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You can't without VR66 but then you loose CH control. It has to do this to prevent temp differential across the heat exchanger which causes issues, once flow temp rises it goes full power until flow temp is 80c. It never does low flow temps like CH.

To add additional clarification, ebus does not control power output as stated, the boiler does that internally to maintain the target flow temp requested. Even with all the VRC stuff, the boiler is still non the wiser about room/outside temps, that part is handled by VRC. VRC is the commander...

D00 is the max the boiler ever goes to regardless of ebus, there is another setting for max kw for HW when using ebus.

There is no exact way of knowing unless you have calculated your losses, if you have an 18kw now and plan on another 10 radiators you could get away with 26kw but if the radiators are huge, rooms huge etc large bifold doors etc etc could push to 32kw. Who knows, your calculations are needed to...

What boiler/model is it? UFH systems can put unique requirements on a system setup due to flow rates and temps.

You need to calculate requirements by getting the KW of all the combined radiators, this will give baseline CH requirement. The HW requirement will be based on your required flow rate, ie only one HW tap/shower running at a time etc etc. Remember that combi boilers are higher KW due to the HW...

I actually find on my boiler on eBus it starts low for about 15-30s then ramps up to max (d00) then once it comes close to flow temp requested by VRC it scales back and just keeps running until the flow temp rises too much where it can not scale back any further and turns off, pump keeps...

Sounds like your d.00 range is too high, you need to set it correctly based on the total output of your radiators, if its too high, pump speed is too low or you have too much bypass happening then you can overshoot before it has time to scale back. My 418 has been ranged to 12 and it does not...

I thought actuation was done with a wax motor even on radiator TRVs, zone actuators on UFH systems are also wax motors.

If you have a wired VRC then OT sensor connects to the boiler, if its wireless VRC then it communicates to the VRC directly. On my 418 it's wireless and d47 is 999 but it shows correct value on the VRC controller. Check d05, this is the requested target flow temp by ebus, it should go up/down...

It should not use more gas as if you were using more then the house would be hotter than the temp you have set, you can not compare day to day when the weather is varying quite a bit at the moment. Remember than VRC is reactive to outside temp drops primarily so it should maintain the internal...

If you do not need the pressure just the flow rates to taps etc you could look into PRVs, might be cheaper than replacing all the taps.

you might need a PRV?

I've got 1910 solid brick house, huge windows etc. So insulation of house will vary this quite a bit.

My house is mostly old 25y+year old Type10 radiators, ile be replacing some of them for Type 21 etc and then my curve should go down

Just checked install for that boiler, there should be a pin called RT, this is for 240v programmers, then remove the 24v jumper link. Page 22 https://www.vaillant.co.uk/downloads/product-manuals/ecofit-pure-1/combi-5/ecofit-pure-combi-installation-and-maintenance-instructions-1943272.pdf ps...

24v is for using a specific Vaillant thermostat or via relay, eBUS is a specific protocol to use the vaillant controls which are the best idea to get full efficiency of those boilers by adding Weather Compensation controls such as VRC720f, its just a two wire connection if using these controls...

You still have to set the heat curve initially, it's way way too low by default for UK homes, mine is 2.3 as its an old 1910 house. Push it up to 1.7 minimum then let it adapt from there, or go higher.

Make a recording and post here

Nop, its a setting on the boiler, it's like a max power but smart wc thermostat is just controlling flow temps, problem is that it may go to max power when it first fires up and its too much. I know how to do it on vaillant but not bosch.