Anyone use a LP tankless water heater??

[tinkerer]

Hello. I am currently in the process of looking for a new hot water heater. I currently have a Bosch aquastar 1600H tankless heater and have had a few problems with it, but for the most part have been happy with it. The reason for getting a new one is the fact that I need one that is able to accept preheated incoming water. I have recently put a hot water coil in my coal furnace and am planning on a solar heater of some sort for the summer. I have been looking at the Takagi Tk-JR2 LP water heater and was wondering if anyone has had any experience with these? I would also like to know your experiences with other brands. If anyone is preheating their water such as I plan on doing, I would love to hear about your installations also.

Thanks!
Ben

[WGB]

I've put a few Takagis in, have one in my shop.
Put one in a new house job, went bad in a year almost to the day, changed it out, that one went out same time frame.
I fought with Takagi over the warranty, took 6 months to get a replacement, then found out they changed that model.
So they must have had issues.
Have a TK Jr running a small radiant heat job I did maybe 8 years ago?
Now they are part of AO Smith.

[WStayton]

tinkerer:

  I too have a Bosch that I was annoyed to find would not accept pre-heated water.

  I am just in the process of assembling my system, though, so I will use the Bosch until I get set up and have solar/wood/I-C-Engine heated water to serve my needs and then will just shut off the Bosch, leaving it in the system so I can relight it if I ever need to.

  For a system where your feed water is of variable temperature and you wsant to have the Water heater in the loop I don't really think that there is a work-around for the Bosch unless you use something like a tempering valve where you mix the Bosch heated water with you "other" water after the heater.  And, even then, I'm not absolutely sure that would work satisfactorily.

  As to tankless water heater's that will accept heated water, I have not heard of ANY that were without issues.

  Wish the news were better!

Regardz,

Wayne Stayton

[WGB]

The model I had problems with is T-K1S no longer made.

Not sure why they wouldn't take preheated water? How hot we talking.
I feed a TK JR with 90 degree return water, units burner modulates down to what the output setting.
Also that install is ok with Takagi and warranty.
With pre-heated water you will not get the full BTU capacity of the unit, not an issue with you because all you care is output temp.

[Ronmar]

The reason for getting a new one is the fact that I need one that is able to accept preheated incoming water. I have recently put a hot water coil in my coal furnace and am planning on a solar heater of some sort for the summer.

I am curious.  You want to collect heat, but you do not want to store it?  One problem immediately comes to mind with the coal furnace.  Stagnant water put in a place that exceeds 212F will boil.  Boiling in a water system is bad.  It can cause overpressures, burst pipes ect...  The only way I see this working is if you collect heat from a peripheral area of the furnace that never exceeds 212F.  But as soon as you begin to draw water thru this system, the low delta will result in a burst of heated water from what is setting warm in the coil, and then greatly reduced temps(close to supply) after that. 

I have never even looked into how tankless water heaters are controlled, so I may be way off base here.  Wouldn't it be more effective to draw heat from a peripheral area of the furnace that stays below 212F to heat water in a insulated hot water storage tank?  This would transfer heat slower, but once the desired  storage temp is reached, the collector coils could safely lie dormant.  The heat would be transfered from the coils to the tank using a small thermostatically controled circulation pump to maintain the tank at a certain temp.  This gives you a large mass of pre-heated water to draw from.  The output of this tank would feed the input of the tankless, with the cutin temp of the tankless set at a point below what the storage tank is storing water at.  When you use hot water, it is drawn thru the tankless, but since it is warmer than the tankless is set for, the tankless dosn't run.  When the storage tank water is finally consumed, and cool supply water finally makes it thru the storage tank to the tankless, the tankless finally cuts in to maintain temperature output.

[Tom Reed]

There is an Aquastar solar model that does exactly what you want.

[tinkerer]

Well, I called Takagi today and visited with them about using preheated or hot water as your supply water on their TK-JR2 tankless heater. They said its fine. What they recommended is that you install a tempering valve before the water heater and temper your water down to 10 degrees below the temperature you have your waterheater set at. The water heater then only has to raise the temperature 10 degrees.

Tom, I looked into the Bosch Aquastar that is set up for preheated water or solar water, but they no longer make it. They said they had to many problems with it and didn't find it feasable to produce anymore so they discontinued it. I don't know if I'd buy a Bosch anyway after dealing with their customer support.

Ben

[getterdone]

i bought a new bosch 1600 ps Lp hot water heater. i haven't hooked my solar water heater to it yet.
it is supposted to hook to solar an work.
one thing i have noticed is that i have very little hot water pressure.
i haven't used it much. it's hooked to a bathroom that we haven't used yet.
what problems are you guys having? i'd like to have a heads up.
i'm not sure i need to check it out further.,but maby i'm not supplying enough gas pressure. thats the cause of low water flow.

