Balancing rads help.....

[Dee]

Your readings are So much lower than mine! How come so low and mine are so high?

I use a multimeter with a clamp to take the readings.

I measure the temperature at same places as you, inlet and outlet, and the  middle of the rads. I have white column rads too, only 4 vertical rads and 2 towel rails.

I balanced on Sunday and took these final readings today once it had all settled.

I'm not technical like you (as you can guess) just want a warm house and bills that don't make me weep!

 

[marshian]

Just now, Dee said:

Your readings are So much lower than mine! How come so low and mine are so high?

 

I'm running a boiler flow temp in very low 30's

 

You are running a boiler flow temp of 60 deg

 

I heat 24/7 with no setbacks - I am assuming you heat to timed schedules or 24/7 with set backs day and night

 

The boiler flow and return difference as well as individual radiator difference between flow and return are always going to get narrower as the flow temp drops

 

Heat Geek sourced https://www.heatgeek.com/do-we-really-need-dt20/

 

Flow Temp Return Temp                 Diff 80 56.0 24.0 75 52.5 22.5 70 49.0 21.0 65 45.5 19.5 60 42.0 18.0 55 38.5 16.5 50 35.0 15.0 45 31.5 13.5 40 28.0 12.0

 

Just now, Dee said:

I use a multimeter with a clamp to take the readings.

I measure the temperature at same places as you, inlet and outlet, and the  middle of the rads.

 

You use the same clamp to measure boiler flow and return too?

 

Clamps are a bit hit and miss especially on pipes - better to use and hand held IR on rads - they aren't expensive and it's a lot quicker as with pipe clamps you have to wait for the temp to stabilise

 

Don't measure rad temp in the middle - you'll get random results - Top Middle OK but not centre of the rad

 

Just now, Dee said:

I have white column rads too, only 4 vertical rads and 2 towel rails.

 

OK be good to know which rads were Towel Rails rads because they are terrible for acting like a great short circuit and returning HW straight back to the boiler and starving other rads of flow without appearing to do that.

 

Just now, Dee said:

I balanced on Sunday and took these final readings today once it had all settled.

 

OK were all rads calling for heat ie TRV's wide open?

 

Just now, Dee said:

I'm not technical like you (as you can guess) just want a warm house and bills that don't make me weep!

 

I'm not technical but I am a bit data driven.............

 

We all want a warm house and bills that don't make us cry 😉 

 

[marshian]

2 hours ago, Dee said:

I can't achieve 12⁰ drop on any of them 

 

 

You have 10 rads in circuit where the DT is 10 or greater (That's pretty good depending on the rad type)

 

You have 6 greater than 12 (one is 16!!!)

 

My only conclusion is your maths is quite poor 😉 

[marshian]

@Dee Lets go back to basics - it's not a test just a few statements to develop understanding of the point of balancing and the benefits.

 

So at a boiler flow temp of 60 deg and a well balanced system Heat Geek table of earlier would expect a return of 42 Deg (You currently have a return of 50 Deg so that's a bit higher than would be expected)

 

So if it's a bit higher then there can be a few potential causes

 

1. Pump speed too high - water is being pushed thro a rad (or rads) too fast and being returned back to the boiler before it's had chance to release the temperature into the room.

 

or

 

2. Too much flow thro a rad (or Rads) leading to water being returned to the boiler too soon (AKA Poor Balance)

 

or

 

3. Rads too small for the heat output required for the room so flow needs to be quicker to raise the mean temp of the radiator to get the room up to temp

 

Why is return temp important for efficiency - well if it's a condensing boiler the efficiency of the boiler improves the cooler the return temp is

 

 

So currently your return is 50 deg so from 50 C at the bottom scale (Return Temps) go up to where it hits the yellow line on the outside of the curve and then go horizontally left and you get 91% - that's the efficiency currently of your boiler when its running with a 50 Deg C return temp

 

Now follow the process taking my return temp of 25 deg and go up to the yellow line on the curve and then go horizontally left and you'll see that it's about 97% efficient 

 

So about 6% improvement (or reduction in gas usage) that's my payback for over sizing my rads to be able to run lower flow temps and buying a boiler that can actually run happily at those flow temps without cycling (My old boiler min flow temp was 39 but realistically the lowest it could actually run was 45 and even then it cycled)

 

Now if I have a target room temp of 20 Deg C in a room no matter what the flow temp I am never going to see a return from a radiator in that room below 20 deg it's only going to be above

 

So If I'm feeding a rad with 30 deg and even if it's a massive rad the minimum temp leaving the rad is going to be 20 deg or more - this is why as the boiler flow temp is lowered the difference between flow and return is always going to get narrower.

So this explains why my drop between flow and return on all my rads is so much narrower or lower than yours. The difference between our boiler flow and returns is because I'm running a flow temp that is 50% of yours.

