Water Heater - Rethinking how "smart" it is to do "scheduled heating" of the typical tank

[dylan.c]

My water heater isn't anything special... just a Lowe's off-the-shelf unit. It's gas, not electric. My temp is below the halfway point of whatever range the controller is configured for. All that said, my water heater basically only runs when we're home using water. Once in the morning for showers... once at night for laundry and dishes. Almost no wasted energy from heat loss. So, for me, the answer is "not worth the risk."

[dylan.c]

I should also mention that I've insulated the first 3 feet of piping into and out of my tank to prevent losses due to radiation. Even installed one of these over my relief valve...

[hubitrep]

@PunchCardPgmr

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 do think liability is part of it, yes. The other explanation is peak demand period load displacement (for which there is a rate rebate program in Quebec). This feature allows one to "turn off" the water heater yet use some hot water during the 3-4 hour peak period without risking the water temp getting too low. Seems to work - this winter I saw our bottom-fed, 3-element Ecopeak heater could take a couple of 5 minute showers without the temperature dropping below that threshold.

@PunchCardPgmr

@aaiyar

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.

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.

IANAE but gotta be careful here, there are tables that show how many hours the water needs to be at a given temp to kill bacteria (e.g. need to reach above 60C/140F for minute-level sterilizing... ).

No home in Qc will have heaters in an attic as even in Montreal attic temperatures can reach -30C / -22F in the winter. People try to keep these in a well-heated part of the home and if it has to be a room that is not fully heated a jacket can be used.

Other factors to consider is actual consumption : in my home of three teenagers, outside of peak demand periods, it would make no sense to turn off the water heater unless we were away for a week or more.

I completely turn off the cottage's water heater because we do end up being away for many days at a time. I graphed the RM3500ZB's water temperature sensor and noted that the heater only drops about 5C/10F per 24 hour period in a 12C / 54F environment (no jacket).

In our situation, at home, there's no point in ever turning off a modern 3-element 60 gallon water heater, except for those peak demand situations.

[aaiyar]

@hubitrep

IANAE but gotta be careful here, there are tables that show how many hours the water needs to be at a given temp to kill bacteria (e.g. need to reach above 60C/140F for minute-level sterilizing... ).

FWIW, Legionella is killed in about 20 minutes at 140F.

[PunchCardPgmr]

Wow,

great discussion on a lot of interrelated topics.

Thanks all.

[RosieUK]

It's not much fun when you come back from holiday and your cold water tank in the loft has a 30° list and your electrics look like an extra in the Titanic because water + electric... Pretty sparkling sparky things..

Happened to my parents. Couldn't have happened to more deserving people. 48 hours it would have dropped - rotted support under the tank. If you have something similar go and check because those tanks are not light and they will make a monumental mess or worse, hurt someone if supports rot or corrode and fail... Thinking about it mine are all wood so I might have a look..

Im not sure my tank size but I have three options. Automatic 6am 45 minutes with voice /bulb indicator, motion/water sensor/water pump trigger 45 minutes with voice/bulb indicator, manual request etc. There's a lockout on the "in the bath" one for 50 minutes.

I usually use hot water (from the tank) for the kettle and the dishwasher (if I'm using immediately) since it'll use less energy to do it that way. I save 20% on the dishwasher energy usage opposed to cold water.

I think in most cases with daily use the time and water used to wait for it to warm here is enough to blow through any nasties, but we don't use recirc. pumps so ymmv.

Has anyone any experience of hot water solar heating, because that'll cut your expense right down and they can be self fabbed, although you'd need lockouts and quick release if you have freezing winters.

Talking of corrosion - due my first dose of "red devil" soon.

[PunchCardPgmr]

@RosieUK

Has anyone any experience of hot water solar heating, because that'll cut your expense right down

This is one "energy conservation measure" that seems very underutilized. It's unreal the temperatures that can be reached to "pre-heat" your incoming cold water. Granted there is a big jump in configuring your typical "off-grid moderate climate system" to an "urban-acceptable-code-compliant cold climate system".

I've seen solar panels (electricity) in places I can't believe they'd bother with it, meanwhile these passive solar water heaters seem to be largely ignored in many places that could benefit from them in the 1st World.

Solar Water Heaters