Nest Learning Thermostat H73 Error

[mmanchev]

Hello, I have the exact same problem as from this topic - https://www.googlenestcommunity.com/t5/Nest-Thermostats/Nest-Learning-Thermostat-H73-Error/m-p/54905...

The same gas boiler, Viessmann Vitodens 100-W, Learning thermostat 3rd gen. Both are working together for like 2 year now and suddenly I got H73 error. I've restarted the thermostat according to this guide from this topic - 

https://www.googlenestcommunity.com/t5/Nest-Thermostats/Nest-thermostat-3th-gen-opentherm-not-detect...

Nothing happened after reseting, H73 was still presented. As it was not working and nothing changed, after several hours the thermostat was back online working like normal. After that if has H73 error on daily bases, and almost at the same time, and back online after the exact time each day. so it's basically 50/50 for 24 hours working/H73 error. I'm quite astonished from this behaviour. Any advice is welcomed.

Best Regards

[Frustratedddd]

Have you had the boiler checked for problems?

I assume you have power to the Heat Link, and a green light showing on the Heat Link?

Do you get 3 green lights on the Heat Link if you press the button?

What was the outcome of the link you posted?

[mmanchev]

All checked, manual mode on heatlink, boiler is working fine, no power outages. Outcome of the reset is the same H73 error. It fixes itself arround 8am and loose connection arround 5:30 pm everyday. Seems like scheduled thing, but there is no schedule in Nest and the boiler hasn't such a thing.

[Frustratedddd]

You say reset, do you mean Factory Reset?

You have no schedule set in the thermostat at all, correct?

[mmanchev]

"Hamburger reset" on the control unit and 30second hold on Heatlink button.

[Frustratedddd]

You have not done a factory reset in that case, just a restart.

I would suggest you do a full factory reset, and that might clear out any glitches if the thermostat has errors.

[mmanchev]

Just did it. We will see if this evening it will happen again.

[Frustratedddd]

OK, but you need to do that in the correct manor, how did you factory reset?

[mmanchev]

I used this procedure:

Press the ring on the thermostat to pull up the Quick View menu. Select 'Settings'. Select 'Reset'. Choose 'All Settings'. You will be prompted to confirm that you wish to erase all settings and return to factory defaults. Choose 'Reset'. Turn the ring to confirm and press 'OK

[Frustratedddd]

OK, let's try the best way to make sure everything is FULLY reset.

Reset like you did, BUT when everything is back to the home screen with the language page. Remove the display from the base plate, and squeeze like you did before ''Hamburger'' and wait until you see the house, then release. - Do that TWICE. Then replace back on the base ready to go.

Next, press the Heat Link button for over 40 seconds until you see a blue pulsing light, do NOT release until the light is a steady pulse. Keep presssed for the 40 seconds. Do that TWICE.

Now setup the thermostat ready for use. leaving any schedules dissabled.

[mmanchev]

ОК, I will do that.

[mmanchev]

Done, will keep the post updated what's goin on.

[mmanchev]

The thermostat threw H73 at the same time like the last 3 days after the factory reset.

[Frustratedddd]

You have the error again now?

[mmanchev]

Yes, H73 at the same time like previous days, after it started to show up.

[Frustratedddd]

I assume you have a wireless connection from display to H/L?

[mmanchev]

Yes.

[Frustratedddd]

I had a similar issue in the past, the way I proved the connection was install a temporary wired connection from Heat Link to display. Can you try that at all, not saying it will work, but worth a go.

[mmanchev]

It’s not possible. The base hasn’t wired connection.

[Frustratedddd]

I thought you have a 3rd Gen, they all have wired bases!

[mmanchev]

Well, mine has just T1 t2 contact which are 12VDC power supply that can be get from Heatlink so I don't think it's possible. The behaviour stays the same, this morning the thermostat was back online about the same time like the days before....

[Frustratedddd]

They are the exact connections I am talking about.

[mmanchev]

Actually there is a new clue. As it repeats at the exact time every day, I've checked my home automation routines and it seemed to be exactly when my garden lights turn on/off and the nest termostat is not working when they are on. So when I switched them off the thermostat imediatelly when back online. They share the same circuit breaker. It like that almost 3 years but here we go. I will separate the gas boiler on an individual breaker and see how it goes.

[Frustratedddd]

That's the reason I suggested a connection wired as temporary connection. That would eliminate any wireless interefernce, or some anyway. Many of these remote bulbs and similar items cause grief with these stats.

[mmanchev]

It's not the wireless connection between the room sensor and heatlink, I believe it disrupts the gas boiler and it's openTherm communication. I've changed the circuit breaker and everything is working, so it's not wireless interference, but most probably electrical spikes that were troubling the gas boiler.

[luciaaa]

Hi, @mmanchev!

Thank you for reaching out to the community. I’m truly sorry your thermostat is displaying the H73 error code; I understand the OpenTherm cannot be detected. I’m happy to assist you! 

To provide you with the best assistance, please share the following information:

• Did the installer verify that your boiler supports OpenTherm? If OpenTherm is supported, were the necessary settings configured correctly?

In the meantime, try the following: 

• Ensure that the power to the boiler is on and that the OpenTherm cables are connected via OT1 and OT2. Please let me know if the wires are connected correctly; if not, try the steps below. 

• Ensure the boiler is still receiving power. If so, restart the Nest Heat Link.

• If restarting the Heat Link fails to resolve the inconvenience, power cycle the boiler by switching it off and then back on at its main power switch.

Please let me know how it goes.

Best regards, 

Ana