Thinking of adding the hot water kit to my Evohome

[jonstatt]

I already installed the EVOHOME system for my heating earlier this week totally successfully and I am very happy.

I have an S-plan system (2 motorised valves), and an OSO unvented hot water tank. There is a bypass loop (via a differential Pegler USV16/22 valve) already installed.

Currently the heating is triggered by a BDR91 installed in place of a thermostat. The original "timer" is still present with the heating permanently set to on. In this way, it was a very simple install and things like pump over-run etc still function as normal (Potterton Suprima 60L)

I just wanted to validate a few things

1) I can leave the heating set-up exactly as is
2) I change the hot water on the old timeswitch to permanently on like the heating and install the hot water transceiver and second BDR91 in the airing cupboard where the motorised valves and S-plan junction wiring is all present
3) Does anyone have any experience on fitting the insertion temperature probe into the immersion chamber on an OSO tank? (i.e. Are there any gotcha's in getting a good fit with the probe in there, or anyone has any videos for fitting the probe on any unvented tank?)
4) I don't need to disable the heating motorised valve because I already have a bypass loop installed

Many many thanks for the help.

[HenGus]

3) Does anyone have any experience on fitting the insertion temperature probe into the immersion chamber on an OSO tank? (i.e. Are there any gotcha's in getting a good fit with the probe in there, or anyone has any videos for fitting the probe on any unvented tank?)

I spoke at length to Oso about this and I asked my installer to follow their recommended solution. My Oso tank is 14 years old and doesn't have any spare ports. Oso's recommendation is to access the tank via the electrical panel. The probe can then be inserted by pushing it up the tank under the insulation. My installer also slid a sleeve of plastic below the probe just to increase the surface area. The wire from the probe is then pushed through one of the wiring grommets and the access panel replaced. It works as Oso said it would, and my unvented tank thermostatic controls have been left in series. Point to note: it is important that the tank thermostat is set at a slightly higher max temp than you require from the Evohome. As I found out, if the installer didn't notice this then the max tank temp will be limited and below the max set on Evohome. I have my HW set at 60C. It drops to 53C (which is user variable) before the actuator/boiler kicks in to heat the water.

[top brake]

I already installed the EVOHOME system for my heating earlier this week totally successfully and I am very happy.

I have an S-plan system (2 motorised valves), and an OSO unvented hot water tank. There is a bypass loop (via a differential Pegler USV16/22 valve) already installed.

Currently the heating is triggered by a BDR91 installed in place of a thermostat. The original "timer" is still present with the heating permanently set to on. In this way, it was a very simple install and things like pump over-run etc still function as normal (Potterton Suprima 60L)

I just wanted to validate a few things

1) I can leave the heating set-up exactly as is
2) I change the hot water on the old timeswitch to permanently on like the heating and install the hot water transceiver and second BDR91 in the airing cupboard where the motorised valves and S-plan junction wiring is all present
3) Does anyone have any experience on fitting the insertion temperature probe into the immersion chamber on an OSO tank? (i.e. Are there any gotcha's in getting a good fit with the probe in there, or anyone has any videos for fitting the probe on any unvented tank?)
4) I don't need to disable the heating motorised valve because I already have a bypass loop installed

Many many thanks for the help.

I would remove the existing heating and hot water programmer while you are at it, it won't be adding anything anymore and will simply be something to go wrong later

The key thing is to retain the existing high limit protection functional

[jonstatt]

I spoke at length to Oso about this and I asked my installer to follow their recommended solution. My Oso tank is 14 years old and doesn't have any spare ports. Oso's recommendation is to access the tank via the electrical panel. The probe can then be inserted by pushing it up the tank under the insulation. My installer also slid a sleeve of plastic below the probe just to increase the surface area. The wire from the probe is then pushed through one of the wiring grommets and the access panel replaced. It works as Oso said it would, and my unvented tank thermostatic controls have been left in series. Point to note: it is important that the tank thermostat is set at a slightly higher max temp than you require from the Evohome. As I found out, if the installer didn't notice this then the max tank temp will be limited and below the max set on Evohome. I have my HW set at 60C. It drops to 53C (which is user variable) before the actuator/boiler kicks in to heat the water.

