The heaters dont do enough gpm for those multiple showerheads. do some homework on gpm for your stuff before you start taking lukewarm showers.

Wow--wood4d--not what I'd call helpful! I am assuming that you know that tankless heaters have multiple sizing (and did I mention the size we would use)? I am assuming you have experience with each brand as that was my question. So, please share your knowledge. I can read the newspaper editorial page for opinion.

I like Noritz, Rinnai and Takagi for whole house units. For VERY LARGE water loads 2 units can be ganged together. You should have an indea of the gpm required and the temp rise (incoming water temps vs desired output temps) and use the manufactures design tables to see if it will work for your need. Gas supply lines (size and pressure) and venting are also variables that are tough to answer on-line.

Bob

Thanks. Yes, we have done the calculations for our gpm and temp rise required and, happily, the plumber has installed these many times before and is not trying to install a 3/4 gas req'mt to a 1/2" gas line (a common problem).

I was more interested in knowledge of the mfgs. I understand Paloma is the Japan's largest supplier, but have read few opinions of their product-performance. Paloma is available at Home Depot which, I admit, surprised me. Takagi and Rinnai come up more often, and most folks with newer units (i.e., not the early equip more suited to European/Asian habits of sparing water use) seem pretty happy--if sized and installed properly. All of these brands appear to qualify for the energy credit.

Since our tub supplier in Alaska mentioned Paloma, I wondered if there was experience with the brand out there.

"-and we know Alaska has colder intake water than Massachusetts in the winter! " WRONG!

The plumbing codes require that direct burial water supply lines must be a minimum of 6" below the average frost depth.

The average frost depth is the greatest depth to which freezing (32DegF)will commonly occur. The actual soil temps from grade zero to frost depth will vary from ambient temperature to 32degF depending upon depth.

From average frost depth to a point approximately 2 times frost depth the soil temps will vary from 32degf to the average geothermal ground temp of 55degF.

Having lived in Massachusetts for a number of years I know first hand that when a line is laid at the code minimum of 6" below frost depth it is common to have incoming water temps at or near 34degF in mid winter thus the incoming water temp may be equal to what you had in Alaska. While the ambient air temp may be much colder in Alaska and the frost depth may be much deeper, none the less the incoming water temp in Alaska cannot be more than 2 degF colder or the line would freeze.

Great point! And good to know the Paloma works in Alaska--at the same or 2 degree colder water than MA. Thanks.

I have a Rinnai 2520 tankless gas and it's been doing fine for almost a year. I've *heard* that Rinnai is the best, but I'm no expert. I do see these installed more often than others, though.

We had a Paloma for 20 years without any problems. We lived in Oregon and it is not as cold. As I remember I think it was the 750? I know we bought the smaller and then went up from there one size. We have moved so I cant go look at it.We raised two girls there with lots of showers. Didnt have fancy heads though. You can only do one thing at a time. Take shower or start laundry etc. Our dishwasher had its own heater so it wasnt a problem.

Share with us the energy credit/rebates for tankless in your locale. (I can't believe the huge variations between local markets.)

Curious as to why you're going tankless? Does your tankless have battery backup to power the ignitor during power failures?

Is this a new house, or existing? Was there a conventional WH there before? Does a conventional WH not supply your needs in the space provided?

I'm actually more curious about responses to the question I posted: any experience out there with recent model, whole house tankless brands. Will greatly appreciate information on my question, if there is any actual knowledge base out there in this forum. Many thanks.

Input water temps can be in the low 80s°F during summertime at my location (near the central Texas coastline).

I have a takagi td 20 and it was more expensive here than the paloma. I talked to many suppliers here and they said that they have been selling them roughly 5 years and have never had any request for parts. Told me that one plumber in particular puts in roughly 150 a year with no issues. we have lots of hot water available in our house, if anything I am having an issue with one shower but it seems isolated in that shower upstairs. We have only had this a couple of months but love it, minusd the one problem that I will fix eventually. Good luck

I learned a lot having to self install a Bosch Aquastar 1600 with no assistance. I live in interior AK where there are no plumbers or techs.

Probably by now you have what you need. none the less, I'll answer some. The brand matters less than the specs. The 'rise' is the temp change between the intake water and the tap. Our year round temp is 35 making 105 the max with a 70 degree rise. Rinnai only has a 50 degree rise

The rise determines the volume of water you can push through at any given time. the higher the volume, the lower the temps will be.

One variable is the propane line in. I did a 1/2" and it provides insufficient BTUs for more than minimimum heating. Besides a bigger pipe, one other option is an inside tank to 'preheat' water passively to room temp.

So, I know your question was about brands but I've wandered through most of them and talked to lots of folks. I am pretty intimate with what is needed.

I have the Rheem /Paloma 5.3 unit (6 months). I am very happy with it and it was reasonably priced. The one thing I have noticed is that it can be a little noisy... not bad, but I do hear it. (It's located in the basement, right below the shower). What I hear are the relays or valves clicking at start-up as well as the blower when it goes into pre-purge mode.

If I had a larger home, I would have gone with the 7.4 unit.
http://www.plumbersurplus.com/Prod/Rheem-Tankless-Water-Heater-RTG-74PVN-1-Indoor-Use/51363/Cat/1126

My lowest water inlet temp was 33 degrees F. this winter in Indiana. The 5.3 heater gave me enough water for a shower and a faucet at the same time in the winter. It doesn't take much water flow to get it started.

The fact that it needs AC has not been an issue for me. If my power is out, taking a shower isn't the first thing on my priority list.

I think the Bosch unit is the only one that uses water flow for the igniter... A lot of people have had problems with that unit.

We have a Noritz feeding 2 bathrooms only. Kept the tank heater for the kitchen and laundry, but it was too far away for regular bathroom use. We've been using it for a little over a year now without problems. It's mounted outside, which eliminated some of the cost associated with vent piping. But not the cost of increasing the gas line.

I looked at Noritz and Takagi mainly. Think I chose Noritz due to slightly bigger burner or flowrate- it's been a while so the memory is a touch fuzzy.

I've debated w/ one of the pro plumbers here about this. I can't run everything that's hooked up to the tankles w/o noticing reduced flow at the outlets (that's 3 lavs, two tub fillers, and 2 showerheads). The pro thought the heater was actually limiting water flow to try to meet its setpoint. I thought maybe my incoming cold water line is too small or that their isn't a direct enough path in terms of pressure drop to the heater inlet to get the flow at the fixtures with everything turned on.

And there's a valve in the crawlspace that I can open and run hot water from the non-electrified tank heater during a power outage.

Rinnais appear to only be available via certified dealers. In our case that would've meant paying someone separate from the plumbing sub who was working on the project anyway. I could buy the Noritz and get it installed by our plumber, which I think saved money over the Rinnai route (even with the $500 incentives the gas co was offering on Rinnai only at the time).

I've had a Paloma PH12 installed in my house since 1990, and the only thing that has broken on it is the metal piece that bends the pilot toward the thermocouple. It burned away after 25 years.

I replaced it, and everything was fine.

In nearly 20 years, the heater has never skipped a beat. Very impressed with my unit.

I’ve had my Paloma since 1983,

raising six children,

it has paid for itself many times.......

1983 is about when this was first posted.

It's time to let the thread go.