Rads only heating at the top.

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sparer

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We've got an old Georgian house that has a system operating rads on 4 floors. The LG is 2.6m from the GF where the boiler and pump is located. There are 2 more floors staggered over 4m (see attached). We've not been there long but we've noticed that the 3 rads on the 2nd floor only get hot at the top. All other rads on the lower floors are piping hot.

I undersdtand that there may be sludge in the upper rads but why aren't the other rads affected?

The other problem may be that the grundfos system pump (located at the ground level) was replaced with a cheaper one. I'm not sure of the specs albeit I remember reading that it would pump up to 6m.

Before I remove the rads and wreck the brand new carpets, is there any merit in investigating the pump first and what would be the best way of going about this?

Thanks
 

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Can you post a photo of the pump label.
How many rads?
Is it a sealed system?
 
H
Johntheo5 said:
Can you post a photo of the pump label.
How many rads?
Is it a sealed system?
Click to expand...
Thanks for the reply. Please see the attached photo. There are 16 rads and it's a sealed system which also heats the hot water.
 

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The pump at 36watts has the same power as my 6M Wilo, but I have only 10 rads.
Can you post a photo of the pump controls LEDs etc, while running and info you may have on the pump, normally, these A rated pumps have 3 fixed speed settings, (constant curve, CC) and a number of CP (constant pressure) and PP (proportional pressure) modes.

If you shut off 3 rads or more do the "cold" ones then heat up?.
 
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The PDF for the pump is here. I had a quick read of it before posting and I could see that whilst the pump was set to the highest setting (yellow), the indicator was flashing meaning the flow was being regulated. I set the pump to unregulated (indicator on permenantly) and 2 of the rads are now hot all the way down. The remaining rad has a weird connection, flow at the bottom left and return on the top left so only the left side gets hot now so that one will need replumbing. I guess I'm going to need a stronger pump if I want to run it efficiently.

What are your thoughts?
 
I had a very quick look, it seems you have the 3 traditional fixed speed CC settings and 3 proportional pressure PP settings,the flashng LED probably/possibly indicates that you were on (regulated) PP mode and you will certainly get a far greated head and flow in CC mode which is what seems to be happening now?, can you post a photo of the setting button and LEDs?. That rad will certainly require replumbing.

How do you know what setting you are on, be it CC1, 2 or3 or PP1, 2 or 3??.

EDIT.
Had another good look through the MIs and yes, as you probably know anyway, you have three CC curves and three PP settings and it was set to the highest PP setting (flashing LED), the highest CC setting will give that extra boost.


1705101702498.png


1705101642435.png
 
Last edited:
Do you mean the TRVs are open full and not turned down?, did going to full pump output
CC3, do anything?.
 
sparer said:
There are 4 rads on the 1st floor that have the trvs turned right down and the rads are cold.
Click to expand...
Are these the hot ones that you turned off? Which are the ones that are cold?

To identify incorrect balancing, you turn off all the hot ones and see if the cold ones get hot.
 
Johntheo5 said:
Do you mean the TRVs are open full and not turned down?, did going to full pump output
CC3, do anything?.
Click to expand...
The TRVs on the 1st floor are set to '1' and have closed due to the room being at the required temperature. Per post #5, the troublesome rads on the 2nd floor are now performing better. Going to CC3 made 2 of the rads hot all the way down and seems to be the solution. The other cold rad is plumbed incorectly i.e. flow in the bottom left and return at the top left however half of it is now hot all the way down. This rad is going to need replumbing.

I think for now, I'm happy that going to CC3 has solved the problem that I had so thanks Johntheo5 for asking for the doumentation for the pump which ultimatly made me read it.

I would like to improve the system so that I can use the PP settings but I think that I'm going to need a better pump for that. Any suggestions on what pump might suit would be appreciated.
 
OK, I gather you are not willing to do the balancing test.
 
JohnD said:
Are these the hot ones that you turned off? Which are the ones that are cold?

To identify incorrect balancing, you turn off all the hot ones and see if the cold ones get hot.
Click to expand...
All of the other rads on the system perform well. It was just the highest rads on the 2nd floor which I had an issue with. It seems that a continuously running pump has solved the problem.
 
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