Combi Boiler OT Max Temp On Water?

Dessy

hi all,

i have a Vitodens 100-W WB1B combi with the Open Therm setup, all seems to work fine instructions from Tado were spot on. on setup though i was to believe it was heating only and the boiler would continue to govern the hot water which is fair enough, but since fitting, the hot water doesn't seem as hot and changing the stat on the boiler has no effect, on the Tado thermostat setup for Open Therm it said choose Hot Water present, does the tado have any control ie max temp setting or governing the temp as it flows?

thanks for any help

MJ_Poole

this is exactly what I am trying to find out too

when in relay control could set the max temp for heating and dhw on the boiler front panel, now set up for open therm and those settings arn't available, but doesn't seem to be anything in app to allow max setting for how water

johnnyp78

You should have a square for hot water on the app, if it’s not there check you’ve set Tado correctly for open therm hot water control https://cdn.brandfolder.io/607DGEMS/as/7k4rssnm8hbmr6mjf94qmck/104210-DIGITAL-ST01IB01-INSTALLER_MANUAL-TA-EN-00-V3.pdf

MJ_Poole

Ok, so for a combi boiler should the HW setting in the thermostat configuration still be set to on ? ( I had set it to off)

this does then show the HW square on the app, but this seems to enable a schedule for hw control which doesn't make sense for a combi as hw is on demand when taps are open not on a schedule ?

does have a temp setting, what I don't wat is for it to be turning the boiler on and off if the hw temp falls below set level as that makes no sense for a combi

johnnyp78

Well that would be impossible as a combi gives hot water on demand, so unless you have a back up tank (quite uncommon in combis) it isn’t going to turn on unless you open a tap.

The schedule is for setting hot water temperature, not on or off. On my combi if you set the water temperature to off, it gives control back to the boiler, but you might as well set it for 45c or thereabouts for the whole 24 hours, or maybe a little cooler overnight.

If you’d prefer not to be able to set the temperature through the app, leave it set to off.

johnnyp78

Btw your Opentherm settings may be overriding the max heating flow temperature too - it’s a good idea to get Tado support to set it to 55c for maximum efficiency.

MJ_Poole

OK Thanks

will turn it on and set temp to what I want, so I should probably have schedule set for 24 hours ?

so really schedule would allow you to have different max temps for hot water at different times ?

but it is still only going to actually come on when taps are open

Yes getting heating flow set correctly would be good too, how I do I get that done ?

johnnyp78

Contact Tado support directly for max heating flow and tell them what temp you want - there’s a chance your boiler might override it but depends on its Opentherm implementation. I have mine set to 55c on the boiler and told Tado support to do it too just to make sure.

Exactly right on the hot water schedule. Some combi boilers have a preheat function to get it up to hot water temp quicker but I think this gets overridden with Opentherm anyway.

Like I said, on mine when I set the water temp to ‘off’ in the app, it just gives control back to the boiler, but yours may be different.

MJ_Poole

think on mine it must be set by opentherm, when in relay control the boiler has settings for max HW and heating temps but in open therm mode those are removed and instead it shows what the actual temp of both is

thanks for info on HW configuration anyway, think I understand it now

MJ_Poole

OK so thats not what actually happens if I set a schedule and a temp on the hot water then when the temp in the boiler falls below the set level the boiler fires regardless of if taps are on or not to take it back up to the temp

So it I'm not using any hot water for quite a while it means the boiler can fire every few hours for a minute or so as the temp cools down. Not really what I wanted as I only want it to fire when the taps come on for hat water (it does that too). If I set HW to off then that stops if firing up on it's own but then seeps the HW temp is fixed at 55 with no way to adjust it which is hotter than I want.

If I turn off HW control in the config in the smart thermostat it still looks like it sets a temp and fires up the boiler if it goes below it, but with no control of schedule or temp

So best I can do is to set HW schedule to off

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MJ_Poole

I have ensured the boiler is set to Eco Mode. Tado keeps changing it back and turning off Eco Mode

If Tado Hot water schedule is running the Tado turns Eco Mode off. If I turn schedule off for hot water then I can set Eco Mode and it stays in Eco mode. The issue then with HW set to off I have no control of the temperature of the hot water and it stays at the default 55 degrees level that Tado sets when HW is set to off.

I've checked this by setting Eco mode on Boiler then starting the HW schedule on Tado then checking mode again on the boiler and its been Turned off again, so Must be Tado doing this

johnnyp78

Your best bet might be asking Tado support if they can turn it off remotely, like they do with setting the max flow temp.