Best, affordable way to monitor individual hard-wired appliances

Hello all

I still haven't started my OpenEnergyMonitor system yet but we've recently moved house and all my previous plans have changed as a result.

Our new house has only got electric heating which I guess makes things easier to monitor, but the fact that all heaters are on the main ring main for the flat makes it difficult to pinpoint certain devices.

We have 3 convector heaters which are wired via a fused connection unit into the ring main, and one oil filled radiator which is plugged in a standard socket with a timer. I would also like to monitor the immersion heater which is also wired via a FCU to the ring main. In my opinion not the best option to have so many heaters on the ring main but the landlords electrician recently rewired the place and that's how he had done it.

What sort of options are there for monitoring single appliances? The immersion is the highest current at 3kw, the convector heaters are between 500w-1.5kw. I'm happy and competent enough to do the wiring if necessary, I could even house a transmitter of some kind in a spare pattress box next to each FCU if needed and use a CT sensor around the live cable for each one. 

My ideal plan would be to have an emonTX with CT sensors at the consumer unit monitoring all circuits, then individual sensors on heaters and some other appliances, I can then subtract the readings of those from the whole ring main reading and work out what everything else is using.

What do you all suggest? Ideally I'd be looking to spend no more than £20 for each individual sensor if possible but will consider higher if that's unrealistic.

Thanks in advance :)

Robert Wall's picture

Re: Best, affordable way to monitor individual hard-wired appliances

£20 per appliance is a bit restrictive if you're thinking of measuring current, but as the appliances you mention are all fixed loads, you probably only need to know whether they are on or off, and you can compute the current / real power knowing only the voltage. So I'm thinking in terms of a JeeNode, you still need a power supply and you still need to detect that the appliance is on, though that is simply done with a neon lamp and a LDR or similar, giving good isolation; or maybe if the JeeNode was powered from the switched side of each appliance, then simply saying "I'm on" at regular intervals would be enough and no input sensor would be needed. I'm assuming your emonTx will report Voltage to allow you to do the power calculation in emoncms.

JD's picture

Re: Best, affordable way to monitor individual hard-wired appliances

Adding another emonTX's seems easiest since they are ready to go.  Put a CT on each breaker of interest in the breaker panel and the resulting cost per breaker is not that high.

Otherwise how about JeeNode Micro?  Or Moteino?  Both will be above 20 however.  Not counting the analog front end, calibration, programming time etc.

Robert Wall's picture

Re: Best, affordable way to monitor individual hard-wired appliances

JD - That's OK where he has individual feeds, but specifically NOT for the appliances that Fitzy mentions that are all on the same feed.

JD's picture

Re: Best, affordable way to monitor individual hard-wired appliances

Hi Robert - Maybe I don't know what "ring main" is.  I assumed that meant "breaker panel" in US terminology.  Does it mean something else?

EDIT:  I googled it, and it seems "ring main" is something else altogether!  I've never seen anything like that here in the US.  http://en.wikipedia.org/wiki/Ring_circuit

Fixed link - BT

 

Robert Wall's picture

Re: Best, affordable way to monitor individual hard-wired appliances

Two nations separated by a common language!

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.