I need a new hot water tank and I currently use HomeAssistant to automate some things around the house based on excess solar. I’d like to control the immersion to power it up off the solar. What’s an easy way of doing it? I’ve looked into iSolarBoost but is that overkill if I have HA and how would that interact with my other automations? Could I just go with a simple 20A double pole smart switch?
If you dont mind it being a simple 0 or 3kW then a smart 20a switch is the easiest. It's only if you want to vary the current when you need to look going down the iboost/eddi route. Just make sure that the switch is upto the task though, no dodgy cheap thing off ebay. check that it can sustain 13+ amps continously.
Search "immersion" on here, there are lots of posts, and some about controlling with HA.
I have gone with a T-Smart thermostat so no wiring changes needed and controllable with HA
simont how’s that going for you? What’s the lifespan like?
I think one other option is to use a contactor to do the actual switching, then you can use an everyday low-power wifi smart switch to control the contactor.
A Shelly 2PM might be a cheap option
deanjesper I've had it running for about a year with no issues
deanjesper This is the integration I use in HA
deanjesper Agreed. The Shelly 2PM is only rated at 10A per channel, 16A max across two channels https://www.shelly.com/en/products/shop/shelly-plus-2-pm#node-y5ay57r3d3ffm
The Shelly 1PM says its rated at 16A https://shellystore.co.uk/product/shelly-1pm/
But I'd still go with a proper high power switch, or relay controlled by the Shelly as immersion heaters are high power devices usually on a dedicated circuit. A proper switch like the T-smart is going to be easier to wire up.
geoffreycoan A proper switch like the T-smart is going to be easier to wire up.
This is why I chose it, its a bit expensive, but you literally remove the existing thermostat and connect the new one. No need to drain the tank or make any changes to house wiring. takes about 10 minutes
I've had the T-Smart for over a year no bother. App is a bit rough and ready but it's an immersion heater...so who cares.
Nice to know what temp the tank is even if I no longer use it to divert excess solar (export pays more)
simont I debated whether to put one in myself to use excess solar in the summer, but concluded in the end not to as I've got an ASHP that's wired into the tank thermostat for quick-boost hot water. I figured trying to keep both the ASHP wiring and any separate controller both 'happy' was too hard work.
Plus the ASHP only uses 1-2kW to heat the hot water daily in summer and I have it programmed to heat up around mid-day, so it wasn't going to be cost effective either.
I have the T-Smart controller on my immersion which can be made to run with HA
Ive had mine for two years now and works a charm through I use it through Homekit not HA
What I think I use the most oddly is not the smart on off but the ability to know if the water is hot 🙂
I installed the Timeguard WiFi switch at the weekend. Pretty easy to use.
Does the T-smart let you control the temp of the water or just show how hot it is?
Hook Does the T-smart let you control the temp of the water or just show how hot it is?
Yes its a thermostat / controller so can set a temperature to heat to
This is in home assistant
Sorry I didn't spot you'd mentioned it in the speed read of comments - whoops
Immersion on:
I have had the original iBoost since 2004 - calculate it has saved me nearly £1000 in gas costs over that time.
Just had an AIO installed in December so it's use is going to be less going forward - but I still want to retain it for use in the brighter months. My model allows 200W to escape to the grid before it diverts anything to the immersion heater.
I intend to install a smart 20A wifi switch in parallel to the iBoost - so that when I move to Agile I can make use of the the cheap slots to heat the cylinder. Considering what switch to purchase now and favouring a Sonoff POW 20A as I already have a lot of Sonoff gear. These can also be controlled by Home Assistant so hopefully I'll be able to automate charging by detecting cheap Agile slots - just need to increase my yaml knowledge.
Ivan Parallel feeding the iboost and mains into the immersion? I thought that the iboost installation instructions say that is a no no?
Ultima357 I have the original model, not the + version. The original installation instructions make no comment re. 'other electrical controls' but I note that the later + model instructions do.
Your comment has prompted me to think about this a bit more and I think you're right and this is a bad idea. The iboost works by enabling a variable voltage to the immersion heater and it's unlikely to like an instantaneous grid voltage being applied to the discharge terminals! Thanks for the comment!
My fall back plan was to use a Switchbot - as I've seen others do, to switch on the manual boost feature. This looks physically messy but I'll give it some more thought.
Ivan Yes I think the iboost gives modulated DC, so best avoid parallel connections. You could use two 3kw switches to isolate the iboost, then apply mains but again the iboost says no switches should be placed in the feed to the immersion. I did have one in line with my iboost which they claimed voided the warranty when it failed so learned the hard way. But that said, I can't really believe that an inline switch can cause failure. I use a 3kw WiFi controlled switch on my iboost to control it when I'm on holiday, so benefit from export payment first and then get hot water for when I return. Simply switching it on and off.
Ultima357 I can't really believe that an inline switch can cause failure
the immersion has a temperature activated switch built in, "the thermostat" so no it can't !