Anyone familiar with Rheem smart waterheaters? - Page 1
Forum section: electronics / projects

author: electromotive
author_rank: Regular Contributor
timestamp: March 05, 2019, 05:19:34 pm
content: I've got a basic (but brand new) Rheem water heater. It seems to me that there isn't much difference between it and a network enabled smart heater (i.e. I could pick up a few parts on ebay and add a lot of functionality). By chance, do any of you fine ladies and gents have the *smart* version?This control box (over the topmost element) and a small bit of wiring seem to be the only difference, but I need to find someone that has one so I can verify the wiring behind this controller:

author: ajb
author_rank: Super Contributor
timestamp: March 05, 2019, 06:07:10 pm
content: As with most things like this, the hardware is the easy part, and as you surmise, is probably pretty darn simple. The trick is that with a bit of carelessness/design oversight, it would be very easy for whatever software runs the thing to cause trouble ranging from wasting a bunch of energy to creating enormous mess, or possibly even structural damage to your house if the relief valve isn't set up properly.Best to leave the existing electromechanical thermostats (there are usually separate thermostats for the top and bottom heaters) and thermal cutouts in place as a last line of defense, and add your controller in between the supply and the existing appliance wiring (maybe bring out the two heaters separately, you could probably improve performance a bit by controlling them independently). You can set the existing thermostats to a relatively high (but still safe) temperature, and then use your controller to reduce the temperature by turning the whole appliance supply on and off if that's what you're after. That way the worst case scenario is that your water heater runs hot and wastes energy.

author: IDEngineer
author_rank: Super Contributor
timestamp: March 05, 2019, 07:29:44 pm
content: Slightly off topic: Almost all of the energy consumed by a natgas water heater goes to actually heating the water. Ever notice that virtually all gas appliances have spark igniters now - except water heaters? It's because even the pilot flame helps keep the water warm, unlike virtually all other pilot flames where their heat is basically 100% waste.Every appliance in my house that can be natgas fired IS natgas fired. My electrical power goes out many times a year, but I literally cannot remember a natgas "outage" in my entire lifetime and I've lived in four states, multiple homes in each, in widely varying climates. That's decades of uninterrupted natgas service. Put as much on natgas as possible, switch to LED bulbs, and you can run your entire house on a relatively small generator when the power goes out. All-electric homes cannot do that because there's several kilowatts in the water heater... several more in the oven and cooktop... several more in the furnace or baseboards... etc.Maybe you're using an electric water heater because you don't have an option. But if you DO have an option, gas (natural or propane) is the way to go. You'll have hot water no matter what the electric company does.EDIT: Being completely objective, one downside to gas water heaters is their thermal hysteresis. The water temperature can vary by 10-20 degrees as a consequence of the design of the thermocouple+valve design that doesn't require external power. Thus I try to take my shower after someone else does, so the water heater has kicked on and is headed for the top of its hysteresis range.I don't know if electric water heaters have tighter temperature regulation, or if there's anything but bang-bang style controls on their heating elements. I haven't been able to find an off-the-shelf cooking oven with linear control of its heating elements so I doubt water heaters are any better.Sorry for the distraction, just a "favorite cause" of mine. We return you to our regularly scheduled programming....

author: electromotive
author_rank: Regular Contributor
timestamp: March 05, 2019, 09:39:30 pm
content: Natgas would be nice, but there's a weird sort of situation going on. About 20 years ago, a company called Horizon came through and planted new yellow plastic gas lines all over creation. Before that, you had your choice between three different truck loaded/offloaded suppliers. Long story short, Horizon went bust -- the lines are there, but they aren't in use. If you live in the city (I don't) a company called Columbia Gas (I'm in the U.S. -- weird name, I know) has lines everywhere. Didn't matter though -- they never got close to where I life. However, when Horizon went bust, they all became greedy. My home is total electric, and it's cheaper to run everything on electricity than it is for my parents to run their home on a combination of gas (range, furnace) and electric (water heater).We're planning on adding some energy diversity soon in the form of whole-home generation and a solar array with Tesla-style backup.

author: IDEngineer
author_rank: Super Contributor
timestamp: March 05, 2019, 11:21:54 pm
content: Quote from: electromotive on March 05, 2019, 09:39:30 pmSounds like the dark fiber situation after the .COM bust in the early 2000's. Players laid cable everywhere, then went under. Other companies picked up the infrastructure for pennies on the dollar and started renting/leasing it out to other companies without hooking anything up to it at all. Just renting dark glass in the ground.QuoteNot weird at all! Here in the Pacific Northwest every fourth company has "Columbia" in its name. The largest river drainage in the region is the Columbia River. And so forth. And as every schoolchild knows, "Hail Columbia" is the official "Song of the Vice President of the United States".

