New Vaillant install - are the Vaillant controls worth it?

[Alchemyst]

Hello - hoping someone could help me in decision making please...

Due to replace an aging standard system boiler and hot water tank with a combi boiler. Plumber has recommended a Vaillant EcoFIt Pure 830 30kw (one he installed for us in a previous place and worked well).

As background, current house has 3 bedrooms, 1 bathroom (with bath inc overhaed shower). Kitchen is due to be renovated this year, and likely a wet UFH will be installed. Loft extension would hopefully happen in a few years, adding an additional bathroom with bath & shower).

Is the 30kw sufficient for the end state described above?

My main question though - I'd like to utilise the modulating features of the boiler. As I understand it, the only thermostat that can do this for Vaillants eBus platform is their own thermostat/controller (previously Tado's system did, but apparently no longer compatible with newer Vaillants).

If I wanted a wireless thermostat that can handle 2 zones and is internet controllable, it would be

SensoComfort VRC720F (£250)
MyVaillant Connect Gateway (£125) - And I think with the Pure, it cant be powered by the boiler, would need an additional PSU (unlike the Plus)

And in future, if wanting to utilise a second zone:
Wiring Centre VR71 (£210~)

Thats a significant outlay for a controller/stat that can module/load compensate - how much money does it actually save? Would I just be better off with a Hive multizone setup that just tells the boiler to fire/turn off (though has the benefit of linked Smart TRVs) for much less? (Sadly it does seem the latest Hive's support OpenTherm, but not eBus).

 

[ScottishGasMan]

Firstly I'd ask if you really need to zone the system at all? If its reasonably well balanced and you have TRVs in the rooms that could suffer from overheating due to high occupancy/solar gain etc then what benefit are you getting from making the system more complicated.

IMO smart TRVs are just a gimmick more than anything, although it depends what's important to you what way you want to go with the controls.

If you kept it one zone you could happily use the sensoROOM which comes with the gateway, still gives weather compensation via local weather station readings, and still gives you the benefit of being able to see faults etc should they arise on the app.

FYI there are two part numbers of the gateway, one comes with a VRA 42 card that powers the gateway from the boiler so no need for an extra 3-pin plug socket, but its dearer that the other one so depends how much of an inconvenience getting it to a nearby plug socket would be.

Also if you did go down the sensoCOMFORT route it would get the same 10-year warranty as the boiler so at least the control would be covered under the same warranty.

If you're looking at it from purely a savings point of view, then I'd agree that its expensive kit and not going to suddenly 1/2 the running cost of the boiler. The running cost saving for heating could be as much as 10%, but I'd not expect more than that.

FYI I'm heavily biased towards the Vaillant equipment, so there will be other views that you could take into consideration, theres no real right or wrong, just what suits you at the end of the day.

As far as the boiler capacity goes, 30kW will heat a small castle, its only really the hot water requirement that needs attention. If you going to have 2 bathrooms with baths and showers in them, 30kW combi is fine using one at a time, if you want to use them both at the same time, I'd strongly advocate for sticking to a system boiler with a cylinder, combi flow rates are limited to ensure that the water is at a useable temperature even in the winter when the incoming cold water could be 1 degree, The 30kW pure is limited to flow 10 litres of hot water per min, split that between 2 baths or showers running at the same time and its not going be anything like what an unvented cylinder can give you

 

[Why Not Indeed]

My main question though - I'd like to utilise the modulating features of the boiler.

To be clear, the boiler will modulate the output down taking account of the CH return temperature, without weather compensation.
What weather compensation will do is adjust the flow temperature, taking account of the outside temperature. The assumption being that the warmer it is outside, the lower the heat loss.

 

[Alchemyst]

Thanks @ScottishGasMan.

Firstly I'd ask if you really need to zone the system at all? If its reasonably well balanced and you have TRVs in the rooms that could suffer from overheating due to high occupancy/solar gain etc then what benefit are you getting from making the system more complicated.

If you kept it one zone you could happily use the sensoROOM which comes with the gateway, still gives weather compensation via local weather station readings, and still gives you the benefit of being able to see faults etc should they arise on the app.

I'm honestly not sure - it seemed to me that it was the done thing to separate/isolate the UFH as an additional zone. And tbh, I can see us wanting to maintain a temperature in the kitchen and heat no other part of the house. I didn't realise SensoRoom comes with the internet gateway mind.

TRVs Im not too fussed about either tbh, would just be a benefit with Hive. Though I doubt Id use them to fire up the boiler to just warm one rad etc so maybe moot.

