Software stops working after a a few days?


I assume L and N are the other way around but such a hack should be done with a tester screwdriver and knowledge of the house wiring setup.


Not sure I understand this. The internal wiring of the cable having the wrong colours would be very unusual. But I’m also not sure how either the L and N should be affected by the pi making a change to the heating pin? There were no problems until the HeatingMode was turned on.


What the furnace is expecting to return from the thermostat is the L. The thermostat on the other hand has no way to understand which is N and which is L so it accepts that the installer wired the thermostat with the correct terminal block labels.
Your situation I suspect may come from my previous concern (check with a tester screwdriver) or the fact that the furnace is on a different phase or is getting powered from a separate circuit breaker.


The thermostat will be on a different circuit breaker though. I’ll try and explain again. L, N and H were wired correctly to my boiler and this works absolutely fine (freezing aside). You suggested in your second post that the power could be an issue (though I’m not sure how) so I removed the L and the N from the boiler and wired it in to a separate mains cable (with L and N wired correctly), which will be on a different circuit. Again, the original setup worked fine (aside from the random freezing).

We seem to be going from one issue to another though. Ultimately I’m just trying to eliminate the mains coming from the boiler being the issue causing the freezing (though I’m honestly not sure how it could be). I appreciate your time with this, but I feel like we’re going in circles. I’m certainly not an electrician, so I can only understand or do so much.

Do you have any recommendations for what else to test? Because I can’t use a thermostat that’s going to keep freezing. Not only is it unreliable, but it’s also dangerous if it won’t shut the heating pin off when it freezes. I could buy a tester screwdriver, but I don’t want to go on a fools errand.


I don’t have knowledge of your house wiring setup so I can only suggest solutions that have worked in the past and fit certain scenarios I have faced.
What has been an issue before was that an old house a friend installed HestiaPi in did not support such a thermostat due to the following:
The furnace although it was providing L and N wires it was actually expecting a passive circuit to simply return the L line back on the H wire. This is the case with all old thermostats that you turn a dial by hand.
When he installed HestiaPi, the HestiaPi was always underpowered and occasionally when the furnace was to turn on or another sudden spike in electricity need like a hair dryer, oven or tumble dryer an instant voltage drop would trigger a grey out of HestiaPi leaving it frozen.
After troubleshooting for some time and finally replacing with a completely new unit we realised it was the wiring that caused it. Running a separate line of L and N from the house solved the issue straight away for good. Your house may be different so, yes, I cannot suggest something else I am afraid.


Ok, this sounds like a similar scenario. Except my original dial thermostat was a 3 wire setup, whereas the way you described this makes me think your friends thermostat was a 2 wire setup? Additionally in my setup, the L coming from the boiler was powered by the timer on the boiler itself. Obviously I couldn’t have the HestiaPI not always be powered, so I used the electronics manual for the boiler to re-wire to a permanent live contact instead.

Also to clarify: My house wiring has a ring circuit specifically for the boiler, which wires to the thermostat. Intrigued by what you mentioned though I tried starting a bunch of high power stuff at once including the oven and microwave to eliminate it as a cause and there definitely appears to be no correlation between electricity spikes and the HestiaPI freezes as far as I can tell. Though this doesn’t eliminate it being an issue with the boiler itself, but so far there’s never been a freeze connected with the boiler starting up or shutting off.

So, back to re-wiring the L and N. To keep this as simple as possible, because there’s obviously something I’m not understanding. What are you suggesting I test? As far as I can tell you want me to use a tester screwdriver to determine which is L (powered) and which is N from the cable I have coming from the house wiring (separate circuit)? But I am genuinely completely baffled as to why you even think this could be backwards. Functioning socket, functioning cable, correct colour coding. Unless you’ve got this confused with the L and the N wiring originally coming from the boiler, in which case I’d understand the scepticism. But that’s not part of the equation here, as it’s now un-wired in order to test the house wired solution.

What I am more concerned about is where you suggested there would be a problem with them being on a different circuit breaker (though I thought this was the entire point??), because they absolutely will be.


It was actually a 3 wire setup. L and N were providing mains power. It was simply prone to voltage drops due to the furnace supply capacity in Ampere as it was designed for old type passive thermostats where a simple flickering indicator light bulb was the only consumption.

My concern about the RCD being tripped leads me to believe that there is a leak to the Ground-Earth wire (usually yellow and green) and not between L and N. This is something you will need investigating either with a tester cable or with a mains light bulb and 2 wires.
The bulb should light when connected to L and N.
The bulb should trip the RCD when connected to L and Ground.
The bulb should neither light nor trip the RCD when connected to N and Ground (I think).