[Derb]

Hi Fellas. For years now I have used a 40 gallon header tank as high as I could place it up in the top pitch of my roof which is fed from town supply through a ball cock. This in turn feeds the 180 gallon electric hot water cylinder on a 2 ft tank stand on the bottom floor in a cupboard which backs onto the woodburner with a 7 kw water heating coil. Initially the plumber stuffed the installation up and the shower was useless but I ripped his work out and ran the cold water feed for the shower up to the header tank and this balanced the pressure and fixed the problem. In summer, with the black header tank close under the iron roof, you can have a hot shower using the regulator in the cold position. In the winter we can turn off the electric element and cruise on the water heated by the burner alone (our power bill is lower in the winter with cooking, water heating and clothes drying using the burner). The wood burner initially was fitted with a larger coil but it was forever boiling the water so I fitted a smaller one. I figure if I fit a solar panel on the roof I can pre-heat the header tank using thermo-syphon for more savings. I considered using a mains pressure cylinder but was in the too hard basket with the wood burner and would have lost my pre-heat system. Stuck with the KISS principle and header tank. Cheers.

[tinkerer]

i bought a new bosch 1600 ps Lp hot water heater. i haven't hooked my solar water heater to it yet.
it is supposted to hook to solar an work.
one thing i have noticed is that i have very little hot water pressure.
i haven't used it much. it's hooked to a bathroom that we haven't used yet.
what problems are you guys having? i'd like to have a heads up.
i'm not sure i need to check it out further.,but maby i'm not supplying enough gas pressure. thats the cause of low water flow.

I currently have a Bosch 1600H LP. I've had it for 5 years now. It doesn't have a standing pilot but instead has an ignitor that is powered by the flow of water to light the burner. It works fairly well. Our water is about 55 degrees in the summer and 50 in the winter. We are on our own well and use a "jet" type pump. That's where one of our problems has been. My pressure switch is set at 30-50. The minimum water pressure required by the water heater is 30 psi. It sometimes doesn't want to light when the pressure is low and you have a small stream of water going. It will also sometimes stop heating when the pressure gets low and you are using a small stream of water. I have bumped up the pressure a little and it definitely helped. We've also had to get used to not using just a trickle of water at the sink. "really makes sense...try to be conservative by installing a tankless water heater and then use more water lol" But.. as irratating as it may be, its not the water heaters fault. If we had a submersible we could run a little more pressure and I think it would be fine.

The other problem that has surfaced recently is the heat exchanger has developed a leak. It was fine earlier this spring but five or six weeks ago I noticed quite a bit of green dust and flakes on the floor below it. I opened it up and noticed that its got a leak somewhere. Its not a dripper  or gusher leak, but its definetley leaking. The heat exchanger coils are green and discolored. I can clean them and in a few weeks they are all corroded up again. I've contacted Bosch about the problem as the heat exchanger "supposably" has a twelve year warranty. It doesn't sound good at the moment as far as them replacing the heat exchanger. They don't like the idea that I installed it myself very well.  I took pictures of the install and did a bunch of measurements for them.  I installed it following the directions to a "T".  New stainless vent and all. I guess we'll see what happens.

Ben

[mbryner]

Hi tinkerer,

I do pretty much exactly what you are asking about.  We just built our house; moved in in January 2011.   I have a Rheem RTG-84DVP on-demand water heater.   We preheat our water in fall/winter/spring w/ a masonry heater (wood stove).  There's a water coil in the back of the firebox.   It has a differential temp controller which warms a 500 gallon highly insulated concrete tank under the basement slab.    The 500 gallons just acts as a heatsink.   In summer it doesn't do anything because the solar panels aren't installed yet (the tank is at 68 deg currently), but in winter it stayed between 100-120 degrees.   Incoming well water goes through a 100 ft copper coil heat exchanger in the 500 gal warm water tank to preheat the water.   Then it goes through the Rheem tankless water heater.   Works great so far, but there are a few bugs:   If the incoming water is too close to set temp of the water heater (i.e. 110-120 deg), the tankless doesn't fire up.   It seems to need a 10-20 degree differential.   Preheated below 100 or above 110-120 seems to work fine.   

My design is similar to what Ronmar suggested a few posts back, except that I have the coil directly in the hottest part of the firebox.

Here's my website about installing the pre-heat system:
http://www.docbryner.com/mossy_hollow/Thermal_Storage.html
And for our off-grid house:
http://www.docbryner.com/mossy_hollow/Home.html

Marcus

[Ronmar]

My design is similar to what Ronmar suggested a few posts back, except that I have the coil directly in the hottest part of the firebox.

Marcus
   You are circulating water thru the firebox coils whenever you have a fire going right?

[mbryner]

Yep, otherwise we'd have a big steam bath in the mechanical room! 

[mike90045]

My plumber has sold me on the eternal hybrid water heater.
http://eternalwaterheater.com/products.html
it's a tankless, with a 2 gallon tank to prevent what the trade calls "cold stacking" when a low flow situation is sensed and you get a blast of cold water. It uses a short burst of flame to keep warm in freezing weather instead of an electric heater.

So, I'll wait and see how it works out when it's installed.

I will be preheating with solar and firebox coil.

[WGB]

My plumber has sold me on the eternal hybrid water heater.
http://eternalwaterheater.com/products.html
it's a tankless, with a 2 gallon tank to prevent what the trade calls "cold stacking" when a low flow situation is sensed and you get a blast of cold water. It uses a short burst of flame to keep warm in freezing weather instead of an electric heater.

So, I'll wait and see how it works out when it's installed.

I will be preheating with solar and firebox coil.

  More units like like this one out there all the time.
It's hard to find in specs but this unit has a buffer tank too, a big plus.
Here is one that has a simalar set up and does radiant floor heat for under 2 grand!
http://www.navienamerica.com/rearning/tank.aspx?skin=tank