does balancing increase efficiency?

[UpgradeME]

should point out that your pump should be on max and if anything is possibly undersized. Your particular boiler has a coil type heat exchanger with a high resistance and as such requires a decent size pumpto prevent any issues.

Hi Micky,

Looking through the Vaillant manual, the ecoTEC 418 requires a min flow rate of 12.9 litres per minute (or 0.77 m3/h). The water pressure loss (metres head of water) is 1.38m at 773.86 litres per hour (0.77 m3/h) (see pic).

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• UpgradeME
• 13 Mar 2011
• 1

I have around 4m head between the F&E and boiler, the pump sits roughly in the middle @ 2m. Looking at the Grundfos specs (see pic), if I use the lowest figure (2m), the pump delivers the following flow rates:

Speed I = 0.9 m3/h
Speed II = 1.6 m3/h
Speed III = 2.1 m3/h

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• UpgradeME
• 13 Mar 2011
• 1

As the boiler requires 0.77 m3/h, Speed I looks to be a bit of a push but II & III both look to give acceptable flow!?

If I'm getting this all wrong (very possible lol), I'd really appreciate if anyone could point out my errors!!

P.s. I realise that I've not accounted for the resistance in the 28mm copper pipe between pump and boiler... is there a way to calculate that?

 

[UpgradeME]

2) I changed the pump speed to II (middle setting)

Pump must be on 3

Why? - As long as I have enough flow through the boiler (12l/min which I should get via the ABV settings) doesn't a lower pump setting give me a greater drop in return temp to the boiler? (or am I missing something here?)

Because that's what the book says.

Which book?? (See my post above) - If it should be on III, I don't have a problem with it, I just want to understand the reasons!

 

[bengasman]

Because that's what the book says.

Which book?? (See my post above) - If it should be on III, I don't have a problem with it, I just want to understand the reasons!

M.I.

 

[UpgradeME]

Because that's what the book says.

Which book?? (See my post above) - If it should be on III, I don't have a problem with it, I just want to understand the reasons!

M.I.

Which Manufacturers Instructions would they be bengasman??? - I've read the Vaillant Installation manual and used what I thought were the relevant figures above.

The Grundfos Installation Instructions can be found here as quoted from above to give flow rates. In there it says

"The best speed setting is the lowest setting which gives adequate circulation around the system with the correct flow/return differential temperatures, as specified by the boiler manufacturer. Uneven heat distribution may indicate that balancing of the flow is required to each radiator."

Could you show/tell me where I missed it?

Thanks.

 

[mickyg]

manuals and calculations are all well and good but experience is more valuable. Trust me, I've worked on 100s if not 1000s of these boilers and a 15/50 on an 18kw wants to be on max.

 

[UpgradeME]

manuals and calculations are all well and good but experience is more valuable. Trust me, I've worked on 100s if not 1000s of these boilers and a 15/50 on an 18kw wants to be on max.

I agree, experience is a very valuable asset! - What would the symptoms be for too low a setting?

 

[mickyg]

manuals and calculations are all well and good but experience is more valuable. Trust me, I've worked on 100s if not 1000s of these boilers and a 15/50 on an 18kw wants to be on max.

I agree, experience is a very valuable asset! - What would the symptoms be for too low a setting?

intermittent S53 error codes, poor circulation, boiler modulating oddly erratically, inability to balance system correctly. Not to mention its not particularly healthy for the heat exchanger

 

[UpgradeME]

manuals and calculations are all well and good but experience is more valuable. Trust me, I've worked on 100s if not 1000s of these boilers and a 15/50 on an 18kw wants to be on max.

I agree, experience is a very valuable asset! - What would the symptoms be for too low a setting?

intermittent S53 error codes, poor circulation, boiler modulating oddly erratically, inability to balance system correctly. Not to mention its not particularly healthy for the heat exchanger

Thanks Micky. I'll watch out for those whilst optimising the setup. If it makes a difference, I've range rated the boiler to 12kW (the Rad + cylinder output) via d.0 and as far as I can tell, don't have the above symptoms with speed set at II.

Once fully balanced, I'll compare the d.41 figures when the pump is set at II & III to see how much difference it makes to return temp at the boiler.

 

[mickyg]

at 12kw you'll be ok at speed 2.

 

[D_Hailsham]

P.s. I realise that I've not accounted for the resistance in the 28mm copper pipe between pump and boiler... is there a way to calculate that?

These may help:

Small Bore Heating Systems

Copper Tubes in Domestic Heating Systems

 

[ajrobb]

Given that the 415 has a lower design flow than the 418, if the 418 requires 12.9 l/min at 18 kW, can it be throttled back to 8.6 l/min at d.0 setting of 12 kW? Otherwise the temperature rise won't exceed 13 °C.

 

[ironman1]

While all this info may be 'interesting' , i've never found anything more accurate than my HAND when balancing radiators.

Little tip...................when using Drayton TR4s balancing is almost a non issue. ...CAUTION..only use these on a CLEAN system. .........not advised to use these TRVs where output of radiator is above 8,000 BTUs.

 

[UpgradeME]

Given that the 415 has a lower design flow than the 418, if the 418 requires 12.9 l/min at 18 kW, can it be throttled back to 8.6 l/min at d.0 setting of 12 kW? Otherwise the temperature rise won't exceed 13 °C.

Looking at the 415 figures, it's max output is 15.3 kW and a min flow rate of 10.8 L/min. The designed 20C drop at 12kW is with a flow rate of 646 L/hr. As the 415 and 418 are so similar, I agree that if the 418 is rated (via d.0) to 12kW I would need a flow rate of 646L/h or 0.65 m3/h.

I've now measured the vertical drop between boiler and pump which is 2.4m. If I look at the Grundfos specs, a 2.4m head gives the following flow rates to the boiler:

Speed I = 0.75 m3/h
Speed II = 1.5 m3/h
Speed III = 2 m3/h

Does this mean the best setting to acheive the biggest drop at the boiler would be Speed I, giving 0.75m3/h or 12.5 L/min flow @ 12kW?

12.5 is slightly lower than the 12.9 minimum flow of water listed in the Vaillant manual, however, would that 12.9L/min be for it's 18.9kW output?

@ajrobb - How do I calculate the maximum tempature rise from those figures? I'm not sure how you calculated the 8.6 l/min or the 13C rise?

 

[UpgradeME]

While all this info may be 'interesting' , i've never found anything more accurate than my HAND when balancing radiators.

Little tip...................when using Drayton TR4s balancing is almost a non issue. ...CAUTION..only use these on a CLEAN system.

As you have probably gathered, I'm from a technical background and like the detail! - I know the experienced will use their hands, maybe after I've balanced it 'technically' I can learn/feel the difference with my hand and remember should I need to do it again!

I do have Drayton TRV4s fitted, I had fogotten that they can also be adjusted and know they are set to default values (I fitted them).... However, could you explain why balancing is a non-issue with TRV4's?

 

[ironman1]

[
However, could you explain why balancing is a non-issue with TRV4's?

Take a look @ the size of orrifice @ valve entry. , hence the reason for not using these type valves on certain size radiators ' ever wondered why temperature differential is an issue when fitting these type valves on larger radiators? , tube has it's limits of what can be 'pushed' through it , take a radiator with a 18,000 btu heat load , will require 15mm full bore tube to satisfy demand , this is the reason the Drayton won't cut it , pretty much self balancing when used on smaller radiators , same for 22mm tube , has a max rating for 42.000 btu , but still you see systems that require 70.000 heat load being piped in 22mm.

I would take a bet my 'hand' does just as good a job as anything else you're using , quicker too.