CountryByNet.com Forums :: Gas water heater

Dave, the gas valve in the millivolt self generating safety pilot system is nearly balanced and doesn't require much to open or close it (self boosting?) and so the little thermocouple doesn't have to produce much power. We have 4 propane gas logs in the house and they are all this sort of arrangement and have piezoelectric (clicker) ignition for the pilot. The self generating millivolt system can be used with a thermostat just fine if the wiring run is not too long or too fine of wire as the resistance can be to great for the puny source.

There are even electric fans that you set on a wood stove and the heat generates enough power to run them for heat circulation. The Ruskies used to have a unit that sat atop an oil lamp and made enough electricity to run a small xistor radio.

About the little water heater in-line with the big water heater. If the run to the little heater from the big heater is very long you will not like the results, even if you insulate the run. You start out with a short wait to get hot water and then the influx of cold water stored in the "hot" water pipe cools the water you get from the faucet to an unacceptable level before it starts back up in gemp as hot water fresh from the tank mixes in. I did this and know how it works. I replaced the little tank with a recirc pump. That was my mom's house. For our house I just started out with a pump (I may be slow but I am not stopped!)

There are choices about how to control the pump:

1. run it 24-7 as it isn't all that expensive but my duty as Energy Conservation Officer at SUBASE San Diego did a behavior modification on me and I just can't feel good about running it all the time even though you have to shop around to find a cheap timer to make it pay to control it. (Harbor Freight and it has worked perfectly)

2. use thermostat to cycle the pump when the pipe mounted thermostat senses the water is cooling down. AquaStat is more expensive than a timer by a fair margin.

3. Use a timer to ensure the water circulates during times of probable use

4. Use a timer in series with the T-stat so the water is not allowed to get cold during certain time periods but the pump doesn't run all the time it is enabled by the timer.

5. Use a timer in parallel with the T-stat so if the water cools down the pump runs or during set times it just runs and yo have INSTANT hot water with no chance timing involved.

I never tried #1 and think it is better for a hotel or dorm.

Tried #2 and the available T-Stat (AquaStat) I could get lets the water cool too much between runs and so getting an immediate hot shower is like winning the lottery. Still it saves wasting toooo much water waiting for hot water most of the time and is generally acceptable but baffles the less technically savvy (read, wife.)

I intend to try #4 next and set the timer for two periods a day, one for the morning time slot most likely to cover our showers and again in the evening when we sometimes shower.

For kitchen use I would at least use a timer to cover the period of time the hot water is used and off for the 8-10 hours or whatever when it isn't used. Insulate the hot water run and the return line so you aren't creating a small to medium size hydronic heating system that will run all summer and contribute to A/C loads.

It is your project but I strongly suggest that the recirc is vastly superior to another storage tank type water heater. It beats the "instant" heaters too, especially when you have a water heater already. A small (3/8 inch) return line is big enough and a itsy bitsy pump is all you need. I have a brass pump with impedance protected motor and plastic (resin?) impeller that is water lubricated and should last a very long time indeed. Be sure to put a check valve in the return line so you can't suck water back through the pump.

The only problem I had was an intermittent check valve which sometimes worked and sometimes let cold water get sucked to the shower through the return line. IT was made in China and corroded up really fast. It has been replaced with a better quality valve and works fine. Oops, there was one other problem. When the pump was installed the luck of the draw (AKA Murphy) ensured that there was a small screw inside the PEX tubing. The screw was sucked into the pump and jammed it. I got curious why the system was not working and investigated. When I found the screw it was of a size and type about appropriate to hold the impeller on the shaft. I returned the pump and they gave me a new one. Later we all had a laugh as the screw was not a part of the pump and had just accidentally got into the tubing during transport. (Thanks Mr. Murphy!)

I think the pump will be as trouble free and likely more so than a little heater. When you do your remodel maybe you can plumb in some return lines and use balancing valves to ensure recirculated hot water to any part of the plumbing you care about. If I had it all to do over with this new house I would use a larger plastic sleeve in the slab and run a 3/8 return line with every hot water line and insulate every hot-recirc pair. Wellll maybe not a recirc line with every one but every main line so hot water would only be a few seconds away from any point of use.Then there would be hot water nearly instantaneously available everywhere. To do this you only have to have returns on the ends of the long main runs. That is, if you use a trunk and branch layout. We did on the advice of our plumber so the recirc system helps a lot of the house. I like it so much I would have expanded the return line network if I had only known how wonderful it would be.

Pat

"I'm not from your planet, monkey boy!"

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