SONOFF SNZB-02LD LCD Smart Thermometer (Probe Version) max safe temp

Ideas & Suggestion
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Hello,

I have a question about the SONOFF SNZB-02LD LCD Smart Thermometer (Probe Version).

I recently purchased this device and installed it on my central heating boiler, which usually reaches temperatures of up to 99°C.

I understand that the stainless steel probe itself can measure temperatures up to 115°C, so I assume the probe tip is within a safe operating range. However, I would like clarification about the cable connected to the probe.

The probe is not placed directly in hot water. It is inserted into the boiler’s steel temperature pocket / enclosure. The slot is larger than the probe, so about 5 cm of the probe cable also goes inside the steel enclosure together with the probe.

My questions are:

  • Is the probe cable insulation also rated for temperatures close to 99°C?

  • Is it safe for a portion of the cable to remain inside that steel enclosure at that temperature?

  • Or is only the metal probe tip rated for high temperatures, while the cable could degrade over time?

I would appreciate an official clarification on whether this installation is safe for long-term use.

Thank you.

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Hi, I see you had the same idea as me. I use it in a storage tank to measure the temperature of water for heating.

I think the cable is ordinary and is not intended for direct exposure to temperature and for the reason that the insulation does not contain silicone.

The probe itself can handle it. I bathed the probe in 100 degree water when I cooked wild boar sausages for about an hour.

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I had still haven’t received any reply for my question. I had also emailed itead support for about 2 days but still have not received answer. Can anyone from Sonoff reply please ? Thank you ! @MichaelLearnsToCode @Milk ( not sure if i had tagged the right persons )

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Hi, I have forwarded your issue to Sonoff customer support. They have confirmed receipt of your email and are currently reviewing and processing it. They will get back to you shortly via a formal email reply.

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You are amazing @Milk ! Thank you for your always prompt support ! :1st_place_medal:

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Hi, can I use the thermometer just like you have?

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Hello @Jojkoba , this is the message i had received from support:

Dear Derex,

Thank you for your contact.

The cable’s outer sheath is made of PVC and has a temperature resistance of approximately 60°C; it is not suitable for boiler temperature measurement.

Thank you for your time.

Regards,

Frankie in SONOFF

I had inserted it with just the metal probe inside, and testing it. Not so accurate as if it was full inserted. I am thinking to modify it a little bit and add PTFE tube over the first bit of cable near the metal probe. When i will find that tube i will try inserting it again and test.

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I heat the water in the boiler to 60-65 degrees, which is a usable thermometer in my case.

Thx

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If that’s a hot water storage tank, I’d be concerned if the water temperature reached anywhere near 99 Degrees C. Although, is it fed from a solar heating system of some sort? Why is it so hot?

It is a good idea to use ptfe sleeving on the cable though.

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Hi @Ramsdale . The storange tank is a Puffer. A hot 1000 Litres water collector from my wooden central heating system. I usually heat the water until 90 - 99. I had days when the gauge was showing 120 degrees, and nothing happened, luckily. I had forgot the air intake manually open. This is the reason i want to monitor it and set a remote alarm.

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I assume that my furnace is a solid fuel furnace and heats a 1000L+ tank for heating.

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Hallo Derex

Make a insert of metal to put in the tank whit a hole fit for the probe leave the cable outside the insert problem solved

Greetings Arjan

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That’s a good idea @adrost . I will try that. Thanks