That old chesnut balancing radiators?

[FlyingBrick]

Having had a new boiler installed and looked up the information on balancing the radiators in the house could somebody explain to a beginner why you balance them up with all thermostatic valves on max? i.e. My Westherm on position 5.

I understand the balancing of the system for the required temp drop on the outlet and the bypass valve adjustment but I never have my thermostats at full blast in the house. Around one third of my rads are set to position 2 on the Westtherm. Only the main living room is set to 4 out of 5 and two rooms not used are on tick over at 1.

So as this is my normal running set up for many years in the house why would you not adjust the balance of the rads with these actual real live settings? Many thanks for your patience as I am not a CH plumber. Open vent condenser boiler runs at around 72*C and return is around 52*C at plus 6*C outside temp.

 

[shambolic]

Because all things being equal and all that.
Have a proper think about it and how TRVs actually work then if need be come back to us.

 

[Diyisfun]

Because all things being equal and all that.
Have a proper think about it and how TRVs actually work then if need be come back to us.

Why cant you just answer the question....OR is it boiler related....Drrrrr

 

[shambolic]

No but logically do YOU know how a TRV works?
It will open and close depending on room temperature so that's a variable factor that you actually don't control due to ambient temperature etc.
So when setting up the best you can do is have them all open full ( if room temp warm then some may be closing a bit but let's assume they are all cold).
This ensures the flow through the flow and return is the same on all rads but we know closer ones heat up sooner.
So the factor you can change that won't automatically alter due to temp is the lock shield valve to slow the water speed through the rad.
You do know typing " how to balance radiators in a central heating system" into a search engine would be quicker than registering and coming on here to ask.
Now I've wasted another 5 minutes of my day.
Hope the explanation helps the OP but I really despair

 

[shambolic]

Because all things being equal and all that.
Have a proper think about it and how TRVs actually work then if need be come back to us.

Why cant you just answer the question....OR is it boiler related....Drrrrr

Ps who asked you? Why don't you tell him?

 

[FlyingBrick]

Apologies for asking the question.

But having had a gas safe engineer install the boiler and not balance up the system or set the bypass valve I was trying to understand how it all works.
My thoughts were that if the thermostatic valves were set at a position lower than full on then the valve would never be at full flow as the valve would be held at that specific flow level. When I get home from work then the temp of the house would be the same in all rooms at start up. so the bypass flow would be different than having all the valves fully open.
Yes some of us aren't all geniuses. Sadly I am not even close to that but I help out with bikers asking simple technical questions because we all have to start somewhere in life.
I can rebuild gearboxes and tune engines plus repair most electrical devices, but cannot be clever at everything.
I don't despair when the same technical question comes up over and over again with members using our forum but answer as well as I can.

So I personally apologise to shambolic for wasting 5 min of his time.

 

[snes]

Instead of a (perceived) sarky apology, why not just hit the "Thanks" button.

Remember, he is a pro, helping others for free.

 

[shambolic]

@flyingsparks if you try to set the flow through the lock shield when the TRVs are all at different flows then when these flows automatically change then your lock shield won't know this so your settings will all be out.
That's why you do it with TRVs open full.

 

[D_Hailsham]

But having had a gas safe engineer install the boiler and not balance up the system or set the bypass valve I was trying to understand how it all works.

There are some installers who believe that a system with TRVs is self-balancing, but I've never heard of one who thinks bypass valves are self-adjusting. I do hope it was an automatic bypass and not just a gate valve.

My thoughts were that if the thermostatic valves were set at a position lower than full on then the valve would never be at full flow as the valve would be held at that specific flow level.

Unfortunately you appear not to understand how a TRV works. When the room is cold (more than 2°C below required temperature) the TRV is fully open. As the room approaches the required temperature the valve start to close down, reducing the flow rate through the rad, until the flow is just enough to maintain the set temperature. If the room gets too hot (people, TVs, sun etc) the TRV continues to close down until it will be fully closed at 2°C above the set temperature.

The purpose of balancing is to set the maximum flow through each rad and ensure that all rads get their required share of the total flow. You therefore have to be certain that the TRV is not varying the flow while you balance. Removing the TRV head is safest.

 

[FlyingBrick]

Thanks D-Hailsham

Next week will take off the TRV heads to make sure nothing is pressing down on the valve spindles. Have 14 rads to set up as the original bypass valve was seized and not changed. There is now a Danfoss AVDO ABV installed in the bypass pipe as the engineer had not replaced this or balanced the system before Christmas when it was installed. The boiler was fluctuating up and down then turning itself of two to three times at warm up.

 

[Agile]

I would say that you should be getting your installer to set the ABV and balance the rads.

Hopefully now you will see why the TRVs all need to be open while balancing. But is that not explained in the FAQ on this site?

Tony

 

[mogget]

Assume you turn the heating on from cold, all the TRV's will be open, assuming you're heating all rooms. So you balance the system with the TRV's open.

The auto bypass should open to maintain the minimum flow through the boiler as the TRV's close, and for pump overrun if its an S-plan system. Modulating pumps and bypass valves don't play too well together. To advise on a setting we'd need to know model of boiler and pump if separate.

Disclaimer, I'm a diyer not a pro.

 

[Agile]

I would be more positive and say that generally a smart pump ( in smart mode! ) is incompatible with an ABV.

But then most smart pumps I see are being used in the manual mode anyway!

Tony