system with an on demand electric heater. I dont like changing Henry's well thought out systems though this did get me thinking. The swap was simple, worked well, saves considerable weight, significant increase in engine room space, low maintenance and easily replaced if and when needed. No doubt some deal breaker downsides I haven't thought of? Any thoughts or advice appreciated.

Cheers 

Bryce Procter 
SV Seamaster ll
SM 2000 #467


luvkante
 

Sorry,

I have to be frank:

This idea is, politely said, not very smart.

Martin
AMEL 54 #149 CHIARA


Mark Erdos
 

 

 

While this makes perfect sense for a home, I see a couple of setbacks for an installation on a vessel. The first one being you will not be able to use the engine/genset heat exchanger to heat water. This means having to us electricity. The second thing is the amount of electrical energy needed to instantly heat the water. I imagine it would be on par with an electric kettle - 10 +/- amps at 220vac. Of course if you plan to live on a boat and be plugged into shore-power, this is a non-issue.

 

With best regards,

 

Mark

 

Skipper

Sailing Vessel - Cream Puff - SM2K - #275

Currently cruising - French Polynesia

www.creampuff.us


On 7/22/2022 3:57 AM, Bryce Procter via groups.io wrote:

I was recently watching a random YouTube where the boat owner was replacing his storage hot water system with an on demand electric heater. I dont like changing Henry's well thought out systems though this did get me thinking. The swap was simple, worked well, saves considerable weight, significant increase in engine room space, low maintenance and easily replaced if and when needed. No doubt some deal breaker downsides I haven't thought of? Any thoughts or advice appreciated.

Cheers 

Bryce Procter 
SV Seamaster ll
SM 2000 #467


Craig Briggs
 

I had an on-demand propane unit in the head on a prior boat. Worked great although the temperature control was a bit coarse. Only a few people were asphyxiated by these units.
--
Craig Briggs - s/v Sangaris / SN68  Tropic Isle Harbor, FL


Eric Meury
 

search for my post about converting the elements to a 12/24 volt element.  and rigging the bmv 712 with a battery protect from victron to create an solar dump load of you will.  you will retain hot water via gen or engine as and the excess solar during peak time will create enough electric to keep the water hot each and every day.  worled for us on our santorin


On Mon, Jul 25, 2022, 12:11 PM Craig Briggs <sangaris68@...> wrote:
I had an on-demand propane unit in the head on a prior boat. Worked great although the temperature control was a bit coarse. Only a few people were asphyxiated by these units.
--
Craig Briggs - s/v Sangaris / SN68  Tropic Isle Harbor, FL


Bill Kinney
 

Bryce,

The answer is "it depends."  How do you use your boat?  If your boat spends most of its life connected to shore power, and if that is the only place you want to use hot water,  then an electric tankless water heater can work well.  

For a cruising boat that typically is off the grid, tankless systems are very problematic, no matter what the random youtuber might say.  If powered by propane, you'll be shocked how fast a propane tank empties. That might not be a problem if you are cruising in a populated area, but once you go remote, you'll find it necessary to go without hot water at least sometimes. Safe installation of a propane water heater is not impossible, but it is very difficult. Aside from the issues with additional propane plumbing, you also need to arrange exhaust in such a way that you can be 100% sure it can never be blown into the living space.

If DC powered, you'll put a huge load on your batteries, and if powered by AC, you'll again put a huge load on the batteries, and likely need a significant upgrade to your inverter.  Of course you COULD run the generator  every time you wanted hot water, but that would hardly be efficient or convenient.

Another input for "it depends" is where you use your boat.  For us, we are usually in climates where we don't really care about domestic hot water at all. We have actually been at the dock here in Grenada for about 2 months and haven't even turned on the hot water heater. We find that water coming out of the tap at 30C is quite sufficient for our needs. When we have been in colder climates, our normal cycle of running the generator for 90 minutes every other day gets us all the hot water we need.

Bill Kinney
SM160, Harmonie
Port Louis, Grenada.