Struggling to lower flow return temperature

NannaH

The lounge rads are taking longer to heat up, around 20 mins now .  

I had to tweak the big one as it wasn’t fully hot after an hour this morning so another quarter turn seems to have done it. 

I’ve ordered a pair of clip on thermometers for the pipes. 

Havent checked the boiler readings as my airing cupboard is full of washing on a rack

[Deleted User]

NannaH said:

The lounge rads are taking longer to heat up, around 20 mins now .  

I had to tweak the big one as it wasn’t fully hot after an hour this morning so another quarter turn seems to have done it. 

I’ve ordered a pair of clip on thermometers for the pipes. 

Havent checked the boiler readings as my airing cupboard is full of washing on a rack

There is a bit more science to radiator balancing than just playing around with one of two lockshield valves:

https://ukradiators.com/advice-centre/the-simple-guide-to-balancing-radiators/

The other problem not often mentioned is that old heating systems with cast iron boilers were designed based on a flow to return temperature differential of 15C not 20C. It follows that if a flow differential of 20C is to be realised with a condensing boiler then bigger radiators may be required in some situations. A clean heating system also helps.

NannaH

System was cleaned out in November, magnaclean is very clean now.   If the system didn’t have brand new inhibitor in it, we would be putting in a bigger bathroom radiator over xmas.   It can wait till next autumn.  

Return flow temp is now 50° so that will do for now.   Only losing  10 degrees in the system but hey ho,  the house is warm and we’ve used 480kwh of gas in 9 days. 

[Deleted User]

Yesterday I examined the lockshield valves for the first time in 40 years!  Basically the lounge rad has never felt quite as hot as some of the other rads nearer the boiler (been in this bungalow for just over a year now).  So when I checked my rads every single one of the the lockshields was wide open!  Am now awaiting what I hope will be a more accurate IR thermometer to measure temperatures across all the rads and at the boiler itself.  As an interim though most lockshields were turned down (1/4 turn open) to try and get more flow to the problem rad (left open).  So far the lounge appears (to the touch) to be heating up at the same rate as the other rads but need to measure the temps accurately across the rads to be sure of a 'good balance'.

Q)  My CH system is fed via a combi gas boiler.  What should the temp drop between the inlet and outlet of each rad be in an ideal system? Is it 11-12C or should it be 20C?  Or does the 20C figure relate to the drop at the boiler inlet and outlet pipes?  Seen conflicting stuff on the web....

chris_n

11-12 is the figure that is historically used, 20 seems to be quoted for fully spec'd condensing boiler installations and heat pumps. When I say fully spec's I mean with larger radiators to cope with lower flow temperatures, reading many threads on here that is often not the case. 

[Deleted User]

chris_n said:

11-12 is the figure that is historically used, 20 seems to be quoted for fully spec'd condensing boiler installations and heat pumps. When I say fully spec's I mean with larger radiators to cope with lower flow temperatures, reading many threads on here that is often not the case. 

Today I played around with an IR thermometer - just a fairly cheap one from 'The Jungle' fully expecting it to be absolute rubbish, being returned pronto and me being none the wiser.  Tested it against my 'ordinary' Hg thermometer which said 22.5C dipped in a bowl of warm water - the IR was a little lower at just over 20C so at least in the right ball park.  The CH heating had just fired up again so was able to get readings from all 7 rads until the CH went off again.  It was much more evident which rads were warming up first from both the numbers (inlet and outlet side) and there was a clear drop from the inlet side to the outlet in the range 10-11 deg C although one or two were outside this range.  Will persevere over the coming days making marginal changes to the lockshields now that I have a faster way of measuring temperatures. 

Matt_OX4

Which IR thermometer did you get if you don't mind sharing?