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Old 03-02-2013, 12:55 AM   #1
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pre-warming cold water supply to tankless heater


Considering a 110 volt 10 gal heater at lowest setting during cold months and off during warm months.

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Old 03-02-2013, 01:22 AM   #2
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pre-warming cold water supply to tankless heater


Welcome!

Seems to defeat a fair amount of the energy savings of the tank-less.

Is this a current installation and you are having a problem with existing tank-less?

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Old 03-02-2013, 02:51 AM   #3
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pre-warming cold water supply to tankless heater


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Considering a 110 volt 10 gal heater at lowest setting during cold months and off during warm months.
Would not do anything. A Tankless will only engage to heat the water, when it senses flow through the piping. Otherwise, it just sits there doing nothing but collecting dust and looking all pretty.

Suggest if you are shutting a place up for Winter, turn off the Gas, drain all water lines, toilets, the tankless, then pour RV anti-freeze down the drains to keep the traps from freezing. Also suggest shutting power off to the place.

Now if you are going to have a caretaker check up on the place, just set your heat at 60, leave everything else alone, and have the caretaker once a week flush the toilets, run water into the sinks, tub/showers, run the wash machine every other week, pour some water down the floor drains about once a month.

Also do a walk through to check for any situations that need to be kept an eye on, like burnt out light bulbs, damage to the property, making it look lived in also.
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Old 03-02-2013, 07:29 AM   #4
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pre-warming cold water supply to tankless heater


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Considering a 110 volt 10 gal heater at lowest setting during cold months and off during warm months.
Are you having problems with your tankless keeping up with your hot water demands only in the winter? or are there sometimes in the summer too?

If summer and winter, your tankless is just too small, and a 10 gallon preheater won't help much, and will make it even worse in the winter.

A 120 volt water heater can maintain a 20 degree temp rise at a max water rate of .5 GPM. If only 10 degrees are needed, it can do 1 GPM. So in the winter, you would only benefit from it for a short while at any GPM rate above 1 GPM.

What brand and model number tankless do you have.
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Old 03-02-2013, 09:09 AM   #5
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pre-warming cold water supply to tankless heater


I would suggest a few dozen feet of finned pipes dissected out of baseboard radiators. Mount them running back and forth on the basement wall or ceiling where no one will bump heads or shoulders or knees into them.
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Old 03-02-2013, 09:28 AM   #6
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100 foot of 3/4 inch baseboard would only hold 2.49 gallons of water. If the basement was 35 degrees warmer then the incoming water, that 100 foot of baseboard would only be able to put 6,460 BTUs an hour into the water. Or 107.66 BTUs per minute. So it could raise the incoming water temp to the tankless by 10 degrees as long as he doesn't use more then 1.2 GPM, and his basement air temp is 35 degrees warmer then his incoming water temp.
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Old 03-08-2013, 12:14 AM   #7
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pre-warming cold water supply to tankless heater


I have 220v 120amp Bosch tankless that heats water sufficiently in our mild summers but not quite during our equally mild winters. Our climate swings between low 70s in summer and low 40s in winter. I was hoping to give back those 30degrees or something like it with a small reservoir of room temp (60-ish degrees) stored indoors just before entering the tankless supply. We have a 32-panel solar array which has been able to keep up with our annualized power needs. I wondered if the lowest setting on small tank heater might even be used only if necessary at harsh demand events...
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Old 03-08-2013, 06:54 AM   #8
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pre-warming cold water supply to tankless heater


You could set it to vacation, so it just barely warms the water. And if you wanted to, you could connect an outdoor thermostat to it so it only comes on hen the outdoor temp is below X temp.
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Old 03-08-2013, 09:04 AM   #9
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pre-warming cold water supply to tankless heater


I have a well, so in the spring I am going to harvest a decent used electric tank that somebody sent to the landfill, Paint it high temp flat black, and use it as a solar batch collector up front of my new tank type water heater. My intent is to temper the incoming water before it hits my HWH.

I have no problem with hot water, as I replaced my 40 gallon with a 50, but I have people living here that think hot water is free. I don't see how you can get dirty enough going to school to require a half hour hot shower.

You can sure tell they haven't been in the military. Especially the Navy.
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Old 03-08-2013, 09:06 AM   #10
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Hmm. Sounds good. I didn't know HWHs had vacation settings, and I did not know there was an outdoor thermostat I could have manage the HWH's power supply. Is there going to be a trick to finding these things?
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Old 03-08-2013, 12:23 PM   #11
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pre-warming cold water supply to tankless heater


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I have a well, so in the spring I am going to harvest a decent used electric tank that somebody sent to the landfill, Paint it high temp flat black, and use it as a solar batch collector up front of my new tank type water heater. My intent is to temper the incoming water before it hits my HWH.
OT: Chances are you would have to try several times since the most likely reason a water heater ends up in the landfill is because the tank has sprung a leak.

The tank itself does not make a good solar collector because it has to be covered and insulated at night to avoid heat loss from the water inside. Liiquid filled solar collectors have (or should have) a pump circulating system that shuts off at night to prevent taking heat away from what is being heated and dissipating the heat out in the solar collector.
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Old 03-08-2013, 02:36 PM   #12
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pre-warming cold water supply to tankless heater


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Hmm. Sounds good. I didn't know HWHs had vacation settings, and I did not know there was an outdoor thermostat I could have manage the HWH's power supply. Is there going to be a trick to finding these things?
The outdoor stat can be a standard one used for heat pumps with a relay at the water heater to energize/de-energize the water heater.

I was thinking gas water heater hen I said vacation, but electric water heaters cn be set to their lowest setting which is about equivalent to the vacation setting on a gas water heater.
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Old 03-08-2013, 04:36 PM   #13
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pre-warming cold water supply to tankless heater


I'll check into that. Sounds like exactly what I want.

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