On Demand Hot Water

Nick Badame Refrig/ACC · September 25, 2007, 07:04:58 PM

Yes Ron,

Injector [orfice], gas valve, and throttle disc all need to be replaced as well as doing a check on the LP pressure when done

to insure that you don't exceed 11 in of water collum.

My 12 gal electric h2o heater recovers in 40 min's and will stay hot for 2 days...... Never had a problem of no hot water even when my 3 kids are along..

When the day comes that it brakes, it will only take $15 dollars to repair it. [2500watt element]

Nick-

captain ron · September 25, 2007, 07:19:16 PM

I have a 2 gal. electric I will keep as a backup but have always wanted a propane on demand system. I have a huge propane tank mounted that is not being used. I may have jumped the gun a bit on this one but you know how I am, I get a thought about making something work and I jump in head first. How much do you think I'll have in converting to LP?
It only needs 1/2 to 2 gal per min. water flow to operate.

pvcces · September 25, 2007, 07:46:37 PM

Ron, be sure to allow for the combustion air and flue gas the on-demand water heater needs. Their needs are generally greater than for a regular water heater.

For what it's worth.

Tom Caffrey

Christyhicks · September 25, 2007, 08:02:32 PM

I think that counting on 1/2 gallon per minute flow rate to activate and run this unit is, well, let's just say that they "claim" it, but the reality is that very low flow is a PITA for tankless water heaters. We find that the more flow you have, the better they work. The problem is never "not enough hot water", but rather it is a problem with the unit shutting down on overtemp.

I'm serious. . .take a look at the Excel water heaters on Ebay. . .see if they have any LP ones. That little unit I've got in my office is reminiscent of the old Paloma's you would occasionally see in RVs, many years ago.

I don't sell them, and have no interest in them, but we've sure worked on a lot of tankless units and this little buger seems like it would be perfect for the bus converter. Christy Hicks

Sam 4106 · September 27, 2007, 08:18:41 AM

Hi Nick,
When I needed some high temperature sealant recently, I went to the automotive section of the hardware store and got some Permatex Sensor-Safe Blue RTV Silicone Gasket Maker, NO. 6BR. It is rated for 500 degrees, that was high enough for my need. There is also Permatex Ultra Copper Maximum Temperature RTV Silicone Gasket Maker, NO. 101BR, rated for 700 degrees. See www.permatex.com. In the event that you ever need a high temperature sealant, they are available.
Thanks, Sam 4106

Busted Knuckle · September 27, 2007, 08:15:27 PM

Quote from: busnut104 on September 25, 2007, 06:33:32 PM
I did just what you are talking about, I can heat my coach, pre heat the eng. and my domestic hot water. I have a precision temp lp unite. Or I can do all the same from the eng while traveling.

Inquiring minds want to know how you did it! What did you do? And please by all means please post pics and details! Ron has cut up everythink in th shop waiting to here how this was done, and I'm afraid the shop is next! FWIW

BK

Hartley · September 27, 2007, 09:12:40 PM

Ron,

I have one of those that I got a couple of years ago...

They need 2 to 3 gallons per minute to activate and keep running...

They also require a high flow gas regulator rated for 100,000 btu.. Or simply to say
enough flow to cause a 30 lb propane tank to frost up in about 10 minutes.

The conversion process is very very involved since there are rows of tiny nozzles
in the injector bank. each must either be replaced or resized for less flow.

LP Gas has a higher BTU content than Natural Gas.. So they use larger orifice/nozzles for NG.
( If you don't change them you will burn black soot out the stack...)

The fuel regulator valve is also slightly different, it has a different part number in the manual.

You may find that space, fuel and venting requirements will haunt you.. The exhaust temps can peel paint off if the heat blows back onto the surface of the bus.

There is a specific demand LP water heater made for RV's.. It's just expensive.. It also totally vents everything outside.

The Bosch will get everything in the bay very hot because it wasn't designed for confined spaces and those open flames in the burner area may not be the wisest to have. They also won't work if there is a breeze.. The burners blow out easily....BOOOM....

Dave... $:-\$

captain ron · September 28, 2007, 09:49:00 AM

Thanks guys for crushing my dreams, Back to the drawing board.

TomCat · September 28, 2007, 10:18:10 AM

Quote from: DrDave-Reloaded on September 27, 2007, 09:12:40 PM
Ron,

I have one of those that I got a couple of years ago...

They need 2 to 3 gallons per minute to activate and keep running...

They also require a high flow gas regulator rated for 100,000 btu.. Or simply to say
enough flow to cause a 30 lb propane tank to frost up in about 10 minutes.

The conversion process is very very involved since there are rows of tiny nozzles
in the injector bank. each must either be replaced or resized for less flow.

LP Gas has a higher BTU content than Natural Gas.. So they use larger orifice/nozzles for NG.
( If you don't change them you will burn black soot out the stack...)

The fuel regulator valve is also slightly different, it has a different part number in the manual.

You may find that space, fuel and venting requirements will haunt you.. The exhaust temps can peel paint off if the heat blows back onto the surface of the bus.

There is a specific demand LP water heater made for RV's.. It's just expensive.. It also totally vents everything outside.

The Bosch will get everything in the bay very hot because it wasn't designed for confined spaces and those open flames in the burner area may not be the wisest to have. They also won't work if there is a breeze.. The burners blow out easily....BOOOM....

Dave... $:-\$

With all the options, it's $1000 and worth every penny!

Jay
87 SaftLiner

FloridaCliff · September 28, 2007, 10:28:01 AM

Ron,

I have a SW12DE that is a 12 gallon, propane or electric 110vac water heater.

http://www.folandsales.com/catalog.asp?prodid=489489&showprevnext=1

I bought this as an almost new takeout from a wrecked RV for 325.00/579.00 new.

I have only used the 110 side and it works great, has an electric start for the propane.

I am switching to an electric only as it fits my usage and setup better.

If you would be interested in buying it(275.00), let me know and I will bring it to the rally at the cove.

Cliff

captain ron · September 30, 2007, 08:33:42 PM

Cliff, the web sight won't load. Can you send pictures and specs please?

bubbaqgal · October 01, 2007, 04:48:16 AM

Ron, it loads on my puter, come on over and you can check it out. Cat

TomCat · October 01, 2007, 06:45:21 PM

Ron, if you have enough propane capacity, you may want to consider this unit. http://precisiontemp.com/pt_rvmd_twintemp2.html The TwinTemp2.
Like a Webasto or AquaHot, it will meet your hot water, and hydronic needs using fuel or electricty, but uses propane instead of diesel.
My propane is $1.85/gal delivered, has been within 10 cents of that price for over 3 years, and I feel is quite the bargain.

Jay
87 SaftLiner

captain ron · October 01, 2007, 10:18:29 PM

At over $4,000.00 I don't think so

TomCat · October 01, 2007, 10:38:09 PM

Quote from: captain ron on October 01, 2007, 10:18:29 PM
At over $4,000.00 I don't think so

Seems like the JR is around half that amount...or was when I first asked about it.

Jay
87 SaftLiner