New boiler suggestions

FreeBear

BUFF said:

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).

Anything that uses eBus/PlusBus is not even a contender. The Worcester Bosch EMS bus, although proprietary, has been reverse engineered. With the EMS-ESP project, I can exchange data with my home automation system, but compatibility is not assured if WB has made changes to the EMS protocol or boiler. Then again, OpenTherm is open to interpretation by manufacturers so full functionality is not guaranteed.

FreeBear

Another alternative that has been suggested by a local installer - Navien - Can't see much in the way of reviews, and suppliers of spare seem to be few and far between.. Any thoughts ?

ThisIsWeird

FreeBear said:

Already have a location in mind to install a combi - Something around 25KW should suffice.

Cold water flow rate is ~10l/min...

Hi FB.

Are you saying your incoming CW flow rate is 10lpm?

FreeBear

ThisIsWeird said: Are you saying your incoming CW flow rate is 10lpm?

Yup. As measured at the tap by way of timing how long it takes to fill a 5l container (31 seconds).

ThisIsWeird

Surely that's completely inadequate for any combi?

FreeBear

10-15l per minute is typical for most houses in England & Wales. At 10l per minute, a 28-30KW combi is (apparently) recommended. If you have a lower flow rate, then a smaller (say 24KW) boiler would be suitable.

ThisIsWeird

Hmmm.

That pitiful (soz - now't personal, like) flow rate needs to be shared betwixt H & C.

ThisIsWeird

What's the delivery pressure like?

FreeBear

ThisIsWeird said:

What's the delivery pressure like?

Dunno. Would need to find a decent pressure gauge and test.

plumb1_2

FreeBear said:

ThisIsWeird said:

What's the delivery pressure like?

Dunno. Would need to find a decent pressure gauge and test.

and take your flow rate at different times of the day 
plus is the tap you are using for the test, does it have any restrictions fitted, ie cheap ballofix instead of a full bore valve. Thin/ narrow flexible tap tails.