Does the heat coming through the window cause problems other than the one with your thermostat? My windows like your face west and heated not just the entry but also the loft upstairs, which on turn heated the upstairs bedroom. It was very difficult to get upstairs cool enough for sleeping in the summer. I bite the $2,000 bullet and had motorized custom shades
installed. I was willing to take a chance of limited life span of motor as I close the shades on,y once in May and don’t open them back up until once in September. That lowered the temp enough in foyer/loft/bedrooms by over 8 degrees in early evenings.

THe morning and afternoon sun is full on. You don't want to touch the front door handle at mid day in the summer. The heat upstairs is a problem as well. But I place a small box fan on the floor by the vent and that works wonders. I thought about blinds but I really like the light. And in the winter, the heat is n the hallway is amazing :)

Three alternatives come to mind, there may be others too;

1) Retain the existing location of the thermostat but replace the actual stat with a different one that will take temperature readings from a wireless remote sensor or remote control instead of at its own location. Meaning, the thermostat location remains in position A in the entry hall, but you have a different thermostat installed in the same place, one that will turn the equipment off and on by referring to a remote sensor that you can put in location B or C or wherever you think a more representative reading can be obtained. These are usually wireless. Or,

2) If you're going to relocate the thermostat position and have new wire pulled to put it into a different location, why wait a few years? Do it now. Or,

3) Get a thermostat from the Honeywell RedLink line. To use that, an equipment control unit is wired and placed on a wall near your equipment. A Redlink thermostat (that is battery powered and capable of fully wireless operation) is put on the wall where you want the new thermostat to be. The themostat will communicate using its own wireless system (not Wifi) with the Honeywell equipment control module where the equipment is located and the entire operation will be seamless and as if wired as far as you're concerned. The Redlink product line is fully accessible over the internet from apps if you'd like that capability too but an internet interface unit is required. They're inexpensive.

I have two Redlink thermostats that operate just as described, used because pulling new wire was going to be difficult when new equipment was installed. They work great.

Honeywell, Nest Google, and Ecobee offer thermostats which work with remote sensors. I believe they use WiFi, but I would not be surprised if there are models which use Blue Tooth. The Nest sensor doesn't have to be wall mounted. You can move it to different locations as needed. I suggest reading the reviews on Amazon to determine which work the best.

I also suggest you should see what it would take to move the thermostat to a better location. You can plan ahead and install extra wires in the event you want to upgrade the HVAC equipment in the future.

Most modern, programmable thermostats have a "temperature offset" adjustment. You can set the thermostat to read 2-4 degrees lower than the actual temperature at its location. So, if the temperature in your entryway is 80 degrees, the thermostat will read 76 degrees and the AC won't kick in until the entryway is 80 degrees (that way the rest of the house won't be freezing). This isn't any different from just setting the thermostat to 80 degrees!

I think the problem in this case occurs when the sun is shining and the hallway becomes much warmer than the rest of the house. When the sun is down the temperature differential is much smaller. Adding an offset is not going to work well in this case.

I agree, adding an offset will do nothing. The problem cited is that the temperature reading at the entry hall location is hotter than the rest of the house. No matter what the setting of the thermostat, gauging off and on by the temperature in the entry hall will not provide a satisfactory result in the rest of the house.

Another task to address the problem is to think about shading the window (as already mentioned) or improving air flow through that room/area so that its temperature is not so disproportionate to other parts of the house. Whether or not the thermostat is relocated.

"Is there anything I can do until then?"

• Honeywell Home RCHT9610WFSW2003 T9 WiFi Thermostat with 1 Smart Room Sensor
• Honeywell THX321WFS2001W T10 Pro Smart Thermostat with RedLINK

So interesting you should recommend that. I have a Honeywell T5 unit that I loved. Until today. We had to replace our router and now it won't reconnect to the wifi. No matter what we do. So it works fine, but I can't use the wifi function. I was with the Honeywell folks in chat and it was fruitless. I googled the problem and it may be that the upgraded router may not be compatible with the thermostat. So, I think I'm gonna move it when I replace my HVAC and get a different brand thermostat.

Y'all are awesome. I've been on Gardenweb (now Houzz) for years and I've never gotten bad advice. In fact, more than once, these forums saved my keister.

Is your router set to transmit on the 2.4 GHz band? It won’t connect to the thermostat If it is not.

I'm going to have to check and see. I know it has the capacity for 5G (if that is the correct terminology) but don't know the setting yet.

Why are you suggesting to disable the 5.0 Ghz band on a dual band router? If the thermostat doesn't have that band capability, it won't see it whether it's broadcasting or not. Or am I missing something?

I agree with Elmer. Disabling the 5.0 GHz is not going to have an affect on the 2.4 GHz transmission. By default routers will transmit on both bands unless someone has turned one of them off.

