17 Watts for each smoke alarm!

[Spunagain]

Hi All
I have been looking at ways of controlling my electricity base load at home and got myself an energy monitor.
After finding a base load of over 250watts I did some digging and found 3 culprits:

• My printer was drawing 50watts in idle mode
• My Surround amp was drawing another 50 watts in idle mode.
• My 10 mains smoke alarms installed as part of a loft conversion are drawing 17 watts each all the time!

The smoke alarems alone are is costing me over £150 pounds a year.

So googling does not seem to show the power consumption for quoted "Energy Saving" replacements.

Can anybody recommend any mains alarms which have stated power consumptions?

Many thanks!

[Spunagain]

They are AICO LTD Ei141RC which is a radio linked system, and has a pp3 battery back up. The "back-up" batteries seem to only last a year or two which seems to be less than the battery only alarms used to have!
Google suggests they are very popular!

The label claims 0.8W but this is clearly wrong.

I have disconnected a load of the and the power drops on the energy monitor by 17 watts for each one!
The monitor is a new Owl and seems pretty accurate based on measurement of lights as they come on and off.

The muppets that did the loft mucked up so many things that I would not be supprised if they are fake Chinese knock offs.

[Spunagain]

Hi Hairyben
You are right! I have had a quick look under the "Easifit base" and there is at least one extra wire - there are brown, black, grey and earth one of which I guess is the signal wire. I was thrown by the web page which said Radiolink compatible, not realising you have to fit different bases.

It does not explain the excessive load on each of the detectors unless they are either fake, all from a faulty batch or the 0.8W spec on the label is let's say "optimistic".

[Spunagain]

lost in espace said:

Mine are 9W

Thanks! Is that measured or on the label?

Peeking inside the detector it is all very analogue. The power supply look like it uses a big series capacitor to drop the mains voltage and the rectify it to give a DC supply. I am not sure how efficient these are but where they could be consuming the stated 0.8 watt, they may show a much higher VA (Volt-Ampere) due to a very bad power factor, which may be confusing the energy meter sensor.

eliot said:

Same ones as I use. Grey wire is the comms link. All my critical loads like these are on a dedicated subpanel which has its own watt meter - i cant see any difference in consumption when i pull the breaker (5 devices).

Thanks eliot. Very sensible! My installers however have put the 2 kitchen ones on a dedicated breaker, the rest of the ground floor ones on the ground floor socket breaker and 1st floor ones on the 1st floor lighting circuit. Which is a little worrying if the sense line becomes live. (Have I mentioned they were muppets?)

I think this means I need to isolate all three circuits to safely work on any one of them.

I am not sure if damage can be caused if some alarms are live while some are powered down?

hairyben said:

Regardless it could be either so OP check your own first if fiddling around as muddling them can damage aico alarms.

I think my next steps are
1) Borrow a decent calibrated Fluke Ammeter from work and measure the actual current into and voltage across a couple of the sensors. Armed with that I can see if they are really consuming that much and if so I can reach out to Aico and see what they propose.
2) To check all the alarm bases are wired together correctly

Thanks all for your help steering me in the right direction, I will report back when I have some new measurement.

[Spunagain]

Well a bit of faffing and borrowing a couple of meters I am getting 245V at the mains:


And I measured the current with a couple of different meters and I get:


or



Taking the lower one. P = I x V = 0.048 Amps x 244.8 Volts = 11.8Watts!

You can see on the photo on the meter label it actually says 230V, 40mA, 0.8W which does not make sense! 230 Volts x 0.8 Amps is 9.2 Watts.

A call to Aico in the morning I think!


I also noticed the Voltage in the loft dropped to 238.9V when I plugged the Tesla into the 7kw charger!


Edited to add - please do not try this at home unless you know what you are doing. Mains electricity is very nasty. I connected up with the plug out, plugged in, switched on, took photo, unplugged. I did not touch anything while it was live.

Edited by Spunagain on Thursday 1st June 09:11

[Spunagain]

Aico have been very helpful and got back to me quickly.

The have send me a pdf which explains that the straight Volts x Current measurement does not work as smoke Alarms are capacitive loads.

This means V & I are out of phase where I lags V

So the actual Power = V(instantaneous.) x I(instantaneous.) which is lower because they are not at the peak levels at the same time.

And to measure it you need a special meter which takes account of the Power Factor (the delay between V & I).

My only worry now is that my electricity meter is not smart enough to take account of power factor.

My next step to make sure is to shut off everything except the smoke alarms and see what my old fashioned spinning wheel electricity meter is recording.

[Spunagain]

A quick google suggests modern digital meters do sample the voltage and current instantaneously to get the correct power numbers.
It is not clear to me how the old fashioned motors behave with a reactive load.

I had to have a mains powered smoke alarm fitted in every room and hall and landing for building regs as I have had a loft conversion done. It was either that or fit fire doors in every room.

[Spunagain]

Dave_ST220 said:

Just done a test for you (same make of smoke alarm). We have 4 (with a Co alarm on that circuit-same make) and with only those on they are taking 4W in total. I now know the battery back up in my mirror clocks have failed & have taken the opportunity to synchronise all clocks in the house

ETA, we have 4 including the CO, 3 smokes.

Cheers Dave that tallies with the quoted 0.8 watt allowing for a little production variation.

Is yours an old mechanical meter?