That is extremely helpful information! Thank you so much. If your OSO tank is 14 years old, it is right at the changeover period in models from OSO but I suspect you have the same as mine. Mine is the series 20 unit, and the install guide is at http://www.osohotwater.co.uk/images/...ion-manual.pdf

[jonstatt]

I would remove the existing heating and hot water programmer while you are at it, it won't be adding anything anymore and will simply be something to go wrong later

The key thing is to retain the existing high limit protection functional

Thanks. The reason I was going to leave the original programmer was just incase I move home and want to put everything back as it was, and take the EVOHOME stuff with me!

I hear you on the high limit protection. This is provided by the "built-in" thermostat which has an adjustable component and a fixed high limit component, and I will do as suggested by HenGus, and connect the two thermostats in series (with the OSO one set higher than I would ever want the water temperature) but that leaves the safety mechanism in play.

[HenGus]

I have the OSO Indirect 20RI - 250 Litre unvented tank with 2 actuators. The BDRs are connected to the two motorised actuators. Like you, I had thought about taking Evohome with me should I move house, but I doubt that this is a sensible thing to do. It's a selling point and, secondly, given the pace of technological change I might well do better leaving everything in situ and going for the next generation of smart controls.

[jonstatt]

I have the OSO Indirect 20RI - 250 Litre unvented tank with 2 actuators. The BDRs are connected to the two motorised actuators. Like you, I had thought about taking Evohome with me should I move house, but I doubt that this is a sensible thing to do. It's a selling point and, secondly, given the pace of technological change I might well do better leaving everything in situ and going for the next generation of smart controls.

We have the same cylinder type (20RI) except mine is the smaller 210 litre. So whatever worked for you will work for me.

I have worked out the wiring. The OSO thermostat goes between connections 6 and 8 on the S-Plan wiring block. 7 is unused. So all I have to do is move one side of the OSO thermostat from 8 to 7, then connect the Honeywell BDR91 to connections 7 and 8 (8 is also the connection to the motor). In this way, both thermostats are in series.....job done

Thanks again.

[sharpener]

Thanks. The reason I was going to leave the original programmer was just incase I move home and want to put everything back as it was, and take the EVOHOME stuff with me!.

You might also want to keep the original programmer for two other reasons

(i) pending resolution of the "random boiler demand" issue (see other thread) you will be able to guarantee the system is definitely OFF during the small hours or any other time you want to be sure of it.

(ii) the original programmer may have other features like a Change or Advance button to allow you to turn the heating off when you go out knowing it will come back on at say 4 p.m., or a Boost button for an extra hour's heating if you are up late watching TV

both these are possible with the Evotouch but not with a single button push, which is why I have kept mine in circuit (ironically it is a Honeywell 799!)

[jonstatt]

Yesterday I installed the hot water kit. From a procedural perspective, everything went exactly as planned. HenGus's very useful information on where to put the probe worked perfectly with the OSO tank. For safety and the ability to test fully, I connected the original OSO thermostat in series with the EVOHOME BDR91. I validated the success of the probe position by setting the OSO tank to 60 degrees and the EVOHOME setting to 70. I wanted to see what temperature EVOHOME thought it was when OSO cut out at 60 degrees. Sure enough, and perhaps somewhat surprisingly EVOHOME reported exactly 60 degrees when the OSO tank cut-off.

I configured the EVOHOME controller by removing the boiler on demand relay and setting up as an s-plan two zone set-up instead (of course the original BDR91 was fully reset to ensure it only functioned in it's new role). On the face of it everything appeared to be working but I have some "issues" I am working through

1) I switched the hot water off. I switched the heating to off (which in reality is a 5 degree control). All zone temperature readouts were 18 degrees or higher. All of a sudden the heating BDR91 turns green even though all radiator valves are closed. I have a bypass loop so there were no horrible bangs or anything. BUT the Suprima 60L detected that after a few minutes that the water it was heating was getting too hot (because the bypass loop is of course quite small). As a result the boiler went into temporary lockout with a red flashing light. I say temporary, because as soon as the temperature drops the boiler reactivates without intervention. After about 5 minutes the BDR91 deactivated on it's own. I saw this happen about once every 2 hours. This morning I removed the batteries from the controller and rebooted to see if it will make any difference.

