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OT Demand water heaters
By FishbonzWV, Section Remote Living Posted on Wed Aug 25th, 2004 at 04:14:00 PM MST
Anybody using them ?

I know this is off topic but since a lot of you are off grid I thought I'd ask.
We've got a farm that has no power or electricity but we do have N.Gas. A couple of years ago a I got tired of fiddling with the generator in the mourning and night and installed a battery bank and a Trace 1012 inverter. This spring I added a PV panel to keep the bank happy.
Now it's time for running water.
I got a 1000 gal tank and a 12v pump...built a roof washer (going to catch water from the 3 stall tractor barn) and ready to run the line to the camp.
So, does anyone use an on-demand water heater? Any suggestions or comments?
Just need a small one and the only one I've found online is an Aquastar 38B.
I also saw Coleman now makes a 'Hot Water on Demand' but I don't think it's for a real on-demand use.
Thanx
Bonz

OT Demand water heaters | 17 comments (17 topical, 0 editorial)

Re: OT Demand water heaters (3.00 / 0) (#1)
by ibedonc on Wed Aug 25th, 2004 at 07:22:02 PM MST
(User Info)

I have a 12kw electric one , My Wife said that was the best idea I come with yet , no more the kids yelling that other one used all the hot water , I do not have access to NG and propane is getting to expence and , I can make my own electric , even if I have to use a Diesel gen and run it off WVO (Biodiesel)

it work great, only on when you need hot water which is a lot less then a tanked one

Re: OT Demand water heaters (3.00 / 0) (#2)
by cvo on Wed Aug 25th, 2004 at 07:26:10 PM MST
(User Info)

Bonz,
I have the Bosch AquaStar 125B model, don't know about the 38B, but I can tell you that this heater is really nice, no problems, great hot water and easy on the fuel. I use propane because of my remote cabin and its cheap.
It only comes on when you tell it.
The 125 comes in a NGas model. Bosch at 1 time had a chart that you could plug in your requirements/usages and you'd pick the model that suits your application.

Your water pressure and inlet water temperature must meet the heater's requirements for it work well.

If you intend to preheat the inlet water by solar you must have a heater designed for this purpose.

Re: OT Demand water heaters (3.00 / 0) (#3)
by Vtbsr on Wed Aug 25th, 2004 at 07:30:57 PM MST
(User Info)

I am running the Aquastar 125 b. This one will heat the water up to your required temp if you are preheating with solar or wood. It modulates the flame so if the water is coming in hot the flame comes way down. Most heaters will just heat a set amount. Having a storage hot water heater is like running your car full time, when it is parked in the garage.

Re: OT Demand water heaters (3.00 / 0) (#4)
by Tom in NH (tom@altenergyweb.com) on Wed Aug 25th, 2004 at 09:58:49 PM MST
(User Info) http://altenergyweb.com

We got a Rinnai on demand water heater last fall. Love it. We went from using one tank of propane every five weeks for cooking and hot water to one take every six months. There is plenty of hot water. Only two things were a little different and we had to get used to it: 1. A blower comes on when you turn on the hot water. I noticed the sound at first, but now I don't. 2. It takes a little bit longer to get hot water out of the tap than it used to. We're talking seconds. Nothing serious.
We liked the Rinnai so much we went out and bought two Rinnai furnaces for this winter. They make top line products.

Re: OT Demand water heaters (3.00 / 0) (#5)
by Wolfie1 on Thu Aug 26th, 2004 at 06:07:34 AM MST
(User Info)

Are there on-demand water heaters for entire houses rather than single rooms? What sort of size unit (physical size and spec) does a house need. How much does one of that size cost?

Martin.

Re: OT Demand water heaters (3.00 / 0) (#8)
by FishbonzWV on Thu Aug 26th, 2004 at 03:43:14 PM MST
(User Info)

Wolfie,
I saw Aquastar makes model 240 & 250...says good for two simultaneous showers. Quite pricey tho $1k+.

[ Parent ]

Re: OT Demand water heaters (3.00 / 0) (#16)
by nack on Tue Aug 31st, 2004 at 02:19:38 PM MST
(User Info)

Aquastar 240 is actually a Takagi TK-1 in Bosch trim. I have one (TK-1) running a 5 person house and two showers at the same time is never a problem, although 2 showers plus laundry will get you a shot of lukewarm water. The 240/TK-1 will fire if triggering flow rate is acheived, regardless of pre-heating. This is one of the reasons it has been superceded. You probably won't find a Bosch branded 240 any more, but there are still some Takagi TK-1 heaters on closeout deals, google for "tankless water heater". I got mine for $695 from some place in Texas whose name eludes me now (Low Energy Systems?). My gas bill went from about $65/mo to $17/mo. If you preheat, you will probably want to look at the newer models which monitor inlet temp and refuse to fire if in temp is equal or greater than out temp setting.

