Plausibility of 2 gallon electric hot water heater?

softdown · August 2017

Living in one of the coldest regions of the continental U.S., solar often falls short of providing water suitable for washing. Being a camper at heart, I don't need a lot of hot water. Laundry is done at my Denver bungalow every two weeks. I like to wash more than every two weeks of course. Having spent 14 months in various casts after a significant climbing fall, washcloth bathing is pretty familiar.

I could not resist an older 2 gallon unused, still in the box, Reliant electric hot water for less than $50. It consumes 1400 watts but is insulated and is a small 2 gallon unit. Convenience lies in simply plugging it in. The heating element carries a lifetime warranty which means nothing at this time other than pointing at a somewhat likely robust heating element.

I plan to gravity feed it from my 200 gallon holding tank. The hardware store plumbing guy sold me two brass 1/2" male to male fittings for the inlet and outlet at $4.50/each. Perhaps possible corrosion issues makes this a wise choice? I already have 1" Spears valves to control water flow. Plus T's and hosing. So hooking it up looks like $9 for the brass fittings...so far.

Experienced off gridder's see a problem with this? Perhaps I should put a timer on the electric plug and only run it during solar hours.......

My unused propane hot water heater is 50 gallons and would consume a lot of propane.

jonr · August 2017

Running it during absorb makes the most sense to me, although it only needs ~.3kwh. Maybe build a foam box for it and fill it with cellulose to reduce cool down.

softdown · August 2017

jonr said:

Running it during absorb makes the most sense to me, although it only needs ~.3kwh. Maybe build a foam box for it and fill it with cellulose to reduce cool down.

That sounds quite logical though I am not temperamentally suited to baby sitting the unit so closely. I already have too many items to babysit.

Estragon · August 2017

+1 on the insulation. A small water heater will have relatively large standby losses because of the surface area to volume ratio.

softdown · August 2017

Estragon said:

+1 on the insulation. A small water heater will have relatively large standby losses because of the surface area to volume ratio.

Agreed....and I have veritable roomful's of insulation. Plus I don't have to worry about "cooking the unit" like it is possible to do with refrigerators that may use various construction techniques.

BB. · August 2017

Spear seems to make only PVC/CPVC material valves rated for 73F nominal maximum temperatures (i.e., cold water only). You will probably need a "heat trap" of some sort to prevent the heat from rising up to the voltage (i.e., both cold water and hot water pipes should go "up" to the heater (or, for example, up the sides of the water heater to the top, if top pipe connections). This will keep the cold water valve cool, and prevent hot water from "leaving" the hot water tank and costing you wasted energy.

Also, if I recall correctly, you have very cold weather/winters... Ability to drain system/preventing freezing will be important too (not that a guy from sunny California needs to tell you this

).

And the Brass couplings (and 6" of brass pipe or so) is a good transition from iron pipe (and water heater tanks) to copper systems (if not using a dielectric union).

-Bill

softdown · August 2017

BB. said:

Spear seems to make only PVC/CPVC material valves rated for 73F nominal maximum temperatures (i.e., cold water only). You will probably need a "heat trap" of some sort to prevent the heat from rising up to the voltage (i.e., both cold water and hot water pipes should go "up" to the heater (or, for example, up the sides of the water heater to the top, if top pipe connections). This will keep the cold water valve cool, and prevent hot water from "leaving" the hot water tank and costing you wasted energy.

Also, if I recall correctly, you have very cold weather/winters... Ability to drain system/preventing freezing will be important too (not that a guy from sunny California needs to tell you this ).

And the Brass couplings (and 6" of brass pipe or so) is a good transition from iron pipe (and water heater tanks) to copper systems (if not using a dielectric union).

-Bill

Could we get a little more technical? Though you likely saved me some grief while pointing out the curious rating for the Spears valve. PVC valves are frequently uses in irrigation and aquariums. So I will use a brass valve,

There will be no real system. Just gravity feed from the holding tank...the temperature in the sunroom never drops below 38F that I recall. Warms up nicely during the day since this area is rated as an alpine desert....very sunny.

jonr · August 2017

A timer on from 3pm to 3:30pm is probably "good enough".

softdown · August 2017

jonr said:

A timer on from 3pm to 3:30pm is probably "good enough".

Almost always in Float by noon. Right now I would lean more towards ~ 11am - 1pm.

It has no thermostat setting. It probably runs much hotter than I need for bathing.

I have no real expertise on my Absorb and Float cycles. Having installed the electronics in a cool, dark spot that takes an effort to get to. Some people study their charge controller doing it's work, I do not.

Estragon · August 2017

IIRC, anything over 120°f is a scald hazard.

Photowhit · August 2017

If you have abundant sun and your talking about using where you have the signature setup...

