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Old 03-29-2004, 09:09 PM   #1
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tankless hot water heater

Antiqua Has anyone replaced their hot water heater with the tankless system? If so, how did you do it and was it difficult? We would like to do this with our AS as we always run out of hot water and I hear these systems provide hot water as long as the faucet is turned on...
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Old 03-29-2004, 09:23 PM   #2
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We put one in our house. Works fine once it gets up to speed. You wait longer than with a tank for "hot" water so I don't think it would be good for running without a water hookup. They raise the water temperature a certain number of degrees. So if you have one that brings it up 70 and you put in water at 40 you can have 110. Very hot. Check the temperature rise on any unit you consider. Plumber have not problem putting it in and connecting the city gas.
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Old 04-04-2004, 01:24 PM   #3
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The European tankless hot water heaters give hot water instantly and run on propane. I'd love to have it if I could tolerate propane. The electric one especially at 110v can bring water up 40-50 degrees from the tap water temp. 22o volt works much better. Look at energy star ratings- gas/propane ones in a house can pay for itself in one or two years. Look under marine water heaters, or tankless water heaters in google. I'm using a 110 volt point of use at the shower to boost the heat immediately. Staying mostly in the south, cooler showers are nicer. Silver suz
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Old 04-04-2004, 03:24 PM   #4
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Precision Temp makes a tankless water heater for RV use. It will fit into the same hole that a 10 gal tank type water heater uses. see Precision Temp

The caveat on these things is that it takes a lot of energy to heat water and on demand heating means large energy flow. The RV 500 brags about 940 gallons of hot water from a 20 lb propane tank. It runs at about 50,000 BTU, which is about max for RV appliances. The unit uses a modulated burner for 12,000 to 50,000 BTU and costs about $700 or so. I have seen mostly good reviews from users.
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Old 04-05-2004, 12:14 AM   #5
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Thanks for the info! The current standard hot water heater doesn't last long enough and I can't wait to replace the darned thing!
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Old 04-05-2004, 04:54 AM   #6
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Originally Posted by imeynstein
Thanks for the info! The current standard hot water heater doesn't last long enough and I can't wait to replace the darned thing!
???? My '85 has the original hot water heater. As do many others of that age and older.

Mark
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Old 04-05-2004, 07:08 AM   #7
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I took a look at that site....anyone here have a scorched outer skin from using their hot water heater as the web site claims?
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Old 04-05-2004, 09:36 AM   #8
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I would consider keeping the old hot water heater if it wasn't in sad shape. It makes horrible loud noises when it is running and it has turned the outer door black!!! I haven't found anything to help with the discoloration yet. I think I will try 'Barkeepers Friend' as it claims to remove just about any stain, however I am concerned with its' abrasiveness as it has the consistency of comet--therefore I am going to use it in a very small area around the vented slots only and not on the skin just to see what it will do. It it scratches with only gentle pressure, then I will keep looking for an alternative solution...
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Old 04-05-2004, 11:49 PM   #9
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Personally, I think that the instant tanks are not as good as some folks claim them to be on LP gas unless you fulltime. According to the posted site, that info conflicts with some of the info some folks have posted about these tankless units.....
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Old 04-06-2004, 12:28 AM   #10
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Originally Posted by Silvertwinkie
Personally, I think that the instant tanks are not as good as some folks claim them to be on LP gas unless you fulltime. According to the posted site, that info conflicts with some of the info some folks have posted about these tankless units.....
I don't know what full timing would have to do with how good the system is, only in making it easier to amortize the expense, which is about twice that of a tank version.

A 50,000 BTU LP burner is about equivalent to 15 KW electricity. Its much easier to get 50,000 BTU of LP in most RV's than it is to get 15 KW.

Say you take a ten gallon shower and need to warm the supply water from 60F to 100F for a 40F raise in temperature. This is 80 lb of water heated 40F or 3200 BTU. This will get you maybe 15 showers an hour with the RV 500 tankless going full tilt (assuming you have the water supply and waste handled). Another way to say this is that you can get 150 gallons of very warm water an hour or a flow rate of a bit more than two gallons per minute. This is in the typical range of RV water pumps and shower heads, I think.

