Atwood gas/electric low capacity

[Al and Missy]

Just bought a 2002 trailer with the combination gas and electric water heater. It works on gas, sort of, but not on electric. I suspect electric element is bad

Before I invest much time in the electric side I have to solve a capacity problem. The unit lights normally and runs to shutoff. After shutoff there is only about a minute of good hot water at the bathroom sink, then it gets cold. The unit had been winterized. When I looked at the drain plug it was filled with sediment. My theory is that the heater is full of sediment and that has reduced the capacity. Does that sound reasonable?

I read the thread on here about flushing, but I wonder if the sediment is so bad as to reduce the capacity that much what is the likelihood that flushing will clean it out? Won't the sediment be hardened and difficult to get out? Any suggestions?

Thanks,

Al

[Protagonist]

Sediment can reduce the tank capacity, but that much sediment would be unlikely in my opinion. Surely you or the previous owner would have noticed mud coming out the water heater drain when it was winterized if that was the case.

Another possibility is that you have an overly-large air bubble in the water heater's tank. I had that problem once, but was able to solve the problem quite simply. All I had to do is open the pressure relief valve at the top to bleed air— with the heater turned off to avoid being scalded— while the pump was running to allow more water to run in. I could only guess at how long to leave the relief valve open, so I hit on an easy way to measure: Fill the water heater until water ran out the open pressure relief valve, which means that the heater is brim full. Then shut off the pump, crack open the drain until about a quart of water runs out, then shut both the drain valve and the relief valve. That leaves you with a quart-sized air bubble in the top of the tank, to allow for expansion and contraction as the water is heated or cooled.

[Al and Missy]

Originally Posted by Protagonist

Sediment can reduce the tank capacity, but that much sediment would be unlikely in my opinion. Surely you or the previous owner would have noticed mud coming out the water heater drain when it was winterized if that was the case.

Another possibility is that you have an overly-large air bubble in the water heater's tank. I had that problem once, but was able to solve the problem quite simply. All I had to do is open the pressure relief valve at the top to bleed air— with the heater turned off to avoid being scalded— while the pump was running to allow more water to run in. I could only guess at how long to leave the relief valve open, so I hit on an easy way to measure: Fill the water heater until water ran out the open pressure relief valve, which means that the heater is brim full. Then shut off the pump, crack open the drain until about a quart of water runs out, then shut both the drain valve and the relief valve. That leaves you with a quart-sized air bubble in the top of the tank, to allow for expansion and contraction as the water is heated or cooled.

Thanks Protag,

I hadn't thought about that and I agree the air bubble is a more likely candidate, but wouldn't bleeding the air through the hot water output line leave a bubble of the correct size or one too small? How would a too large bubble survive? Always when I transition from "shore water" to tank water or back I bleed the air from the hot water lines before turning on the heater.

Al

[Bill M.]

Sounds like it is time to replace it. Not a real hard job and you can get them fairly inexpensively on the internet. My 6 gallon unit has adequate capacity for several showers and recovers fast. I do not go along with the bubble theory because the hot water should come out near the top of the tank. I put in the gas-electric but seldom run it on electric. If I was doing it again I would save the $100 difference and just go with the gas. We have on trailer that sits on a permanent lot but we still use the gas because it is cheaper than the electricity.

[Al and Missy]

Originally Posted by Bill M.

Sounds like it is time to replace it. Not a real hard job and you can get them fairly inexpensively on the internet. My 6 gallon unit has adequate capacity for several showers and recovers fast. I do not go along with the bubble theory because the hot water should come out near the top of the tank. I put in the gas-electric but seldom run it on electric. If I was doing it again I would save the $100 difference and just go with the gas. We have on trailer that sits on a permanent lot but we still use the gas because it is cheaper than the electricity.

That's the way the 6 gal. was on my Safari. The amount of hot water that is generated with this trailer is so small that there is a minute or so of good, really hot water at the lavatory which is directly over the heater, enough at the shower across the hall to take a quick shower but the temperature goes up and down, and only warm water at the kitchen sink. I'm going to do a quick check of tank capacity and see if any kind of flushing helps and then replace it, I think.

