Water Heater...

Oscar13601

What are you guys using as far as water heating is concern. I'm thinking on a GAS TANKLESS water heater. What are your thoughts on that setup? I was told that Electric is better, but I'm trying in not to deplete the batteries for this purpose. Any thoughts are appreciated...


OM

PS: I'm thinking also on the stove to be GAS

BB.

Re: Water Heater...

Natural gas or propane?

On grid or off grid?

-Bill

icarus

Re: Water Heater...

Heating water with battery based is hugely inefficient! If you have enough sun to charge batteries, you are way better off building a solar hot water heater, which will be orders of magnitude cheaper,,, and orders of magnitude more efficient in terms of actually heating water.


I suggest a demand gas fire hot water heater. (lp or Nat.) idealizing heating solar preheated water. If, on the other hand, you live in a climate where A/C is used regularly, consiider a hot water recapture A/C system,, one that make your A\C run more efficiently, and give a bonus of " free" hot water.

A location would help folks come up with cogent answers,

Welcome, and keep in touch,

Tony

Just as an FYI, resistance electric heat for anything, is very kwh intense, and is to be avoided with a battery based system if at all possible. Cook with gas, heat water with gas, and heat space with gas (after doing all conservation and potential non PV soar options)

t

solar_dave

Re: Water Heater...

We have a single 4x10 solar thermal plate collector with an 80 gallon storage tank (actually an unwire electric heater). We back up with a high efficency nat gas 50 gallon. We use about 36 therms of nat gas annually.

LucMan

Re: Water Heater...

Oscar13601 wrote: »

What are you guys using as far as water heating is concern. I'm thinking on a GAS TANKLESS water heater. What are your thoughts on that setup? I was told that Electric is better, but I'm trying in not to deplete the batteries for this purpose. Any thoughts are appreciated...


OM

PS: I'm thinking also on the stove to be GAS

Check your water quality before you decide on a tankless water heater. Hard water will require frequent acid flushing of the heat exchanger and reduce service life.

waynefromnscanada

Re: Water Heater...

LucMan wrote: »

Check your water quality before you decide on a tankless water heater. Hard water will require frequent acid flushing of the heat exchanger and reduce service life.

Couldn't agree more. I used to be involved with a few of them and if the water is not both clean and very low in mineral content, the results are VERY unsatisfactory after the first few weeks. Even at the best of times, overall they aren't what they're cracked up to be.

Oscar13601

Re: Water Heater...

This is to be installed in Upstate NY and it gets very COLD in winter. What is really meant by hard water? what system will you guys install that will work? I'm looking at NAVIEN NR 210A tankless GAS...

waynefromnscanada

Re: Water Heater...

"Hard" water, is water with high dissolved mineral content. These dissolved minerals come out of solution when the water is heated, they then coat and build up on the internal parts of the water heater, and depending on the minerals, can be very corrosive as well.
Images of what hard water can do:
https://www.google.ca/search?q=hard+water&hl=en&client=firefox-a&hs=CQq&rls=org.mozilla:en-US:official&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=5xIUUKDkAsmgrAH7_YGADA&ved=0CH8QsAQ&biw=1280&bih=573

westbranch

Re: Water Heater...

we have a Navien, good product, reasonable warranty service, but prone to the 'hard water ' problems as are all the 'instantaneous' heaters.
Our whole house id heated with it as is the DHW... the first unit packed it in in one year 2 years so far on unit 2...
We also have a water softener/conditioner and it is MANDATORY or no warranty!

hth

BB.

Re: Water Heater...

Remember that a tankless water heater cannot withstand freezing unless it has freeze protection--which may or may not work:

Freeze Protection: Takagi has installed freeze-protection devices to help guard against permanent damage to the heat exchanger in the event of below-freezing temperatures. Although these devices will attempt to protect the unit, there is no guarantee that they always will, such as in the case of power loss to the unit. This type of damage is not covered under warranty, so great care should be taken to avoid freezing conditions.

Each unit has a freeze-protection sensor mounted to the fan. It senses the incoming or ambient temperature. When the temperature drops below 37°F, the unit will turn on ceramic heaters located around the heat exchanger and water lines. Again – any type of power failure would cause this system not to work.

