Atwood gas/electric low capacity

[Jammer]

Originally Posted by Al and Missy

Well, the bypass valve is the common element between the two heating mechanisms, for sure. I'll try to get a look at it tomorrow. The bad news is if it need to be replaced I'm going to have to pull the heater to do it.

You might want to try turning it the other way (to what should be the "open" position), first, just to be sure it isn't set up backwards or something.

[Al and Missy]

Originally Posted by Jammer

You might want to try turning it the other way (to what should be the "open" position), first, just to be sure it isn't set up backwards or something.

That's an interesting point. The rig was supposed to have been winterized, but according to standard positions, the bypass valve was closed (perpendicular to the pipe) as were the inlet and outlet valves. I just assumed that they had not opened the bypass valve. But if the bypass valve was open, wouldn't I get warm water from the cold side of the faucet? When I turn the faucets to cold, I get pure cold water, not warm.

Maybe they didn't use the bypass valve because they winterized it with RV antifreeze.

I just measured the temperature of the inside wall of the tank with my IR thermometer with curious results. The top was around 97 degrees, the bottom was around 100, and the center was below 80. That seems odd. It may just be due to the reflectivity of the tank wall since I was shooting horizontally and the top and bottom were curving away while the middle was perpendicular to the measurement line.

In about an hour I'll go drain the vinegar solution and see if any deposits come out.

Al

[Al and Missy]

Originally Posted by Jammer

The recovery rate is based on a 90 degree rise. That is typical in northern states where the incoming water temperature is close to 50 degrees and the water heater is set for 140. With the higher incoming water temperature you have in Florida (usually close to 70 degrees), the rise is considerably lower. There is also some water that won't be heated right away due to a thermocline effect, about 10% of the capacity usually. So you are only heating 5.5 gallons. 5.5 * 70/90 / 7.4 * 60 minutes= 35 minutes.

Thanks for the definitions for the standard - I put in 3.5 gallons of Vinegar that had been sitting out in about 45-50 degrees and about a gallon of water at the same temperature because it was in a hose roole up on a reel.

Al

[Al and Missy]

I went out to drain the vinegar solution and the heater was running. I waited until it shut off and made another temperature measurement. It was about the same as the first. Nothing came close to 140 degrees. The highest temperature I measured was 115 up on the top of the tank, presumably in the air bubble.

After it shut off I drained the tank. After soaking in the hot vinegar solution for 2 hours, the water came out crystal clear. I don't think I have a sediment or calcification problem.

Tomorrow, if I can figure out an easy way to do it, I'm going to jumper the thermostat and let the emergency cutoff shut the heater down. I think it is the same temperature as the thermostat, just serves as a redundant means of turning off the heat. My new thermostat and ECO kit will come on Friday.

I was confused about the bypass valve. It is in front of the heater on the inside. It should be easier, if not easy, to take out and inspect. That's the next step after bypassing the thermostat.

Al

[Siegmann]

I would also suggest measuring the actual water temperature. The thermostat should get it to 140 and the ECO a lot hotter.... not sure exactly, but it would be scalding.

[Al and Missy]

OK. I shorted out the thermostat (labelled at 140 degrees). The heater ran substantially longer and the temperature at the top of the tank got up to around 125 degrees before I turned it off. The ECO is labelled at 180 degrees, and did not open. There was still an odd vertical temperature gradient in the tank, cooler in the middle and warmer at the bottom and the top. This gradient occurred prior to opening any faucets so should not have been caused by cooler water flowing in. I turned on the water at the lavatory and observed the same phenomenon as before, i.e. the water was at first very hot, then cooled then warmed. But the hot water lasted longer and I ultimately got hot water at the galley sink which I had not seen before. I also ran some water into a plastic cup and measured the temperature with a candy thermometer. The measurements were consistent with the IR measurements on the outside of the tank. I also operated the bypass valve. My conclusion is that it is correctly set and operational.

I am considering the possibility that the cold water entry pipe inside the tank has broken off. The pipe directs the cold water to the bottom of the tank. If it has failed, then the cold water enters at the middle. I'm not sure how I would confirm that without a bore scope, but if the new thermostats don't correct the problem that's probably my last test before just giving up and buying a new heater.

Al

[Siegmann]

I do not know if the gradient you describe is abnormal, particularly if it is small. Look at how the flue runs in this photo:

http://beamalarm.com/Documents/water..._cut_open.html

Depending on where you measure the temp, I could see it warming more at the bottom and top of the tank, where you are closer to the flue, if it has not had time to thermally mix.

The idea of the broken cold water entry pipe also sounds a stretch. Check out this pic:

http://rvtravel.com/blog/rvnow/2008/...ential-rv.html

It would have to break right at the bend in the pipe. Possible, I guess.

I would still try to open up the bypass valve to see if it is closing properly.

[Al and Missy]

Originally Posted by Siegmann

I do not know if the gradient you describe is abnormal, particularly if it is small. Look at how the flue runs in this photo:

http://beamalarm.com/Documents/water..._cut_open.html

Depending on where you measure the temp, I could see it warming more at the bottom and top of the tank, where you are closer to the flue, if it has not had time to thermally mix.

The idea of the broken cold water entry pipe also sounds a stretch. Check out this pic:

http://rvtravel.com/blog/rvnow/2008/...ential-rv.html

It would have to break right at the bend in the pipe. Possible, I guess.

I would still try to open up the bypass valve to see if it is closing properly.

I'm going to feel really stupid if it is the bypass valve. I'll try that tomorrow.

