Tankless water heaters

[dmadam]

I am considering puting a tankless water heater in my 83 Limited. I went to a link for them at the topof one of the forums but every unit said "not suitable for RV use". First why are they advertising here if they are not suitable and second why are they not.

Way back in '89 I put one on my first RV. An '83 Toyota flip top which had no hot water. Mounted it over the kitchen sink and it worked fine. I thought doing in in my AS would be a piece of cake but really would like to know what the dangers are.

Thanks
David

[BobbyW]

Bosch RV-500 Tankless water heater for Recreational Vehicles

http://www.gaswaterheaters.com/boats...V500/index.htm

This particular link has a very good FAQ sheet. I have never dealt with this company or heater. I just had the link for information.

The links at the top of the page are just generated based on keywords. In this case it is probably "water heater".

[dmadam]

Thanks BobbyW, Thats exactly what I'm looking for. Had not seen that one. It cost about 30% more that the others but then thats the RV life!!.

David

[camphost]

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Originally Posted by dmadam

I am considering puting a tankless water heater in my 83 Limited. I went to a link for them at the topof one of the forums but every unit said "not suitable for RV use". First why are they advertising here if they are not suitable and second why are they not.

Way back in '89 I put one on my first RV. An '83 Toyota flip top which had no hot water. Mounted it over the kitchen sink and it worked fine. I thought doing in in my AS would be a piece of cake but really would like to know what the dangers are.

Thanks
David

I am considering the installation of the tankless bosch rv 500 water heater..would appreciate a posting on how this unit works for you. Let me know how your installlation goes. I will be installing to an old #10 atwater in 1976 ambassador model airstream.. Thanks

[smily]

$ 879.00
Yeeeeeooooww! Now that IS hot water, it burns my butt.

Buy the ten gallon water heater and lots and lots of LP!

Smily

[camphost]

I am considering the installation of the tankless bosch rv 500 water heater..would appreciate a posting on how this unit works for you. Let me know how your installlation goes. I will be installing to an old #10 atwater in 1976 ambassador model airstream.. Thanks

It is so clear it is hard to see

[smily]

Am I reading you correctly, you are replacing a 10 gal water heater in your 1976 Airstream?

That is the first I have heard of an OEM 10 gallon in an 1976 Airstream.

Is it OEM?

I was under impression that all AS trailers in that era came with 6 gallon WH's.

I was merely saying that I would move to a 10 gallon with all the bells and whistles before I would come off that kind of money for a WH. "IMHO"

Smily

[bryanl]

Originally Posted by smily

Am I reading you correctly, you are replacing a 10 gal water heater in your 1976 Airstream?

My '75 Ambassador came with a ten gallon. A previous owner replaced it with a 6 and had to add a patch for the hole left behind.

The RV500 is the only RV specific inline water heater I have heard about. Reports from users have generally been positive. Some have found sources for it at under $700. I have also heard rumors that the mfg is providing a hydronic heating option that would allow it to substitute for or replace the RV furnace (there are some homebrew projects for this out there, too).

Its main advantages over a standard hot water heater include efficiency and continuous hot water availability, which could be useful with full hookups. A standard 6 gal tank water heater doesn't allow for two or more showers of any significance in a row and its 15k BTU or so burner takes a while for recovery.

The main disadvantages include cost and a small battery current requirement.

[Morning Dew]

I'm about to buy one of these units. I'm sick of worring about hot water, especially when i'm at a full hookup site. THe unit i'm buying is a refurbished unit for $200 less than retail with a no questions 1 year waranty. i'll let you guys know how it performs when i get it installed.

[thenewkid64]

Originally Posted by smily

That is the first I have heard of an OEM 10 gallon in an 1976 Airstream.

Is it OEM?

I was under impression that all AS trailers in that era came with 6 gallon WH's.

Ken,

The Overlander (74) that I had came with a 10 from the factory. In the 70's I think the 10 gallon was part of the international package IF you had a tub. Part of the reasoning was that to fill the tub would take all ten gallons

[dmadam]

Brian
I would love to get feed back on the unit. I am currently remodeling mine and then spending 6+ months per year in it. good luck.
David

[Over59]

Doesn't look water friendly if you are off hookup and waiting for the wwater to heat. I have a large gas unit in my home which is not as good as the larger oil tank was for really hot water.

[markdoane]

Is it possible (if money were no object) to put a small tank heater downstream from the tankless heater? I'm thinking this would overcome a frequent complaint about tankless systems, which is the time required to fire up and reach termperature. I think that would overcome the problem of water wastage when all you need is a quart of hot water to wash a few dishes.

[Anon]

My father bought a brand new 31 footer back in 1973 and it came with the ten gallon as well. All of us kids were young then and he ordered the trailer with the tub and the hot water upgrade came with the tub. Just a little FYI.

Lou

[Janets Husband]

Originally Posted by markdoane

Is it possible (if money were no object) to put a small tank heater downstream from the tankless heater? I'm thinking this would overcome a frequent complaint about tankless systems, which is the time required to fire up and reach temperature. I think that would overcome the problem of water wastage when all you need is a quart of hot water to wash a few dishes.

Don

It is possible with the right amount of money, but...

Water wasting waiting for it to get hot is a function of distance from the heating appliance to the faucet, volume of the water pipe, temperature of the captured water in that pipe, and the rise time of the heating device.
The way I see it you must over come these obstacles.

The best way to do this is shorten the run from the heater and speed up the temperature rise time.
This can be done by placing a tank type water heater right at the faucet but you just gave away the advantage of a tankless heater.
Give and take.
You might look at a small electric tankless heater (Point of Delivery), I have seen them in plumbing stores and could be adapted to take care of your problem.
The only problem I see is you could only use it when hooked up to shore power.
Give and take.
I am not aware of any small gas powered under sink units.
Good luck with your quest.

[bryanl]

I think you are going to get hot water from a tankless just as fast as you would from a tank. Either way, the problem is the water currently in the lines. One of the more interesting ideas I have seen for this problem was credited to Trailer Life and suggests putting a valve in the hot water line that will release water back to the supply tank. Then you can purge the cool water in the hot water lines without wasting water.

A tankless water heater that requires time to fire up and reach temperature would be pretty much useless. Avoiding this lack of utility is why their burners are 4x more powerful than those on a tank type, why they don't store water, and why the flow sensor is important.

For the water lines in an RV, figure about 44 feet of line per quart of water. This is 2 lb. From the input side of the tankless to a shower might be half this length or 1 lb of water. 40k BTU/hr (RV-500 output) is 11 BTU/sec and flow is likely to be about 10 lb/min or 1 lb in about 6 seconds. (please check my math before taking this too seriously!)

I read this as indicating it will take about 6 seconds to purge the hot water line and this would allow a tankless heater like the RV-500 to apply a 70F temp rise to the water going through it in this time.

I don't think the ignition lag in a tankless is going to be of much significance in this scenario as that is only a fraction of a second plus a second or two to transfer the heat.

Usually, people use hot water tanks and then place tankless heaters at the point of use as a means to avoid line purge wastage, not the other way around. You can find a lot of 'under the sink' low rate tankless water heaters in home improvement stores.

Oh, and by the way, Note that these electric under the sink tankless things are about 5,000 BTU/hr at most as that is a typical 15 Amp circuit.