Remotely controlling electric wall heaters

LCARS

Member
Hello, I've been lurking for a while but first time posting.

I've got a home that I spend about half the week away from and I really need to be able to control the temperature of the house when I'm away. I'd like to be able to dial down the temperature so I'm not spending money to heat an empty house, but also not be too cold so pipes freeze etc. The only real problem is that the house is entirely heated using about 10 standalone electric wall heaters. There's no central control or thermostat, just a knob on each individual heater controlling the temperature. The knobs don't give you a very good sense of what the temperature is going to be either, it's not really a thermostat, but rather just numbers 0-9. I have a wood stove for when I'm there, which cuts the expense out of the electric heaters, but no system on earth is going to automate that :p

I would post a link to the type of heater I have but my new account status doesn't let me do that yet. So we're clear, we're not talking about a baseboard heater, it's recessed into the wall and no wires visible.

I've yet to take one of the units out of the wall to look at the inside, but I'm assuming there would be someplace that I could wire in a UPB or Z-Wave relay to power on/off the heater. My question is this though: all the relay modules I've seen so far are wall receptacles, not meant for behind the wall use. I don't want to do any modifications that would be unsafe, but I really don't like the idea of having the controller be on the wall. I'd rather have it be tucked away so that everything looks the same as it does now on the outside.

How have other people automated their in-wall electric heaters?
 
Well, it'll definitely be helpful to know more specifics once you can post links - it only takes a couple of posts. In the mean time, have you thought much about how you'd like to know when to turn the heaters on/off? And will you want temperature specific control of each one, or maybe turn on a group of them based on a single temperature reading?

And, do you have any other automation equipment already in place? UPB, ZWave, an Elk or HAI, etc?

Without seeing it, I'd have to guess that the existing on-wall controller is a basic mercury switch that either completes a 24vac circuit or just closes a set of contacts. The numbers should vaguely represent a temperature setting. That is easy enough to replicate with just about any system.

Also - as far as keeping everything hidden, it's almost guaranteed you'll need to be able to run wires out of the heater unit to wherever your controller is - be it a plug in module, thermostat, etc. What it's plugged into can ultimately be hidden somewhere; as long as you can run the wires. If the wires are in a hot area, you need to make sure the wires are rated for those temps and you'll be fine.

Once you answer some of those things it'll help... in the mean time, you have options - anywhere from using any standard ol' thermostat (z-wave communicating, wifi, standard, etc) - the catch is if the unit runs off contact closure instead of 24vac, you'd have to run a 24vac power supply and connect a relay rather than direct connect - but it's perfectly doable. Or any sort of relay closure would work just fine as well controlled by the system of your choice.

Last but not least, if you're up for a challenge and like programming, there's even the CAI board people are talking about here - that can close relays and accept temperature sensors - so that's completely doable too.
 
Thanks for the reply Work2Play,

Here's a pic of the heater, there's 5 of this type in the house, the rest are a bit different but similar:

5iyR1.jpg


Unfortunately, no marking on it to indicate a manufacturer/model. Perhaps that will be more clear once I open it up.

I haven't decided on a automation technology, but I think I'm leaning towards UPB if only because I've heard it's really reliable.

I'm planning on using a wall plug type computer to be an always on device connected to the internet to control from. I've got a USB temperature sensor based on this design and I'm planning on just coding up some hysteresis routine to turn on/off the heaters. The first set of heaters I want to do this for are all in one open area so I think I'll just need the one temperature sensor to start out.

I was assuming that I would just turn the dial to 9 (all the way on) and just control the heater by turning on or shutting off all the power to the unit. However, Work2Play, it seems like you were suggesting controlling it through the existing "thermostat" on the device?
 
Perhaps it wouldn't be a good idea to just shut off the power, now that I'm thinking about it, the heaters probably have a cool down period where just the fan is going but no heating element. That would complicate this..
 
I would be careful with whatever you do. If something fails and the heaters stay on for an extended period of time you could be dealing with a fire. They may or may not have a "cool down" period. If not, the safest way to manage this would be to allow the built-in thermostat to still function so that it would still shut off on its own before getting too hot in the event that your system fails. If you set the built-in thermstat so that it shut off around 80 or so (something a bit higher than you would ever actually want), you could then use a relay to turn on/off power to the entire unit with an external thermostat. You would need a high amp relay for this task. Once the relays are installed, an off the shelf programmable/networkable thermostat could be used to control the relays.
 
IMHO electric heaters shouldn't be run unsupervised. I would think a simpler solution would be to just shut off your water and drain the pipes when you leave for extended periods of time. For your toilets add antifreeze so they don't freeze and crack. I used to have a vacation home and I went though that ritual every time I left even though I had central HVAC.

But if you really want to automate them, there are inline fixture modules for UPB and ZWave, you might find one rated high enough for your heaters. You could set the heaters at a low level, and use those to control the power possibly combining with some sort of temperature sensor and central controller that you can use to write the rules. Maybe something like a Vera. You might also consider some fire/smoke alarms and water/freeze sensors so you can at least get notified if something happens.
 
Lou, that's a good idea to still only have the original thermostat set to the maximum level I'd want it at. wuench, I already have monitored smoke detectors in the house and the point is well taken that I need to thoroughly think this through before I implement anything.

