Ideal Logic Max C30 + Google Nest Thermostat 3rd Gen Opentherm Setup

[nexonb]

Hi, I had a professional install a Nest 3rd Gen Thermostat on my Ideal Logic max boiler which supports OpenTherm but he didnt wire it for opentherm and left it in on-off mode. When I asked why he said the boiler doesnt need it. Is this correct? What would I be missing with this setup. I just want to have the best and efficient setup as possible. Would really appreciate any advice. Thanks.

 

[muggles]

Probably got someone who doesn't understand OT or how to fit it. Did you specify you wanted the OT connecting when you booked the installation? Definitely worth doing even though the modulation on the Logic is rubbish

 

[nexonb]

Yeah, I asked about OpenTherm. Do you know what features I would be missing without Opentherm right now?

 

[Deleted member 267285]

Yeah, I asked about OpenTherm. Do you know what features I would be missing without Opentherm right now?

There’s no features as such, it’s more an output adjustment so the boiler doesn’t need to be on as high when nearing the desired temperature.

 

[nexonb]

There’s no features as such, it’s more an output adjustment so the boiler doesn’t need to be on as high when nearing the desired temperature.

Thanks! Yeah I noticed the temperature was at 75*C which is the max I have it setup and it remained the same even after reaching the desired room temperature of 22*C.

 

[Deleted member 267285]

Thanks! Yeah I noticed the temperature was at 75*C which is the max I have it setup and it remained the same even after reaching the desired room temperature of 22*C.

I think you’re getting mixed up. The desired room temperature is just that, the 75 is the boilers flow temperature, but the gas is modulated down when opentherm is used.

 

[nexonb]

I think you’re getting mixed up. The desired room temperature is just that, the 75 is the boilers flow temperature, but the gas is modulated down when opentherm is used.

Ah okay, I saw a youtube video where the guy sets the radiator temperature at 75 degrees and if the set room target is met or within a few degrees it would ease off with the radiator temperature, but on my Ideal boiler the radiator temperature is always at 75 degrees even after it met the target. The boiler display shows "On at 75*C, Radiator Target 75*C, Set by Room Stat". I'd assume with opentherm it would work similar to the video I'm talking about?

https://www.youtube.com/watch?v=gZcy0sruFfA&t=4366s

 

[nexonb]

Hi,

I just wanted to provide an update on this. The guy who installed my Nest Thermostat said it can be configured for OpenTherm but it might damage the boiler circuit board? He said he spoke to Ideal who said that the boiler only supports up to 24V whereas the Nest Heat Link can go up to 42V. I asked him if this can be limited to match the required power and he said it cannot be done and it will most likely fry the boiler PCB.

I have no idea what he said is true or not, if what he says is true then why even have opentherm on the boiler in the first place? Any help would be appreciated. thanks.

 

[RandomGrinch]

He said he spoke to Ideal who said that the boiler only supports up to 24V whereas the Nest Heat Link can go up to 42V.

The OpenTherm standard supports an open circuit voltage of up to 42V.
If Ideal boilers can not handle more than 24V, then it is them not complying with the standard!
As it is, the signalling voltage is usually far lower.
I haven't found Nests OpenTherm voltage in the technical specs, but there is at least one source that has measured the output on a scope at around 17V.

Tado Controller, Opentherm Gateway, Navien Oil Combi Boiler. - Domoticz

So the question is, when is a standard not a standard?

 

[Harry Bloomfield]

Yeah, I asked about OpenTherm. Do you know what features I would be missing without Opentherm right now?

Rather than the boiler running near flat out, until it hits the set room temperature, and maybe over shooting, wasting gas. When it nears your set temperature, the boiler will be able to gradually reduce it's output, until it just kisses the temperature, with no overshoot. Once there, the boiler can just trickle along, avoiding the frequent noises of the pipes expanding and contracting. All much more efficient.

 

[Harry Bloomfield]

Yeah, I asked about OpenTherm. Do you know what features I would be missing without Opentherm right now?

Get they guy back, and tell him to do the job properly as you have paid for it.

 

[nexonb]

Thanks for the replies, I really appreciate the help. I spoke to the guy and asked him to come back to set it up and he agreed to do it next week. I also spoke to Ideal live chat again and they said there are no issues so I don't know where this guy is coming from with the voltage being an issue.

I found this guy on the Nest Pro website and he was listed as Nest certified that's why I asked him to install it, when he came in for the initial installation I kept asking him if Opentherm was being setup, and during the setup on the actual Nest unit itself he set it as on/off mode and I changed it to Opentherm thinking he forgot to switch it, but it gave an error. The guy was confused about what I did and he couldn't even back out of the Opentherm menu to set it back to on/off until I reverted the setting for him and he then said Opentherm is weather compensation which requires a unit to be fit outside the building.

I do not know how this guy is Nest Pro certified and apparently he has been installing boilers for 10+ years. His whole attitude was trying to scare me into thinking I might void warranty on the boiler by having this "incompatible" setup that could fry the PCB.

Now my only concern is if this guy messes up something (might lack knowledge) and then goes "I told you so". Is there anything I should look out for when this guy comes back?