You bought a communicating system... if the temperature from outside isn't displaying, it's not communicating. Simple and as hard as that.

standard mode is not communicating mode, communicating mode is not standard.

In a communicating system what makes decisions from input received? If the input is "nothing" - it has nothing to make decisions from. IE: standard mode.

They noted that the "outdoor temp" shown on the display, which was supposed to be taken from a physical sensor located at the compressor, was not showing up properly because of a wiring issue.

I am not a Lennox system communication expert, but I suspect the temperature outdoor temperature is used by the system's software algorithm to determine how the speed should be varied for heating and cooling. The temperature data is sent from the condenser to the thermostat through a serial protocol. The fact that no temperature is appearing suggests this serial communication is not working. It is difficult to tell for sure, but it seems like the thermostat and furnace has been wired as a non-communicating 2-stage set up. You are not getting the full benefits of the expensive system you have paid for.

I suspect the reason this was done is the installer does not know how to wire a communicating system, or the old wiring is not able to transmit the low voltage signal levels of the serial interface. It could be poor wiring connections. Cross talk between wires could degrade the signal levels and cause problems. A new wire bundle may have to be installed.

My suggestion is to call the installer and tell them you want the temperature displayed on the thermostat and you want the system wired in communicating mode. That will force them to do something to resolve it.

+1 Austin Air

I would not accept this. I'd at the very least be calling the installation supervisor.

IMPO

SR

"They said they had to do part of the wiring in "standard mode" and another part in "communicating mode", but they assure me it was all running properly."

Also called "Legacy" mode. It's either communication mode or legacy mode - can't be part one and part the other!

Thank you all for the input! I did not realize that the outdoor sensor was integral to the communication feedback loop for the system, I thought that communication only referred to the zones and tstats inside the house. I will push back!

"But, I do want to be sure that the communicating system is properly configured, since if I understand correctly, if it is NOT set up right, it will run in 2-stage mode which is less efficient than fully variable, and defeats the purpose of buying a variable speed system and a fully communicating zoning system."

I can't verify that your HVAC contractor installed the equipment and/or controls properly. That said, you can operate the EL18XCV in either communicating or non-communicating mode. In non-communicating mode, you'll forgo wi-fi communication and some advanced diagnostics, but you'll still get the variable capacity operation you're looking for. Here's an excerpt from and a link to the installation manual for the EL18XCV:

The EL18XCV unit will provide full variable capacity operation when installed with a conventional 24VAC non-communicating two stage cooling or single-stage cooling thermostat. The EL18XCV outdoor control has advanced control algorithms using the EL18XCV suction pressure sensor to provide true variable capacity operation.

https://tech.lennoxintl.com/C03e7o14l/VIu12Ch2uV/507955-01a.pdf (pg. 12)

This would suggest the modulating function is controlled by a timer on the furnace board. Not the best solution for such an expensive installation!

Running this machine in non-communicating mode with a control that is designed for "communicating mode" is counter productive.

If you paid for a communicating control, those controls aren't cheap... Why would you want anything but communicating mode for a control you paid for? Certainly there are many ways to do something... The advantage in a modulating / variable speed system is the ability to ramp up and down as needed the split second it's needed. The difference? waiting 20 mins from a timed standpoint if the 24v signal remains active to ramp up. IMO, you lose alot of the benefits of the machine doing such things.

The choices in modulation in standard or legacy mode on this machine are decided by suction pressure on this machine. So if they got the communication aspect wrong... how big of a leap is it to suspect refrigerant charge probably isn't right either? It's very easy to over charge these kinds of systems.

If the system is running in communication mode, how much more input does the machine have? It likely has humidity reading built into t-stat, temperature inside, temperature outside, refrigerant pressures and so on. All this info is passed to all equipment in communication mode... to make run decisions from in a split second.

Typically variable speed has the advantage of ramping up and down via 1% steps. Manufacturers that put all their eggs into communication based systems break this chain if any one piece of the equipment suffers communication problems. They put fallbacks in there as a way to avoid the system becoming a paper weight. At some point it might resort to that if the control is no longer made etc. However, that time is not now, being new out of the box.

The OP should, of course, get the full range of capabilities they paid for in good working order. In the interim, they're at least getting the full range of variable capacity operation.

In non-communicating mode, you'll forgo wi-fi communication

I don't think this is true. The Lennox iComfort S30 thermostat was installed. There would be no reason to turn off the WiFi radio unless there is how the thermostat is set up to work in non-communication mode.

The EL18XCV outdoor control has advanced control algorithms using the EL18XCV suction pressure sensor to provide true variable capacity operation.