You could just run a full size water heater, put a timer on this or a full size water heater. I have been running a 3600 240 water heating element off of 120 (at @900 watts) for 5 years. It's worked out okay, Takes perhaps 4-5 hours in the summer when in coming water is warm and 7-8 maybe in the winter when water comes in very cold. You could setup a 'holding tank' inside to preheat the water to inside temps.

jonr · August 2017

That makes sense to me (other than the cost of a larger tank). With lots of excess power, I'd enjoy real showers and use the 2 gallon tank under some sink.

softdown · August 2017

I have an unused 50 gallon propane tank that some bloke talked me into. Everything freezes for six months out of the year...except for the bedroom and sunroom. The sunroom dips into the 30's, when I am making breakfast , at times.

People think I have a life of leisure because of good solar and a large "place"....it is actually a shop. They could not be more wrong. I am simply tired of a lot of people and idiotic government. I would rather be poor than graft a higher income from such.

bsolar · August 2017

thats still alot of watts .. i have a '600 watt' single element in my regular 30 gallon heater .. works fine ..heats faster than you might think, 2 hours or so ..

Photowhit · August 2017

bsolar said:

thats still alot of watts .. i have a '600 watt' single element in my regular 30 gallon heater .. works fine ..heats faster than you might think, 2 hours or so ..

I'm calling Bull, I have a 900 watt element in a 30 gallon tank and in 2 hours it can not raise water more than 10 degrees or so per hour...

Here is a chart of the rough amount of energy required to increase water by volume of the tank in 1 hour, they show 1.6 Kwh for a 20 degree rise....

http://www.tempco.com/Engineering/wattage_estimation_tables.htm

mike95490 · August 2017

In a water heater, you get a pool of heated water floating at the top of the tank. It starts off just as a gallon, then 2. The lower part of the tank is still cold

littleharbor2 · August 2017

mike95490 said:

In a water heater, you get a pool of heated water floating at the top of the tank. It starts off just as a gallon, then 2. The lower part of the tank is still cold

Which is why the cold water inlet goes to the bottom of the tank and the hot outlet draws from the top of the tank.

BB. · August 2017

Most full size water heaters have a "dip tube" that runs from the inlet on the top to the bottom of the water heater (puts the cold water at the bottom and prevents mixing cold and hot water).

Sometimes dip tubes fail and water heaters seem to have much less hot water capacity because of the broken dip tube.

-Bill

softdown · August 2017

A neighbor started using an "instant on" with a 5 gallon propane bottle and is happy. Those instant on's cost more than regular water heaters as I recall.

Since I have this little tank, I may as well use it. I can take nice big showers in Denver bungalow.

littleharbor2 · August 2017

I have one of the cheapest, lowest output "instahot" type propane powered water heaters. It sells for less than $100.00. It has never failed to operate and works great. Granted it only heats fast enough for a single load. Ours is used for a outdoor shower on our RV. They come in a wide variety of outputs and price ranges. We have a Bosch brand at our Baja house. They are a bit more expensive.

mcgivor · August 2017

littleharbor2 said:

I have one of the cheapest, lowest output "instahot" type propane powered water heaters. It sells for less than $100.00. It has never failed to operate and works great. Granted it only heats fast enough for a single load. Ours is used for a outdoor shower on our RV. They come in a wide variety of outputs and price ranges. We have a Bosch brand at our Baja house. They are a bit more expensive.

With regards to Bosch instantaneous water heaters, keep your purchase receipt for warranty claims, the heat exchanges are prone to failure by leakage, the warranty is good, as long as the reciept is available, based on experience, 3 failures in 3 installations, same problem.

littleharbor2 · August 2017

mcgivor said:

littleharbor2 said:

I have one of the cheapest, lowest output "instahot" type propane powered water heaters. It sells for less than $100.00. It has never failed to operate and works great. Granted it only heats fast enough for a single load. Ours is used for a outdoor shower on our RV. They come in a wide variety of outputs and price ranges. We have a Bosch brand at our Baja house. They are a bit more expensive.

With regards to Bosch instantaneous water heaters, keep your purchase receipt for warranty claims, the heat exchanges are prone to failure by leakage, the warranty is good, as long as the reciept is available, based on experience, 3 failures in 3 installations, same problem.

In my case one came with the house,(no receipt), still works, I bought a brand new one for $50.00 from another homeowner in Baja. He installed a new shower valve and tiled the shower, only to find the flow rate of the shower isn't high enough to spin the heaters impeller fast enough to generate spark. I would have removed all water saving features of the shower valves/head. He gave me an extra copper heat exchanger as well, but no receipt as far as I know. I will look through whatever paperwork I may have gotten with it. It has been sitting for over a year now and I don't recall if I ever did get paperwork.

Marc Kurth · August 2017

Must be the Mexican water

littleharbor2 · August 2017

Marc Kurth said:

Must be the Mexican water

Bad stuff, that Mexican water. Especially the brackish stuff in our campo's well. Its below sea level. Surprisingly it works fine for showers, dish washing and laundry.

softdown · August 2017

littleharbor2 said:

Marc Kurth said:

Must be the Mexican water

Bad stuff, that Mexican water. Especially the brackish stuff in our campo's well. Its below sea level. Surprisingly it works fine for showers, dish washing and laundry.

