automation of gas water heaters

[JHZR2]

Hi,

gas water heaters dont have electric connections... they have a temperature selector that is set and forget... and the temperature is maintained.

Say that you wanted to automate the maintenance of a gas water heater temperature, like with a thermostat type setup. This way you can set the water temperature of the heater from, say, the kitchen, rather than the basement. This is useful if you want to turn down the temperature during the day if going out, or if youre just gong away for a few days.

Yes, I know, its laziness, but it would be an interesting project.

My fiancee's parents have a timer on their electric water heater... but its easy on electric - a whole different animal.

Any suggestions???

Thanks!

JMH

[ July 17, 2006, 01:07 AM: Message edited by: JHZR2 ]

 

[XS650]

For a modern well insulated gas water heater with pilot light, there isn't much point in turning it down. The pilot light alone will keep the water at temperature so the main burner doesn't have to come on.

I have come back from 2 week trips with our water heater turned off except for the pilot light and the water was hot enough for a comfortable shower. Our pilot light is one of the newer small pilot lights.

 

[JHZR2]

interesting!

Thanks!

JMH

 

[Shannow]

but I saw a system where a guy ran the cold water pipe to his shower, but ran it along the waste pipe, hving installed about a 6' length of near horizontal waste pipe for the purpose.

The draining shower water heated the cold water, meaning he used more "cold", and less hot. Saved him a reasonable amount of energy with a family of 5.

 

[Razl]

That's called a drain water heat recovery system. If I recall, about 90% of the heated water goes down the drain as wasted energy. An because water clings to the walls of the drain pipe, this unit can recover about 50% of that lost heat by pre-heating your incoming cold water. I looked into a company GFX that makes them, but I have not gotten around to buying one (about $500) yet. The payback is quicker with high usage, electric heaters. I have a low usage high efficiency gas heater. New house, too many other things to buy first.

Instead, I bought a $18 water heater banket rated at R15. I plan to frame out 1/2 of the basement so the heater is not exposed to the "cold" side of the basement.

As stated, timers don't really make sense on gas heaters because of the pilot light. Assuming your dishwasher has a water heating element (most do), the best thing to do to save money is lower the thermostat as low as comfortably possible. You'll know the right spot when you can turn the shower all the way to hot (so you're not blending it with cold water) and it's comfortable. Also, wrap all your exposed hot water pipes with foam wrap, including the first 2 feet of pipe that goes into the cold side of the heater. Make sure you tape the seam or get the kind that is self sticking.

 

[thooks]

What has been said about the well insulated tank holding temp is true.

But tank-type water heaters are on their way out. I personally wouldn't buy one today.

I'm all about using gas to heat water and cook food on a stove top, but I wouldn't put in anything except an instaneous gas-fired water heater.

http://www.rinnai.us/products/waterheaters/index.asp builda a first-class water heater.

 

[labman]

I put tankless water heaters in the same over hyped category as hybrid cars. They only make sense for those that are extremely wasteful of hot water or have high usage for some other reason. Most of the gas ones have a minimum flow rate of about 5 gallons of water. Put a quart bottle under you kitchen faucet and turn the hot water on. At 5 gallons a minute, it should fill it in 12 seconds. Is that how you use hot water?

I looked into the tankless units hoping to locate one in my crawl space under where most of our hot water is used. No deal. The units may be small, but they require such large clearances they actually take up more room than a tank. If you don't locate it closer to the point of use, you still have the same wait and wasted hot water until hot water replaces the water that cooled off in the pipe.

The time came to replace our 25+ year old water tank last week. I went out and bought a conventional one. Still have some details I should be working on since I relocated it closer to the water usage, although still in the garage. I also updated to a stand keeping it up off the floor and less likely to set inflammable vapors on fire.

 

[Laminar Lou]

quote:

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Originally posted by labman:

I also updated to a stand keeping it up off the floor and less likely to set inflammable vapors on fire.

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Good idea, my Uncle lost his house from a water heater that ignited gasoline vapors from a lawn mower. Lost a beautifully maintained 240ZX in the process.

What you are talking about is the defacto building code now at least in Los Angeles. That and some reinforced strapping in case of earthquake.

 

[Razl]

Labman, I think you have it backwards. While a tankless heater will never "run out of hot water", it makes no economical sense to use this type of heater in high usage applications.

A tankless water heater makes sense when you've got a house where hot water is used infrequently (such as morning showers, evening laudry). That way, your tank type heater is not keeping water hot the other 22 hours of the day waiting for you.

The min. flow rate is a shortfall of tankless as you've pointed out.

 

[JHZR2]

That is one of the things Ive heard as a 'con' of the tankless... if you just need a real low flow, like for washing dishes, there might be issues. Similarly, if you have long runs of pipe through the house, it may take longer to get hot water out, of say, a second story shower diagonally oppposite the water heater, when a tankless is used, compared to a tank heater.

Also, not that its a real issue... but when the power goes out, no hot water with a tankless system.

If I get a 40 gallon A.O. Smithy conservationist heater, set at a relatively lot temperature, with an energy factor of 0.63... how much worse off could I be than with a tankless, especially if I turn it down when going away for more than a few days?

