Converting to an on-demand water heater

Topic: Converting to an on-demand water heater (Read 2900 times) previous topic - next topic

Re: Converting to an on-demand water heater

Reply #25 – December 15, 2011, 12:24:59 pm

Quote from: wolfe10 – December 15, 2011, 09:37:23 am

Steve,

Not sure you want your newer inverter/charger (I assume that is what you are adding) with its higher amp draw than the OE converter AND a high amp electric heating element for the new water heater on the same circuit. Each should have its own breaker in the 120 VAC breaker box and you should verify that the wire is sized for the new load.

Brett

Hi Brett,

Perhaps I didn't explain myself well. The inverter is getting power from a 10/3 cable (common trip 30 amp breaker) from the main panel, and a 10/3 cable returns from the inverter to feed a subpanel. The original electrical panel is gone, replaced by two new panels.

What I'm thinking is to completely remove the original converter, and use that AC circuit (20 amps) to power the water heater (dedicated only to the water heater). With the converter gone, seemed like a good use for an otherwise unneeded circuit.

Do appreciate your concern and thoughts. Thank you.

Worth mentioning - the original panel had an aluminum bus, and I noted on one the hot legs going on, and a few of the wires coming off the breakers - oxidization. The copper wire end was turning black. I showed an electrician friend this and asked about it. He told me it's the result of the dissimilar metals. The new panels have a copper bus.

Steve

Re: Converting to an on-demand water heater

Reply #26 – December 15, 2011, 12:42:52 pm

Re: The Girard tankless heater - I did a lot of reading on the different types of RV water heaters available, and what I found was a lot of people were very unhappy with the Girard heater, the big complaint being that you have crank up the flow to lower the temperature, instead of mixing in cold water. Many felt this was too wasteful of water when boondocked, and most folks went back to a tank heater. I have no direct experience so cannot say one way or another. If you google "Girard water heater problems" you'll find a lot of threads posted.

The big complaint with the Precision Temp unit was performance on a windy day. Makes ordering the optional wind cover mandatory. Most people seemed happy with them; some had repeated issues that led them to chuck them as well. Most people seemed to agree a tankless heater was not suitable for boondocking. Again, no direct experience myself.

What swayed me back to the Atwood unit was the 3 way heating capability. If I'm plugged in, I don't use propane to heat the water. That, and parts are readily available from numerous sources. Lastly, it's less than half the price of a Precision Temp unit. Just seemed the best choice overall.

Steve

Re: Converting to an on-demand water heater

Reply #27 – December 15, 2011, 12:58:07 pm

Thanks for that perspective Steve! Since my own water heater is out right now and is 12 years old, we are probably going to put a new one in and are considering the idea of on demand units. I have one in my house and have grown attached to it... Setting th temperature and not having to juggle the cold water mix is such joy. Sounds like the RV units don't work that way...
Don

Quote from: Merle Hench – December 15, 2011, 12:42:52 pm

Re: The Girard tankless heater - I did a lot of reading on the different types of RV water heaters available, and what I found was a lot of people were very unhappy with the Girard heater, the big complaint being that you have crank up the flow to lower the temperature, instead of mixing in cold water. Many felt this was too wasteful of water when boondocked, and most folks went back to a tank heater. I have no direct experience so cannot say one way or another. If you google "Girard water heater problems" you'll find a lot of threads posted.

Re: Converting to an on-demand water heater

Reply #28 – December 15, 2011, 01:08:32 pm

Don - is the plumbing there to hook up to the engine heat?

Re: Converting to an on-demand water heater

Reply #29 – December 15, 2011, 01:09:32 pm

The Atwood three way WH in the 97 U270 is OEM and works like a top. It is 10 gals. and I've never run out of hot water taking very long showers whether using the electric or propane feature. I'm very satisfied with its performance.

(edit): The electric heating element was replaced by FOTn in 2003 when I purchased the coach with a 6 month warranty. It has been performing as expected since.