In freezing climates where the unit is installed inside, Takagi recommends that the freeze protection sensor be relocated outside if possible or at least attached to a surface that more accurately reflects the temperature of the incoming air. An extension cable is provided with each unit for this purpose.

In addition to the sensor, the backflow preventer (Part No. TV-TV03) MUST be installed wherever air at below-freezing temperatures may be drawn down the exhaust pipe into the heater a backflow preventer used by the venting manufacturer is acceptable. This device shall be installed on top of the heater. Although the backflow preventer helps to limit the flow of freezing air, it does not block all of it. In very cold climates, care must be taken to insure power to the unit, and to eliminate any negative air pressure conditions in the building that would promote cold-air flow in the heater. If this cannot be avoided, the unit should be thoroughly drained to prevent damage.

Also, many tankless water heaters are installed outside--So you have pipe freeze protection to worry about too.

Again, is this a grid tied/natural gas home, or off grid/propane location?

And, how much hot water do you use... Gas Tankless water heaters save money because they sit around "cold" when not used. If you use a fair amount of hot water during the day/night, the actual amount of energy used to heat the water is roughly the same (i.e., both units are around ~80% efficient or so making hot water).

If you are on grid, and have reasonably priced electricity, Heat Pump type water heaters can be very cost effective (typically 2x more efficient than resistance heaters). However, very cold regions/basements (below ~52F?) they become much less efficient and have backup resistance heaters to make up for the cold weather.

-Bill

westbranch

Re: Water Heater...

Navien's heat the DHW directly, and are not recommended to have a fluid other than straight water

icarus

Re: Water Heater...

One of the advantges of the "old fashioned" standing pilot demand water heaters (Paloma/bosch) is that the pilot keeps the water course free from freezing. I turn the pilot off most of the time, but at temps below -20 I will leave it lit over night. I also have a thermal stack damper (not quite legal!) in the flue, which reduces heated air loss from the house, and keeps cold from migrating down the stack.

As for hard water, I have little experience with demand water heaters in such installations, but my guess is that a major issue with a demand, is also likely to manifest itself in a conventional water heater sooner or later.

Bottom line, I have used demand water heaters for over 20 years with no troubles. My original one is still in service.

Tony

sawmill

Re: Water Heater...

I've used a Rinnai instant heater for 10 years. Like the fact one can dial the water temperaure needed for the job at hand. Zero problems, occassional flush with white vinegar for build up. Mounted outside-- during extreme cold I will let a trickle of water flow through for additional freeze protection. The small flow does not ignite the burner. One can also use two electric valves one NO & one NC to drain the heater during extreme cold. I opted for the KISS principle.

Oscar13601

Re: Water Heater...

I'm building a cabin (vacation), but the town calls it a 1.5 family house. I'm planning on OFF GRID, and PROPANE. I'm planning on getting a 500 GAL (PROPANE) tank just for the water heater and the cooking stove. I'm also thinking on a wood stove for interior heat.
It gets very COLD in that region like I mention before. Any suggestions... As far as the solar system, I want to start small but solid. Then, I'll add more panels and goodies to bring it up to where I want. I'm looking at Grundfos 16SQ10 Well pump. Also I'm thinking to get a Xantrex 120/240V 4500 Watts inverter.


OM

BB.

Re: Water Heater...

Problem with vacation homes and solar is that the cost per kWH of power "used" can become fairly expensive. Sun is available "full time" but you only use it part time--So you have to have a system large enough to power weeks/month at time, and the rest of the time, there is no place to use the available solar power.

Tend to suggest a smaller system to power lights, laptop, small TV, etc... And use a genset for the large stuff (pump to cistern, propane fridge, microwave, vacuum cleaner, washing machine, etc.).

If/when it becomes a full time home, then you can re-address the battery bank/solar array/inverter size (some folks keep the small system for a guest cabin and use the new system for the permanent home).