I believe the typical tank type water heater burner is about 15,000 BTU and 6 to 10 gallons of storage. The tankless burner is about three times bigger and it is also more efficient (the reason why avoiding skin scorching is a claim for the tankless as the exhaust temps are much lower)

Either way, you aren't going to get far towards a typical household shower (150 gallons if I remember the claim in my last water bill newsletter) with any RV water heater. But the tankless will allow you to take a longer shower than will a tank type and you can get the temperature hotter by reducing the flow a bit. When a tankless runs through its tank, you either wait for it to reheat or rinse with cold water.
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Old 04-06-2004, 05:27 AM   #11
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In an RV application, according to the site (unless I misread it), it takes a fairly large BTU to get it going (which we all know that LP takes longer to heat things and at elevations, even longer). Most folks that fulltime might see the benefits as they might have larger LP tanks, might be at lower elevations, might have a fresh water connection, etc. Those that use the HWH seasonally and/or boondock, might never the the benefits vs cost and fuel consumption for the typical RV application. I figure if they worked well in most of the RV environments, RV builders would have started installing them a while ago, yet, I haven't seen any on an average coach. The system as advertised does not seem to work well off a fresh water tank, meaning, that if you used the shower in your coach as designed with the quick shutoff, etc, they tankless system, the way I understand it stops heating, whereas a fulltimer might shower or use the tankless system similar to how folks use hot water at home.

Thats kinda what I was getting at. Keep in mind what I've posted is based on the site linked and basic understanding of LP gas and tankless heaters. I don't have any real world exp with them......yet, but my gut tells me that for the average seasonal RVr, the tankless system's cost and performance based on type of use, might not make it as great of a value IMHO.
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Old 04-06-2004, 06:41 AM   #12
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Quote:
Originally Posted by imeynstein
I would consider keeping the old hot water heater if it wasn't in sad shape. It makes horrible loud noises when it is running and it has turned the outer door black!!!
The loud noise and soot are symptoms of maladjusted or a partially blocked burner tube. The black stuff should come off with th black streak remover they sell at CW and a sponge.

If the heater was replaced at some point the RV tech may not have properly adjusted the burner and that is why it roars, that could also be the reason for the sooty exhaust. It is a simple adjustment of the air shutter on the main burner tube. You want the flame to be blue to the tips with just a touch of yellow at the ends, and no roar. one screw is all that holds the slotted air shutter in place. It is right by the thermostat.
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Old 04-08-2004, 05:58 PM   #13
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On the water heater topic--- my Atwood shuts down after the burner light for a few minutes, not enough to heat the water very much. It has a replaced board in it, and I don't see any adjustments. What are the opinions on replacing the burner with a electric hotrod? Saw them at Camping world the other day. When it does burn the flame is nice and blue by the way.
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Old 04-08-2004, 07:43 PM   #14
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Alan,

Check the flame probe. It is the electronic replacement to the thermocouple. If it is heavily corroded or missing it will cause the heater to lock out if it does not sense temperature. Should be on a clip with the igniter spark thinghy.
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Old 04-09-2004, 03:59 PM   #15
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OK! If I can figure out which thingy to check I will do so. Thanks
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Old 04-09-2004, 10:56 PM   #16
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I too question how good the tankless RV-500 unit is for the folowing reasons:
It is awfully small, most tankless home water heaters such as the Aquastar125 are almost 3 times the size and the Aquastar125 is rated for one use at a time, one shower, one load of wash etc. That said, I am considering a larger model for my house.

