Hello. This is my first post on here, so be gentle.
I have a project which has almost succeeded. It's an internet-enabled controller for a wet-electric storage heating system using a Raspberry Pi. But you don't need to know all the detail as the problem is in one area: using SSRs to control 3 immersion heaters.
The SSRs are Fotek SSR-25DA 25A /24-380VAC details here.
The GPIO pins of the Pi when high, provide 3.3v DC to contact 3 of the SSR with contact 4 connected to one of the Pi's gnd pins. When high, light is visible from the little LED window in the SSR though it is quite faint.
On contacts 1 and 2 of the SSRs, we have supply and load for the immersion heaters. (The neutral and earth are uninterrupted but the live is interrupted by the SSR).
With the immersions supply isolated and the controller running, I've checked the voltage across contacts 3&4. It is indeed 3.3v and rock-steady.
With the immersions supply live, I could hear sounds from only one of the immersion heaters and much quieter than normal. By the end of the night, there was hardly any increase in tank temperatures.
I have temporarily bypassed the SSRs so I now have the immersion heaters controlled only by their own thermostats (and they are working fine). The intention is to have a variable tank target temperature to minimise standing losses on days when not much heating will be required.
I just can't work out what is wrong but I suspect the SSRs may be faulty. I haven't checked any AC voltages, mainly because I prefer to keep my hands well away from live mains. I don't think it can be incorrect polarity on the DC side as, firstly I've checked and double-checked and secondly, the LEDs do light up.
Is there anything else that I can have got wrong?
I have a project which has almost succeeded. It's an internet-enabled controller for a wet-electric storage heating system using a Raspberry Pi. But you don't need to know all the detail as the problem is in one area: using SSRs to control 3 immersion heaters.
The SSRs are Fotek SSR-25DA 25A /24-380VAC details here.
The GPIO pins of the Pi when high, provide 3.3v DC to contact 3 of the SSR with contact 4 connected to one of the Pi's gnd pins. When high, light is visible from the little LED window in the SSR though it is quite faint.
On contacts 1 and 2 of the SSRs, we have supply and load for the immersion heaters. (The neutral and earth are uninterrupted but the live is interrupted by the SSR).
With the immersions supply isolated and the controller running, I've checked the voltage across contacts 3&4. It is indeed 3.3v and rock-steady.
With the immersions supply live, I could hear sounds from only one of the immersion heaters and much quieter than normal. By the end of the night, there was hardly any increase in tank temperatures.
I have temporarily bypassed the SSRs so I now have the immersion heaters controlled only by their own thermostats (and they are working fine). The intention is to have a variable tank target temperature to minimise standing losses on days when not much heating will be required.
I just can't work out what is wrong but I suspect the SSRs may be faulty. I haven't checked any AC voltages, mainly because I prefer to keep my hands well away from live mains. I don't think it can be incorrect polarity on the DC side as, firstly I've checked and double-checked and secondly, the LEDs do light up.
Is there anything else that I can have got wrong?