New boiler suggestions

FreeBear

Looking ahead to next year, I'm probably going to have to replace my vintage Baxi back boiler. The CH plumbing will be rationalised and new radiators fitted (so no need for a power flush). Already have a location in mind to install a combi - Something around 25KW should suffice to power six largish radiators and two small ones (total of ~8.5KW @ Δt50°). Cold water flow rate is ~10l/min...

Want/need OpenTherm compatability so that I can interface to my home automation system. Current candidates are -

Ideal Logic2 C24 (2y warranty)
Worcester Greenstar 4000 25kW (5y warranty) - Locked in to the proprietary Bosch EMS system.
Intergas Eco RF 24 or 30 (10/12y warranty) - Very few authorised installers in my area..

Vaillant boilers are not really an option as the ones I've looked at don't support OpenTherm, and Baxi are also a bit hit & miss. Any other suggestions, comments, or recommendations ?

tacpot12

The Intergas is potentially a good option. I have an Intergas HRE OV 24. The downsides (apart from a lack of installers) are that 

• the gasket around the combustion chamber needs replacing every 3 years at cost of c£25. 
• the flue terminal is not very well designed and is prone to wind-driven rain being sent down the air-inlet side of the flue which ends up in the PCB. We had this a couple of times, and had the RCD trip in the consumer unit. I got no reply for Intergas when I asked if they would talk to our installer about what options there were to solve the  problem. The installer couldn't help either, so I fitted my own wind-guard, but this invalidates the warranty! But I can't have water leaking into the boiler for the next 20 years. If you want the Intergas I would only recommend having it if you are also prepared to go with the Twin-flue option, which means two holes in the outside wall. This solves the problem with wind-driven rain in a way that doesn't invalidate the warranty.

The Intergas boilers are known to work well the Honeywell Lyric T6 Thermostats, which are Opentherm. 

The latest Intergas boilers have greater range of modulation which will help save money at this time of year, and there is one model with an integrated flue gas heat recovery system for greater efficiency. You don;t really need a 24kW boiler for your house. The heating load doesn't justify it, but you will benefit from the larger boiler when it comes to heating your hot water, so a boiler that can modulate down to 3-4kW for space heating and give you 24kw for hot water heating would be better.

Intergas don't require the installer to be approved. The boilers are simple when used with Honeywell controls, so there aren't any complicate features that installers need training on, unlike Vaillant. 

I've been trying to persuade my parents to have a new combi boiler to replace their back boiler, and have been looking at the Worcester Greenstar 4000 for them. They've not decided to have a new boiler yet so I have no experience of them. 

plumb1_2

Viessmann 

john.h

plumb1_2 said:

Viessmann 

As above.

macman

Another vote for Viessmann. Standard 5 year warranty. A 12 year warranty is available for a slight extra cost (mine was £100 extra in 2019).
The Vitodens -100W combi comes in 25 or 32kW versions.

FreeBear

Viessmann - Plus points. Stainless steel heat exchanger.

Negative points - Built in HW storage tank (46l ?). So presumably this needs to be heated before hot water can be delivered to the tap. Documents are very vague (read non-existent) about OpenTherm compatibility or wiring up an interface. Looks like "cover off" to gain access to the connectors, therefor Gas Safe engineer required.

Intergas - Plus points - Good documentation about connections and is OpenTherm compatible. Access to the PCB is via a drop down panel. 10/12 year warranty.

Negative points - Parts, expensive (ouch). Copper/aluminium heat exchanger (looks pretty robust though). Reliability issues with water ingress damaging the PCB (would a conformal coating help ?).

tacpot12

Another plus points for Intergas combi boilers is that there is no diverter valve to fail. 

smjxm09

I spent a year researching boilers and went for the Ideal Vogue boiler in the end. It came with a 12 year warranty, as it was installed by an approved installer. Has a stainless steel heat exchanger, and is open therm compatible although I went for the Ideal Halo smart Wi-Fi interface.  The boiler is also made in the U.K. The Halo Wi-Fi option is a great bit of kit, as the boiler can be controlled by my smart phone. I could never go back to wall controls. Also the Halo works with Google Home and is voice command compatible.

