Optimum boiler set, flow and return temperature

22 Dec 2005
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United Kingdom
I have a Glow worm Ultracom 24hhxi boiler that has the useful function of easily being able to see the flow and return temperatures.

My boiler has been set up with a target flow temperature of 73 degrees. The difference between flow and return temperatures is around 12 degrees.

What should you expect these to be if the system is operating at it's maximum efficiency?

The heating works well set up as it is but there is quite a bit of flow noise. The pump is set to speed 2 so i'm wondering if i can turn the pump speed down to reduce the flow noise and also increase the system efficiency by increasing the flow and return differential.

All comments appreciated.
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You could try turning the pump down but you need to check the differential temperature across the boiler and ensure it is no more than 20 degrees otherwise you may find the boiler throwing up fault codes.

Of course the average temperature of the radiators will fall and if sized by traditional calculations may not be sufficient to heat the property in this cold weather.

The return temperature will be lower increasing boiler efficiency a little, ignore the efficiency increase of the pump...it's only going to be a few quid a year. The hot water cylinder will also take a little longer to heat up.
So what would be the optimum set boiler set temperature?
If the return is 55° C or lower then the boiler will be condensing well.

That means the flow can be up to 75° C but the lower it is the more efficient the boiler operation.

Weather compensation aims to heat with the lowest flow temperature necessary to provide the required heating.

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I get a very good plume from the flue, so it looks like its condensing well :)

My boiler doesn't have the weather compensation option.

What does it do? Try to balance the flow temperature with the return temperature?

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