Re: Converting to an on-demand water heater

Reply #30 – December 15, 2011, 01:21:26 pm

Yes, ours has the heat echanger on it. Through a bucket miscalculation, I lost about 2 gallons of coolant! Oh well, I guess it is time to change it anyway...
Don

Quote from: Gayland Baasch – December 15, 2011, 01:08:32 pm

Don - is the plumbing there to hook up to the engine heat?

Re: Converting to an on-demand water heater

Reply #31 – December 15, 2011, 02:43:43 pm

Wow, lot of posts on this subject. I skimmed through most of them, but didn't see any mention of how big a gas line connection is required for a tankless or on demand heater. I thought about installing a tankless water heater using natural gas in the house, but didn't do it as it required an increase in the size of the gas pipe to the heater. A major job as the gas pipe went down inside a wall from the attic to the bottom floor (2 floors). A motorhome should not be as difficult to re-plumb if required, but maybe a consideration. If you are wondering why the gas line is in the attic; that's where the furnace and air handler for air conditioner are located. After the furnace the gas line branches off to other appliances (stove, fireplace, water heater).

Re: Converting to an on-demand water heater

Reply #32 – December 15, 2011, 09:44:14 pm

Gas line size is very important, I learned. I suffered with a too small a supply line on my home unit, till I re-read and got the major large required size flex piping. Not sure I am ready for a on demand in the coach, as it will encourage the running of water, which is usually tank water for us. We tend to fill and use the tank on most short trips. Refilling when we run out, or are headed out of the campground.

Re: Converting to an on-demand water heater

Reply #33 – December 16, 2011, 07:19:08 am

Quote from: acousticart – December 15, 2011, 12:58:07 pm

Thanks for that perspective Steve! Since my own water heater is out right now and is 12 years old, we are probably going to put a new one in and are considering the idea of on demand units. I have one in my house and have grown attached to it... Setting th temperature and not having to juggle the cold water mix is such joy. Sounds like the RV units don't work that way...
Don

Hi Don

,

Something you can add to your coach that I spotted the other day, while searching for a kitchen faucet, is a shower mixing valve that regulates the temperature, so once you get it where you want it, it will keep it there. Did not appear to be any bigger than a standard mixing valve. Don't have a link, but I saw it on Amazon.

It has occurred to me that a common cold weather irritation in the stick and brick with regards to showers is waiting for the hot water to get hot, and then having to keep cranking it warmer as the cold water lines empty out of room temperature water and outside (cold) water is drawn in. I don't see this being the case in the coach, as the plumbing distances are much shorter than in a house.

I like the idea of an on-demand heater, but just don't see it as ready for primetime for RVs. For peace of mind, I'm going with something that has a proven track record and happy owners.

Here's an idea I've been toying with - RV solar water heating. Water is circulated from your hot water tank to a roof-mounted solar collector/heat exchanger and pumped back into the tank. A thermostat regulates temps. A small pump attached to the tank does the circulating. Might not work well in colder weather (heat loss too great), but would save power in warmer weather. Of course, a leak in the system could be a disaster, and freezing weather would also be a consideration. Something portable might work. Will think on that some more.

Steve

Re: Converting to an on-demand water heater

Reply #34 – December 16, 2011, 10:07:27 am

I've heard of folks collecting the shower water in a bucket until the water gets to temperature. This collected cold water is then used for toilet flushing/washing dishes, anything that does not need potable water.

Re: Converting to an on-demand water heater

Reply #35 – December 16, 2011, 10:22:55 am

Peter,

We routinely did that on the sailboat. With every gallon (remember, 8.3 pounds per gallon) of water having to be hauled out to the boat in the dingy, hoisted onto deck and poured into tank fill, one learns very quickly to be conservative with water use OR becomes very strong from the weight training.

Re: Converting to an on-demand water heater

Reply #36 – December 16, 2011, 01:14:44 pm

Quote from: wolfe10 – December 16, 2011, 10:22:55 am

Peter,

We routinely did that on the sailboat. With every gallon (remember, 8.3 pounds per gallon) of water having to be hauled out to the boat in the dingy, hoisted onto deck and poured into tank fill, one learns very quickly to be conservative with water use OR becomes very strong from the weight training.

