Water heater with solar setup

[justinm001]

I don't have a shower in my RV yet and plan on adding soon along with a hot water heater. I seem to make quite a bit of excess solar and have seen others use their excess solar to heat their water tanks. The problem is I take showers in the morning so the water would likely need to stay warm all night, which might not be possible.

Space is also a concern as I don't want a huge water tank taking up a lot of my storage. So I'm thinking about using a tankless along with a tank but unsure if the tankless should be before or after the tank or if its even possible to use tankless as I'd like a fancy shower with high GPM. I have one of these laying around I could use but is 30amp and only .68gpm.

Rheem Performance 3.5 kW 0.68 GPM Point-Of-Use Tankless Electric Water Heater RETEX-04 - The Home Depot

Get hot water for your home, office or remote space with this Rheem tankless electric water heater. This energy-efficient water heater delivers an endless hot water supply and consistent temperature with

www.homedepot.com

Maybe scrap the tankless idea, get a custom 10gal very well insulated tank built and have a 48V 1500w heater element and 2 120v 1500w hot water heater elements installed. Have solar run excess to 48v all the time then shore/inverter heat the other 2 when I turn it on.

I'm unsure how realistically hot water lasts and how long it'll take to heat up. Also unsure if there's other options like hydronic that I should consider. Cost isn't nearly as important as comfort, convenience and optimizing space.

 

[efficientPV]

Point of use tanks are worth considering. I use a Boach ES2 which is only 2.5 gallons in series with another tank. 4 and 6 gallons are available. A small tank heats up fast and with a 120V element it can also plug in any AC. I run mine off 60VDC array voltage, I assume you have at least that much. I have 2 hot showers in the morning with heating from the day before.

 

[justinm001]

one of my goals is to optimize space in this coach, especially basement bay space. Above my black tank 28x36x24 there's about 8" of space so thats at least room for 20gallons in a custom tank and room for extra insulation. Plus it'll be nice to have a warm tank above the black tank to keep it from freezing in winter.

I'd like to build something where I wouldn't worry about usage and can have a nice shower head with normal 2gpm flow so if half hot half cold 10 minute shower would use 10gal hot, i'd think. From my reading most solar RVs are charged up by noon then afternoon solar is wasted while in float then morning replaces overnight usage. This means my solar would want to keep water hot for 24hours.

So I guess my question is would it be possible to heat my water to 160deg after 24 hours its around 130degrees? If I can do this with excess solar then I can set my 120V to 120deg then in theory it'll only kick on after I take a shower when switched on.

Also i'm reading it 2.47wh per gal per degree so 247w to raise from 1gal 50deg to 150deg and 5000w for 20gallons. I'll have 3600w solar so with other usage it'll be about 2 hours of sun to heat the water. This seems perfect for my needs as without AC/heat i'll have tons more than that.

 

[efficientPV]

My experience is 2.8W/degree is typical which includes some heat loss. One comment is horizontal tanks are poor due to cold mixing with hot. If something is made custom, include some baffles to make the path long so mixing doesn't occur.

 

[Aussieguy]

seeing as you are adding the shower...

use a LOT of insulation around the heater and the pipes.
we use to have OFF peak hot water tank with good insulation we could last all day until the next night

If you got sewer connection to the RV..... great to have nice hot long showers
if you are on gray tank ..... watch your water usage and have a tote.

 

[SamDeleted]

if you are on gray tank ..... watch your water usage and have a tote

Or just leave the tap open lol

 

[justinm001]

I'll be going with pex-a which I've already replaced the bathroom with and will be putting heat wire in the piping with a lot of insulation.

Seems I have about 100gal grey/black combo tank, which is perfect for our day/weekend camping.

Good thinking about the horizontal tank. I have a couple other spots that'll work. They had a 2.5gal tank before just for the sink I ripped out. It'll be some square tank with foam insulation up against the walls of my basement that has closed cell foam insulation.

 

[0truck0]

Seems like my water tank (typical RV propane/electric 6-gallon) would stay hot or warm all day. I used to heat it at home on shore power then have hot water that night after travels. I did not add extra insulation either so that is a good idea to make it last longer.
I use a much more cumbersome method now, but it works for me...

 

[Aussieguy]

Or just leave the tap open lol

only if parked on grass
otherwise too easy to get caught on a concrete pad

when we was kids had a outside bucket.... for the kitchen sink.
always overflowed and the whole park was a smelly slop bucket.

 

[justinm001]

only if parked on grass
otherwise too easy to get caught on a concrete pad

when we was kids had a outside bucket.... for the kitchen sink.
always overflowed and the whole park was a smelly slop bucket.

Mine has a dump button right on my dash so could be like Dave Matthew's bands bus and just dump while driving. Lol I'm totally kidding.