2) What is the frequency of updates from the temperature probe transmitter? They seem to be less frequent than 4 minutes. I have validated the signal strength is 5. Also, the updates to the gateway/app is VERY infrequent. Whereas if a radiator valve temperature updates on both controller and app within a couple of minutes, there is a massive lag for updates reaching the gateway/app for hot water. After having a shower, the controller read 54, whereas it took 15 minutes before the app showed this update!

3) In another thread I mentioned that nobody knows the duty cycles and minimum runtime the boiler is driven at in this mode as the options in the firmware disappear. I hope top brake will be able to find out (I know he is trying to get this information already, thanks ).

4) How do you get the probe transmitter unit open again. It's easy to get to the battery compartment, but without totally destroying the casing I couldn't see how to get to the wiring part again. I don't need to in fact...I was originally just wanting to double check something but gave up. When I snapped it closed it snapped really hard implying it is being held very tightly indeed.

[top brake]

Yesterday I installed the hot water kit. From a procedural perspective, everything went exactly as planned. HenGus's very useful information on where to put the probe worked perfectly with the OSO tank. For safety and the ability to test fully, I connected the original OSO thermostat in series with the EVOHOME BDR91. I validated the success of the probe position by setting the OSO tank to 60 degrees and the EVOHOME setting to 70. I wanted to see what temperature EVOHOME thought it was when OSO cut out at 60 degrees. Sure enough, and perhaps somewhat surprisingly EVOHOME reported exactly 60 degrees when the OSO tank cut-off.

I configured the EVOHOME controller by removing the boiler on demand relay and setting up as an s-plan two zone set-up instead (of course the original BDR91 was fully reset to ensure it only functioned in it's new role). On the face of it everything appeared to be working but I have some "issues" I am working through

1) I switched the hot water off. I switched the heating to off (which in reality is a 5 degree control). All zone temperature readouts were 18 degrees or higher. All of a sudden the heating BDR91 turns green even though all radiator valves are closed. I have a bypass loop so there were no horrible bangs or anything. BUT the Suprima 60L detected that after a few minutes that the water it was heating was getting too hot (because the bypass loop is of course quite small). As a result the boiler went into temporary lockout with a red flashing light. I say temporary, because as soon as the temperature drops the boiler reactivates without intervention. After about 5 minutes the BDR91 deactivated on it's own. I saw this happen about once every 2 hours. This morning I removed the batteries from the controller and rebooted to see if it will make any difference.

2) What is the frequency of updates from the temperature probe transmitter? They seem to be less frequent than 4 minutes. I have validated the signal strength is 5. Also, the updates to the gateway/app is VERY infrequent. Whereas if a radiator valve temperature updates on both controller and app within a couple of minutes, there is a massive lag for updates reaching the gateway/app for hot water. After having a shower, the controller read 54, whereas it took 15 minutes before the app showed this update!

3) In another thread I mentioned that nobody knows the duty cycles and minimum runtime the boiler is driven at in this mode as the options in the firmware disappear. I hope top brake will be able to find out (I know he is trying to get this information already, thanks ).

4) How do you get the probe transmitter unit open again. It's easy to get to the battery compartment, but without totally destroying the casing I couldn't see how to get to the wiring part again. I don't need to in fact...I was originally just wanting to double check something but gave up. When I snapped it closed it snapped really hard implying it is being held very tightly indeed.

1) sorry cant help as not on site with you
2) the CS92 gets it's setpoint and differential 'mission' from the evohome then communicates the measured temperature when appropriate according to the setpoint and differential you have set in installer mode
3) watch this space
4) remove battery cover and batteries, there are 2 latches that you need to carefully prise open with a terminal screwdriver