Worcester Greenstar - Am I getting the right advice???

[pugliese]

About a year ago I had a new central heating and DHW system installed. Greenstar 24i System boiler with a pressurised hot and cold water system and UFH to the ground floor. The controls are a Heatmiser system and a thermostat on the hot water tank.

I was told by the plumber that the heating & DHW controls on the boiler (1 to 6) should be set to max 6 as the hot water is controlled by the tank thermostat and the UFH temp by the heatmiser system. I took his advice, but painting outside the other day I found that the vapour coming out of the boiler flue was very hot, so I tried turning down both hot water and heating controls on the boiler to the min setting of 1 - the boiler flue gases now appear a lot cooler, the hot water temp is fine but the boiler seems to be running for longer when the hot water is scheduled to be on. Unfortunately it is too warm to test the UFH (super insulated house!)

Clearly there is a trade off here, but what are the best settings for this type of system?

 

[leakydave]

If you turn the boiler stat down to 1 you will fire the boiler for far longer for it to get the hot water and UFH systems to temperature. A condensing flue should not be above 80° in my opinion.

You have a choice of greater heat loss over a shorter period or less heat loss over a longer period. Personally I would run the boiler at 5 or 5½.

Your installer was right about the thermostats on UFH and cylinder. they should cut off the boiler when they have reached their target temperature. UFH takes a long while to warm up so the heating performance will be worse with the boiler turned down to 1 on your dial.

 

[pugliese]

If you turn the boiler stat down to 1 you will fire the boiler for far longer for it to get the hot water and UFH systems to temperature. A condensing flue should not be above 80° in my opinion.

You have a choice of greater heat loss over a shorter period or less heat loss over a longer period. Personally I would run the boiler at 5 or 5½.

Your installer was right about the thermostats on UFH and cylinder. they should cut off the boiler when they have reached their target temperature. UFH takes a long while to warm up so the heating performance will be worse with the boiler turned down to 1 on your dial.

Thanks Dave. I think running the UFH at a lower temp is preferable as the half a dozen times the heating has come on this winter, overheating has been the problem

 

[Agile]

We have not been told how the UFH is installed.

In the UK its usual to have a separate pump and a blending valve which is usually just set to a single temperature and no adjusted to vary the UFH temp.

Does your controller adjust the boiler flow temperature? If not then it should be set to 70 C when heating the hot water ( and the cylinder to 60 C ).

Tony