new to evoHome - existing Honeywell wireless room thermostat

[mart1711]

Dear all,

Apologies for a lengthy post and probably some very basic questions.

Being a little tired of the wrong part of the house being too warm or too cold respectively I have just ordered the Honeywell evohome WiFi Controller and the Honeywell evohome Radiator Multi Zone Kit (aka HR92s)

My current boiler is a Worcester Greenstar Ri, and I believe the heating system is wired up as an S-Plan with two motorized valves, a wireless Honeywell Room Thermostat (CM727 http://www.honeywelluk.com/products/...ats/TPI/CM727/), and a dual channel timer for HW and CH. I have attached a photo for clarification. The cable coming on from the top right part of the photo comes from the timer.

DSCN0066_resized.jpg

I have this idea that converting to Evohome might not be that challenging (that is if I want it to control CH only), but am going on a number of a assumptions and would be extremely grateful if someone could confirm or deny the below...

From looking at my current setup I am assuming that

a) my current setup is one, where once there is demand from the hot water cylinder thermostat or the room thermostat, the respective motorized valve opens, and the valve itself is then sending an on signal to the boiler + pump?

b) My current room thermostat is already using a BDR91 as visible on the photo, which is the same box the new evoHome WiFi Controller can be linked to

c) When I receive the WiFi Controller I can just take the batteries out of the old CM727 thermostat, follow the unbind procedure on the BDR91, and then bind the new evohome WiFi Controller to the existing BDR91

d) That when I then further pair up all the HR92s with the new WiFi Controller I'm pretty much "done" as far as the CH goes - I can then switch the timer to "continuous", configure the HR92s as different zones, and if one of them drops below the set temperature it will operate the CH motorized valve through the existing BDR91, which will then turn on the pump and boiler through the existing wiring, in the same way it would have done so with the single wireless room thermostat - difference being it now does this "from every zone"

e) That I do NOT configure the BDR91 as a boiler relay in evoHome, as it controls a motorized valve

e) That I could, if I wanted, add another BDR91 to control my second (HW) motorized valve. That this new BDR91 would be linked up with a new CS92 transceiver that would in turn be connected to a CS92 strap-on sensor. I would have to follow the wiring from the current strap-on sensor (which is a Honeywell L641), which probably runs to the current junction box and controls the HW motorized valve. This would be disconnected, an instead the new BDR91 would be connected to that motorized valve.

As I said I'm completely new to this. I hope this makes sense and would be extremely grateful for any answers.

Please let me know if anything is unclear

Many thanks - Martin

[g6ejd]

a) my current setup is one, where once there is demand from the hot water cylinder thermostat or the room thermostat, the respective motorized valve opens, and the valve itself is then sending an on signal to the boiler + pump?

Yes, boiler+pump

b) My current room thermostat is already using a BDR91 as visible on the photo, which is the same box the new evoHome WiFi Controller can be linked to

Yes

c) When I receive the WiFi Controller I can just take the batteries out of the old CM727 thermostat, follow the unbind procedure on the BDR91, and then bind the new evohome WiFi Controller to the existing BDR91

Yes

d) That when I then further pair up all the HR92s with the new WiFi Controller I'm pretty much "done" as far as the CH goes - I can then switch the timer to "continuous", configure the HR92s as different zones, and if one of them drops below the set temperature it will operate the CH motorized valve through the existing BDR91, which will then turn on the pump and boiler through the existing wiring, in the same way it would have done so with the single wireless room thermostat - difference being it now does this "from every zone"

Yes, the Evohome will provide the programmer function from that point forward. YEs, every zone will then demand heat as required.

e) That I do NOT configure the BDR91 as a boiler relay in evoHome, as it controls a motorized valve

Yes, absolutely correct, that's the mistake I made at first, so well deduced. I followed the guided configuration.

e) That I could, if I wanted, add another BDR91 to control my second (HW) motorized valve. That this new BDR91 would be linked up with a new CS92 transceiver that would in turn be connected to a CS92 strap-on sensor. I would have to follow the wiring from the current strap-on sensor (which is a Honeywell L641), which probably runs to the current junction box and controls the HW motorized valve. This would be disconnected, an instead the new BDR91 would be connected to that motorized valve.