If this is true then how does it work with the Lennox EL296V two-stage furnace? Wouldn't the furnace blower speed have to ramp up and down as the the EL18XCV capacity changes?

Dave Johnson,

When I went back to your original post, I now realize the EL296V is a 2-stage furnace. It is called variable speed because at the time of installation, the two speeds for heating and the two speeds for cooling are set. I do not believe they vary once they are set. This furnace does not modulate the operating speeds. We can look at the product manual for the furnace for further explanation.

It has been my experience when an installer does not make the effort to install a feature properly, there is a good chance that other aspects of the installation were also not done properly. My advice is to check and question everything that does not look proper to you

In non-communicating mode, you'll forgo wi-fi communication

wi-fi has no bearing on a communicating system. wi-fi is merely an application that allows the user to control the system remotely --change temp settings, shut the system off etc. Your system can be non-communicating still work with a wi-fi enabled thermostat. Personally I don't recommend any wi-fi type controls for a number of reasons I won't get into here. If you need to control a HVAC system remotely there are better options to do so than via wi-fi.

Communicating systems are "hard wired" to communicate between the various pieces of equipment & the thermostat in most cases. (1 manufacturer has taken the thermostat out of play so users can chose any thermostat they want and still maintain the benefits of a communicating system that communicates info from the outdoor unit to the furnace and back.)

If there is a depreciated value of those "hard wired" communicating connections -- interference, improper materials, improperly fastened and so on... there is no "communication". This communication is like that of a network, like when you connect to the internet. The problem is? The list is long if you ask me. I've installed communication systems as well as trouble shoot systems I didn't install as well as those I did. For the most part they work well, but... this is a repeatable business. It never ends. My job is mostly to mitigate problems as much as possible.

Given that you're having these issues early on doesn't point anywhere good.

The EL18XCV outdoor control has advanced control algorithms using the EL18XCV suction pressure sensor to provide true variable capacity operation.

If this is true then how does it work with the Lennox EL296V two-stage furnace? Wouldn't the furnace blower speed have to ramp up and down as the the EL18XCV capacity changes?

The furnace is variable speed, however this reference is the blower motor - not in reference to modulating furnace. This is why when the furnace has the ability to ramp heat out put up and down we call this "modulating" not variable.

So the furnace in question is a two stage variable speed condensing furnace with 96% efficiency. Condensing furnace is 90% efficient and above. Two stage refers to heating stages that the gas valve operates in. Some may call this low fire and high fire mode.

The variable speed blower is not a fixed speed blower unless: there is a feature to set it as such. Typically manufactures will ship furnaces in a common most used setting. But certain applications an installer can choose from as many as 4 different algorithms in which the variable speed blower will run.

Typically in communicating systems the blower speed is lowered when the system is running in dehumidification mode. This doesn't mean there is no dehumidification at a higher blower speed though. Because there is more than one way to do it to force longer run times.

If you slow the compressor speed? This drops capacity and will force the machine to run longer. Bosch keeps things quite secretive how they do it without communicating from indoor unit or thermostat either one. It works quite well and much less than a proprietary type communicating system.

The Lennox website says the furnace is two stage, multi-speed. I think that's what's causing the confusion. "Multi-speed" usually does not mean variable speed.

Below are excerpts from page 40 of the EL296DFV installation manual. In both communicating and non-communicating modes the blower speed for heating and first and second stage cooling are set at the time of installation. In communication mode you do have the ability to change the speed from the thermostat by going into the installer setup menu.

Indoor Blower Speeds

Non−Communicating

When the thermostat is set to FAN ON," the indoor blower will run continuously at a field selectable percentage of the second−stage cooling speed when there is no cooling or heating demand. The factory default setting is 38% of cool speed.

When the EL296DFV is running in the heating mode, the indoor blower will run on the heating speed designated by the positions of DIP switches 11, 12 and 13. When there is a cooling demand, the indoor blower will run on the cooling speed designated by the positions of DIP switches 5 and 6. First stage cooling will run at 70% cool speed.

Communicating

NOTE − When the EL296DFV is used with icomfort Touch® thermostat, proper indoor blower speed selections are made by the communicating thermostat. When the thermostat is set to FAN ON," the indoor blower will run at setting determined during system configuration. When there is a heating demand the fan will run on heating speeds for firing rate. When there is a cooling demand, the fan will run on the first stage and second stage cooling speed set using the icomfort Touch® thermostat in the installer setup mode. The factory default is based upon 400 CFM a ton.