For example, using PV watts with fixed array tilted to latitude and a 2kW array with 0.52 off grid system derating for Massena NY:

"Station Identification"
"City:","Massena"
"State:","New_York"
"Lat (deg N):", 44.93
"Long (deg W):", 74.85
"Elev (m): ", 63
"PV System Specifications"
"DC Rating:"," 2.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 1.0 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 44.9"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","14.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 3.13, 106, 15.37
2, 4.28, 128, 18.56
3, 4.97, 162, 23.49
4, 5.12, 152, 22.04
5, 5.02, 147, 21.32
6, 5.55, 152, 22.04
7, 5.55, 156, 22.62
8, 5.23, 146, 21.17
9, 4.44, 125, 18.12
10, 3.67, 111, 16.09
11, 2.44, 71, 10.29
12, 2.32, 75, 10.88
"Year", 4.31, 1531, 222.00

Such a system will provide ~111 to 162 kWH per month for 9+ months of the year... And, more than likely, if you are there during the winter, a backup genset will be pretty much needed for week+ stays (depending on weather, etc.).

A 2kW system at ~$10 to $20 per Watt installed (just a guess), will be on the order of a $20,000 to $40,000 system (self install vs retail)... Possibly upwards of $5 thousand less depending on your component selections and how much work you will do yourself.

Assuming 3.3 kWH per day or ~100kWH per month system, a "2 day battery" with 50% maximum discharge would be:

• 3,300 WH * 24 volts * 1/0.85 inverter losses * 2 days * 1/0.50 max discharge = 647 AH @ 24 volt battery bank
• 3,300 WH * 48 volts * 1/0.85 inverter losses * 2 days * 1/0.50 max discharge = 324 AH @ 48 volt battery bank

Not saying this is the "optimum" for your needs--Just trying to put some lines in the sand and see where you want to go from there.

3.3 kWH per day is "enough" for a basic/modern off grid home--But certainly will require you to practice conservation and load control.

-Bill

icarus

Re: Water Heater...

500 gallons of propane for cooking, water heat and water heat will last ,,years in a vacation house. We use, full time, ~10 gallons a month. As for the fridge, the equation gets more and more in favor of a conventional fridge the greater percentage of time you use it. A conventional will use .5-1kwh day, and is pretty easy to come up with using PV. I wished I had gone conventional with a bigger PV, and will probably convert if and when my fridge dies.

BB.

Re: Water Heater...

One thing to note--Tony/Icarus is hours in the middle of nowhere--and as I recall--actually living on an island (and the whole boat/sled and water/ice timing/issues).

When he needs to bring propane, he is wrestling large tanks by hand.

So, price, delivery, etc. are also a point of concern/comparison too in the solar PV (and solar hot water/thermal) vs propane power issue.

-Bill

waynefromnscanada

Re: Water Heater...

Oscar13601 wrote: »

I'm planning on getting a 500 GAL (PROPANE) tank just for the water heater and the cooking stove. Also I'm thinking to get a Xantrex 120/240V 4500 Watts inverter. OM

Does you're propane supplier charge rent on that 500 gal tank? They started charging rent on ALL sizes of tank here decades ago and kept bumping up the rent till many people are giving up on propane. The bigger the tank, the more they charge us
"Starting small" with a 4500 watt inverter? That's like starting out with a small airplane, either a Boeing 747, or an Airbus A380. lol

Oscar13601

Re: Water Heater...

Wayne,

Is funny you mentioned Aviation. I'm a captain for United Express. I'm starting with the 4500 W inverter. But, I'll be adding the PV's and batteries slowly until I get 4000-4500W total PV power.

Cariboocoot

Re: Water Heater...

Small, off-grid cabin? 4500 Watt inverter & array?
Did I just see a rabbit in a waistcoat go by exclaiming "Oh! My ears and whiskers!"?

icarus

Re: Water Heater...

Why in the world would you need a 4500 watt inverter for a small system? FYI 4500 watts on a 12 volt system is ~375 amps,, your re gng o need a whopping if battery bank to power it. Even at 24 vdc it is over 150 amps, and even a big bank will go to low voltage disconnect pretty quickly if you attempt to load its to that current.

