Honeywell evohome

[Vicko0903]

Hello,

I have just purchased eco home and would like some advice to install it.

The TRVs ect I understand it’s the receivers I would like some clarification on.

We have moved into a house with a system boiler so have a hot water storage tank and boiler. It is a pretty standard set up of a hot water tank upstairs in an airing cupboard and the boiler downstairs. The programmer/timer is also in the airing cupboard and a thermostat is located in the coldest part of the house.

I have therefore purchased the hot water and ch evohome kits.

I have two bd91’s am I correct that these will replace the programmer/timer? I think have the receiver to the sensor for the hot water tank which I’ll also put near there (ensuring 30cm away from each other and metal!)

What will replace the thermostat??

Thanks

Victoria

[G4RHL]

A Control Panel provides overall control wherein rooms or zones are designated and schedules set up. This also connects via Wi-Fi to the internet. It can I understand be used as a thermostat itself although I have never done that.

The TRVs - HR92s - on each radiator act as the thermostat for each room or zone, when they sense the set temperature needs to go up or down, they send a signal to the BD91 telling it to switch the boiler on. The whole system operates without a central thermostat.

Your second BD91 as you note operates the valve for the stored hot water, the sensor telling it to go on or off as the temperature fluctuates. Again the times for this can be scheduled.

Yes keep the BD91s and the sensor at least 30cms apart and if you can 30cms away from the hot water tank. Mine is, just!

The app for your mobile phone gives you remote control of the whole system.

You can, as an alternate, use a freestanding, or wall mounted thermostat, instead of relying on the thermostat on the HR92s. I use one in my lounge but generally the HR92s are adequate at controlling the temperature.

It’s a great system. Had mine running for just over 3 years now.

[dty]

It depends on how your system is configured at the moment. The most likely thing for replacing an existing system is that the 2 x BDRs will control your valves (either 2 x 2-port values, or 1 x 3-port valve), and the orange wires from the valves will fire the boiler.

Note that if you choose to put an HR92 TRV on every radiator, you will need to ensure your system has some kind of bypass.

[duckworp]

It depends on how your system is configured at the moment. The most likely thing for replacing an existing system is that the 2 x BDRs will control your valves (either 2 x 2-port values, or 1 x 3-port valve), and the orange wires from the valves will fire the boiler.

Note that if you choose to put an HR92 TRV on every radiator, you will need to ensure your system has some kind of bypass.

Could you explain to me the bypass? I am not very technical so don’t understand the engineering side of the system. I have HR92 controllers in every room upstairs and have the whole open-plan downstairs on an evo room thermostat where each rad has an old fashioned thermostatic valve. Do the downstairs rads act as this bypass I require?

[G4RHL]

When a boiler switches off because the required temperature has been reached the pump will often continue to help dissipate the heat before eventually it switches off - pump overrun. If the pump is doing this it would have problems if all radiators were switched off so some sort of bypass is needed so the pump is not pushing against itself but at least providing some circulation. I don’t have a boiler with a bypass as part of the boiler or it’s installation but I have one radiator in a downstairs WC which does not have a TRV on it. This is my bypass. Always warm in there!

[duckworp]

When a boiler switches off because the required temperature has been reached the pump will often continue to help dissipate the heat before eventually it switches off - pump overrun. If the pump is doing this it would have problems if all radiators were switched off so some sort of bypass is needed so the pump is not pushing against itself but at least providing some circulation. I don’t have a boiler with a bypass as part of the boiler or it’s installation but I have one radiator in a downstairs WC which does not have a TRV on it. This is my bypass. Always warm in there!

Thanks. Would you know how to check if a boiler has a bypass?

[G4RHL]

Thanks. Would you know how to check if a boiler has a bypass?

No idea but am sure somebody here with greater knowledge of these more modern systems will step in and advise shortly.

[HenGus]

‘Google’ your boiler model along with ‘installation and servicing guide’. Most guides have a boiler schematic. Some older systems have a gated bypass ( a pipe around the pump with what looks like a stop****) rather than an automatic bypass.

[Dan_Robinson]

What model boiler is it?

I design systems so that bathroom rads etc, are defacto bypasses because the boilers I fit (and most modern boilers in general) have modulating pumps making auto bypasses a pita.

[duckworp]

What model boiler is it?

I design systems so that bathroom rads etc, are defacto bypasses because the boilers I fit (and most modern boilers in general) have modulating pumps making auto bypasses a pita.

Worcester Bosch 35cdi

[Dan_Robinson]

With the poor modulation rate of that thing I would definitely leave the bathrooms out of the Evohome system. Gives it something to do during low demand times.

[duckworp]

With the poor modulation rate of that thing I would definitely leave the bathrooms out of the Evohome system. Gives it something to do during low demand times.

Oh, they are already on Evohome. The downstairs has no HR92s and is on a room thermostat. The Hot Water is on 24/7 - is that sufficient for the boiler to keep busy? Or should I simply set the HR92 in one of the bathrooms at a high temperature where it is calling for heat 24/7? Thanks for your help here by the way.

[a62vw]

Hi Victoria,

Whilst evohome is designed to be installed by trained, competent installers, it can be tackled by competent DIY'ers who are familiar with design and operation of central heating systems, and the necessary precautions you need to be aware of before undertaking such work.

Although aimed primarily at trained trade professionals, we do have a free online training course explaining how to install evohome that you may want to look at:

http://youlearn.honeywelluk.com/course/evohome

I hope this helps.

Kind Regards,

Vaughn

[rvb99]

You don’t want the bathroom HR92 set to a high temperature as it will cause the boiler to fire to reach that temperature. It would be better to remove the bathroom HR92 completely . Simply remove the HR92 , set it to the minimum bathroom temperature you require and then place it on a shelf on its own in the bathroom . In this case if the bathroom is cold it will cause the boiler to fire , but for most of the time the open TRV ( no HR92 attached) on the bathroom radiator will cause that radiator to be used as a bypass. Note that this solution means that the bathroom max temperature is not controlleable and with the trv now open at 100% it may get quite warm. In our case the bathroom radiator was already fitted with a manual valve that we leave open at around 50% and I have an HR92 on a shelf to monitor the temperature and if necessary ( very very seldom) call for boiler heat . If not any of the the above you will need to add a separate bypass pipe circuit.