Quick check on how T87RF2033 (Wireless Thermostat) works

[Ubernoob]

I have Evohome fitted at my property (has been fitted for past 12 months), I previously has British Gas Hive. What drew me to Evohome was the ability to see DHW termperature and the ability to add the wireless rad valves. I have a log burner in my front room, which is where my CH thermostat was, the front room would get hot with the burner on and therefore the rest of the house would be cold. With Evohome I have located the wireless control panel in the main bedroom and have HR92 wireless rad valves in the front room. I have a one zone CH setup. With my current Evohome setup the front room HR92s can be turned down when the log burner is running, so the room receives no CH heat but the rest of the house is warmed.

But I have a stupid problem! The damn Evohome controller is incredibly bright, even on night setting and on the lowest brightness setting (poor software design IMHO, there should be an option to turn the screen off at set times). To get over this I'm considering installing Honeywell's wireless thermostat in the main bedroom and use this for the CH zone control and moving the Evohome controller to another room. My question is, can the wireless thermostat be the CH zone control? Or does the Evohome controller need to be the CH zone control?

Thanks - Adrian

[DBMandrake]

Yes you can use a wireless thermostat in place of the built in sensor of the Evotouch no problem, however the existing system you are describing doesn't really make sense to me.

So you are saying that the only HR92's you have in the house are in your "front room" (living room ?) and that you therefore only have one zone, if so, what is your evotouch's sensor measuring in your bedroom if there is nothing for it to control, since there are no HR92's in the bedroom ?

With the Evohome there are two possible modes of operation - you can either choose to have a "conventional" single zone configuration with no HR92's at all, where the Evotouch's built in temperature sensor is used to fire the boiler just like a conventional single wall stat. There is one "zone", but no radiator controllers, thus no independent control of different rooms.

As soon as you add any HR92's to the system you are in a second mode of operation where every configured zone must have HR92's. In this mode you can't have one zone (front room) with HR92's and another zone (bedroom) with the evotouch sensor but without any HR92's in that room. It's been confirmed by Honeywell support that this configuration will not work.

So perhaps you can explain a bit more clearly what your configuration is and how you set it up, as it sounds to me that the Evotouch's built in sensor can't be in use at the moment.

[Ubernoob]

The HR92s are not bound to the heating control i.e. When they call for heat they are not controlling the boiler. They are just regulating the temperature in the front room when the heating is on. Does that help?

[DBMandrake]

The HR92s are not bound to the heating control i.e. When they call for heat they are not controlling the boiler. They are just regulating the temperature in the front room when the heating is on. Does that help?

Ok, understood. That also means that you won't be able to schedule the front room either, since scheduling requires the HR92's to be bound.

Seems like an odd way to do things ?

Are you using the bedroom as the Evotouch's temperature sensor zone to maintain a comfy night time temperature in the bedroom ? If so I assume you're aware that when it brings on the boiler to keep the bedroom warm that the rest of your house will also come on unless you have manually turned the other TRV's down, including the unbound HR92's ?

Also, do you have any TRV's in the bedroom turned right up ? If not, the radiators may not be able to satisfy the temperature set by the evotouch, which would cause your boiler to run all night long in a vain attempt to reach the bedroom target, only succeeding in heating the rest of the house but not the bedroom ?

Your money would be better spent on getting some more HR92's than a T87RF wireless wall stat - keep in mind that HR92's have their own built in temperature sensor too, and are cheaper than a T87RF.

Buy an HR92 for the bedroom and shift the Evotouch to the hallway or somewhere similar to solve your night time light issue, and bind both bedroom and front room HR92's to the Evotouch and schedule them.

You'd still need to manually turn down other TRV's at night but you'd have a lot more usable system! All the wall stat would buy you is the ability to move the controller to another room and still measure the bedroom temperature, but I'm not 100% certain that you can use an external sensor for a single zone configuration where you have no HR92's bound, so it could be a waste of money to buy the T87RF only to discover that you can't use it that way. (Does anyone know ?)

I started with very few HR92's as well (at first one, then three, now I have six) and getting HR92's onto as many radiators as possible is key to getting the most out of the system otherwise you're not really getting any benefit from it.

This is particularly important if you want to schedule the bedroom(s) to be warmish at night but without other parts of the house also being heated unnecessarily during the night. I was quite shocked at how much gas I got through when I started scheduling 16 degrees in the bedroom at night with manual TRV's around most of the rest of the house as those rooms were being heated during the night even though they were only set to 1!

Now that I have HR92's on all rooms that aren't left manually turned right down the bedroom can be scheduled at night and the downstairs rooms (including hallway) all remain set to 5 degrees during the night and don't come on at all.

[Ubernoob]

I purposefully haven't bound the HR92s to the boiler as I don't want to call on 24kw heat for just one room. I'm not utilising the controller to maintain a nighttime temperature in the main bedroom, it was just the logical place to put it outside of the front room (lounge) - the main bedroom TRV is fully open.

[DBMandrake]

I purposefully haven't bound the HR92s to the boiler as I don't want to call on 24kw heat for just one room. I'm not utilising the controller to maintain a nighttime temperature in the main bedroom, it was just the logical place to put it outside of the front room (lounge) - the main bedroom TRV is fully open.

In that case I'm not really sure what you hope to achieve with your system as it is currently configured.

What makes you think one room will call for 24kW of heat ? That would have to be a real monster of a radiator as our 3 moderately large radiator panels in our living room only add up to about 2600W

The radiator will only draw as much heat from the boiler as it is able to radiate, the boiler will throttle back heat output in kW automatically to maintain the set flow temperature. Just because you have a 24kW boiler doesn't mean that it is putting out 24kW worth of heat every time it is running, nor that it is burning 24kW worth of gas...

As well as that the Evohome system uses TPI control of the boiler when there is only a small heat demand such as one room trying to maintain a constant temperature - so it would only fire the boiler for a short time like 1-2 minutes in every 10 minute cycle. The Evohome system is actually really good at being able to control the boiler to output only a small amount of heat when there is only a small heat demand, so I think your fears are based on some false assumptions.

[bruce_miranda]

In this mode you can't have one zone (front room) with HR92's and another zone (bedroom) with the evotouch sensor but without any HR92's in that room. It's been confirmed by Honeywell support that this configuration will not work.

Are you sure? Currently I have 11 zones with HR80s in them but the evohome controller is on the Landing where there is no radiator. The evohome's internal thermo is just being used as a Landing temp display with no HR80s bound to that 12th zone. Everything appears to work fine with no errors. I just set the setpoint of the Landing to a constant low temperature just to avoid a situation when the Landing zone fires up the boiler.

[IM35461]

I just got one of those for the Kitcvhen as the HR92 is really close to the back door.

Anyway, I thought at first I had the wrong gadget as the instructions gave no information relating to Evohome and it would not bind.

However, a YouTube video shows how it is done https://youtu.be/prDupxp5lWA

One last observation (unless it is not working) is that it is not listed Installation Menu / System Summary?