Al

[Al and Missy]

The shutoff valves are on the side of the heater between the heater and the cabinet wall. I can't reach them, my hands are too large. I had to get my wife to reach up in there and turn them on. I'm glad they moved easily.

Al

[dznf0g]

To answer the question of removing calcified or lime deposits, remove the drain plug and install an appropriate threaded fitting with hose attached to it. Close the shutoff valves to the house plumbing, use a funnel while holding the end above the tank, open the pressure relief valve and pour in a couple gallons of straight vinegar, tie the hose end up on something and let it soak for a day or two. Drain and get a flusher wand from Camco and flush it out with fresh water , accessing through the drain port. Repeat as necessary. I do this every year or two to prevent mineral buildup.

Here is a pic of the hose I made up for this service:

[dznf0g]

Here's the flusher wand I was referencing:
http://www.walmart.com/ip/29764286?w...516272&veh=sem

[Jammer]

Originally Posted by Al and Missy

Just bought a 2002 trailer with the combination gas and electric water heater. It works on gas, sort of, but not on electric. I suspect electric element is bad

This is common. In my classic the electric element is readily accessible from below the lav sink. I believe the slideout is similar in this regard. It's an easy repair as long as you have a wrench and socket that's up to the task. The elements sometimes stick, sometimes don't. I have a 3/4" drive socket set that has the right size socket, which works great. The cheap hardware store tools they sell next to the electric elements are less effective but will work if it isn't too badly stuck.

Before I invest much time in the electric side I have to solve a capacity problem. The unit lights normally and runs to shutoff. After shutoff there is only about a minute of good hot water at the bathroom sink, then it gets cold. The unit had been winterized.

Your unit is equipped with a winterizing bypass valve that connects the hot and cold water lines together to allow antifreeze to be pumped through without filling the water heater tank.

The problem you describe can be caused by leaving the bypass open, a common mistake. Be sure it is shut. It is between the hot and cold shutoff valves.

[Al and Missy]

It turns out the problem with the AC side was the over-temperature shutoff which has a manual reset. It is now working on AC. I'm going to try to diagnose the propane side next.

The volume is not restricted, and it does not seem to be calcified, but I will have to try the vinegar bath to be sure.

The bypass valve is closed and the shutoff valves are open.

Al

[Jammer]

::shrug:: There may be something wrong with the bypass valve. Might be something to double check. Maybe it's not closed quite all the way. Just sayin'.

If you're concerned about calcium buildup, take a look around inside the tank. A small flashlight, a section of rope light, or a cyalume stick will fit through the drain plug opening, then look around with an inspection mirror.

I believe the thermostat on these is a contact type that is held against the wall of the water heater by a clip. Might want to be sure it's held securely. (Mine doesn't have a resettable limit switch so I'm not quite sure what other differences there may be)

[Al and Missy]

Originally Posted by Jammer

::shrug:: There may be something wrong with the bypass valve. Might be something to double check. Maybe it's not closed quite all the way. Just sayin'.

If you're concerned about calcium buildup, take a look around inside the tank. A small flashlight, a section of rope light, or a cyalume stick will fit through the drain plug opening, then look around with an inspection mirror.

I believe the thermostat on these is a contact type that is held against the wall of the water heater by a clip. Might want to be sure it's held securely. (Mine doesn't have a resettable limit switch so I'm not quite sure what other differences there may be)

Good point about the valve. I didn't try to turn it, just looked at it.

I'll pull the over pressure valve and look in there while shining a light in the drain plug.

Al

[wvstreamer]

AL
Please report back on progress.
Dave

[Al and Missy]

OK, here's the status....
The AC and propane sides now both work in an equivalent manner. After an hour or so on electric or after the propane has run and shut off, the initial water from the faucets is very hot - probably a good 160 degrees, but it doesn't last. After 10 or 15 seconds it gets to just feeling warm and then will stay that way for several minutes, probably 6 gallons or so. I disassembled the galley faucet and made sure that the mix valve wasn't clogged or improperly assembled.