The Precisiontemp website has specs for the RV-500 that say:
" there is an 85 degree rise per gallon per minute."
and
"at 2 GPM of water 20lbs of propane will produce over 940 gallons of hot water"

I cant really find any more information than this on their site or anywhere on the web.
What I am wondering is what is the temperature rise at 2GPM? I doubt its 85 degrees, and how hot is the "Hot Water" in the second quote above

The Aquastar125 has a 125,000 BTU input and has and does 2GPM @ 90 degree rise and 2.4 @75 degree rise
The RV-500, as stated above, does an 85 degree rise per gallon per minute. but it has a 53,000 BTU input
Sooooooo... comparing the Aquastar home unit which is designed for one use at a time (one use being a 2.5gpm use) My guess would be, based on the Precisiontemp specs (or lack thereof) that the RV-500 would be able to generate less than half that. Now 2.5GPM could be considered a lot for an RV shower, and maybe... maaybe at a 40 degree rise the RV-500 could do 2 or 2.5 GPM, but I think if you wake up on a chilly morning and wanna take a hot shower and have a 35 to 45 degree inlet water temp, which is not unusual in many parts of the country.... your shower is gonna be 75-85 degrees, which I guess is tolerable -but its not hot. Maybe the RV-500 is better than that, maybe worse, Im just sceptical when the manufacturer doesn't list the rise over a variety of flows, or at least at the flow which is most important- the shower.
The RV-500 is costly at over $800 and you must also consider your application. If there is a waste and water hookup, maybe the RV-500 would be a better option, the hot..err.... warm shower would be continuous, but if you have to worry about your grey tank filing up, or running out of fresh water when boondocking you arent gonna stand there with the water running constantly for 20 minutes taking a shower. In that situation woudn't you rather have your short spurts of shower water much hotter thant 80-ish? Especially if the tank style water heater costs much less?
-now if you ran 2 RV-500s in series.........

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Old 04-09-2004, 11:12 PM   #17
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Originally Posted by amfab
The Aquastar125 has a 125,000 BTU input and has and does 2GPM @ 90 degree rise and 2.4 @75 degree rise
...
My guess would be, based on the Precisiontemp specs (or lack thereof) that the RV-500 would be able to generate less than half that.
If you read my previous post, you will see similar conclusions, I think. The RV500 is rated at 50,000 BTU/hr which is about 40% of the Aquastar model you cited.

But also keep in mind that the RV500 is rated at about 4 times the heating capacity of the normal tank type RV water heater.

Comparing household water heaters to RV water heaters is probably good only to get an idea of the limitations of the RV lifestyle.

What an RV use of the RV500 would get is a more efficient water heater that would not be completely useless after only 5 gallons. It could also replace the furnace burner with appropriate additions.

The Aquastar is nifty in that it doesn't need electrical power like the RV 500 but it is not built for RV application. I also don't know whether your typical RV propane system could feed it properly.
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Old 04-10-2004, 02:12 AM   #18
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I was comparing the two units only to give some idea of what the output in usable hot water of the RV500 is because the manufacturers specs on the website do not provide this information. I was not suggesting the use of a home unit in an RV application.
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Old 04-17-2004, 01:23 PM   #19
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Aquastar 125 for RV ?

"The Aquastar is nifty in that it doesn't need electrical power like the RV 500 but it is not built for RV application. I also don't know whether your typical RV propane system could feed it properly."


I am restoring a 31' Sovereign & am considering using an Aquastar 125 home unit...if I can find a good place to mount it.
Why would RV propane feed be a problem ?
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Old 04-17-2004, 02:58 PM   #20
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I am restoring a 31' Sovereign & am considering using an Aquastar 125 home unit...if I can find a good place to mount it.
Why would RV propane feed be a problem ?
There are two limitations. One is the capacity of your regulator (although most of these will handle maybe 200,000 BTU) and the other is the size of the tubing. You might need to use half or 3/4 inch ID tubing to provide the 100,000 BTU of propane needed. There isn't much leeway here.

But your biggest problem with a home type instant water heater is likely to be the flue and proper ventilation.

Most of the folks I have seen who own the RV500 seem quite happy with them. They fit into the same space a typical 10 gal water heater would and provide hot enough water for a good shower. The only negatives I have heard involve a slight delay in getting hot water.

I am thinking that the flow rate to work the Aquastar might be a drawback on its use in low volume water situations.

Good luck with the remodelling! Keep us posted on what you learn!
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