Water heater timer for Marathon?

Ghcoupons

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We have a 50 gallon Marathon electric water heater. I’m curious if a timer that prevents it heating water over night is a good idea. They’re so efficient I wonder if it even comes on at night enough to justify a timer. The main reason I’m asking is we plan to someday go solar and I’m looking to reduce nighttime usage where realistically possible. I want to pick away at usage before installing an array.
thank you and happy new year!
 

snoobler

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Not sure about Marathon specifically, but there are timers specifically for that purpose, so it's a legit use.

Electric hot water is generally not done off-grid except in the case of a "dump load" where you have excess solar energy and store it in your hot water tank.

The ultra-high efficiency heat-pump type units use dramatically less power than traditional ones. Even then, a 4500W load to top them off that comes on randomly requires a lot of additional inverter capacity to handle it. Bigger inverters waste more power.

Solar direct water heating with a small supplemental electric heater also make a lot of sense for off-grid when compared to a 4500W beast.
 

Ghcoupons

New Member
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Not sure about Marathon specifically, but there are timers specifically for that purpose, so it's a legit use.

Electric hot water is generally not done off-grid except in the case of a "dump load" where you have excess solar energy and store it in your hot water tank.

The ultra-high efficiency heat-pump type units use dramatically less power than traditional ones. Even then, a 4500W load to top them off that comes on randomly requires a lot of additional inverter capacity to handle it. Bigger inverters waste more power.

Solar direct water heating with a small supplemental electric heater also make a lot of sense for off-grid when compared to a 4500W beast.
Which timer would you recommend? The marathons big soling point is their insulation so they don’t lose heat from the water already heated. We’ve lost power for days and still had very warm water from our marsthon, which is what sold me on them along with the no rust probability.
 

snoobler

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Intermatic is a good brand, and it also appears to be the only game in town.

Pick the model that meets your unit's voltage/power/current needs and pocketbook.

Example:

 

Hedges

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I use that exact timer for my espresso machine. The HF electronic one didn't hold up long enough.

The water heater will come on when it wants to, often after usage results in lower temperature. That could be night depending on your usage habits.
Timer is one way, but that would leave it on during a cloudy day when you might want to conserve battery power.
Photocell controlling a relay would enable during daylight, but unless adjustable wouldn't limit to times of good sunshine.

Battery voltage or state of charge could control it. Some charge controllers and some inverters have relays with adjustable settings and purposes.

Better would be to enable it when there is surplus PV production, which could include during absorption for lead-acid batteries.
Ideal is to adjust power delivered to exactly match surplus. SMA used to have a dump load controller for that purpose.

Control of loads should take priority over storage of electricity. It is lower cost, higher leverage.
 

2009Bounder2020

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ive been off grid 8 years now. no way would i try to run an electric water heater. Propane is way more efficient for heating water.
 

Hedges

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In the summer you will have surplus PV (unless it's all used for A/C)
In winter, how much if any power savings will hybrid give?

Possibly pure resistance heating would serve as well?
 

snoobler

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I plan to have a "dump load" to capture additional solar as resistive water heating. With the 6kW and the potential expansion of another 10kW and crazy good solar:

1614233496583.png

I'll be looking to turn on stuff just because I can.
 

2009Bounder2020

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True.. location , location, location... Im in northern IL , i would have to triple the panels and my experience here with heat pumps is once real winter sets in they dont work that great. but the tech might be better these days. We did a well /geothermal for the AC which works well here, in the winter i use my excess PV in our shop and we use the hot tub more often so we burn it like that.
 
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