35Kw Combi Boiler - Which make

[NewToAllOfThis]

We have been told we need a 35Kw combi boiler and looking for recommendations as to which make to buy. We will have traditional radiator central heating and 2 showers off the gas boiler.

 

Would appreciate any feedback on remote controlled boilers, are they worth it.

[TonyT]

My plumber only installs viesmann boilers, he’s a fan of them.   

[Mr Punter]

Worcester and Vaillant are also good.

[Oz07]

Last year city plumb were doing brilliant deals on glow worm, mag filter, flue and 10yr warranty. The independents couldn't touch them. Sure they are a re badged valliant anyway now? Plus buying British!

[James Newport]

All the plumbers round my way who quoted recommended Baxi boilers, although they were happy to fit Worcester and Vaillant as well. The only reason they came up with for one make over the other was that Baxi were better for getting hold of parts, or that Worcester had started charging for stuff that used to be included. Can't quite remember the specifics, only that the reason for one make over another were pretty tenuous. 

 

My Baxi has been fine for 18 months, but my sister's ended up needing a circuit board replacing after six months. 

 

In a previous house I had a Vaillant combi that had a teeny tiny thermal store inside the combi, which meant that hot water would start in a few seconds, rather than the 30 seconds that is now life with this Baxi. 

[Dave Jones]

if the installer is Ideal approved you get a free upgrade to a  5 year warranty.

[James Newport]

10 hours ago, NewToAllOfThis said:

Would appreciate any feedback on remote controlled boilers, are they worth it.

Like with Hive or Nest?

 

There is a standard called Opentherm that allows for far greater control of the boiler from a smart thermostat. Typically all thermostats do is turn the radiator output from the boiler on or off, which is exactly how a wall thermostat works. Opentherm allows for them to do things like turn the temperature of the central heating water up or down, or pick up info from things like a temperature sensor in the flue. I assumed my top of the range boiler would come with this, but it turns out what I needed was the top top top of the range version. 

[Oz07]

I just go for whatever recognised brand is doing the longest warranty. If you can get 10 year warranty I think you can then start to whittle down on price who cares about parts availability. 

[Nickfromwales]

Vaillant 938 if you want to run 2 showers simultaneously. 

On 20/08/2021 at 07:10, James Newport said:

In a previous house I had a Vaillant combi that had a teeny tiny thermal store inside the combi, which meant that hot water would start in a few seconds, rather than the 30 seconds that is now life with this Baxi. 

You'd have had the 937 or 938. 2x7.5L tanks to give 15L stored instantly available DHW. Cracking boiler, fitted loads of them with zero issue. You do need a very good cold mains supply though to get the full potential from this boiler ( as with every combi, it is completely cold mains dependant ) and ideally you would run a 22mm cold supply to replace the existing, or run a new 15mm dedicated cold feed directly to the boiler from the stopcock. Not doing these peripherals will result in mediocre DHW flow rates even with the best "high-flow" combi's. You need the shoes to go with the hat   

[tonyshouse]

Veissmann 

[Nickfromwales]

17 minutes ago, tonyshouse said:

Veissmann 

With recent chat here about over-complicated / non-functional controls, and zero success from the  support given from Veissmann, I would stick to something more established and wider recognised for ongoing maintenance / service / repair.

Edited August 21, 2021 by Nickfromwales

[markocosic]

That viessmann 'issue' was refusal to RTFM about how the boiler is supposed to operate and set it into an appropriate mode...

 

 

Vaillants are decent.

 

One thing to be aware of is their choke flow valves.

 

Combis could be overloaded if the hot water flowrate is too high. That would cause the water to run cool and screams from the shower. It is considered more useful if the temperature was maintained but the pressure drops a bit instead. (then your thermostatic valves shuttle across and rebalance flows to maintain the outlet temperature at a lower overall flowrate)

 

They achieve this by limiting the water flow rate through the boiler with a choke flow valve. (even with loads of pressure the flowrate will never get high enough that the boiler cannot achieve 45C outlet with 5C inlet temperature.

 

Sounds good? Maybe yes if you're in Europe and you have good (say 30+ litres/minute at 3+ bar) water pressure. In the UK the water pressure is often lower than that which the (European) boilers were designed for, and you can find that they never achieve full output sure to insufficient flowrate OR that achieve the output but so much pressure is lost across that boiler that none of left for the shower.

 

Ditch the choke valve (e.g. on a vaillant 824 it is the cold inlet valve that had the tiny orifice - swap for a plain hot water outlet pipe and an external full loop) and they'll work a little better on cold supplies that are less brilliant.

[JohnMo]

I chose an Atag A325ECX, it can take preheated water which increases the flow rate, have a thermal store upstream, cold water passes through the stores DHW Coil before going to combi.  Store used as a buffer for UFH and has solar PV connected to immersion.  So always sits at about 40 degrees.

 

You can go open therm if you want, but have just removed and gone simple route, basic thermostats but with self balancing actuators on the UFH manifold and run UFH 24/7 at a low temp using a mixer and pump after the store.