This is a new house for me and the original owner left the heaters on when he left, and he owned the house for close to 20 years before me. I'm really just looking for a way to lower the normal temperature but not have to shut the heaters off completely. This is a house that I return to every weekend so it would be a pain to drain the pipes every week.
 
Ah, OK - I see now the existing thermostat... I was imagining a remote dial... but that doesn't change much. With a manual I might be able to get more info online; otherwise you can open up the cover and check out that dial. It may be a potentiometer with adjustable resistance, or it may be the mercury switch type I was originally thinking. Depending on how that switch works, you might be able to override the dial through simple contact closure. I'd guess it probably acts kinda like a thermostat just not accurate enough to have temperature markings on.

In doing that though, I would want something super-reliable with some safeties in place... like I wouldn't use UBP unless there were auto-off timers built in just in case.

Others have offered some good ideas too that I kinda like as a potential alternative... instead of taking over control and replacing the dial, you could affect the power to the heater instead. Depending on how the house is wired, there are a few options. If you're really lucky and all the heaters share a circuit, you could use a UPB-triggered contactor to switch a high-power load on and off. If they're more individual, then look into an inline relay that can handle the load of the heater.

If it were me, I'd probably aim for replacing the function of that dial first out of simplicity, but using parts that are super reliable with some failsafe mechanisms; but if you don't have that equipment in place and the experience, controlling the power to the whole heater might be easier and safer.
 
Most dials on the heaters are mechanical thermal switch, open and close depends on the temperature setting - triggered by heat expanding metal. It probably does not have mercury switch, which must drive another relay to turn on and off the power. I think this kind of dial probably don't use any relay at all.

If the heaters are original built-in, then they probably have separate circuit breaker for each heater. It might be easier to put some optical isolated solid state relays to switch heaters on and off by wiring them near the breaker box. You can use WebControl to directly turn on and off those optical isolated relays, setup on/off schedule, or remotely turn them on or off. Or if you want to invest in UPB/Z-Wave, you can wire the UPB to turn on/off the optical isolated solid state relay. Those optical isolated solid state relay are pretty cheap on eBay. You can easily find 25A, 60A or even 100A ones, search "solid state relay" on eBay will show a lot of them. Make sure also get heatsink, since you will run some heavey load through them.
 
1st off, with an installed unit like that I seriously doubt that there is any fire danger. Electric bill shock is a DISTINCT possibility though. ;-) Even if the fan were to stop, I doubt it would overheat and cause a problem- just the way things like this are designed, assuming that it is UL listed, and properly installed of course.
Bigger picture, what exactly are you trying to accomplish? If you just want the pipes to not freeze, then you could just set the thermostats down to keep it just warm. Or do you run the electric in addition to the woodstove when you are there?
 
1st off, with an installed unit like that I seriously doubt that there is any fire danger. Electric bill shock is a DISTINCT possibility though. ;-) Even if the fan were to stop, I doubt it would overheat and cause a problem- just the way things like this are designed, assuming that it is UL listed, and properly installed of course.
Bigger picture, what exactly are you trying to accomplish? If you just want the pipes to not freeze, then you could just set the thermostats down to keep it just warm. Or do you run the electric in addition to the woodstove when you are there?

I do agree, expect if you tear into it. Personally, I would not alter the contents of a unit such as this, especially since it is 20 years old. If you bypass its built-in dial temp control, you may be bypassing one of its main safety features. I would stick with trying to switch it via its main power supply. And, since it is 20 years old, it probably does not run a cooling fan after the heating element kicks off, but that would certainly be worth confirming before shutting it off via the main power.

And as fwd03 mentioned, the webcontrol unit could work out nicely for you. It can be programmed to be a full out thermostat and it is internet enabled. You would need the webcontrol, a temp probe for it, and a (or multiple) high amp relays. You would actually need two relays since the webcontrol unit can only switch a ttl level relay and you aren't going to find any high amp relays that switch at ttl level.
 
Different ways to skin a cat I guess... but I still prefer the idea (if it were me) of getting control of that dial instead of controlling the unit via the power. But I'd treat it like I was retrofitting the heaters to become thermostat-controlled appliances instead of that knob... so whether you're there or away, you could set a desired temperature and forget it... and be able to access and control that temperature remotely as well.

If the knob is a simple mechanical switch of sorts, then replacing it with something smarter actually seems safer to me - because if there are cooldowns or other safeties, they should still work exactly the same. I'm not saying the thing will catch fire if it needs a cooldown and doesn't get it - but if so, it'd be better for the longevity of the device if it does its thing.

At this point though, there's a lot of good ideas on the table - but it's pure speculation until we can get some answers about how the place is set up... now that it's the weekend, hopefully the OP will be heading back today to do some exploration.
 
now that it's the weekend, hopefully the OP will be heading back today to do some exploration.

Yep, heading there this afternoon and will take a look at things. Thanks for all the many suggestions you guys have made, this forum is awesome :)
 
Here's pics of the unit opened up: http://imgur.com/a/NzXF4

Opening it up reveals some stuff for us:
  • It 240v / 4000W (um, wow?)
  • It's made by Marley Electric Heating model K404A (link to PDF manual)
  • Date code 1299 sounds like it's 12 years old, not 20.
  • The dial looks like a pot to me (but what do I know?)
Each heater in the house has it's own breaker in the main electric box for the house.
 
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