I have a hot springs hot tub that uses about 25% of my overall usage. This time of year we usually only use it on weekends and with all the rain and cold not much at that.
The hot springs controller has a “summer mode” that cycles the small circ pump and heater to maintain a much lower temperature but I found that it is too low if you actually want to use it.
So, I am considering installing a relay (connected to my home automation system) to cycle power to the heater during periods that I know there is no chance we will use it. That should reduce the overall usage as the lower the temperature of the water, the lower the losses. I understand that the heater will run longer when it has to catch up, but I am guessing that overall, the heater will run less. Freezing is not an issue for us, it gets cold but not cold enough to worry about it.
I think you will save money doing it like you said even though it will take a lot of energy to get it heated back up. As it is now, even keeping a lower temperature there is “heat loss”. No matter what you do the heat loss will always exist.
I know people with timers on their water heaters that completely turn them off at night or on vacation and they all have told me it has lowered their electricity use.
I think with a hot tub you will realize bigger savings than a water heater especially seeing that it’s 25% of your usage.
There are certainly savings to be had then, no question - whenever you can reduce the Delta-T you save.
If you have time of use pricing for your electricity, you can save even more by timing the cycles of the hot tub to favour your off peak electricity rates as well.
I use an HS110 to control our small 3 person plug-and-play hot tub. I programmed it so that it runs as little as possible during mid an on-peak electricity rates and focuses must of it’s run time during off peak electricity hours, and I’ve achieved some savings that way. As for lowering the temp, unfortunately, being a plug and play unit (120V) it can take a very…very long time to recover from any significant drop in temperature so I do tend to just leave it at 104 in the winter. In the summer however, I do plan to reduce it’s run time even more and let the temp drop off through the daytime and overnight hours as recovery will be much faster when it’s +30 out vs -20.
The only thing to keep in mind is to make sure that you leave things setup so that you do get enough basic filtration. Even if you don’t need heating, you will still need filtration - not getting enough will result in your sanitizer levels getting low (assuming you use a bobber style brominator? They require water flow to work) and scum build up and such, especially if the pump switches off not long after a bather load.
Same here, hot spring hot tub that we convert to a ‘cool tub’ in the summer time. Our panel goes down to 85 which is where we leave it for the summer time. Our tub is older but I believe it has two pumps, one which is just a pump and one which is pump/heat.
The one thing I did notice was that the small rectangular piece of foam which is at the connection between the two lid halves leaked a lot from the factory. I replaced the velcro and sealed the ends and have noticed a ~10% savings in the winter which is a ton.
Your relay idea seems like it would work, potentially contact hot spot support to see if cycling the controller is ok? I have had to fix some things on my controller and they use a lot of right-on-the-limit components and ‘indoor only’ components like buttons/led screen etc.
How long did it take for your Sense to detect your heater? I got the first pump but am waiting for the heater still…it is a little confusing because it is an extremely high wattage and is very distinct. The only thing close is the dryer but the wattage is on a different scale. Was considering getting the extra Sense probes just for the hot tub but it would be nice if it could find it on its own.
My Hot Springs hot tub actually has 3 pumps, the small one is always on for circulation and flow through the heater and the other pumps are jet pumps. My sense actually picked up the heater pretty quickly but often confused it with our electric oven which was also 4K watts. We have since replaced the oven with gas so that is no longer an issue. Unfortunately Sense never picked up the small always on pump, it is lumped in with always on and is about 50 watts. Cycling the heater has actually worked out pretty well, the only down side is that you need to remember to turn the heater on ahead of time if you want to use it. I put it on a schedule so it would heat it up on weekends when it gets the most use.
BTW, if you ask Hot Springs they will tell you not to modify it in any way. I just interrupted the power from the breaker that feeds only the heater, the power to the controls and pumps remains always on.
I have a friend who was suggesting simply tap the temp sensor. It’s reading the resistance of the circuit, so if you disconnect the circuit it will read as infinite one direction (infinitely hot?), or if you short the circuit it will read the other direction. Once you know which is which you should be able to short or disconnect the temp sensor to convince the tub that it’s MORE than warm enough. The cycling of the tub water will continue but the heater will be off until the temp sensor is reconnected the normal way.
This should allow you to remotely control the tub with any sort of low voltage relay instead of having to spend well over $150 on a 240v 50 amp relay.
The real trick is figuring out how to control it. Perhaps all I care about is TOU, prevent it from coming on when it’s costing me 50¢/kWh. You could also control it with a schedule if you only use the tub on weekends or whatever.
But there is an even more important way, heating the tub with excess solar. So if the solar is sending power back to the grid it would be better to feed that to the tub or the Tesla, perhaps not both at the same time. It would be great if Sense could be in charge of a list of devices that can be turned on remotely in a defined order as more power is generated and turned off in reverse order if the sun is disappearing.
In the winter, we use a solar pool cover for out tub. We’ve found that even at temps down into the teens, the temp only drops a max of 2 degrees F over a 12 hour period.
I broke down and bought a Dewenwils Outdoor Wi-Fi Smart Box for $69. It has the ability to be controlled by an app, but won’t show me the energy used or be programmable with a published API. Fortunately the tub has been detected by Sense so I’ll see it there. I can put the Smart Box in timer mode so I can have it turn on at noon (peak solar) and run for 1/2 an hour every day and then on days we are gonna use the hot tub we only have to heat it up a little bit more to get it to temp.
Perhaps I’ll figure out how to run it only on sunny days, but that’s down the road. Just waiting for the interconnect whip to arrive so I can install it.
