tankless water heaters in cold climate

[Dave L.]

You've got the right idea of maybe using more than one. See Takagi-usa.com. They have support in Canada. I'm happy with one that I installed.

Dave

[TURTLE]

This is Turtle.

I called Glen Johnson who works at the warehouse at his house and ask him about supply water temp. verses the out put temp. of the water about the Rinnai Continuum type tankless hot water heater. He said at any temp water supply from

33ºF water the unit will supply 96ºF to 140ºF water all day long at 8.5 GPM. Over the 140ºF may be a problem but just cut back to 2 shower at one time and go back to 180ºF water out put .

Now just a not here. 140ºF water will blister a human or burn the hide off you. also 180ºF water will kill most humans.

TURTLE

[TURTLE]

This is turtle.

That is what the shell is for to not let it burn them.

TURTLE

[cthorne111]

I was wondering if anyone in a cold climate (Canada or likewise) has used the tankless heaters. I was thinking of getting two to replace an old hot water heater but want to be sure this will get the water hot enough. The cold water temp from the tap here is 42F.

[Richard J Kinch]

Bunk.

32 deg F rising to 96 or 140, that's 64 to 108 BTUs per pound, or 534 to 901 BTUs per gallon, or 4540 to 7660 BTUs per minute at 8.5 gpm, or 272K to 460K BTUs/hr, assuming 100 percent efficiency, which equates to 80 to 135 kilowatts, or 333 to 563 amps of 240 VAC.

Does this unit come with a hookup to Niagara Falls, or perhaps the Alaskan pipeline?

[Oscar_Lives]

What does it do to Turtles?

[trader4]

"I was wondering if anyone in a cold climate (Canada or likewise) has used the tankless heaters. I was thinking of getting two to replace an old hot water heater but want to be sure this will get the water hot enough. The cold water temp from the tap here is 42F. "

RTFM This is one of the most basic things that is specd.

[m Ransley]

I have a small Bosch 117000 btu and my water has been at 33f- 34f incomming at -17f. Even at 33-34 incomming I never have to have the Bosch on high to take a warm shower or it would be to hot. A 180000 btu Rinnai will do maybe 3 water reduced showers at 34f incomming no problem, and definatly 2.

An Electric would need 120A for 1 shower.

Why 2 tankless, One sized properly can handle alot of load. Rinnai is the most efficient tankless unit I know of. Rinnai also has built in freeze protection to -30f.

[m Ransley]

I assume you want gas tankless

[Beachcomber]

See below for a more practical example and accurate calculation.

Who uses 8.5 gpm? Shower restricter inserts in the USA are restricted to a maximum flow of 2.5 GPM.

Incoming water is at 42F not 32F, so a rise from 42F to 96F (a good hot shower) is 54 BTU per pound.

If one gallon of water weighs 8.33 lbs, that means a one minute shower uses 20.82 lbs of water requiring a rise of 54 BTU or 1124 BTU's per minute. This x60 is 67440 BTU/hour.

One kiloWatt is 3412 BTU so:

A one hour shower would consume 19.77 kwh A one minute shower would consume 0.33 kwh

And a realistic 10 minute shower would consume about 3.33 kwh

For the instantaneous power load, a one hour 2.5 gpm shower with a 54F rise consumes 19.77 kwh, which at 240 volts = 82 amps whether you use the shower for 1 minute or 60 minutes.

82 amps is still pretty high, but it is nowhere near 333 amps of 240 VAC as erronously stated above.

Few residential pass through DHW heatingunits will be rated at 80 amps but 40 amp 240V units are quite common. In fact, if you are going to go with two electrical units like this, the manufactuer recommends putting the plumbing in series.

Only problem is if every time you turn on the shower your neighbors' lights dim (because of the >80 amp demand draw, your neighbors and the power company may give you a hard time.

Beachcomber

[m Ransley]

No propane?, Put 2 60a together you get 120a

[m Ransley]

You must have cheap subsides Hydro to only want electric. What is your kwh cost. There are alot of electric units avalaible, they are cheaper than gas and perform well if sized right. For one use shower look at Bosch for starters, probably at you local big box. If electric is that cheap there then you will find localy what works and what is crap. I pay

125kwh, you must pay near .04 to be competitive to gas.

[cthorne111]

Gas is not available here, electric is the only option. I couldn't find an electric that would seem to do the job with only one unit. Plus from what I know there is a limit of 60 amps for any one breaker. So one 80 amp would be out of the question. I was just wondering if anyone has the double electric design and if it works well with cold incoming water temps.

[Andy Hill]

I'm in one of the banana belts of Idaho. Input temp is in the low 50s, and we do OK with our Takagi TK-2. Another 10 degrees down would be a problem with our usage...I'd probably have to not run the dishwasher or washing machine while taking showers.

Check the output curves for the unit(s) you have in mind -- you'll probably run into a bit of output restriction with 42F input water. Gut feel, no problem with two gas units, probably OK with two electric units; iffy with a single gas unit; no can do with a single electric. Really depends on how many hot water users you want to supply at the same time.

[Beachcomber]

Don't forget to figure your operating costs. Let's say you have two

10 kWh units plumbed with the water line in series or 20 kWh total.

Let's estimate that a 10 minute shower will use 1/6 of the 20 kWh or

3.34 kWh per 10 minute shower.

If you are fortunate to live in say... Washington State, then you might be paying 8 cents per kWh , in which case that 10 minute shower would cost you $0.27 for that 10 minute shower.

In a high utility expense place like Vermont, electricity is something like $0.14 per hour, so your 10 minute shower would cost you $0.47

Hopefully the utility company won't charge you a demand charge for that 20 kWh that

Beachcomber

[Richard J Kinch]

My calculations derived from the absurd claim that the unit would deliver

8.5 gpm "all day long" with a 64 to 108 deg F rise in temp. The error is yours in your cavalier dismissal of "who uses 8.5 gpm". Whether anyone does or not, that was THE CLAIM.