What is the truth as regards condensing boilers

[man100]

What is the ideal return water temperature required to get the best out of a condensing boiler.

Some say around 50 degrees on my boiler that means a temp. setting of 60 degrees outgoing, Baxi say return should be min. of 13 degrees less than outgoing and to run unit at 80 degrees.

Some heating engineers I have asked frankly dont seem to know they often give me different figures.

Does it depend on the make of boiler?

 

[bolshy]

Also depends on the age and size of your radiators. It's there to heat your house.
Condensing occurs at all return temps, but best efficiency is at returns of below 55 ° C. If your radiators are oversized and can work at a differential of 20 ° C, then your flow can be 75 ° C or less.
Standard differential for many boilers is quoted at 11 ° C.
As all systems are different, you can't guarantee this differential across all radiators, but if they're heating the room effectively, the lower your return temp, the better.
Personally, I wouldn't mess with a working system over a prospective 2 -3 % increase in efficiency.

 

[Agile]

If you told us your boiler model then we could reply more closely taylored to your own boiler.

Tony

 

[ALEC1]

the lower the return temperature the greater the efficiency on all condensing boilers.

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Right now for example, my system has a flow of 56c, and return of 54c, and a room of 21c

Vaillant have the best offer: with the VRT 350 and 470, then Viessmann with the vitotronic 200, and broag and the I sense.

Some manufacturers supply an outdoor sensor which lowers the flow temperature in line with outside temperature, the cooler the weather the warmer the radiators...

 

[man100]

If you told us your boiler model then we could reply more closely taylored to your own boiler.

Tony

Thank you and the others for your interest and advice.

My boiler is a Baxi duo tec 28, I have 7 rads including bathroom towel rail I believe the system is around 12 kw.

Tvr valves on all rads except room with room stat and bathroom rail, I have a return flow temp gauge on pipe at the boiler.

Boiler is at the moment set at 60 and return is 50.

The boiler was fitted around 2yrs ago to replace a 30yr old one.

If I increase the boiler temp to either 70 or 80 the return is approx 14 lower.

All the tvr are at 4 the room stat rad is balanced with the lock shield to allow the rest of the house to warm before stat shuts off.

 

[ALEC1]

baxi do have compensation controls which will automatically lower the return temperature..with out compromising comfort.

modern boilers are best installed with constant flows and varying temperatures as opposed to varying flows caused by TRVs and constant temperatures