I often wonder what happens when saltwater is used for showers, dish washing, and laundry. Other than leaving some salt and calcium residue...

Sailors did not often have the luxury of freshwater until pretty recently. I do not recall saltwater R/O systems being viable even 30 years ago. Though their only real difference is running at 800-900psi instead of 40-125 psi. Brackish R/O systems are run at pressures commensurate with the level of salinity of course.

Estragon · August 2017

Some boats have RO waremakers, but most just have freshwater tankage. A quick freshwater rinse after seawater wash does the job.

The main problems with seawater are; it promotes corrosion, and the head gets smelly.

littleharbor2 · August 2017

softdown said:

littleharbor2 said:

Marc Kurth said:

Must be the Mexican water

Bad stuff, that Mexican water. Especially the brackish stuff in our campo's well. Its below sea level. Surprisingly it works fine for showers, dish washing and laundry.

I often wonder what happens when saltwater is used for showers, dish washing, and laundry. Other than leaving some salt and calcium residue...

Our brackish water isn't drinkable, obviously. For dishwashing We do need to towel dry our dishes and silverware to avoid haze and spotting. For showering it doesn't seem to be a problem. shampoo and body wash works just fine. Again towel drying is recommended, lol. The washer and dryer are going to be added next month but many of our friends and neighbors use clothes washers regularly. I imagine they might not last as long as if they were used with pure fresh water.

jonr · August 2017

Sounds like a low salt concentration which could probably be removed with common residential RO systems (up to 100 psi).

bfitzgerald · October 2017

There are many opinions on the subject of hot water heating in off grid systems. Because solar electricity is not cheap to generate, most people will consider using only the free, excess power to heat water. That's what I do. We have an off grid seasonal cabin, used continously May - October (5+ months ). We use propane for the stove/oven and for water heating. Prior to switching to our hybrid electric/LPG we used only the Atwood propane water heater. We could run the heater for about 3 weeks on a 20 lb tank unless there were lots of people (more than 6) at the cabin. We have a dishwasher which we use every day or two, depending on number of people. My best estimate is that we used from 1 to 1.5 lbs. of propane per day, probably 80% of it for hot water. Showers are not normally a big consumer of hot water. We have a wood fired hot tub and a clean but cold lake. Most people, but not all, find that sufficient for keeping clean but people can shower anytime they wish.
Since installing our opportunity hybrid system, our propane use is now 100 lbs per 150 days, or about 1/3 lb per day. (Stove and hot water heater now run off of one 100# tank.)

My system consists of the following:
Schneider XW 4548, Schneider MPPT 150-60, 3000 watt array, 16 - US Battery 420 ah L-16's, Atwood 6 gallon LPG water heater (pilot light model), GE 8 gallon 120v (1500w) water heater, 12v activated 120v 1500w ac relay.

The electric water heater feeds the propane heater. I keep the thermostat on the propane heater colder (but still plenty hot) than the non adjustable electric heater. From May thru August 90% of our hot water is solar generated. Thay percentage drops pretty quickly as the days get shorter, but that is included in my averages. One thing to note is that I use the pilot light model Atwood heater. The pilot alone keeps the water hot, in fact hotter than the reduced thermostat setting. I don't know how much propane the the pilot uses, but it can't be much.

The electric heater is controlled by the relay which is controlled by the charge controller. I have it set to turn on the heater when the batteries reach 60 volts (absorb setting) and turn off at 49.9 volts, .1 volts below the recharge setting. I have kept a very watchful eye on the batteries, checking SG regularly and they seem to like this setting. The heater never comes on at night or if is really cloudy but the gas heater takes over seamlessly.

We use between 9 - 12 kwh per day, the variables being automatic dishwasher, laundry, and extra running of the water pump (220 volt submersible) to change the hot tub water (500 gallons). We can manage consumption during cloudy periods, the dishwasher, for example uses 2 kwh between washing and heating water. Some might say that they want or need more hot water capacity, but we find that we have plenty and never run out.

This setup works pretty well for our system and needs. I hate hauling propane all by boat or over the ice in winter. One tank a year now.

Brian

westbranch · October 2017

If you have any amount of hardnwess to your water you wn=ant to make sure you hae a TOP LINE water softener otherwise the warranty on your Instantaneous heater can be voided.. My experience- 3 high efficiency DHW heaters and all failed, the one with a small tank < 10 Gallons (Lenox Complete Heat now discontinued) and a couple of Korean with a ''10 year warranty'' that suddenly was in jeopardy as the water softener was failing to do the job on 64 grains of harness plus 5 grains of dissolved IRON from a FeRO-Bacter... bad stuff on porcelain.
toilets!
Stick with the old style tanks..

softdown · October 2017

Surprised to see some action on this old idea. I have decided that heating water with propane is so comparatively fast and efficient that I will likely continue doing it that way.

I have six large solar water "heaters"...........4' x 10' I think. I should get off my rear and get at least one working. Made in the 80's......good chance they would still work I think. Unless the interior copper piping ruptured....which is always possible.

Plausibility of 2 gallon electric hot water heater?

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