Not to mention from rowing around to every other boat in the anchorage borrowing 5-gallon jugs. 70 gallons of water requires more jugs (14 or so) than you can conveniently carry on a 30-something sailboat.

We solved part of the water issue by using a 2-gallon spray tank. We heated a gallon of water to a nice temperature on the stove, filled most of the tank, pumped it up a few times, and took a shower. We could both take a shower in one fill-up. If the ocean water (and air temps) were warm enough we'd soap up with the tank, rinse by jumping over the side, and then rise off the salt with the tank.

And if we got a nice rain shower we all headed topsides!!!

Craig

Re: Converting to an on-demand water heater

Reply #37 – December 16, 2011, 02:35:20 pm

And we thought we had it tough with a FT that carries 100 gallons of fresh water ..... Maybe I won't consider a yacht after all.

Gary B

Re: Converting to an on-demand water heater

Reply #38 – December 16, 2011, 03:22:07 pm

Thanks for the suggestions Steve, I believe that Dave K. Posted a how to on the balancing mixing valve... I will have to look into that option. I am not sure I even understand what it does VS. an ordinary mixing valve, but it sounds cool! Or hot:). Speaking of water heaters, I pulled the drain plug on mine (or what I thought was the drain plug!), and there is something still in there that seems like it will never come out. I wonders if maybe it is some sort of check valve, or? Got nothing! Here is pic of it, anybody know what it is? Since our 3-way water heater was working when I took it out, if I could be sure the tank was good, I would think about getting new Styrofoam insulating kit for it, clean it out really well and put it back in. On the other hand, it is a lot of work and maybe the peace of mind of having a new unit before beginning full timing might be worth the expense (about $600 for a new 10gal 3-way with heat exchanger). Any comments?

Quote from: Merle Hench – December 16, 2011, 07:19:08 am

Something you can add to your coach that I spotted the other day, while searching for a kitchen faucet, is a shower mixing valve that regulates the temperature, so once you get it where you want it, it will keep it there. Did not appear to be any bigger than a standard mixing valve. Don't have a link, but I saw it on Amazon.

Re: Converting to an on-demand water heater

Reply #39 – December 17, 2011, 12:20:36 pm

Don,
PO must have installed a plug with an zinc anode on it. The anode deteriorated to the point where it's disconnected from the plug and is stuck in the hole. I would just push it through into the tank, do a flush with one of those clean-out wands and reinstall the plug. There's other thread conversations about this but you really don't need an anode for the Atwood tanks. The anode should eventually totally dissolve and you will see it come out as you do flushes of the tank.

Re: Converting to an on-demand water heater

Reply #40 – December 17, 2011, 03:29:23 pm

Thanks John,
Reading up on the Atwood anode thing... Found out that the anode for aluminum tanks should be magnesium vs zinc. I will try soaking with a vinegar solution (as suggeted to me by another forum member) for awhile and see if it loosens up. The WH is out right now and it will be awhile before I will be ready to reinstall the old one or put a new one in, so not in a rush ATM.
Don

Re: Converting to an on-demand water heater

Reply #41 – December 18, 2011, 12:07:51 am

On saving shower hot water when boondocking: Dick Ward posted a mod about a year ago (I think) that added a timer and valves and plumbing to circulate water from the hot water taps on the shower and the lav back to the fresh water tank, so when you were going to take a shower, you would trigger the timer and all the hot water in the lines would be sent back to the tank for some set-able period until ready for a shower. Very clever solution for boondocking!

Adding a circulating pump for quicker hot water

It's somewhere down on my to do list...

