Increasing delta t

[Matt0029]

How do you increase the delta t on a modern condensing combi boiler? The pump is self modulating. Is it a case of turning lock shields down. Upon fitting am getting a 6 degree flow and return difference on alot of installs. Thanks.

 

[doitmyself]

Which boiler are you talking about?

 

[Matt0029]

Ideal logics

 

[ShaunCorbs]

Rads the correct size that will play a big part aswell pump speed and balancing

 

[John.g]

How do you increase the delta t on a modern condensing combi boiler? The pump is self modulating. Is it a case of turning lock shields down. Upon fitting am getting a 6 degree flow and return difference on alot of installs. Thanks.

Any idea of the heating demand and the combi boiler output and oil or gas?.

 

[Matt0029]

Any idea of the heating demand and the combi boiler output and oil or gas?.

The heating demand all the rads added up is 13kw. A 24kw combi is fitted. It's gas fired.

 

[ShaunCorbs]

What boiler ? (Make)

 

[Scott_D]

You can’t range rate logics.
You can add weather comp though.

 

[John.g]

The heating demand all the rads added up is 13kw. A 24kw combi is fitted. It's gas fired.

This is a bit long winded but might show different methods of achieving similar results.

Even though that boiler is fitted with a modulating UPM3 pump I would think its running in a very high head/large flowrate mode to enable 24kw output in HW mode, and I would think probably unlikely that the boiler logic changes it on CH mode. your readings would suggest ~ 20 LPM, if so then in HW mode, a flow temp of 80C will give a deltaT of 17C and a return temp of 63C.

Re your query of reducing the deltaT, obviously throttling the rads will increase the deltaT but at reduced rad output, for example if you run with a flow temp of 70C and you throttle the rads to give a deltaT of 20C and return of 50C, the rad(s) output will be reduced from 13kw to 9.5kw, a far easier but with not quite the same rad output is to simply reduce the flow temp, if you reduced the flow temp to 59C then the deltaT is only 6C but the return temp which determines boiler efficiency is still reduced to 53C with a rad output of 8.8kw,
if you reduce the flow temp to 50C, the deltaT will only be 4C but the return only 46C with rad output of 6.1kw. This is how weather compensation works, it reduces the flow temp to achieve lower return temperatures (even with very low deltaTs) = greater boiler efficiency.

Should also have asked what the boiler flow temp was to give that deltaT of 6C?