Looking for low or no phantom power usage gas tankless water heater...Tagaki pulls 6 watts.....

Off Grid Mountain ManOff Grid Mountain Man Registered Users Posts: 23 ✭✭✭

Hi, 

I live off grid on a PV system - so every watt counts!

I just ordered a "Tagaki Jr" tankless gas on demand heater - but just found out it pulls 6 watts 24/7 - meaning 144 watts a day doing nothing......pulls 73 watts when in use, but as I only use it maybe 15 - 30 minutes a day, I can live with that. 

I'm wondering if any of the other brands, that don't use a pilot (I have to haul all my propane canisters) use any less?

I need a heater that can accept a hot water feed (at times that is) from my solar hot water heating system - and will simply allow the hot water to flow through without using any electricity or gas........that Tagaki will allow this, but always still pulling the 6 watts. 

In summer, this 144 phantom watts would be an annoyance, but not a huge problem, but I'm in a canyon, with only 3 good hours of mid winter sun, so it could be an issue then, say 5 days of no sun in a storm, that adds up to 720 much needed watts!

If I can't find a better heater, and return this one, I will have to rig up a switch, and have the hassle of having to "switch on" everytime I want hot water during low sun times.......

Thanks for any and all thoughts, and/or advice!

Comments

  • BB.BB. Super Moderators, Administrators Posts: 28,186 admin
    Just to clarify (we all have made this mistake in the past as we learned):
    • 6 Watts * 24 Hours per day = 144 Watt*Hours per day
    Watts is a "rate" (like miles per hour)... And Watt*Hours is an amount of energy used (like driving 60 miles per hour * 2 hours = 120 miles driven).

    Phantom loads can be a big deal (loads that are there but don't seem to do anything useful, or are "hidden).

    Sometimes, using a separate switch (or timer) to turn on the device (heater) when needed (i.e., two hours in morning, 4 hours in evening) can save a fair amount of energy... But that can cause issues too (some devices do not like to be powered down when in "standby").
    • Also, watch for other issues... For example, if the tankless heater is outside or unheated space--If you have freezing weather the tankless heater can need power to keep the unit from freezing (turning off, the unit can freeze and be damaged).
    There are other brands that use water motion to spark a flame. And other that may use a D Cell battery to run the spark ignitor (for many months or 1 year plus life).

    But many of these units do not have "active water temperature control" (as you adjust the hot water flow rate, your hot water temperature will fluctuate).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • EstragonEstragon Registered Users Posts: 3,043 ✭✭✭✭✭
    I have a Rinnai tankless, and it does use some power just being on. No pilot, so just enough to light the LED display and keep flow sensor alive. Not sure of the exact amount, but it's less than the draw needed to get the inverter out of sleep mode. In winter, when I turn out the lights, it's lights out for the tankless as well. If I really need hot water in the middle of the night, I'd have to turn on a light to wake up the inverter.

    I'd be firing up the generator before 5 days of no sun anyway, so the bit used by the tankless really isn't a huge issue for me.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • petertearaipetertearai Solar Expert Posts: 366 ✭✭✭
    yep i have the bosch 16H . Water flowing provides the spark
    . But as you say i dont think it is suitable for pre heated water
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . victron battery monitor . 24 volts 450 ah surette batterys . off grid  holiday home 
  • Off Grid Mountain ManOff Grid Mountain Man Registered Users Posts: 23 ✭✭✭
    Thanks for the replies - I will need to remember to say "watt hours"!!
    I'm putting my heater inside - so the anti-freezing gizmo on it won't be an issue.
    The problem I'm having is everyone, including various forums, sales reps, etc, tells me about this or that heater  "pulls a little you won't notice", or "not much"........which if you have grid power, no problemo, but as us off grid folks with limited sun in winter know, EVERY watt counts at times....everyone had "told me" this Tagaki doesn't pull much, but then I find out it's 144 watt hours a day - which to me, is a HELLUVA lot in the long term - in winter anyway.
    Unless I find another high quality unit that pulls less, I guess it's the Tagaki with a power switch.  Tagaki tells me turning it off and on daily shouldn't be an issue.........?
  • EstragonEstragon Registered Users Posts: 3,043 ✭✭✭✭✭
    Out of interest, I just tested my Rinnai with a kill-a-watt. ~6w while booting up (takes ~30secs), then settled at 1-1.5w resting. Whatever unit(s) you end up considering, maybe plan on testing actual resting wattage. Maybe the Tagaki takes 6w max idle, but mostly lower?

    My Rinnai modulates output based on required temp delta from incoming cold and outgoing hot setpoint & flow rate. I use it for infloor radiant heating loops via heat exchanger, as well as for domestic hot water, so should work with (somewhat, eg 100-120°f) preheated water.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Off Grid Mountain ManOff Grid Mountain Man Registered Users Posts: 23 ✭✭✭
    edited September 6 #7
    I have a Solahart solar hot water system, and at times - summer - full sun - the water can be REALLY hot - actual temp can vary - but Tagaki tells me anything under 180 degrees will work with it......everything in my system is a brand new set-up so it will be a learning curve for a while!  I do have a kill-a-watt meter, and I am finding many things pull more power than the manufacturer claims - for instance, just bought an "energy star" TV that is supposed to pull less than 30 watts - and it pulls 50......etc etc...
  • EstragonEstragon Registered Users Posts: 3,043 ✭✭✭✭✭
    I imagine the Rinnai would just pass water that hot through, but I don't know. I keep it set to 120° in summer when guests are around, and up it to 140° in heating season, when anyone here knows it's hot. At that temp, it can scald.

    I use the ES ratings as a rough guide, but in actual use, the KAW often is quite different. Now that outside ambient is cooler, for example, the porch fridge used < 1kwh/day average in the last week. In hotter weather, it would be more like 1.5-2kwg/day. TVs can vary a lot based on ambient light/brightness settings etc.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • petertearaipetertearai Solar Expert Posts: 366 ✭✭✭
    yep the TV s tend to have an energy saving mode , screen is dimmed somewhat , ok for evening viewing . but hopeless for daytime .
    I assume they test in energy save mode .
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . victron battery monitor . 24 volts 450 ah surette batterys . off grid  holiday home 
  • MichaelKMichaelK Registered Users Posts: 79 ✭✭
    I bought this unit from Sportsmansguide.
    It's powered by D-cell batteries.
    In the summer, it supplies luxuriously hot water.  In winter though, with water near the freezing point, it supplies only enough water for a marginally acceptable shower, running at very low volume.  There might be one size unit larger than this one.  I'd get that.


    15 Renogy 300w panels,  Midnight 200 CC, 8 Trojan L16 batteries, Schneider XW6848 NA inverter, AC-Delco 6000w gen.
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