You might serieously consider a smaller more efficient inverter for most of your loads. You could also consider using your genny to pump water, so tht your largest (likely) peak load is eliminated from the inverter. by over sizing your pressure/delivery tnk, you can pump water once a day to minimize run time.

Tony

CDN_VT

Re: Water Heater...

................

VT

offgrid me

Re: Water Heater...

I use an ecotemp tankless water heater. It works well but is very sensitive to water pressure. I have had it for about a year with no problems but my water is very soft 30ppm dissolved solids. I use about a hundred lbs/ 25gal of propane for the summer for hot water and cooking. The only reason I can imagine the need for a 500gal propane tank is if you had a large propane generator. A 100lb tank is only about 170lbs total weight when full and can be carried by one person for filling.
Ned

ywhic

Re: Water Heater...

I too am looking at the EcoTemp line.. they make an indoor model FVI12-LP for slightly higher and hooks to LP..

I think forklift type 60 tanks are ideal.. not too heavy and a good amount of gas..

My numbers for my location (SW Texas) seem higher than most that say 5 hours of sun..



I was looking at some Point Of Service 110V models that just plug into an outlet and have a temp setting on them.. but I'm still torn as they use like 1300-1500w heating elements.. I'd have to heat it for an hour before a shower (then switch it off) and hope 3-4 gals is enough for the shower..

In the summer hot water probably for my location could be collected and heated outside.. its the fall and winter that have me concerned..

BB.

Re: Water Heater...

Al, in your region, all Solar Thermal system would be ideal for heating hot water. A rough rule of thumb is 20 gallons of hot water per person per day and 1/2 to 1.0 square foot of solar collector per gallon of hot water. In theory, you could get away with a 10 square foot collector for most of your hot water needs.

There are also very easy batch water heaters... Get an old (or new) 20-40 gallon electric hot water heater. Strip the outside/insulation from the tank and put it in an insulated glass covered box.

If you eventually need more hot water, a heat pump water heater is going to give you 2-3x the amount of hot water per kWH of electricity vs a resistance heater. Cheap/rugged and "who cares"--Other than breaking the glass, there is not much to attract "attention".

www.builditsolar.com will give you some good ideas.

-Bill

CDN_VT

Re: Water Heater...

Reading only now !
glad IT's my 25 yo system .

VT

Cariboocoot

Re: Water Heater...

"A 100lb tank is only about 170lbs total weight when full and can be carried by one person for filling."

HA! Wait 'til you get old, boy!

A 20 lbs. tank lasts about a month here for on-demand hot water and stove.

In Texas I'd be thinking solar hot water for sure.

BB.

Re: Water Heater...

If you do go with solar hot water--A pressure and temperature safety valve and anti-scalding valve is just about mandatory--It is easy to develop very hot water temperatures in such systems.

www.solarroofs.com has been used by a very happy poster here (solar guppy) for install it yourself solar hot water systems.

-Bill

icarus

Re: Water Heater...

As a reluctant "expert" on propane tanks, havng moved thousands of them over the years, on should note that they are available in many sizes from small 1 gallon, to five gallon (standard BBQ tank) up to 100# I have graduated down to 60# in later years, since getting the 100# out of the pitching boat has gotten old. (I did rig up a davit, but still,,) It should also be noted that tanks should always be transported up right for safety.

Also, has been noted, chaining smaller tanks together to essentially one tank large enough to deliver enough gas to large appliances or liquid gennies is possible, with as many tanks as you wish.

Tony

CDN_VT

Re: Water Heater...

Edit :
Since the Internet Rules .

VT

icarus

Re: Water Heater...

I think it is an Ontario transport reg, that they be transported up right.

O2 tanks are especially dangerous, I have seen a video of an O2 tank fall and break off the valve, sending the valve off as a projectile, with the tank going the opposit direction as a missile!

I don't worry about the "marine police". We transport in an open small boat, miles from anyone else. Only very rarely do we see MNR conservation officers looking for illegal fishing. They then emphasize PFDs. More often we see them in the winter on skidoos since they can actually get to our lake without too much trouble. Then they care about helmets on skidoo drivers!

Icarus