Re: Converting to an on-demand water heater

Reply #42 – December 18, 2011, 12:29:12 am

Quote from: acousticart – December 16, 2011, 03:22:07 pm

Thanks for the suggestions Steve, I believe that Dave K. Posted a how to on the balancing mixing valve... I will have to look into that option. I am not sure I even understand what it does VS. an ordinary mixing valve, but it sounds cool! Or hot:). Speaking of water heaters, I pulled the drain plug on mine (or what I thought was the drain plug!), and there is something still in there that seems like it will never come out. I wonders if maybe it is some sort of check valve, or? Got nothing! Here is pic of it, anybody know what it is? Since our 3-way water heater was working when I took it out, if I could be sure the tank was good, I would think about getting new Styrofoam insulating kit for it, clean it out really well and put it back in. On the other hand, it is a lot of work and maybe the peace of mind of having a new unit before beginning full timing might be worth the expense (about $600 for a new 10gal 3-way with heat exchanger). Any comments?

Don,

I would replace it if I were you. We had our original heater (same as yours) develop a leak about 2 years ago, and I replaced it with a new one. Couldn't get the model with a heat exchanger delivered in time to meet our travel schedule, and I went with a 2-way (120V + propane), which has been fine. The styrofoam insulation on the new ones keeps water plenty hot all day while we're travelling.
BTW- Atwood says not to use an anode on their tanks. - Not needed since they are aluminum.
And BTW2 - reconnecting it with reinforced flex hose, (instead of PEX,) makes the installation a whole lot easier!

Re: Converting to an on-demand water heater

Reply #43 – December 18, 2011, 02:46:35 am

Quote from: Peter & Beth – December 15, 2011, 01:09:32 pm

The Atwood three way WH in the 97 U270 is OEM and works like a top. It is 10 gals. and I've never run out of hot water taking very long showers whether using the electric or propane feature. I'm very satisfied with its performance.

I agree wholeheartedly, Peter. The Atwood 10 Gal. Aluminum units, treated and cared for properly, are another reason that the U270's shine in their simplicity and longevity. We've never had a complaint or problem with ours in 12 years. A mud dauber screen (and simple cleaning annually) and it's good to go, never short of hot water on or off the road.
One issue that many ignore is NEVER consider a sacrificial anode of any flavor, Magnesium OR Zinc. I know the unit won't last forever, but exactly the same unit will be my first choice when I need to replace it.

Quote from: acousticart – December 16, 2011, 03:22:07 pm

................Speaking of water heaters, I pulled the drain plug on mine (or what I thought was the drain plug!), and there is something still in there that seems like it will never come out. I wonders if maybe it is some sort of check valve, or? Got nothing! Here is pic of it, anybody know what it is? .................................................

Don,
Your previous owner did you an unintentional disservice, removed the NYLON (or maybe it is TEFLON) drain plug and installed a sacrificial zinc (mostly aluminum) anode in the the drain fitting. That is in direct conflict with the ATWOOD owner's manual for our three way heaters. The aluminum/zinc fitting story is as follows:
The aluminum/zinc sacrificial anode provides very little driving current to protect an aluminum tank, especially when softer water happens to be in the tank, so it isn't providing any protection to speak of...........it is just creating issues as follows:

The AL/ZN anode produces about 1000 times it's volume in corrosion byproducts

That's just junk that sits in the tank or gets deposited downstream in all the pinch points/ wrong places

The original AL/ZN anode starts to expand the day anyone installs it and it becomes hard, if not impossible to remove it (what you've experienced)

The AL/ZN anode crumbles off the center core mounting rod, junking up the bottom of the heater and the mounting rod itself becomes weak and sacrificial (again, what you've experienced)

Free aluminum molecules/radicals get carried along in the hot water stream and they do all kinds of ugly things to liver, brain, kidney, spleen and neural systems

All because someone wanted to be a good guy and protect the aluminum shell of the heater (in contradiction with the OEM's directions).

I don't believe vinegar will dissolve it.
If it were me , my choices would be:

If I could grasp the broken anode core rod with needle nosed vise grips, I'd keep gently working on it (it may be soft enough to yield the expanded material enough to work it back out of the drain opening). Then I'd thoroughly flush the sacrificial junk out of the tank each month, for several months.