Yes, completely correct. You could use the wire from the existing tank-thermostat as it will go the junction box. The wiring diagrams in the installation guide are set-out identically to the junction box, so the probability of making a mistake is minimal.

If you do fit another BDR91, make sure it is at least 30cm (radius) from the existing BDR to help prevent communication issues.

I foresee a straight-forward installation of your new system.

[mart1711]

This is brilliant, thank you very much!

[DBMandrake]

If you want the Evohome to control and schedule your hot water, you'll want the Hot water kit as well, which includes the CS92 and another BDR91.

The CS92 provides a strap on or immersion sensor depending on whether you have a vented or unvented hot water cylinder. The second BDR91 is then wired to control the hot water zone valve, while the original one you already have should be wired to control the heating zone valve. (Which it probably already is)

You then bind the two BDR91's as heating and hot water zone valves and do not bind any boiler relay, if you are using the zone valve contacts to fire the boiler.

I don't think you can buy either the Wi-Fi controller or the Hot water kit without the included BDR91's so you may end up with a 3rd left over BDR91. It is possible to use a three BDR91 configuration where two control the zone valves and the 3rd controls the boiler directly instead of using the switches in the zone valves - this is the configuration I have, although I'm not sure that there are any huge benefits in it over a two BDR91 configuration in hindsight, as hot water overrun is the only feature it really adds.

By the way, I see you have a bypass gate valve (the red knob) rather than an automatic bypass valve. While it's not critical, I'd recommend that next time you drain down your system for yearly maintenance you replace that with a modern Automatic Bypass Valve, particularly if you plan to use HR92's on all radiators and not have any bypass radiator.

They're not expensive and fairly easy to fit if you've done a bit of plumbing before. A gate valve in this location is the "old fashioned" way of providing some bypass when radiators close down, but the problem is it always flows even when radiators are open causing inefficiencies, and conversely it doesn't flow enough (too much pressure differential) when all radiators close - adjusting it is fiddly and always a compromise.

An automatic bypass valve is an adjustable spring loaded pressure relief valve - you set it to a pressure between 0.1 and 0.6 bars typically and it will not open at all when sufficient radiators are open but will automatically open to regulate the pressure when few/no radiators are open and the pressure tries to rise. This is definitely recommended on a system where all radiators have HR92's fitted, and it can also help reduce radiator noises when only one or two radiators are on.

[DBMandrake]

Sorry, I take that back.

On further inspection it looks like that red gate valve may be a balancing valve for your hot water cylinder indirect loop.

It's hard to be certain due to the pipes disappearing in the walls and under the floor so not all of the piping is visible.

In that case you probably don't have any automatic bypass valve - so you must leave one radiator open and uncontrolled. If you want to put HR92's on all radiators you will need to fit an automatic bypass valve, but they are recommended in building regulations now anyway so it's a good idea to have one.

I notice your pump is also installed with the control board at the bottom - this is definitely not recommended by grundfos, (I have the exact same pump as you which I fitted about a year ago and its in the installation documentation) the control board should be orientated to the sides or above the housing.

[paulockenden]

I'd recommend that next time you drain down your system for yearly maintenance....

WHAT?????

Does anyone (apart from Simon, obviously!) do that?

P.

[DBMandrake]

WHAT?????

Does anyone (apart from Simon, obviously!) do that?

P.

Not sure if that reply was slightly ironic or completely serious but no, I imagine that "most" people just keep running their system without any maintenance until it breaks and then call the experts to fix it! I assume that people on this forum are just a little more proactive though.

I remember when we were renting a flat for four years the yearly "maintenance" performed under maintenance contract by the gas provider, paid for by the owner of the flat was to basically check for gas leaks, turn the heating on and see if all radiators got hot and then leave! 10 minutes tops. They didn't even so much as attempt to bleed air from the radiators, let alone check inhibitor concentration or do any sort of flush/refill, over the entire 4 years we were there.

