07-17-13, 05:55 AM | #11 | |
Master EcoRenovator
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Quote:
For instance , turn it off at nite , after your regular bed time . Turn it off early enough , before you regularly get up , to allow it to bring the water up to temp , so you can have HW for your shower . The schedule can be made more complicated than that . God bless Wyr |
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07-17-13, 08:12 PM | #12 |
Helper EcoRenovator
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OK, but with most things in life, the devil is in the details.
What's the temperature of the water when you turn off the heater? What's the temperature of the water just before you turn it back on. What's the capacity of the heater. From those three numbers, you know how many BTU's it's gonna take to get the water hot again. Time is not a factor, it's all about the BTU's. That's also the number of BTU's of waste heat that your air conditioner will have to get rid of. If the water temp changes a LOT, you need more insulation on the water heater. If it's not a lot, you can make a linear estimate of the heat lost at maximum temperature vs the heat lost at lower temperatures as the water cools...that we already calculated. My guess is that, for a well insulated water heater, the difference is in the noise level. The bottom line in all this is that it takes about the same amount of energy to reheat the water as you lost by turning it off. All you're saving is the difference between the total heat lost at max temp vs the total heat lost at an average temperature about half way between the two temps we measured above. That's the extra heat your air conditioner has to take out. And that having microsecond resolution in when you turn it on or off is inconsequential. Hence, the question about thermal time constant. You may discover that turning it off at all is mostly wishful thinking. But, it's all about the exact details of your particular situation. |
07-18-13, 02:08 AM | #13 | |
Master EcoRenovator
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Something else , if the hubbie , wifey & crumb crunchers are away from the house in the day time , a second off cycle saves more , except on the weekend ( indicating a need for a somewhat / potentially more $$$ time clock that can be programed for a different schedule on the week ends ) . A different thought , in an all electric house , especially with resistance heat , only , the lost heat in winter is not really wasted . It helps heat a small part of the house . ( If the WH is not out in the garage . ) God bless Wyr |
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07-18-13, 07:44 PM | #14 | |
DIY Geek
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I don't have crumb crunchers, but I am running an idea I found on waterheatertimer.org It uses an old Decora switch sized Intermatic 7 day programmable digital timer I bought from my local Habitat ReStore. I'm only using 3 of the 7 on/off cycles available. I still don't understand why most water heater timer manufacturers still use mechanical timing devices? The HF digital timer I suggested above is actually more sophisticated than my Intermatic timer. The HF timer will do groups in addition to individual days, groups can be: MTWRFSS, MTWRF, MWF, TR, SS (M=Monday, T=Tuesday, etc). The Intermatic doesn't do groups of MWF, TR. I really need to get another one and gut the mechanical timer out of my sprinkler timer. I'm using that HF timer to cycle the dehumidifier in my garage. |
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08-19-13, 02:18 PM | #15 |
Administrator
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Has anyone made a 220V timer out of a 110V timer? That would be an awesome write up.
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