An electric water heater happens to be one of of the larger annual electric loads for many and it would seem reasonable to not be heating that any more/longer/often than your need for a certain quantity of water at or above a certain temperature. Thus the desire to use HA to impart some smarts on the tank. (This discussion is not intended to apply to On-Demand Water Heaters)
When I noticed this feature that appears to insure (force) a "minimally safe temperature maintenance"
This prompted me to ask the question, which I have asked myself before when considering "smartening up" my highly insulated water heater,
'WHY MESS WITH THIS....If I am willing to accept a minimum set-point threshold of 120-122F on my water heater (on municipal water), and everything I read says not to go below that out of precaution (Legionnaires’ Disease)'
Granted there are long blocks of time in any home where the hot water is not being used. But if the temperature in that tank drops below 120F for some time I'm thinking it might have to be brought up to 140F+ to "sanitize" the subject microbes if they are present. Not that this is a huge concern in most municipal water systems or homes. But still. The warnings are there.
So without studying the actual energy use/ temperature / re-heat cycle vs health risk balance I'm left wondering....is it worth it to smarten up the water heater ?
@PunchCardPgmr understand the more you let it cool and then heat up to temp will use far more energy than simply "topping off' and maintaining a set temp. Now if it's a vacation home, I could see that. Essentially turning off the unit while the place is uninhabited and turning it on the day before you get there.
I would argue it is not worth it. How high would the water temp have to be set to “sanitize?” For how long? How much would that offset potential savings?
Legionnaire’s disease, as it’s called, is easy to prevent; just keep potential water sources at the minimum recommended temp to inhibit growth of Legionella, which the built-in mechanism is designed to maintain.
I've recently undertaken the task of preliminary design for a water system for a laboratory remodel situation (so admittedly the situation may not be the same for a home). Anyway, maintaining water source-temperature is one thing. The second thing is eliminating or minimizing dead-legs, where water doesn't flow very much. Depending on their distance from the heater, these can be at a comfortable temperature for Legionella to grow, and it'll probably grow in biofilms. Portions of biofilms can be periodically shed, and end up being aerosolized when water is passed through sprayers and things of that nature.
Even for tanked water heaters, for several years, my electric water heaters are turned on for only 1.5 hours in the morning, and 1.5 hours in the evening. They are set at 140-145F. So even though the tanks get below 120F during the day, they reach a temperature that kills Legionella twice a day. And I also flush the tank annually. When I was younger, I did it every six months
FWIW, I've been doing this for 10+ years. Without any Legionella issues (although I do recommend reading my previous post in this thread). Just make sure that your tank temperature is set to 140-145F. My annual saving for each water heater is about $125. It used to be about $75 a year 10 years ago, but our electric rate has burgeoned quite a bit in the last 3 years.
Tanks are very well insulated. So the temperature drop in my attic (where my tanks are) over 12 hours is something like 15-20F (depending on ambient temperature).
I leave my 50 gallon heaters on for 1.5 hours in the morning and 1.5 hours in the evening. The savings per heater per year works to be about $125 at the rates I'm paying currently. The savings were about $75 per heater per year when I first set this up some 10+ years ago.
Either way, there are substantial savings associated with using a water heater timer (or some other smart device) to determine when an electric water heater is on.
These are the exact nuances I wondered about...that balance of cost between time off, full reheat to a bug killing temp, and overall savings. Good to hear your outcomes, and that you've lived with it as such for that long.
Thanks
P.S. Your experience suggests that NOT using the Sinope min temp override feature would be in order to get the most savings. Curious why they put that in there, liability?
I have a large house requiring 80 gallon tank when at full useage.
My setup was to install two 40 gallon tanks in series and i control the first tank to turn on only when we are home during peak periods. This also provides some back-up when an element fails, and it doubles the recovery rate when on.
We run 2 75's in tandem (they both drain at the same time). You can see here in the pic that I built a manifold in which I can cut off either tank and remove in case a repair is needed leaving the house to run on 1 75....
I started out in tandem (parallel), but had issues with the balance- one drawing more than the other. Scaling would significantly effect the balance. I found series connection to be more reliable a connection.
But I am not a plumber so I don’t know the convention. Parallel does make more sense to me though as I can service one or the other while still maintaining function. Just my 2cents.
I've had multiple homes with the water heater in the attic... It isn't that uncommon in some areas - specifically ones that get cold enough in the garage you don't want to put them there, but also have a high enough water table that there aren't basements.
Our home is all gas and has 2 50's in a series on one side of the house and 1 75 on the other side of the house. The series pair made me scratch my head at first because I would have assumed parallel, but I did some reading and found that it is pretty common due to the mixing/balance issue. In theory, it should be the equivalent of having a 100 gal tank (and 2 50s is <$ than 1 75 gal typically - it's really a space issue at that point).
I emphasize in theory because in practice, I actually have to set the first tank significantly lower in temperature than the second tank or the second tank's thermostat/hysteresis gets confused and it never actually fires up - resulting in actually pretty lukewarm water at the tap/shower. I played around with this for a long time and the only solution I could figure out was to set tank 1 at A or slightly below and tank 2 at B or slightly above.
One nice thing about this setup is that I actually have the first tank off most of the time. It's really only necessary when someone wants to fill the jetted tub or we have guests in the house (the 2 50s only heat the master bedroom and guest room, the rest of the house is on the single 75 gal).
