Boiler flow and return temps too low but rads arent......?

[sparkymarky216]

Forums
...

Old conventional non condensing combi boiler. Worcester 24i rsf.

Bungalow (ceiling drop pipes) with 7 rads.

I've bled rads.
Attempted to balance - Got them heating up at similar times now.

Boiler manual states 11 degree delta flow and return. Boiler is set to about 3/4 of max temp.

On the rads, not a problem - I can get 30c delta or just a couple of degrees easily- lots of adjustability on the lockshields.

I see about 60 degrees measured at rad flow and 50 at rad returns. But can adjust to less if necessary easily.

However........ the thermometers I have on the boiler flow and return never seem to go above 50 flow and 23 return. This seems wayyyy to low for a conventional non condensing boiler no?

I have read that such low flow and return to this type of boiler (specifically return) will lead to corrosion of the heat exchanger......as this non condensing boiler will be condensing and the chemicals given off in the flue fall back down and corrode the exchanger....

so how do I increase the boiler flow and return temps? Reduce lockshields further on the rads so the rads aren't giving away so much heat from the system or something else?

 

[ShaunCorbs]

if your getting 60 at the rads but only 50 at the boiler something is wrong with your temp set up

 

[snowhead]

If the thermometers at the boiler are the strap on / clip on type and on unlagged pipes you won't get a true reading.

Try one of them on the flow at the radiator and see what it reads.

 

[sparkymarky216]

Just found another 22mm pipe lurking up behind the rear of the boiler..... which is the flow....I had the thermonetes on what turned out to be the return pipe and a stone cold vent pipe to outside lol.

Apologies!


Next question.....should i measure the boiler flow temperature and set to say 75 degrees c on its dial for this non condensing boiler, then balance rads using lockshields to achieve 11 degrees delta as per the manual......and will adjusting those lockshields affect the temps back at the boiler??

 

[ShaunCorbs]

For non condensing you want the return above 55

 

[sparkymarky216]

Thanks shaun,

Just finished a first warm up before I go onto balancing.

Flow at boiler was 71 degrees and return was 63 degrees.

(Those boiler temps were with all lockshields and trvs fully open to identify the order in which they heat up)

Ok to start balancing off those temp starting points?

 

[sparkymarky216]

Also I'm taping the probes of the thermometer onto the flow and returns....is that going to skew the readings as the tape will not let ambient air get to the probe so the temp probe may read the pipe higher than what it axtually is without the ambient air cooling effect on the probe?

 

[John.g]

The flow temps will be the same as the boiler flow temp,
The heat geek makes a very good case for monitoring the mean rad temperature, measure the temp ~ midway in and midway up/down but you need a thermal gun probably.

Balancing Heating Systems - The Ultimate guide - HeatGeek

www.heatgeek.com

 

[ShaunCorbs]

Thanks shaun,

Just finished a first warm up before I go onto balancing.

Flow at boiler was 71 degrees and return was 63 degrees.

(Those boiler temps were with all lockshields and trvs fully open to identify the order in which they heat up)

Ok to start balancing off those temp starting points?

Tbh if all the rads heat up evenly I would leave as it and monitor

 

[sparkymarky216]

Thanks guys.

Just finished and managed to set all lockshields to give a delta of about 10 to 14 degrees across all rads. The manual says they should be 11 so this should be good enough.

Will see what it's all like when I fire it up tomorrow. Thanks all for your help thus far