If that is not the problem then the next thing to check is the encryption protocol and any restrictions on IP addresses. I could be mistaken, but every new wireless protocol is backward compatible with older versions. So I highly doubt the problem is due to incompatibility with a new router. If you buy a new thermostat there is a chance it may have the same problem. It is worth the time to figure out why the T5 is not joining the wireless network.

@mike_home: "I agree with Elmer. Disabling the 5.0 GHz is not going to have an affect on the 2.4 GHz transmission."

It was probably correlation without causation. I was trying a gazillion things to try and get my T6 to connect. However the 802.11 wireless standard set can make a difference. For example, when I changed my router's 2.4 Ghz standard from "802.11 b/g/n" to "802.11 n", my Sonos speakers would no longer connect. When I changed my router's 5.0 Ghz standard from "802.11 n/ac" to "802.11 ac", neither my computer nor my TV would connect.

What does any of that have to do with my question concerning a thermostat with only a 2.4 band capability?

So Wd, are you saying it is hopeless? I kinda feel like that but don't wanna throw in the towel prematurely

@Elmer J Fudd: "What does any of that have to do with my question concerning a thermostat with only a 2.4 band capability?"

I was agreeing with you but adding that the wireless standard set on the router can have an affect on the ability of a device to connect to it.

@mzdee: "So Wd, are you saying it is hopeless?"

I'd reset the thermostat, delete the Honeywell Home account, and then try setting up the thermostat wi-fi again.

@wdccruise: "For example, when I changed my router's 2.4 Ghz standard from "802.11 b/g/n" to "802.11 n", my Sonos speakers would no longer connect.

If the Sonos speakers only support 802.11b or 802.11g, then they won't connect if the router is only transmitting the 802.11n protocol.

@wdccruise: "When I changed my router's 5.0 Ghz standard from "802.11 n/ac" to "802.11 ac", neither my computer nor my TV would connect."

This is likely the same issue. The computer and TV may only support 802.11n and not 802.11ac which is a newer standard. When setting up your router, you should select as many standards as the router allows if you are connecting to older devices. As a side note the 802.11ac standard only uses the 5 GHz band. If you are set to that standard and turn off the 5 GHz band then there will be no transmission.

The wireless standards have become very confusing but not hopeless. Log into your router and review the settings. You should be able to get it to work with a little trouble shooting and patience.

"I was agreeing with you but adding that the wireless standard set on the router can have an affect on the ability of a device to connect to it."

I think you're prevaricating and making the response to this person more complicated than needed. The answer to my question is, I believe, turning off the 5.0 signal will have no effect on a device with only 2.4 capability.

I've never needed to vary the standard, default, most flexible settings on a router. Has anyone else? You described making changes and then being unable to connect certain devices. Did that surprise you? Changing to more restrictive settings and then having trouble connecting devices is user error, not a hardware/software problem.

OP, if I were in your shoes, I would set the router to normal or default settings and try again. Double check that the strength of the Wi-Fi signal in the thermostat location (using a smartphone or other mobile device) is adequate to support the connection. If all that checks out, I'd get a different router.

@mike_home:

I know how it works. I was giving and EXAMPLE of why merely enabling the router's 2.4 Ghz radio does not ensure that a particular device can connect.

@Elmer J Fudd: "You described making changes and then being unable to connect certain devices. Did that surprise you?"

It was an EXAMPLE. I KNOW what the settings should be. I was NOT surprised. I KNOW how it works. I did NOT make an error. However, the OP is having difficulty connecting his T5 thermostat to his new router. The thermostat will only use the 2.4 Ghz but just turning on the router's 2.4 Ghz radio does NOT guarantee that the thermostat will connect. YOU don't know what standards the thermostat supports. YOU don't know how the router is configured. YOU don't know what the router's default settings are. Jeez.

But you do?

What I do know is that routers are typically shipped with default settings that provide the most flexibility and range of connection possibilities. I also know that routers have historically been fluky devices, often with poor quality control in their manufacture and consequently higher rates of defects in shipped units than usually encountered in electronic devices. Many different brand models can use the same chipsets used by their competitors, there are a limited number of producers. But the firmware of each brand is different and behavior and performance of models with the same innards can vary. Did you know all of that?

Which is why I suggested returning the router and getting another. Maybe even a different brand and or model. I've gotten turkeys before and after encountering erratic behavior or connection problems in situations that should have been simple swap-out and swap in, returning the turkey and getting something different has always resolved the problems.

Haven't resolved either issue yet. I am certain that I will move the thermostat when I replace the HVAC unit in a year or 2. The Honeywell unit never did connect to the wifi. So it is a pricey piece of tech doing what a 7.99 programmable thermostat would do.