Combi Boiler Water Flow Rate Slow or Fast for Efficiency?

David28

I have a combi boiler and when turning on the hot tap I have to let the water run for a while until the water runs hot.
What would use the least amount of gas, turning the tap on and adjusting the flow so that the minimum amount of water (that switches on the boiler) flows and takes longer until the water gets hot, or turning on the tap so that the flow is maximum?
The amount of water that is wasted until the water is hot enough is immaterial as I don't have a water meter.

matelodave

Every time you turn on the hot tap the boiler thrashes away at full blast until the heat has circulated through the heat exchanger and is absorbed by the water that's flowing through the hot tap. Most boilers will then modulate their burners to balance the heat that's being extracted, so it probably doesn't make a great deal of difference because it's the act of turning on the tap that uses most energy.  Running the fan and pump and firing the boiler and then the shut down sequence which runs the pump and fan to dissipate the built up heat. The boiler is at it's most efficient when it's in it's condensing mode, not when it's starting and stopping

The quantity of water that's wasted does have bearing on your consumption as well - if you waste a gallon or so until it gets hot then there will be a fair proportion of that gallon of lovely hot water sitting in the pipework to get cold until you do it again.Say half a gallon, every time you run the hot tap.

What could save you money is to only use hot water when you really need it rather than just turning on the hot tap to rinse stuff - even your hands. Short run-offs will cost far more per litre (or gallon) to heat than say filling a bath or basin where the boiler gets a chance to settle down.

Ectophile

Why waste the water?  I keep a water container handy and use it for watering plants or flushing the loo.

David28

Ectophile said:

Why waste the water?  I keep a water container handy and use it for watering plants or flushing the loo.

I don't have any plants and I think pouring water down the loo went out when they invented the flushing toilet cistern