If that doesn't work, replace with a new Atwood of same model

You also have the option of pushing the broken anode through and then just try to minimize the ingestion of any of the hot water (use only cold water for cooking after flushing any residual hot water from the common plumbing (before each cold water cooking use).
Good Luck and Merry Christmas to all!

Neal

Re: Converting to an on-demand water heater

Reply #44 – December 18, 2011, 02:31:44 pm

Thanks Neal! Excellent and informative post as usual. I think we are just going to replace it with another 3 Way Atwood of the same model. Too bad the PO decided to add an anode... I will salvage the electronics etc. from the old one for spares. It is just too much hassel to put the old one back in and have to deal with all the gunk in it and the possibility of it starting to leak etc. I like the styrofoam insulation on the new ones. Looks much more "tidy" than the cardboard box around the old one.
Don

Re: Converting to an on-demand water heater

Reply #45 – December 18, 2011, 06:11:55 pm

Dave,

We have decided to replace the WH. Looking forward to the improved performence via the styrofoam insulation. What kind of flex hose did you use? The fittings on the both the old heater and on the manibloc appear to be pipe thread, while those braidied stainless steel hoses typically used for home washer hook up use garden hose type thread. Were these one you made yourself to length? If not how long were the ones you used?

Thanks, Don

Quote from: Dave Katsuki – December 18, 2011, 12:29:12 am

Don,

I would replace it if I were you. We had our original heater (same as yours) develop a leak about 2 years ago, and I replaced it with a new one. Couldn't get the model with a heat exchanger delivered in time to meet our travel schedule, and I went with a 2-way (120V + propane), which has been fine. The styrofoam insulation on the new ones keeps water plenty hot all day while we're travelling.
BTW- Atwood says not to use an anode on their tanks. - Not needed since they are aluminum.
And BTW2 - reconnecting it with reinforced flex hose, (instead of PEX,) makes the installation a whole lot easier!

Re: Converting to an on-demand water heater

Reply #46 – December 18, 2011, 08:00:43 pm

Don,
I used braided hose on mine as well when I replaced the WH. Home Depot (or Lowes) should have ones that have NPT on both ends. I don't remember the length I used but they are long enough such that you can set the WH on a stool (face down) and make all the connections. Then it's just a matter of inserting it in without pinching wires or hose. I think I had to re-tighten the fittings again after the first use of the new unit - the rubber seals relaxed a bit and I had some minor drips - it's been good ever since. Another thing that might be different on the new unit is how the AC element is turned on. The old one was independent of the gas control ( lighted AC switch at the foot of the bed). The new one uses the gas control circuit board with a second 12 volt switch (first switch being for gas).

I replaced mine in 2006 with a 3 way. I don't think the "motor assists" is very good on the new ones. It's just a short aluminum tube welded for a couple of inches to the tank. If I remember correctly the old WH had a tube that went inside one end and out the other. In practice the new unit doesn't seem to heat the water nearly as much as the old unit. I wouldn't think twice about just using a 2 way unit next time. Maybe others have had better experience with the new motor assist.

Re: Converting to an on-demand water heater

Reply #47 – December 18, 2011, 10:11:18 pm

Thanks John, that is helpful. I will look for the NPT threaded braided hose at Home Depot. I definitely see how much easier that will make the install!
Don

Re: Converting to an on-demand water heater

Reply #48 – December 19, 2011, 12:04:38 am

Various length NPT braided hose from Home Depot - just like you would use on a sink, etc... I had a tough time getting one fitting to stop leaking on the house side piping, and we ended up replacing it with a shark bite fitting.

The 'winterize bypass system' on the back of my old heater was worn out and the valves hadn't worked for years (I honestly didn't even know they were there). Since we are in FL and would never need to winterize anyway I elected to not duplicate the system.

Re: Converting to an on-demand water heater

Reply #49 – December 19, 2011, 12:08:18 am

The motoraid works as well on the new one as the old. It heats up quickly and the Styrofoam casing holds the heat in very well - far better than the original spun fiberglass roll. I can have hot water 6-8 hours.

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