I have read of this exact set of symptoms caused by a broken cold water feed pipe in a home water heater, that's why I considered it a possibility. I may pull the electric element and look in there; it's a bigger hole.

Al

[Siegmann]

I could see how an internal broken cold water feed in a residential heater would send cold water into the top of the heater, where the hot water feed is. But as you saw in the cut open Atwood tank pic, its plumbing would send the cold water into the bottom of the tank (unless strategically broken at the bend).

I hope it's the valve.... because I'm plum out of ideas. Good luck.

[n2916s]

I think you have found the problem -- the thermostat. You wrote that you bypassed it and it ran longer until you cut it off... I am not suggesting you let it run until the ECO kicks in but how about bypassing it again and let it run until the water out the tap hits 140 (check it every 5 minutes or so). Then start the shower or open the lavatory and kitchen sink taps and see how long until lukewarm.

When you hear hoof beats, think horses, not zebras.

Mike

[A W Warn]

When you are checking the bypass valve, check all three valves to see if the internal rubber washers are still in place or possibly damaged. The valves in my Safari have a really cheap design that allowed the washers to come lose. I had this happen and it did some really weird things to the water flow. Sometimes everything was normal. At times it would stop the hot water flow through the shut off valve at the water heater, even though the hot water shutoff valve was in the open position, making the water flowing through the faucets or shower cold. I finally figured out that I need to replace the rubber washers which took care of the problem for me.

[Al and Missy]

Originally Posted by n2916s

I think you have found the problem -- the thermostat. You wrote that you bypassed it and it ran longer until you cut it off... I am not suggesting you let it run until the ECO kicks in but how about bypassing it again and let it run until the water out the tap hits 140 (check it every 5 minutes or so). Then start the shower or open the lavatory and kitchen sink taps and see how long until lukewarm.

When you hear hoof beats, think horses, not zebras.

Mike

Thanks Mike, but I ordered and installed a new thermostat and cutoff and the problem is still there.

Alan, at this point I think it can only be the valves or a broken drop tube. The shutoff valves are barely accessible to operate. I'll check the bypass valve, and see what I can do about the shutoffs. If I have to change them, I'll have to pull the heater. If I'm going to do that, I might have to consider changing the heater; it is 15 years old.

I think my earlier temperatures measured on the wall of the tank inside the trailer may have been in error. Today I decided to pull the burner tube and check it and the flue tube for blockage. They were clear, but while I had the burner out I used my IR thermometer to check down the flue tube to deep inside the heater. It read around 140 degrees while the inside measurements varied from 120 or so at the top and bottom of the tank to 90 in the center.

I'll investigate further tomorrow and either find the problem or order a new heater. I just don't want to order one and discover it doens't solve the problem.

Thanks to everyone for their suggestions!

Al


Al

[SeeMore]

Al, whenever a contact thermostat is exchanged you should use a thermal conductive paste between the mounting surfaces to ensure accurate reading. This is the product:

http://www.ebay.com/itm/30g-Syringe-...-/391205942743

[Al and Missy]

Early on someone mentioned about the newer heaters having a mixing valve. My heater was original so I didn't think anything about it after looking on Atwood's site and seeing it as a part of the heater. Today I was prepping to remove the electrical heating element to see if I could see the "dip tube".

The first picture is what I have been seeing, i.e. the bypass valve in the proper closed position. When I got down lower and looked under the heater I saw what is in the second picture. I don't know what this is, and it's not on my plumbing diagram, but it is plumbed in parallel with the bypass valve. If that were opening somehow that would explain my symptoms. It is pretty clearly factory-installed, as it is plumbed with the same tubing (Pex?) as the rest of the trailer and clamped with the compression rings.

UPDATE:

Well, it is a check valve and allows one-way flow between the cold and hot circuits.

http://hydronamicengineering.com/product/1212b-mxf-2/

If the pressure on the cold side is greater than the pressure on the hot side by 1 +/- 0.5 psi, it opens. What the ???

I'm going to go buy some 3/8 MPT plugs and this thing is outa here.

BTW, Airstream, ever hear of service loops?

Thanks,

Al

[Siegmann]

Al, I think this is more than potentially embarrassing...

On my rig, that valve is on the line that goes to the exterior water valve in the exterior water compartment.

My water heater isolate/bypass valves (set of three) are on the right side of the heater tank. Try shining your flashlight in there.

[Al and Missy]

Originally Posted by Siegmann

Al, I think this is more than potentially embarrassing...

On my rig, that valve is on the line that goes to the exterior water valve in the exterior water compartment.

My water heater isolate/bypass valves (set of three) are on the right side of the heater tank. Try shining your flashlight in there.

And you would be RIGHT!

THANK YOU, THANK YOU, THANK YOU!!!

I had to contort my body in ways I didn't know I could to even see the bypass valve, right where you said it would be. And it was OPEN. I have now closed it and suspect I have wasted three days and a lot of other people's time on this wild goose chase. I was already in a test to see if removing the check valve solved the water heater problem so in a little while I'll know.

So what would be the purpose of putting that check valve in parallel with the shutoff valve for the outside? Normal usage would seem to be to close the shutoff valve and open the outside valve to drain any water in the line. With the check valve in there, when you open the faucet the check valve will open.

Al

[Al and Missy]

Thanks to Siegmann's tenacity and continued help in spite of my efforts to the contrary I now have hot water everywhere. I owe Seigmann several beers when we meet somewhere down the road.

Al

[Siegmann]

This forum has been a big help to me several times in the past. Glad to be able to "pay it forward". Now we both feel good!