Gas water heater

[Michael]

Yesterday, I was planning on a hot shower before my son's OT session, unfortunately our gas water heater had other ideas, the pilot light had gone out. First time that it has done this in over a year, so I wasn't concerned. Today, it was out again. Do gas water heaters require any type of maintenance and cleaning or should I prepare to buy a new one. We bought the house a year ago and the heater has probably been here since the house was built in the early 70's.

[egon]

Have you checked the thermocouple if your heater has one.



Egon [img]/forums/images/icons/grin.gif[/img]

[Bird]

If it's working OK except for the pilot going out, then I think Egon is right. The thermocoupler probably needs either a good cleaning or replacement.

[Michael]

Don't know what the thermocouple is, but the warning on the side says that the heater has an automatic gas shutoff actuated by high water temperature. The pilot light will not light immediately after going out, but will light 1-2 hours later. I am thinking now that this cutoff has something to do with the problem. I posted prior to seeing the warning.

[egon]

A site showing details of a typical gas water heater firing system. Your case may be different.

http://www.rd.com/content/openConten...ontentId=19531

Egon [img]/forums/images/icons/grin.gif[/img]

[Pat]

A THERMOCOUPLE is two dissimilar metals in contact. When heated they generate an electric current. Self generating safety pilots use them. The electrical energy used to open the gas valve of the main burner when the thermostat calls for heat is supplied by the thermocouple. If the pilot goes out for any reason the thermocouple cools and will not supply electricity to open the main valve. This prevents getting large quantities of gas being allowed to spew out into the room. If the thermocouple is marginal or intermittent it could cause your problem. They are typically available as a separate repair part and are not difficult to install. You just put it where the original one was and wire it the same way.

If your heater is actually as old as you suspect then you might want to just replace it, especially if you have much dissolved mineral content in your water and aren't running a softener. Newer heaters are available that are much more efficient. You can pay more and get a very efficient heater. Fully condensing models can equal or exceed 97% efficiency. Since your current heater lasted so long I would favor getting a high efficiency heater since it will last long enough to more than pay for the extra cost through gas savings. You will have a positive return on the added investment.

Pat

[Michael]

Replaced the thermocouple for $4.49 and it is working fine. Pat, I am probably going to replace the heater in the near future as we are in the process of remodeling and updating our entire house anyway, but the water heater is on the opposite end of the house from where we started. I guess I'm kind of eccentric as I don't want to alter my plans. It's one of those things that drives my wife absolutely crazy, along with the fact that I refuse to borrow money or use a credit card to do all of the work at one time. Thanks to Bird and Egon for the thermocouple tip, saved me a lot of money. I think that I may start a running tally on the amount of money that I have saved by using this site and TBN. [img]/forums/images/icons/grin.gif[/img]

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Score another point for the:....... "Before I pick up the phone and call someone I'll take a look at it myself."..... model of home ownership. [img]/forums/images/icons/smile.gif[/img] That stretched-out hot water heater situation is not unlike what we'll have once our long-term remodel plans are complete. We have considered two different approaches: one is using a very small (six-gallon) H.W. heater under the floor of the kitchen and feeding it from our regular hot water supply so we'd have several gallons of immediate hot water until the hot water from the main heater got there; OR....we could use a hot water circulator pump with a loop system. [img]/forums/images/icons/tongue.gif[/img] Along the same lines as the thermocouple situation, here is something to put into your mental storage...... The new furnaces have a little "finger" that sticks out and "feels" for flame. The "finger" verifies that there IS flame and permits the gas supply valve to remain open and the heater to continue warming up. If the heater has been sitting for a year or two, the "finger" can get a film of rust or corrosion on it and become slightly "insulated" against the heat of the flame and as a result it won't think the flame is there and won't hold the gas valve open. The fix is to clean the finger. [img]/forums/images/icons/tongue.gif[/img] SPEAKING OF THE CBN site and what we can learn from it.........until now i didn't actually know how a thermocouple made the gas valve open. I didn't know if it was expanding gas in the capillary tube or what. As usual, PAT has these things figured out and some of us are beneficiaries of that knowledge. [img]/forums/images/icons/smile.gif[/img]

[Pat]

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

[GaryM]

Pat,

I might suggest an alternative system such as I have at my place. It's a Metlund system Gothotwater

In my master bath, the hot and cold are cross connected with a pump and temp sensor. When I go in there in the morning, I press the button as I stumble to the toilet. By the time I turn to the sink I have hot water available.

The pump runs and forces the cold water in the hot pipe back into the cold pipe, When the temp sensor detects hot water, the pump shuts off until the next button press. If the water at the sensor is already hot, pressing the button does nothing.

Their system can also be installed as a recirculating system.