That was a fairly old sealed system, which required the pressure topping up every 2-3 months, which I informed them of every time they visited but they didn't even try to find the leak or check inhibitor concentration. When I had to disconnect a radiator once the rusty coloured water suggested that there probably wasn't any inhibitor left due to all the top ups...

I also had to bleed the bathroom radiator monthly probably due to Hydrogen build up and told them about this but again nothing was done about it. So yeah, I'm sure that's how much maintenance many systems get.

I'm sure on a nice new clean system a drain and refill with fresh inhibitor every 2-3 years is probably enough but on an older system like mine with radiators in varying states of repair and unknown provenance it seems prudent to do so more frequently. When I drained this time to do the S-Plan conversion the water looked pretty clear, when I filled it back up for a test run I threw in a bottle of X800 and let it run for a few hours and drained again - completely black with magnetite that had been dislodged by the cleaner, so well worth flushing in my opinion.

I guess it all depends on how proactive you are and whether you are starting from a new clean, known system or whether you are trying to salvage and rejuvenate the system you have been landed with when you moved house. I'm sure there are a lot of systems out there in pretty awful state of repair.

[paulockenden]

We have our boiler serviced fairly regularly. (OK, SEMI regularly!). But never once has any heating engineer ever suggested that a full drain down should be part of that maintenance.

It's actually a pig to drain my system because I have lots of loops coming down from upstairs, each with its own drain point. But that's beside the point. Your post above was the first time I've ever heard of anyone draining down on an annual basis, so I just wondered what everyone else here does - i.e. how common this is. But I fear I've hi-jacked mart's thread. Sorry!

P.

[DBMandrake]

We have our boiler serviced fairly regularly. (OK, SEMI regularly!). But never once has any heating engineer ever suggested that a full drain down should be part of that maintenance.

Interesting - because just like the coolant in a car engine the inhibitors are sacrificial and will wear out eventually, especially on an open vented system like ours where air can find its way in. (Or on a closed system that needs periodic topping up) It's surprising how much air is dissolved in fresh tap water.

And while you could just add more inhibitor to make up for the lost inhibitor, the only way to get rid of corrosion debris like magnetite would be a drain or flush. Of course if the system is well inhibited from day one in theory there shouldn't be much in the way of corrosion debris building up.

It's actually a pig to drain my system because I have lots of loops coming down from upstairs, each with its own drain point. But that's beside the point. Your post above was the first time I've ever heard of anyone draining down on an annual basis, so I just wondered what everyone else here does - i.e. how common this is.

I actually have no idea how often people do it either. I only moved to the UK in 2009 and since then this is the first CH system that I've actually owned by way of owning the house and thus been directly responsible for maintaining and forking out on should something I can't fix myself go wrong. So perhaps I'm being over cautious. On the other hand I know the system was very poorly maintained by the previous owner so I've had to make up for lost time in that regard!

This system is actually really easy to drain with a single drain point, and as far as flushing goes what I've found works really well is to leave the pump running on high speed, boiler disabled, then open the drain point which is on the heating circuit return just before the boiler but without turning off the tap that fills the header tank - this causes the header tank tap to keep filling to maintain the level and the fresh water is forced to enter the boiler, go through pump, around all the radiators and then back to the drain tap. I leave it running like this for about an hour and it expels far more crud than just draining with the pump and header tank tap off.

But I fear I've hi-jacked mart's thread. Sorry!

Same here. Sorry mart!

[g6ejd]

I've just drained and refilled and used the Sentinel X100 Rapid Dose system (pressurised can) and found it reasonably easy to dispense, well easier initially I though easier than clambering up to the storage tank, comes with a nice one-way valve that's actually a small rubber 'bullet' that goes in the dispensing pipe to prevent water coming out then gets pushed to the end of the tube when pressurised inhibitor is being forced into the system.

Would I use it again, no, on balance it is much easier to go up to the tank and pour the stuff into the tank and cheaper too

Before the system was cleaned by GBas under the maintenance contract using their pressure flush system/technique it was seriously full of sludge and debris, now it's pristinely clean like always fresh colourless water, albeit it has inhibiter in, I'm going to maintain it like that by using a good inhibitor. Almost silent too, the difference before and after the flush was significant in noise reduction terms.