Why did my plumber install a Combi boiler, when I asked for a System Boiler?

FreeBear

ThisIsWeird said:

SaintPatrick, I'd ask W-B to confirm a couple of things;

1) Any drawbacks in using a Combi boiler as a System boiler? If used as such, does it need a mains supply and a DHW test outlet?

2) Does the Greenstar 4000 System boiler have a Priority Domestic How Water setting?

No need for additional isolation valves or test points on the DHW side. There are already isolation valves built in to the boiler. Without any flow of cold water, the boiler will never fire up in DHW mode (there may be a setting to disable it in the service menu).

PDHW - I think you need a plug-in module to set a different flow temp for hot water and I believe a diverter valve needs to be installed inside the boiler before it will work. Sucky dumb idea.... There is a hack that can be done with a simple resistor*, but the diverter valve is still (probably) required.

 With a smart(er) control that can set flow temperatures on the fly, hacks or (expensive) plug-in modules are not needed. I can't recommend an "off the shelf" control as I don't know what works & what doesn't - A quick search reveals that Tado might work, but you have to make sure it is EMS compatible (not all kits do EMS).

*) Hack for the Greenstar 8000.

 https://www.youtube.com/watch?v=i_FIS8XRm-I

jbainbridge

Talk to the plumber. 

Let us know what happens.

Rollinghome

We had a new boiler fitted a couple of weeks ago and I fully sympathise.  Plumbers seem to have favourite boilers and systems that they want to fit regardless. 

Two of those we had quotes from wanted us to have a combi to replace our open vent system.  We have incredibly low mains pressure, but we live in a 2 storey house and I raised our tank another five feet so that we have a thundering flow that can fill a bath in a flash.  No way did we want to replace that with a dribbling combi.  And two of the quotes, including the one we accepted, referred to the wrong boiler. I checked the boiler as soon as it came in the house.

So decide what you want and ask them to comply with the contract or compensate you. Good luck.