Going crazy can not reduce returns tempreature help help


20 Nov 2021
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United Kingdom
Hi all

All help is appreciated, I have vaillant ecotec pro boiler and 3 stories home, I have read on this forums about the efficiency of combi condensing boiler depends on the returns tempreature so I have tried the following with no help
D19 from 2 to 1, D1 to 8 minutes, back breaking time wasting balancing all radiators to 12 difference inflow and returns. Despite all of this I still have only 4 degrees difference on the boiler D40 is 56 and D41 is 52. The same difference even when the boiler temp was 75. Any ideas how to reduce the difference please I am pulling whatever left of my hair as after almost a month of reading and doing all of this I am still in same place
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Water going from 56 to 52 is the same energy as going from 75 to 71.

The critical thing is now your return temp is below 55 the boiler will actually begin to condensate.
Yes but it means that none what I did had any effect whatsoever, and also it will take longe for the house to heat as I reduced the temp so is it worth it
If you have changed the return temp from 71 to 52 you have made a difference and the boiler will now be condensing.

Yes it may well take longer for a room to heat up, (if your radiators are sized for a ridiculous 80 degree flow temp) but the system should now be closer to the expected load for relatively mild temperatures outdoors.
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Thank you for your reply, I have manged to reduce the return temp just because I reduced the boiler flow temp rather than actually reducing the flow temp due to the work I've done, hence my question if I am missing some trick to manage to reduce the return temp but also increases the flow one, some posts suggested that they achieved flow temp 70 and return of 50 very impressive considering what I have done and thay I actually achieved nothing, same difference between flow and temp whatever tempreature I set the boiler to
Most domestic lockshields have very little valve authority and hence exact balancing is extremely difficult. Usually within a 1/4 of a turn the valve will be allowing so much flow the rad is essentially saturated anyway.

If you think your return flow is higher than it should be, is your house already at a decent temperature? Give it time to settle before taking measurements.
Thank you both, It is more than 24 hours and still same as no difference in the returns flow and house is temp 20.5
And yes all radiators are hot all over
You have not stated what you did to 'balance' the rads.
With the lockshield valve (usually on the return side of the rad) nearly closed you will achieve a high differential temperature, but at the expense of less heat from that rad.
Do you have a two pipe heating system? This method will not have the same affect with single pipe systems.

Have all TRVs fully open. Start up the heating circuit, and adjust the flow temp to about 68C. Adjust any ABV to its highest setting (usually 0.6 bar)
1. Is the pump speed adjustable? Open the largest rad's l/s valve fully, then adjust the pump speed to achieve 10 to 15 C across its flow and return pipes.
2. Close the l/s to the smallest rad ON THE TOP FLOOR, opening it a quarter turn at a time until 10 to 15 C appears across its flow and return.
3. Repeat for the next smallest rad until all the top floor rads have 10 to 15 C across each of them.
4. Check the largest rad again, adjust the speed as per stage 1 above.
5. Repeat 2 to 4 for the middle floor.
6. Repeat 2 to 4 for the ground floor.
Check the boiler primary flow and return temps. If all the loads are showing a 10 - 15C drop then the boiler too must have a 10 to 15C differential. If not you've missed a rad or a by-pass somewhere....towel warmers are a common villain.
7. Gradually set the ABV lower until it starts to pass, then about 0.05 bar higher.
8. Set your TRVs to your desired setting.
9. Set the flow temp to the lowest value consistent with the desired comfort levels.
I know abethe locksheilds as it took me almost a week to balance 10 rads. And am extermly disappointed with the results
I know abethe locksheilds as it took me almost a week to balance 10 rads. And am extermly disappointed with the results
Then you have missed something. I cannot comment on your rate of work, nor on your levels of disappointment with the free advice you have been given; A reasonably competant DIYer concentrating on the job should take no more than an hour to balance 10 rads on 3 floors.

How old is your 3 storey house?
What is the size of your smallest radiator on the top floor, and how many turns open (from closed) is its l/s valve?
The same question for any towel warmers.
Do you have an ABV? What is it set to?
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To answer this and previous questions:

I am not sure if I have a single or two pipe system, I am presuming it is 2

I used a handheld thermometer to adjust the gradianets starting with the radioter that gets warmer first (as per several u tube videos )

I don't have an external ABV, but vaillant has an internal one which has been put to the maximum pressure.

The house was built in 1860

I have 2 twoles warmer (I included them in the 10 number so I have 8 radiators and 2 twoles ) that they proved a nightmare to balance, one of them doesn't have a tvr the other does.

All the TVR were kept on full during the " balancing"

My upstairs and middle floor (4) are single blade they look old, the downstairs one are double blades (not sure how to calculate their sizes)

The pipes coming to radiators all looks thin woul d speculate 8 or 10 mm, apart from one pipe going to one of the radiator and towle warmer (the bathroom was an additional before we bought) that pipe is significantly larger would think about 20 mm both the radioter and the twole warmer were significantly harder to balance than the others

There are 3.5 turns on the LS

Viallant I have had only 0,1,2,3,4 for pump speed so putting it on 1 the lowest I gathered I could not get the 20 degrees diferrance through the biggest topfloor radioters (which is the towel with no TVR)

Any furth advice will be welecmed
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Ima, I asked you how many turns from closed is the largest radiator set to, and you answered:-
There are 3.5 turns on the LS
, and you referred to a towel warmer. This will not be the largest (output) radiator. The largest radiator is the one which is sold as having the highest power in kW or btu/hr. It will be the double panel radiator with the largest surface area.
This means that your towel warmer l/s valve has been set too far open. Close it to within 1/2 turn of fully closed, the same for your second towel warmer, wait 10 minutes, then re-measure the differential temperature across the towel warmer flow and return pipes. Adjust only 1/4 turn at a time; turning towards closed will increase the differential temperature (dT).

You have not stated the current pump setting. Try again with the largest output rad valves fully open.
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Reactions: Ima
So after a long shift today, I did the following as per the advise :
the pump speed is set to 1 the lowest available. Was not able to get it any lower. In order to get a 15 to 20 degrees defferance in ech radioter when boiler temp on 68 (starting with the biggest rad ) I had to work on LS of all radioters and towel and I have manged to achieve that.
Having said that unfortunately the return temp on the boiler is showing 62.
I have checked all the obvious pipes there is no external ABV, the boiler internal one is set to highest. All the LS are almost 1/4 of turn from lock (sorry I miss understood the question previously ).

I must be messing something as if all of the above is right I should get a max return temp of of 53, any further advise, could an ABV be placed underfloor boards or behind kitchen cupboards am all lost here
i am no expert

but if you dont extract enough heat from the pipe /system leaving the boiler it can only return warmer
iff you extract more heat it will return cooler so perhaps a lower rating level or smaller boiler to allow modulation :confused:

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