[ Parent ]

Re: OT Demand water heaters (3.00 / 0) (#6)
by Vtbsr on Thu Aug 26th, 2004 at 06:45:28 AM MST
(User Info)

I installed a Monitor gas boiler with radiant pex tubing, works great. All the info is on www.houseneeds.com

Re: OT Demand water heaters (3.00 / 0) (#7)
by merkurmaniac on Thu Aug 26th, 2004 at 09:52:44 AM MST
(User Info)

Only some of the Bosch product line can handle preheated water. I live in a suburb of Houston TX and just installed an on demand water heater, so i have been doing some research. The Bosch 125B-NG is kind of a base model that takes natural gas. The 125BS-NG is a more sophisticated model, the S standing for "solar" meaning that it has inlet thermocouples or thermistors to read inlet temps on the water. This is the one that I hunted for a while but could not find it cheaply.

I ended up with a water heater from a Japanese company called Takagi. I bought it thru eBay from a seller who must a distributor of theirs. I paid $550. I cost me another $100 in parts to install it and I did the labor myself. It should hopefully cut my gas bill in half. Their whole product line has inlet thermistors to read water inlet temps and calculate the gas required for the desired outlet temp (preset at 120°F. )

My plan is to build a preheater that will use the waste heat of my attic to preheat the water, hopefully up to about 100°F, which should cut daytime gas usage even more, during the summer months.

Richard

Re: OT Demand water heaters (3.00 / 0) (#9)
by FishbonzWV on Thu Aug 26th, 2004 at 03:49:59 PM MST
(User Info)

merk,
I think Takagi makes the Aquastars for Bosch. Saw a reference to them on their site.
I've found the model 38b anywhere between $289 and $440. Pays to shop around!

[ Parent ]

Re: OT Demand water heaters (3.00 / 0) (#10)
by DanB (danb@*no spam*otherpower.com) on Thu Aug 26th, 2004 at 06:17:29 PM MST
(User Info) http://www.otherpower.com/

We have an AquaStar 125B... works like a charm!
I've got no complaints... getting shower water just the exact right temp is a bit trickier perhaps than with a water tank - but not significantly. It's very nice and efficient I think.

Re: OT Demand water heaters (3.00 / 0) (#11)
by Windswept Cypress on Thu Aug 26th, 2004 at 09:50:14 PM MST
(User Info)

Ibedonc,

If you read this, what are some manufacturers/sources of on-demand DC water heaters with links if avail, and any comment on quality and maintenance needs.

TIA
Cypress

Re: OT Demand water heaters (3.00 / 0) (#12)
by mayfair on Fri Aug 27th, 2004 at 11:33:46 AM MST
(User Info)

I've been using a Bosch Aquastar 125HX for about a year and it works well!
Get the "natural gas" version.

It uses a small water turbine to generate a few watts of electricity to light the pilot, then the main burner while the water is flowing. This one is intended for non-preheated water but uses no gas or batteries at all to operate.

It takes 2-6 seconds to light off and requires inspection yearly (dirt, nests in exhaust vent, etc.) and light maintenance every 2 years (lubricate an o-ring.) Water valve should be disassembled, cleaned and checked every 5 years.

Controlled Energy, Inc. (importer?) supplies these in the US. I bought mine for ~$690 delivered.

Re: OT Demand water heaters (3.00 / 0) (#13)
by patty3 on Sat Aug 28th, 2004 at 01:02:12 AM MST
(User Info)

In your reply this statment perked up my interest; "It uses a small water turbine to generate a few watts of electricity to light the pilot" I am looking for something like that myself. Could you tell me how big the turbine is, or better still send a picture of it? I'm also wondering if there is a company that manufactures different sizes of turbines that produce electricity that could be used for other applications, like charging batteries. Thanks Pat!

[ Parent ]

Re: OT Demand water heaters (3.00 / 0) (#14)
by Vtbsr on Sun Aug 29th, 2004 at 07:21:42 AM MST
(User Info)

Hi Pat Try www.harrishydro.com for turbins to charge batteries

[ Parent ]

Re: OT Demand water heaters (3.00 / 0) (#17)
by FishbonzWV on Wed Sep 1st, 2004 at 08:13:07 AM MST
(User Info)

I think he meant milliwatts. Just enough to fire the piezio.

[ Parent ]

Re: OT Demand water heaters (3.00 / 0) (#15)
by thunderhead (mail me from my homepage!) on Tue Aug 31st, 2004 at 02:01:48 AM MST
(User Info) http://www.simon.richardson.net/mailme.htm

On-demand water heaters are the norm over here in Britain. We use a condensing type: so called because the flue gases are cooled to below 100C, which means the water that makes up about 10% of the flue gases gives up its heat of condensation. That makes a difference to fuel bills, although it's a bit difficult to set up. Recently the government subsidy for condensing boilers was withdrawn - just after we got ours fitted. :-)

OT Demand water heaters | 17 comments (17 topical, 0 editorial)

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