How do I balance a boiler

[Pokey38]

I have balanced all the radiators but can not get a 20 deg temperature between flow & return at the boiler end. What do I need to do? Someone told me I have to back the boiler up but how do I do that?

 

[Dan Robinson]

Oh pooh - my condensing boiler only has a delta of 5.1. What am I to do?

 

[Agile]

Poke, why not tell us what diff you actually have?

If there is a cylinder that influences the diff too.

Practically its difficult to get more than about 15-17 C diff on most installations!

That's still enough to give efficient operation as long as the rads are large enough.

Tony

 

[Pokey38]

It's a combi boiler with 7 rads and the diff is less than 10 deg C

 

[D_Hailsham]

It's a combi boiler with 7 rads

That's the cause of the problem.

You have a 24+KW, boiler, probably with a fixed speed pump, feeding about 10kW of rads.

Now, if you are very lucky, you may be able to tune the boiler so it provides the correct amount of heat and adjust the pump speed for heating.

What is the make and exact model of your boiler?

You say the diff is less than 10C, what are the actual flow and return temps?

 

[Pokey38]

I have a worcester bosch greenstar heatslave 18/25 combi, hot water is 50 deg C & the flow/Rtn has a difference of 8 deg C. I can borrow the gear to check the temp tomorrow it measures flow temp / Rtn temp & the difference between them. I have been told by a plumber I need to back the boiler up or something to that effect, but this was while I was out and in a rush so didn't have time to ask him how

 

[Agile]

What temp diff do the manufacturers actually recommend?

A target of 20 C is for condensing gas boilers!

Yours may recommend less.

Tony

 

[D_Hailsham]

What temp diff do the manufacturers actually recommend? A target of 20 C is for condensing gas boilers!

It is a condensing combi oil boiler. The mfr literature say that the available pump head is 4m at max output with a 20C differential.