The price difference is ~$400...

so much to consider and calculate... thanks for the insight!

JMH

P.S. is there a problem if you vent a tankless heater up a chimney????

 

[Brett Miller]

Tankless must be direct vent to an outside wall.

 

[rjundi]

Water holds its temperature very well in an insulated water heater. You may want to do the thermo calcs to see if changing the temperature is actually worth it. You may spend more energy or the same trying to bring its temperature back to the desired level vs keeping it maintained constantly whether in use or not.

 

[thooks]

Tank type water heaters do NOT "keep the water hot all day". Least the ones made in the last 18 years don't. They are insulated well enough where the water will stay warm enough for 7-10 days like was mentioned above.

Tankless water heaters are not hype. No, they are not for a commercial application such as a laundry-mat or NFL locker room.

It has been well proven that they do save the average homeowner about $10-15 per month on their gas bill. Of course, you do need to amortize the extra $400-500 cost of the product and installation. Factor in that amortization the convenience of never running out of hot water.

And nope, you can't be filling up the tub washer, bathtub, dishwasher and take a shower all at the same time. But you can run a dishwasher, front loading washing machine and take a shower. Or have 8 people take one shower after another and never run out of hot water.

 

[labman]

quote:

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Originally posted by thooks:
snip...

It has been well proven that they do save the average homeowner about $10-15 per month on their gas bill. snip....

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This is a perfect example of what I am calling hype. With a gas dryer and service charges, our bill runs less than $30 a month in the summer, likely not that much more than the claimed $10 miminium saving for the gas used to heat water.
If we switched to electric using NO gas for hot water, likely our gas bill would still be $20. No way is a somewhat more efficient water heater going to save us most of what we are spending.

 

[Laminar Lou]

quote:

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Originally posted by thooks:

It has been well proven that they do save the average homeowner about $10-15 per month on their gas bill.

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But how much did their electric bill go up? Where I live heating water with electricity is going to cost me close to twice that of using natural gas. And that depends on what percent I am over baseline, which, if I choose to actually live in the house I am always over baseline. Heck I even went over baseline when I wasn't home for half the month. But that is another story...

 

[JHZR2]

tankless water heaters use natural gas... they dont heat with electric. There is some parasitic electrical use for the control system, but it surely is so low that it is nearly insignificant.

JMH

 

[XS650]

quote:

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Originally posted by labman:

quote:

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Originally posted by thooks:
snip...

It has been well proven that they do save the average homeowner about $10-15 per month on their gas bill. snip....

---

This is a perfect example of what I am calling hype. With a gas dryer and service charges, our bill runs less than $30 a month in the summer, likely not that much more than the claimed $10 miminium saving for the gas used to heat water.
If we switched to electric using NO gas for hot water, likely our gas bill would still be $20. No way is a somewhat more efficient water heater going to save us most of what we are spending.

---

I agree. We have a gas dryer, gas stove and gas water heater. Our total gas consumption in the warm part of the year when we aren't running the house heater runs about 14 to 15 therms a month. About $15 at present rates.

As a SWAG, about 1/3 of that is stove and clothes dryer so we spend about $10/month on hot water and we don't skimp on using it.

 

[XS650]

quote:

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Originally posted by JHZR2:
tankless water heaters use natural gas... they dont heat with electric. There is some parasitic electrical use for the control system, but it surely is so low that it is nearly insignificant.

JMH

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I've used a tankless gas water heater in Thailand. It was right next to the shower in a grass hut and worked great. It was a simple little heater with a pilot light because there was no electricity in the village we were in. As soon as the water ran a few seconds the burner came on full blast and it shut off right after you quit running the water.

Labman nailed it on the pimped up savings numbers. Before you one starts screwing around with tankless water heaters to save money, they need to figure out what hot water costs them now and if there are simple ways to reduce that.

 

[thooks]

quote:

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Originally posted by labman:

If we switched to electric using NO gas for hot water, likely our gas bill would still be $20.

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And your electric bill would go up about $40 per month.

For the one in CA paying $1 per therm, consider yourself extremely lucky. I don't know of another person in the US paying $1 per therm for residential natural gas service. Last time I paid that the year was 2001.

 

[Dark Jedi]

I have an old gas water heater and the burner only comes on prob a few min after I start my shower. other than that I dont see that sucker ever come on again. so I guess the pilot light does keep it warm. I also like gas over electric for water heaters. they are easier to work on and cheaper too. the thermal coupling went out on my gas water heater a few months back and cost $7 to replace. now if it was electric and the sucker broke. I wouldnt know where to start to troubleshoot the prob and have to call in a repair man and cost even more money. I have a gas stove too and unlike electric stoves I dont have to wait till the burner heats up. also with gas my pans bottoms are all nice and clean unlike with electric ranges. so I will always have gas water heaters and stoves in my houses.

seen them use one of those tankless gas water heater on this old house. they set it up to only run the shower.and they did that so even if a tolet was flushed the water stays hot. unlike with a reg water heater. we get the cold shower lol. they said it isnt practical to use as a single unit to heat water going everywhere. thay are used to take some of the strain off gas and electric water heaters.