Does the T4R thermostat modulate on opentherm?

[M1957]

I am looking for wireless thermostats with opentherm modulation.

Can anyone confirm whether the T4R thermostat modulates boiler temperature when used on Opentherm?

I cannot find documentation that explains how the opentherm works on this unit. Whilst it has a Class V erp rating (which is supposedly for modulating controls), so do other models that don't have opentherm terminals - look at the right hand side of the following web pages:

https://heatingcontrols.honeywellho...digital/T3R-Wireless-Programmable-Thermostat/

https://heatingcontrols.honeywellho...red-Digital/T4-7-Day-Programmable-Thermostat/

How are these class v without opentherm?

 

[ianmcd]

No it is an on off thermostat, it doesnt support open therm

 

[muggles]

How are these class v without opentherm?

They aren't - you have to connect via OpenTherm to qualify for Class V

 

[denso13]

This one is for OT https://heatingcontrols.honeywellho...odulating-7-Day-programmable-Room-Thermostat/

 

[dilalio]

I am looking for wireless thermostats with modulation.

Can anyone confirm whether the T4R thermostat modulates boiler temperature when used on Opentherm?

I cannot find documentation that explains how the opentherm works on this unit. Whilst it has a Class V erp rating (which is supposedly for modulating controls), so do other models that don't have opentherm terminals - look at the right hand side of the following web pages:

https://heatingcontrols.honeywellho...digital/T3R-Wireless-Programmable-Thermostat/

https://heatingcontrols.honeywellho...red-Digital/T4-7-Day-Programmable-Thermostat/

How are these class v without opentherm?

And your boiler is....?

 

[muggles]

You need an OpenTherm compatible boiler if you want to connect the OpenTherm terminals. If boiler and thermostat speak different languages, they won't understand each other

 

[dilalio]

Are you suggesting that the boiler has to be capable of reducing gas flow/circulating water temperature i.e. be capable of a modulation capability of at least 5:1?
Can't the thermostat make this happen on it own?

Yes. Boiler needs to be OT ready.

 

[dilalio]

Hhmmmmnnn...

Asking a question and then posting links to documentation that overrides anything we say here!

Another incarnation of @hard work perchance!
Oh, and guess what, that username no longer self-populates when calling the @ tag!

 

[muggles]

Another incarnation of @hard work perchance!
Oh, and guess what, that username no longer self-populates when calling the @ tag!

Has that eejit finally been eliminated? Thank goodness for that!

 

[dilalio]

Has that eejit finally been eliminated? Thank goodness for that!

Not sure... My post hints at OP and hard work being one and same...

@hard work
Or
@dr dolittle
Hmmmn, kinda link there no?

 

[M1957]

I would be glad if posts could be kept focused on my question.

The T4R has OT terminals but I wanted to know more about its functionality. Ideally I would use the T4M but it's not wireless.

 

[dilalio]

well, that just makes you a ****!

Yeah, I'd go along with me being a 4-star chap! Thanks @hard work

 

[denso13]

Can anyone confirm whether the T4R thermostat modulates boiler temperature when used on Opentherm?

https://www.honeywell.com/en-us/contact/support

 

[bernardgreen]

From Honeywell

• Compatible with 24-230V on/off appliances such as gas boilers, combi-boilers and zone valves

• The T4 can be used as a temperature sensing device in an S or Y Plan system

ON OFF control, no modulating,

I would suspect the receiver module's hardware is common to the T4 and T3 range of thermostats but has different software depending on the thermostat ( T4 or T3 ) that it is bonded to.

The OT ( OpenTherm ) terminals on the receiver probably have no functionality at all when the receiver is bonded to an ON~OFF thermostat.

 

[D_Hailsham]

The installation instuctions for the T4R say this about using the OT connections:

OpenTherm® compatibility is offered only by the Receiver Box. The Thermostat will control heat demand as normal but will not show OpenTherm® specific boiler data on the display - Refer to the boiler instructions for how to view the boiler data.

How compatible it is, is debatable as "Control heat demand as normal" is a very vague expression. To meet the OT spec minimum requirements the boiler has to adust the CH flow temperature as instructed by the thermostat. The thermostat does not tell the boiler how to make the adustment - that's down to the boiler control system; it just tells the boiler what flow temp. is required. If the T4R is sending an actual flow temperature to the boiler then it's meeting the spec; but if it's just telling the boiler to turn on and off, depending on the room temp, then it's not meeting the OT spec.

OT specific boiler data is not too important as it's just displaying "useful?" information such as the flow and return temperatures. Depends on how nerdish you are.

A GSR will, hopefully, help by contacting Honeywell and asking what, exactly, the T4R does when controlling an OT boiler.