# understanding 'balancing the system'

#### markyyyyyy

Hi,

It is my understanding that the hot water from the boiler (flow) enters the TRV valve side of the radiator, and continues to all other radiators in the system, entering the TRV valve side, through the flow pipes.

Once it is spread through the radiator, this water (slightly cooler) returns to the boiler via the return pipe, which is the side of radiator where the lockshield is, and the flow pipework is connected to all lockshield ends on the system.

In order to balance the system, you need to adjust the lockshield side of the radiator - this is the part that confuses me.

if the water enters the TRV side of the radiator, how is restricting the flow at the lockshield end going to effect the water that goes into that radiator if it enters via the TRV side?

how is restricting the flow at the lockshield end going to effect the water that goes into that radiator

The water flowing out of the radiator through the lockshield has to be the same volume and flow rate as the water flowing into the radiator via the TRV

ahh i see, so effectively by adjusting the lockshield valve you're effectively controlling the flow into the radiator?

Thanks!

Worth noting, newer generation TRV's can be Bi directional, (i.e. can be fitted on flow or return), the older ones couldn't, and some cheaper ones shouldn't be! (My Girlfriend has a system that howls due to cheap and nasty TRV's, despite telling her Landlord, it took the neighbour to complain before he believed her!)

Otherwise yes, Lockshield is set by the installer to limit the flow through the Radiator, and prevent the first Rads on the system robbing the lions share of the flow, whilst those at the far end remain cold due to lack of flow.

The water flowing out of the radiator through the lockshield has to be the same volume and flow rate as the water flowing into the radiator via the TRV

Is it possible to have otherwise?
Like 3 liters per minute flowing in and 4 out? Or will the flow in and flow out always be equal?

Or alternatively could you have 4 lpm in and 3 out?

Where would the extra 1 lpm come from or go to?

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