Radiator dT nowhere near 20deg

[samiebon1]

Using a thermocouple to measure flow and return on radiators throughout the house and I can't get anything really above 4 or 5 degree dT! This is on a modern condensing boiler.

Only thought is that we're running at 45deg flow temp and whether that's effecting anything.

Not sure what's happening or if I'm thinking of something wrong.

Valves have been twizzled all the way between the ranges.

 

[Notch7]

you really need Dt20, its what the system is design from not how it necessarily operates

and as youve guessed the closer the flow temp is to 20 the harder it is for the radiator to shed the heat.

what is the return temp at the boiler?

is your flow temp fixed at 45 deg? -weather comp would be better

Im only a DIYer Im sure the professionals on here will give you far more valuable advice

Do We Really Need DT20? - HeatGeek

www.heatgeek.com

 

[samiebon1]

Thanks @Notch7. That seems reasonable that its harder to shed when the flow is closer to 20deg.

The boiler flow and return are measuring a similar dT, but i'm now getting sceptical of my thermometer as its measuring 37deg at boiler exit, when the boiler thermometer says 45!

 

[Why Not Indeed]

Pipe insulation? I have got DS18B20 probes cable tied to flow/return pipes on my boiler. The CH flow was quite a way adrift of what the boiler thought it was until I put a bit of foam insulation over the probes, now it's usually within 3°C which is good enough for me.