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 05, 2019, 11:32:43 pm
content: If you know a friend who does HVAC work or are interested in learning, look into DIYing a heat pump water heater out of a cheap window A/C.

author: electromotive
author_rank: Regular Contributor
timestamp: March 06, 2019, 04:40:40 pm
content: Quote from: NiHaoMike on March 05, 2019, 11:32:43 pmMy stepdad does HVAC work. I just started digging into this last night after reading your post. Very interesting indeed.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: March 06, 2019, 05:08:39 pm
content: I have an older version of the smart controller, it's attached to my Rheem hybrid electric water heater (model: Professional Prestige). The base water heater has all the control stuff built in, the 'smart controller' is an add-on. I bought it thinking it would be useful to schedule when the heater operates, but Rheem does not publish their API. They do have a phone app, which doesn't do much for me (the point was to have it automated). It's been installed for ~2 years now, no problems reported. I don't think you're missing much if you have a heater without the smarts.The hybrid heater itself is quite nice, and has the side effect of cooling my basement in the summer. It will still work in the winter, but I switch it to electric-only to keep the basement from getting too cold.

author: DBecker
author_rank: Frequent Contributor
timestamp: March 06, 2019, 07:27:40 pm
content: I wouldn't worry that much about safety, unless you modify the built-in safety back-ups. There is typically an over-temperature cut-out that is separate from the operating thermostat, and the over-pressure relief valve as a last-ditch don't-explode fall-back.Gas water heaters have a one-time thermal fuse, typically something like a Microtemp G4A00 084C, mounted alongside the bimetallic thermostat. This fuse is wired in series with the thermocouple. The thermocouple powers the solenoid that holds in the main shut-off valve. If the pilot flame goes out, the solenoid no longer holds open the shut-off valve. If the tank goes above 84C , the thermal fuse blows: the resin pellet in the fuse melts, and the contacts spring open permanently. The nominal fix is a replacement of the whole thermostat at $200-ish.If you actually care about efficiency rather than simply IoT-ish control, a heat-pump water heater may be the best option. They start around $1K, with a good chance of economic payback before failure.

author: electromotive
author_rank: Regular Contributor
timestamp: March 07, 2019, 08:57:37 pm
content: Quote from: radar_macgyver on March 06, 2019, 05:08:39 pmMind if I send you a PM? Mine is conventionally wired, but I'd like to see how it looks behind your element covers if you don't mind.

author: Tony777
author_rank: Newbie
timestamp: March 08, 2019, 08:14:35 pm
content: Anything that says "smart", just replace with SPY. So SPYING water heater logging your usage just to charge you MORE for using energy during peak hours ! And if you have the HYBRID version then it's taking heat from your house to heat the water. That might be fine if you live in a desert area that is always cooled but it means you are heating the water by COOLING YOUR HOUSE. That isn't good if you are heating your house. And they are more expensive and complicated so will more likely break down. For heat natural gas or propane is the best choice for the lowest cost, highest efficiency and lowest maintenance.I hope this helps.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 09, 2019, 04:25:08 am
content: Quote from: Tony777 on March 08, 2019, 08:14:35 pmNatural gas is usually the cheapest option if it is available, but it isn't for him. Propane is significantly more expensive and a heat pump ends up cheaper in most areas.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: March 09, 2019, 05:36:53 am
content: Quote from: electromotive on March 07, 2019, 08:57:37 pmI've attached a picture under the top element cover, after removing a couple of pieces of foam and a plastic insulating guard. There isn't a conventional thermostat, that's replaced by an emergency cutout in case the main control system was stuck on. I believe the thin white wires are for the main controller's sense wires. Also attached is the controller's debug screen that shows all the sensor values (in F). Compressor was off, so everything besides the tank is at ambient.Quote from: Tony777 on March 08, 2019, 08:14:35 pmWhich is great, I don't need air conditioning! It also keeps the basement dry without needing a separate dehumidifier.