As far as the boiler capacity goes, 30kW will heat a small castle, its only really the hot water requirement that needs attention. If you going to have 2 bathrooms with baths and showers in them, 30kW combi is fine using one at a time, if you want to use them both at the same time, I'd strongly advocate for sticking to a system boiler with a cylinder, combi flow rates are limited to ensure that the water is at a useable temperature even in the winter when the incoming cold water could be 1 degree, The 30kW pure is limited to flow 10 litres of hot water per min, split that between 2 baths or showers running at the same time and its not going be anything like what an unvented cylinder can give you

Unfortunately, there really isnt the space for a decent sized tank, and my wife is done with not being able to shower/bath after the kids have had theirs in the evening! Fully accept we wont be able to run 2 showers/baths at the same time - the convenience of instant hot water at any time regardless of prior immediate use will win out for us personally.

Thanks again, will have more of a read/think about what I need/want!

 

[spile]

I have the wired VRC 470 and I like the heat curves and the way it uses the external sensor. Dislikes - size, loss of date/time if boiler turned off and it’s ugly.
A friend has the wireless version but that has gone faulty so he is looking at replacing it with a hive.

 

[drives]

Unfortunately, there really isnt the space for a decent sized tank, and my wife is done with not being able to shower/bath after the kids have had theirs in the evening! Fully accept we wont be able to run 2 showers/baths at the same time - the convenience of instant hot water at any time regardless of prior immediate use will win out for us personally.

Thanks again, will have more of a read/think about what I need/want!

Is there no space in the loft (appreciating what you say about future plans for conversion but small footprint required for mini plant room?). Particularly if you are going to have two shower rooms.

We relocated (and upgraded) our tank from airing cupboard to loft. Heat loss is minimal with modern cylinders and you shouldn’t be running out of water with a reasonably sized one.

 

[ScottishGasMan]

I have the wired VRC 470 and I like the heat curves and the way it uses the external sensor. Dislikes - size, loss of date/time if boiler turned off and it’s ugly.
A friend has the wireless version but that has gone faulty so he is looking at replacing it with a hive.

They stopped making the VRC 470 about 10 years ago, their two controls ahead by now, and the sensoCOMFORT is a massive improvement on those old models, although the base software that runs the boiler is still the same near enough.

 

[ScottishGasMan]

Fully accept we wont be able to run 2 showers/baths at the same time - the convenience of instant hot water at any time regardless of prior immediate use will win out for us personally.

I can fully appreciate that, so long as you know that its one at a time then the combi is easily big enough, if there was any doubt there is a 35kW version of the ecoFIT that would do 12 litres/minute at a 42 degree temperature rise (Compared to the standard figures which quotes lifting the cold inlet water by 35 degrees to the hot outlets)

That all being said, does it really make sense having 2 full bathrooms if you only use one at a time? Make one an ensuite or WC, save a small fortune and you can get a gold plated heating control! (I'm just kidding, theres nothing to stop somone running a bath in one, getting in, then somone can go and use the other after 1st has filled)

 

[Mister Banks]

I have the wired VRC 470 and I like the heat curves and the way it uses the external sensor. Dislikes - size, loss of date/time if boiler turned off and it’s ugly.
A friend has the wireless version but that has gone faulty so he is looking at replacing it with a hive.

If your friend replaces the Vaillant controls with Hive it will be a big downgrade. Have a look at what Hive can do, it’s not much other than turn the boiler and on and off.

 

[Harry Bloomfield]

I have the wired VRC 470 and I like the heat curves and the way it uses the external sensor. Dislikes - size, loss of date/time if boiler turned off and it’s ugly.
A friend has the wireless version but that has gone faulty so he is looking at replacing it with a hive.

My 470F, has an issue in that the rotating the knob, only rarely does what you intend. Clockwise, should increase values, often as not it decreases - but you get used to it. One day, I'll get around to checking the encoder.

Other than that, the overall control system is great. It controls the heating perfectly, no over shoot, no under shoot - it just 'motors' gently to temperature, and hold it there invisibly, modulating. I can see how it would save gas, but it's worthwhile anyway, for the sophisticated way it controls the room temperatures.

 

[ericmark]

Same boiler, turned on 5 times a day for DHW will show a huge difference in efficacy to a boiler turned on 20 times a day, it is down to energy used to heat the boiler/heat exchanger. Mother's boiler had an Eco and Normal mode, in normal mode there was a reservoir of hot water, so no delay, the boiler still fired up to reheat the reservoir, so no saving, but the difference in time x size of boiler = price to heat up boiler, or as we say at work, price of the match.

So last house instant gas hot water, this house storage tank was oil heated before solar panels fitted, and we would run boiler in summer 4 times a week, around 20 minutes each time, and my oil bill in this house is a lot less as gas bill in last house. This house is much bigger, and detached, the last house a semi. This house doors on each room, the last house open plan, that will also impact on heating cost, but the boiler efficiency is small when compared to how it is used.

A boiler may be super efficient, but keep turning it on/off instead of up/down, and this may be all lost.