Hello. I have a solar diverter that burst fires my 3kW immersion heater on a 1Hz cycle. My old dumb electronic meter hardly ever indicated import - I knew this because I was monitoring the impulse LED with a device that bleeped if it went off (i.e. indicating importing).
I’ve now got an Aclara SGM1411 B smart meter (which, incidentally, contains a disconnector so they can cut my supply remotely). Its impulse LED is useless because it flashes for energy transfer in either direction so it’s impossible to tell instantaneously if it thinks it’s importing. I therefore have to rely on the in-home display. This often indicates import when the diverter is operational, and is racking up cost.
I’m concerned that this meter does not emulate an electromechanical meter as well as the old one, having less “elasticity” to ride over the instantaneous imports when the immersion heater is on. I’ve tried doubling the PWM frequency but it doesn’t appear to make a difference.
Anyone else noticed a change in characteristics with smart meters? Just as dumb meters should emulate electromechanical meters for fairness, so smart meters should emulate dumb meters.
Unfortunately, this seems to be an ongoing issue and from what I can gather, it depends on how the meter is programmed according to the whim of your supplier.
After I complained, my supplier arranged a visit but after I looked at the manual on line and found that the impulse LED cannot be programmed to behave like it should, I cancelled it. I reckoned they wouldn’t be able to do much about import/export dynamics without changing the meter.
I’ve read https://meteroperators.org.uk/download/reverse-running-meters-guidance/?wpdmdl=6963 (and the update) and I didn’t see anything specifically related to this - it’s more about stopping the import register being changed (up or down) on export. Do you know if commercial solar diverters use phase control? I appreciate the potential problem of flickering of lights caused by burst control but the supply to my property is low resistance so this doesn’t happen.
The problem with many commercial offerings is they (and I might even be talking ‘all’) leak some export energy in order to not alarm the customer if there’s occasionally a small import. I don’t know what control strategy most use, but I do know one uses PWM up in the kHz region on the mains waveform (and without mentioning names, it’s advertised as preserving the wave shape). The problem with anything like this is huge and expensive filtering components are almost certainly needed to meet the limits for harmonics.
Ah, so it will use FETs rather than triac phase control, but either way need a filter, which is one reason why I avoided using phase control. I don’t want to have to redesign my system, which has meant I haven’t had to use any gas since I installed it in April! You of course don’t have to preserve a waveform to drive a heating element beyond interference suppression.
And on both sides - mains and output. Which means the control elements see an inductive load, which means you need a way of circulating the stored energy, which means a whole load of complication bearing in mind it’s a.c. And you probably can’t do d.c. - especially if the flywheel components mean the current never falls to zero - because the tank thermostat won’t be rated for that (or possibly more correctly, it won’t have a d.c. rating at all).
Yes, as soon as you chop the mains wave up, the edges generate harmonics. It’s the statutory limit on those that’s the problem.