 

Now lets look at what we want to happen across all the rads in the CH circuit - we want them all to release heat into the rooms - as heat is released the rads get cooler and as a result they all contribute to the drop in the return temp back to the boiler but the return temp is going to be impacted by the level of flow thro each rad

 

Example (with easy Math)

CH system with a flow of 10 Litres per min

4 rads in circuit all being fed with 60 deg water

All the rooms are the same size

All the rads are the same size

So in a balanced system each rad gets 2.5 Litres a min

Each rad has a temp drop of 18 Deg C

The return temp to the boiler is 42 deg C (Ignoring any losses in transmission pipework)

 

Now lets show the impact of "inbalance" in the same circuit everything in Bold above is the same

 

Rad 1 gets 2.5 Litres a min - In 60 out 42

Rad 2 Gets 5 Litres a min - In 60 out 54

Because Rad 2 took 5 Litres per min the remaining rads can only have 1.25 Litres per min each

Rad 3 Gets 1.25 Litres a min - In 60 out 40

Rad 4 Gets 1.25 Litres a min - In 60 out 40

 

What's the temp of the water back to the boiler??

25% of the water is at 42, 50% is at 54 and 25% is at 40

 

The answer is going to be more than 42 - probably around 47 if my back of a fag box maths is close

 

As a result efficiency of the boiler drops from 93% to 91% a difference of 2% all because one rad was providing the easiest path back to the boiler

 

Those rads with very narrow differences between flow and return are my concerns in your circuit - as I've said before Water is inherently lazy it will always find the easiest path to get back to the boiler

[marshian]

@Dee Have you got an ABV in the CH system or do you run a couple of rads with no TRV intervention?

 

I was just thinking that if you do have an ABV if it's set a little too free that could also

 

1. drive up the return temp

2. Lower boiler efficiency

3. Cause furthest rads in the CH circuit to be cold

 

ABV - Automatic Bypass Valve

[Dee]

@marshian thankyou so much for such a comprehensive explainanatio some of which I actually understood! Appologies for the delay in replying but work got in the way. 

 

Boiler:        Flow 60    Rtn 50

 

                   Flow  Rtn             Rad

Bath1.          54     43                45

Bed3           56     45                44

Bed4.          38     54*              41

Kit1.             44     40                45

Kit2.            57      45                45

Loo.            45      52*             46

Hall.            40      55*             40.   No TRV

Landing.     54      40               43

Bed2.          54      51                50

Study          43      29               30 Cold

Bath2.         55      43               47

Bath3.         55      47               49

Bed1 A        49      39               39

        B.        57      46               46

        C.        54      46               44

Dining1       49      47               44  Castiron col

Dining2       52      47                ??  Castiron col

Lounge1      44      41                40  Cold

Lounge2     51       39               39  Cold

* = valves reversed

Pump set to 3

All column rads white

Bath2 and 3 chrome towel rails

All TRVs fully open

Hall has no TRV

Sorry, No idea about ABV. Where would it be?

 

Edited 19 hours ago by Dee
Spelling

[Dee]

I will keep re reading your brilliant explanation until I really understand ....clearly my lack of knowledge is why I can't get the absolute balance perfect! I eill persevere as average gas bill per month is hitting £160

[marshian]

15 minutes ago, Dee said:

@marshian thankyou so much for such a comprehensive explainanatio some of which I actually understood! Appologies for the delay in replying but work got in the way. 

 

Boiler:        Flow 60    Rtn 50

 

                   Flow  Rtn             Rad

Bath1.          54     43                45

Bed3           56     45                44

Bed4.          38     54*              41

Kit1.             44     40                45

Kit2.            57      45                45

Loo.            45      52*             46

Hall.            40      55*             40.   No TRV

Landing.     54      40               43

Bed2.          54      51                50

Study          43      29               30 Cold

Bath2.         55      43               47

Bath3.         55      47               49

Bed1 A        49      39               39

        B.        57      46               46

        C.        54      46               44

Dining1       49      47               44  Castiron col

Dining2       52      47                ??  Castiron col

Lounge1      44      41                40  Cold

Lounge2     51       39               39  Cold

* = valves reversed

Pump set to 3

All column rads white

Bath2 and 3 chrome towel rails

All TRVs fully open

Hall has no TRV

Sorry, No idea about ABV. Where would it be?

 

 

For following rads - close the lock shield 1/8 turn - recheck flow and return after 20 mins if no improvement (ie bigger gap between flow and return another 1/8 of turn on lock shield and recheck after 20 mins

Loo

Bed 2

Dining 1

Dining 2

 

When you've got the DT's better check the rads where you had an issue and especially those towel rails because they are too good 8 and 12 deg on a towel rail means they are either massive towel rails or they aren't getiing that much flow - closing the lockshields on the other rads could increase the flow and drive down the DT - they you will need to do the same with those TR's

 

ABV normally near the pump or could be in the boiler

[marshian]

ABV can look like this

 

 

What boiler do you have?

[marshian]

1 hour ago, marshian said:

What boiler do you have?

 

Baxi 400 Heat Only according to another thread - what kW rating is it?