The advantage of the Viessmann is that it can modulate very low, much lower than the Ideal Logic, which has an inferior aluminium heat exchanger, and lower than the Vogue, although it is a closer match.

Avoid the Hive smart interface, as it can’t modulate any boiler and is basically a smart on off device.

Worcester Bosch boilers also come with inferior aluminium heat exchangers, which are not great for hard water areas.

john.h

FreeBear said:

Viessmann - Plus points. Stainless steel heat exchanger.

Negative points - Built in HW storage tank (46l ?). So presumably this needs to be heated before hot water can be delivered to the tap. Documents are very vague (read non-existent) about OpenTherm compatibility or wiring up an interface. Looks like "cover off" to gain access to the connectors, therefor Gas Safe engineer required.

Intergas - Plus points - Good documentation about connections and is OpenTherm compatible. Access to the PCB is via a drop down panel. 10/12 year warranty.

Negative points - Parts, expensive (ouch). Copper/aluminium heat exchanger (looks pretty robust though). Reliability issues with water ingress damaging the PCB (would a conformal coating help ?).

Viessmann you don’t need to get one with a hot water storage tank, there is a couple of types.  They also work fine with opentherm, it’s in the instructions manual. Mine has been running on Opentherm for about 18 months now. 

BUFF

john.h said:

FreeBear said:

Viessmann - Plus points. Stainless steel heat exchanger.

Negative points - Built in HW storage tank (46l ?). So presumably this needs to be heated before hot water can be delivered to the tap. Documents are very vague (read non-existent) about OpenTherm compatibility or wiring up an interface. Looks like "cover off" to gain access to the connectors, therefor Gas Safe engineer required.

Intergas - Plus points - Good documentation about connections and is OpenTherm compatible. Access to the PCB is via a drop down panel. 10/12 year warranty.

Negative points - Parts, expensive (ouch). Copper/aluminium heat exchanger (looks pretty robust though). Reliability issues with water ingress damaging the PCB (would a conformal coating help ?).

Viessmann you don’t need to get one with a hot water storage tank, there is a couple of types.  They also work fine with opentherm, it’s in the instructions manual. Mine has been running on Opentherm for about 18 months now. 

Except 200 series which use a proprietary eBus, PlusBus.

Bear in mind that the proprietary systems of Vaillant, Viessmann & Worcester Bosch will all do at least as good a job as OpenTherm in terms of controlling modulation (indeed there is apparently some evidence to suggest that they may be very slightly better). 
WB at least will warranty the controls for the same life as the boiler warranty if installed at the same time i.e. up to 12 years*  - 3rd party controls suppliers e.g. Drayton, Hive, Nest , Netatmo, Tado etc. won't do that.

* for the 4000 it is 10 years if installed via an accredited installer (subject to usual t&c e.g. annual servicing, magnetic filter etc.)

macman

FreeBear said:

Viessmann - Plus points. Stainless steel heat exchanger.

Negative points - Built in HW storage tank (46l ?). So presumably this needs to be heated before hot water can be delivered to the tap. Documents are very vague (read non-existent) about OpenTherm compatibility or wiring up an interface. Looks like "cover off" to gain access to the connectors, therefor Gas Safe engineer required.

Intergas - Plus points - Good documentation about connections and is OpenTherm compatible. Access to the PCB is via a drop down panel. 10/12 year warranty.

Negative points - Parts, expensive (ouch). Copper/aluminium heat exchanger (looks pretty robust though). Reliability issues with water ingress damaging the PCB (would a conformal coating help ?).

Only the 111-W has built in storage, the 100-W range are all standard combi's.
One other plus point: it's incredibly quiet.
Mine needed a replacement EV after 4 years (it was split), which was quickly done under warranty. No other issues.