topic Re: What is the maximum current drain allowed on 12V T1/ T2 heatlink output in Home Automation

What is the maximum current drain allowed on 12V T1/ T2 heatlink output

Max71 — Tue, 20 Dec 2022 19:41:42 GMT

Hello everyone,

I am about to install a Nest thermostat here in the UK. For the hot water control I need to switch a 3kW immersion heater which clearly exceeds the relay contacts rating on the heatlink. So I plan to use a solid state 25A 230V relay to handle the current. The 12V SS relay input current is in the mA range. My question is does anyone know the max current drain allowed on the 12V T1/ T2 heatlink output (also used to power the thermostat), so that I can use this as the 12V source.

Many thanks for any help you can give me, Max

Re: What is the maximum current drain allowed on 12V T1/ T2 heatlink output

OannaCG — Thu, 26 Jan 2023 10:14:26 GMT

Thanks for reaching out! I'll do my best to try to assist you. The T1/T2 is used to power the thermostat as you noted, as well. It's not designed to handle any other type of connection. Any other consumer could interfere with thermostat's functionality, as the T1/T2 terminals are used foe both power and communication with the thermostat's display. I wouldn't recommend connecting anything else except for the thermostat.

Re: What is the maximum current drain allowed on 12V T1/ T2 heatlink output

Max71 — Thu, 26 Jan 2023 12:15:44 GMT

OK thanks very much for the reply -I didn't want to risk it so in the meantime I have installed the whole system and decided to use a 230V AC relay connected to HW normally open terminals (5 & 6 with line to 5) on the HeatLink to switch my 3kW water heater element. All works perfectly 🙂

Re: What is the maximum current drain allowed on 12V T1/ T2 heatlink output

OannaCG — Thu, 26 Jan 2023 12:22:25 GMT

Great, please let me know if there's anything else I can assist you with.

Re: What is the maximum current drain allowed on 12V T1/ T2 heatlink output

AlexD — Mon, 30 Jan 2023 09:55:11 GMT

Hi, just wanted to check in. How have things been going, anything else I could try and assist with?

Re: What is the maximum current drain allowed on 12V T1/ T2 heatlink output

Paul_R — Wed, 01 Feb 2023 10:24:16 GMT

Hi there! Since you haven't replied in a while, I'll need to close this thread. If anything else comes up, please feel free to reach out again.