Evohome

[Tony]

New Evohome installing but concerned that you should always have one radiator always open to help the pump , so have all radiators fitted with controllers not sure if this is okay

I have two zones already motorised and would open them manually again is it correct for Evohome?

Tony

[electronicsuk]

It's more about getting heat away from the boiler's heat exchanger than helping the pump, but yes, there should either always be a bypass radiator or the boiler should be fitted with an auto-bypass valve. If you have a combi boiler then there's a good chance it may already have an internal bypass valve - check the manufacturer's installation guide.

Not quite sure what you mean about already having two motorised zones. If you're fitting HR92s then these should be fitted to all except the bypass rad (if you need one), and the motorised valves for all heating zones should be kept permanently open. If you want to control these zones as a whole rather than individual radiators with HR92s, each zone will need a BDR91 relay box and a temperature sensor, whether that be the evohome controller or a T87RF.

[Tony]

Many thanks for the information and I will check about the boiler if it has a bypass valve .
If not then as advised I have a rad that is in the living room and I wanted to control it but this is the open unit for a zone one in the house. What happens when this is not able to control with a DR92 ? In the main bedroom this is the other zone two and it also has an open rad which I wanted to fit a DR 92 again what happens with this rad.

The existing system has two motorise valves to break the heating system

onehave the living as a open valve. All the other have manual rad control on them.

There is a rad in the other and it is also open and the rest has manual controls . I want to control ALL of the radiators.

Any more help would be appreciated

[electronicsuk]

Any bypass radiators will not be controlled by evohome, the result will likely be rooms that are too warm or too cold, as they will heat whenever the boiler is running and the zone valve is open. Ideally, you want HR92s on every radiator, an auto bypass valve on the boiler, and the heating zone valves locked open. That way, you will not need any bypass radiators, and you'll have control of every room.

Although you could do it, I don't see a lot of merit in trying to set up a 2-zone system with a pair of BDR91s, it's an extremely expensive way to get control over just two zones.

[Tony]

Many thanks I now have all thr correct information and as said have all radiators fitted with HR92s and get a bypass valve on the boiler and open the zone valves locked.

I now need to know how easy can the papas be fitted ? . I am able to do everything but not this issue.

Regards

Tony

[Fen Tiger]

I have decided to leave my heated towel rails as bypass radiators so that the towels are always dry. This did cause an overheat in the bathroom but i minimised this by shutting them down using a manual valve so the flow is sufficient to keep them warm rather than hot. I have however noticed an increase in general noise from the system. Im guessing this is related?

[Tony]

I have read that the bypass radiator must Allow at least 10% of the full flow in the system.
I don't know closing the bathroom radiators to still try to control the heating is a good idea.
I have checked my system and I have an automatic bypass valve but my builder ( one of the normal ) did not tell me and indicated that the open radiators could not be controlled . Don't know why?
I was also told that the bypass radiator must also be in the same room as the thermostat.

[electronicsuk]

I have checked my system and I have an automatic bypass valve but my builder ( one of the normal ) did not tell me and indicated that the open radiators could not be controlled . Don't know why?
I was also told that the bypass radiator must also be in the same room as the thermostat.

Tony, what you are talking about is not a bypass radiator as such. With a typical installation, the radiator located in the same room as the electronic thermostat should not be fitted with a TRV, as this can potentially allow the radiator to be shut off and the room thermostat will never sense that the heat demand has been met. It's an energy efficiency issue, but it isn't a problem if you're fitting evohome with HR92s in every room.

[Tony]

I am sorry with some of these silly questions but I think I have all the full information. I am always worried in case the change of my existing system which is still under warranty will bite on me. So I will be putting Evohome on all the radiators , I will use the DR91 for controlling the boiler and based my existing system move the automatic zone valves both to open all the time .hope that will make it a better system as my existing is poor.

[electronicsuk]

I am sorry with some of these silly questions but I think I have all the full information. I am always worried in case the change of my existing system which is still under warranty will bite on me. So I will be putting Evohome on all the radiators , I will use the DR91 for controlling the boiler and based my existing system move the automatic zone valves both to open all the time .hope that will make it a better system as my existing is poor.

Sounds about right. Shouldn't affect your warranty if you're careful - the HR92s can easily be swapped back for TRV's, so you just have to make sure your original wiring and thermostat aren't too hard to reinstate.