Two Zone + Setup

[cm147]

Hi,
Looking for some installation advice.

I have a two zone + hot water setup in the house with three separate zone valves opening the appropriate circuits. Zone Valve 1 for Downstairs, 2 for Upstairs and 3 for HW. Previously i operated the system with dumb TRVs and a Honeywell wireless controller, for upstairs and another for downstairs. Invested in Evohome as over half my TRVs had had it and the LCD screens on the wireless controllers had started to go as well. Both the upstairs and downstairs bathrooms have heated towel rails without any form of control.

I had assumed I could ask the downstairs HR91s to open zone valve 1 when calling for heat, and the upstairs HR91s to open zone valve 2 when they were calling for heat, but it appears the evohome controller only talks to one BDR 91 for all HR91s in the house. At the minute I have it configured so that single BDR91 relay opens both zone valves when any radiator calls for heat - it just seems wasteful for the hot water to be circulating around the whole downstairs loop including bathroom rad, when only an upstairs bedroom is calling for heat.

The only alternative i can find is to create 2 zones and link a BDR 91 to each, then create multiple sensors within each zone or 'room' as it would be called. However that doesn't give the option of specifying different temperatures in each room?

Is there a way of configuring the system to work for me, ie a parent zone (downstairs/upstairs) with rooms within each zone?

At the minute

[Richard]

If you look at page 42 and page 43 of the evohome Installation Guide, evohome has quite strict installation conditions.

When you implement HR91 or HR92's, these must be done on all radiators and a 'figure 4' system installed which removes the need for heating zone valves sub zoning the system... The HR9X Radiator Controllers are effectively replace your heating motorised zone valves.

The radiator controllers are by nature modulating valves and a motorised zone valve swinging around behind them will not obtain the best performance from the system.

I hope that helps?

[cm147]

Thanks for the reply, although not sure if it does help.

My setup is as per the diagram on Pg42, with the exception that i have an additional valve controlled zone for the upstairs (plus one for the downstairs and one for the DHW).

Currently I have the two central heating zone valves wired up to the same relay, and it works fine, albeit that when there is a heat demand from any radiator in the house, both upstairs and downstairs zone valves open. It would be slightly more efficient if only the appropriate zone valve opened, but it appears I would need a second evohome controller to do this?.

[Richard]

Well if you look at page 42, 'Figure 2' it doesn't have any HR Radiator Controllers fitted to it? This is a single zone system with hot water.

Like I said, if you are fitting HR91 or HR92 Radiator Controllers, you really have to follow page 43 'Figure 4' schematic for it to work properly within a floor of a property.

Lots of people misunderstand the system and how to configure it properly because of a lack of experience of the evohome system. Really when you are fitting evohome to a more advanced system (S Plan Plus for instance), it would always be our advice you employ the services of a trained evohome installer to get the best out of the system.

[cm147]

Well if you look at page 42, 'Figure 2' it doesn't have any HR Radiator Controllers fitted to it? This is a single zone system with hot water.

Like I said, if you are fitting HR91 or HR92 Radiator Controllers, you really have to follow page 43 'Figure 4' schematic for it to work properly within a floor of a property.

Lots of people misunderstand the system and how to configure it properly because of a lack of experience of the evohome system. Really when you are fitting evohome to a more advanced system (S Plan Plus for instance), it would always be our advice you employ the services of a trained evohome installer to get the best out of the system.

Thanks for this. I would say that lots of people misunderstand the system and how to configure it because of inadequate instructions! What you describe as 'strict installation parameters', Honeywell describe as 'Sample evo systems' - hardly a nod to a strict parameter.

I believe i have may well havemy system set up as well as it can be. I am keeping the two zone valves that close off the central heating radiators when there is no call for heat from any of the radiator valves. The principle aim is to avoid heating my two bathrooms in the summer when i only require hot water.

I understand the radiator valves are modulating but the pump is only ever binary on/off so if a zone valve swings shut after pump shuts down is there really a loss of performance from the system?

[Richard]

Well if you look at page 42, 'Figure 2' it doesn't have any HR Radiator Controllers fitted to it? This is a single zone system with hot water.

Like I said, if you are fitting HR91 or HR92 Radiator Controllers, you really have to follow page 43 'Figure 4' schematic for it to work properly within a floor of a property.

Lots of people misunderstand the system and how to configure it properly because of a lack of experience of the evohome system. Really when you are fitting evohome to a more advanced system (S Plan Plus for instance), it would always be our advice you employ the services of a trained evohome installer to get the best out of the system.

Thanks for this. I would say that lots of people misunderstand the system and how to configure it because of inadequate instructions! What you describe as 'strict installation parameters', Honeywell describe as 'Sample evo systems' - hardly a nod to a strict parameter.

I believe i have may well havemy system set up as well as it can be. I am keeping the two zone valves that close off the central heating radiators when there is no call for heat from any of the radiator valves. The principle aim is to avoid heating my two bathrooms in the summer when i only require hot water.

I understand the radiator valves are modulating but the pump is only ever binary on/off so if a zone valve swings shut after pump shuts down is there really a loss of performance from the system?

Actually, I said evohome has quite 'strict installation conditions'...

I train installers on evohome and there is only one correct way to do it in every situation. You can fudge the system and it will still work within reason, but to get the best out of the system just working out of the evohome Installation Guide alone will never give you this.

As for the zone valve swinging about, it may work because of the way you have left your system setup, but evohome wasn't designed to work like this. There shouldn't be any uncontrolled radiators. I'm not sure how much clearer I can be about this. Zone valves and no HR Radiator Controllers or no zone valve and HR Radiator Controllers.

[cm147]

No probs thanks. I'm relatively happy its working well now as set up. Draining the system to add controls to the two uncontrolled radiators and a bypass to my oil boiler is for another day, not to mention the additional investment in the zone valves required for likely very little gain.

[Zagamuffin]

good info