Does it matter if boiler is slightly over sized?

[doitall]

For clever guys you lot don't think outside the box very well.

IF what you say is true, and I doubt for one minute the Intergas or Atmos Inter would have a problem being slightly oversized.

You could if it bugs you that much fit a pump over-run type switch, whereas the boiler cuts off for say 15mins on a timer after the room temperature is reach. On a well insulated property you could make it 30mins and probably still not notice the difference.

 

[Dan Robinson]

whereas the boiler cuts off for say 15mins on a timer after the room temperature is reach. On a well insulated property you could make it 30mins and probably still not notice the difference.

Or adjust right parameter

 

[DeltaT2]

the boiler will cycle excessively...but they all do that when you use on-off controls, for the simple reason that they are working to a fixed flow temperature...

You are better off using compensation controls that adjust the flow temperature to match demand..

Whilst modulating controls will undoubtedly be better in this regard, they are still limited by the lower output power of the boiler which, in so many cases even with highly regarded models, is way too high for many a modern home.

[Edit: Apologies, missed D_Hailsham's post where he's already covered this]

Mathew

My point entirely is that the search for the low end modulation is misplaced..as boilers with compensation controls deal with the lowend very well any way. Correctly sizing boilers is the key, and with a house with a 4.2 kw boiler perhaps another fuel should be used...

That's very damning for the gas boiler manufacturers & makes a complete mockery of thier limited technology!!!

Surely 'they' can address the requirement for a lower temperature heating load & a higher temperature Hot water load??!! Many modern homes are going to have the building 'heat loss' nearing the HW requirements??!! Surely that's being considered??

 

[doitall]

whereas the boiler cuts off for say 15mins on a timer after the room temperature is reach. On a well insulated property you could make it 30mins and probably still not notice the difference.

Or adjust right parameter

That requires thinking and a certain knowledge Dan

I could adjust a the fan and pump speed on mine.

 

[Dan Robinson]

 

[doitall]

Think a 4 piper may be a tad OTT for 4.5Kw. What do you suggest the Viessmann 200.

The Intergas or Atmos for that matter will be perfect for the OP.

All he/she needs is an approved installer.