Apparently the water is remaining stratified in the heater tank. The top is very hot, but there is no circulation in the tank and as soon as the top layer of water is gone, it is only warm.

The thermostats that control the temperature of both the electric and propane heating systems are in about the same place, i.e. the center of the horizontal cylinder which is the tank, electric on the inside wall and propane on the outside wall. It is hard to imagine that both the electric and propane thermostats are bad. I did confirm that the thermostat and not the emergency cutoff is what turned off the propane heating. I would just replace the heater if I could rationalize why it is doing what it is.

Al

[Siegmann]

Are you sure the tank is stratified? You could try touching the cold water inlet at the bottom of the tank and see if it is hot.

Try disassembling the shut-off valve that is on the hot water out line. Someone once described how the internal washer/seat/seal had moved inside and was obstructing the hot water flow.

Also, I've never seen one, but I understand there is a new Atwood XT model that heats the water hotter than normal and has a built-in mixing valve. Could the prior owner have put one of these in, and that valve is not functioning properly?

[Al and Missy]

Originally Posted by Siegmann

Are you sure the tank is stratified? You could try touching the cold water inlet at the bottom of the tank and see if it is hot.

Try disassembling the shut-off valve that is on the hot water out line. Someone once described how the internal washer/seat/seal had moved inside and was obstructing the hot water flow.

Also, I've never seen one, but I understand there is a new Atwood XT model that heats the water hotter than normal and has a built-in mixing valve. Could the prior owner have put one of these in, and that valve is not functioning properly?

I'll try the touch test. I can hardly reach the hot shutoff valve. It is on the side between the heater and the wall. If I decide to change the heater I can check it when I pull the heater. No real way to get at it otherwise.

This is the original Atwood heater from 2002, so no internal mixing valve.

I'm going to pull the overpressure valve and drain valves (again) and look inside. I'm also going to do the vinegar flush.

I also realized that perhaps the thermostat is bad (unlikely, but possible) and it is shutting off at a lower temperature and the water at the top is hot. I'm going to bypass it, leaving the emergency cutoff switch in place. I went ahead and ordered the shutoff kit from Amazon. Worth $11 to see if that fixes it before committing to a new heater.

Al

[Jammer]

Originally Posted by Al and Missy

OK, here's the status....
The AC and propane sides now both work in an equivalent manner. After an hour or so on electric or after the propane has run and shut off, the initial water from the faucets is very hot - probably a good 160 degrees, but it doesn't last. After 10 or 15 seconds it gets to just feeling warm and then will stay that way for several minutes, probably 6 gallons or so

Bypass valve.

If you're sure it's shut, then there's something wrong with it.

[Siegmann]

Al, if your set-up is similar to mine, there is (barely) just enough space to get a small wrench on to the retaining nut under the valve handle. You could pull the stem out and look into the valve body with one of those small inspection mirrors that are on a telescoping handle.

If this is possible, I would look at the bypass valve as suggested by Jammer.

[Al and Missy]

Originally Posted by Siegmann

Al, if your set-up is similar to mine, there is (barely) just enough space to get a small wrench on to the retaining nut under the valve handle. You could pull the stem out and look into the valve body with one of those small inspection mirrors that are on a telescoping handle.

If this is possible, I would look at the bypass valve as suggested by Jammer.

Thanks everyone for hanging with me here.

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.

I filled the tank with vinegar and water 2:1 mix and fired off the heater. It only ran about 30 minutes. The specified recovery is 7.4 gal per hour so I would have thought it should have run close to an hour. I'll go out and check the temperature on the exposed inside wall with my IR thermometer.

Al

[Jammer]

Originally Posted by Al and Missy

I filled the tank with vinegar and water 2:1 mix and fired off the heater. It only ran about 30 minutes. The specified recovery is 7.4 gal per hour so I would have thought it should have run close to an hour. I'll go out and check the temperature on the exposed inside wall with my IR thermometer.

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.