Just had new boiler fitted - Flow and Return swapped :(

[Murf520970]

Cant see what difference what side the lockshield valve is on as regarding balancing of the system, your only restricting flow through the rad to balance the flow to the other rads.

picasso i thought trvs on the return cause issues ? to balance it properly whilst correctly controling the heat emitted from the rad requires the trv to be fitted on the flow ? if its on the return are you saying you throttle down the lock sheild on the flow & use the trv as normal to balance it ? i thought its flow valve fully open & return valve open slightly ? how do you do that with a trv opening & closing on the return ? , if so fair doos mate & ive learnt something today but every system ive looked at with that set ups been an issue

 

[SkipFeeney]

Cant see what difference what side the lockshield valve is on as regarding balancing of the system, your only restricting flow through the rad to balance the flow to the other rads.

picasso im not bothered if im barking up the wring tree & look a tit here but i thought trvs on the return cause issues ? to balance it properly whilst correctly controling the heat emitted from the rad requires the trv to be fitted on the flow ? if its on the return are you saying you throttle down the lock sheild on the flow & use the trv as normal to balance it , if so fair doos mate & ive learnt something today

This is my thoughts too, so am i wrong? If i follow the FAQ then the last step is:

Replace TRV heads and set to required temperature

As the TRV is now on the return, if i set the TRV to 3 I am throttling the flow back to the return and the radiator will still be as hot??

 

[Murf520970]

i will give you my experiences with this , i went to a house & the complaint was all rooms roasting hot , they had turned the trvs down to no 1 , in a sense balancing the system because the locksheils on the flow are wide open & the trvs are now turned down so each room got red hot ? how can that be correct . Trvs on the flow turn them down , room gets cooler

 

[Agile]

I am surprised that there seems to be so much misunderstanding of the effects of which end a TRV is fitted.

Also that so many installers still think that somehow a system with TRVs does not bed balancing.

It is obvious to me that a TRV on the cooler end of a rad will better sense the room temperature. But at least one manufacturer does not agree with that.

Tony

 

[picasso]

The lock shield valve is to even out the flow to each rad, the trv is simply closing off the flow (of water) as the room heats up, the best way I can think to putting it is your saying that you will only allow x flow out of the rad and I am saying I will only allow x flow into the rad, its just flow through a rad with a trv to adjust the flow with temp, if that makes sense.

 

[Gasguru]

Normally in a domestic property the TRV does NOT balance the system. The lockshield on the other end of the radiator is used to balance the flow.

Unfortunately many installers are lazy and incompetent and do not understand this simple process.

Take all TRV heads off or set them to maximum. Then balance the system with the lockshields. Providing the pipe and pump are sized correctly it's a very simple process. For flats and small houses it takes no more than half an hour. For large houses perhaps with 20 or 25 rads it may take 2 or 3 rounds of adjustment starting from cold each time.

If you don't balance a system rooms may take a considerable time to heat up (or not at all), and the boiler will short cycle wasting gas and wearing itself out.

It is normal to find a radiator in the zone where the room thermostat is located. This rad should have 2 lockshields fitted to prevent user operation. It must be balanced along with the other rads. However, it will also need adjusting to ensure the zone does not heat up too quick/slow so the room stat does not shut down the boiler too soon/late before the rest of the home is up to temp. Unfortunately it is also very common to find a TRV on this radiator which will clash with the room stat operation. 30years of best practice and numerous trade magazine articles are no substitute for intelligent installers.

Occasionally you find the lockshields fully open but the system is has been balanced using the TRVs. Some TRVs can be preset to give a maximum flow regardless of the temperature setting....they have an adjustment on the valve stem assembly.

 

[D_Hailsham]

i will give you my experiences with this , i went to a house & the complaint was all rooms roasting hot , they had turned the trvs down to no 1 , in a sense balancing the system because the locksheilds on the flow are wide open & the trvs are now turned down so each room got red hot ? how can that be correct . Trvs on the flow turn them down , room gets cooler

If that was the case, the system had never been balanced. Presumably the installer was one of those misguided souls who think that you don't need to balance a system with TRVs as they will automatically balance the system.

The lock shield valve is to even out the flow to each rad

Nor strictly true. The LS ensures that each rad gets the correct flow when the TRV is fully open. The flow will depend on the size of rad;a 2kw rad will require twice the flow of a 1kW, assuming the temp drop across each rad is the same.

As the TRV is now on the return, if i set the TRV to 3 I am throttling the flow back to the return and the radiator will still be as hot??

What on earth does that mean? Flow back to the return?? I'm lost for words.

 

[SkipFeeney]

Sorry.. I think what i am trying to say is that when the TRV is on the flow side and the TRV reaches its set temperature then the flow of water to the radiator is restricted thus cooling the room down.

If the TRV is on the return side then the water to the radiator (via the flow) is not restricted, it is still coming through at the same rate - so how does this cause the temperature of that room to drop and the radiator "closed off"? All that i can think is happening now, is that the TRV is restricting the flow of water going into the return?

I may have this wrong, i am only a DIYer I thought that the water gets pumped through the flow side, then circulates around the radiator then out the return side back to the boiler.

 

[mogget]

Water is (very nearly) not compressible. So if you block the return, no more can come in the flow. Thus the radiator cools down.

 

[picasso]

The lock shield valve is to even out the flow to each rad

Nor strictly true. The LS ensures that each rad gets the correct flow when the TRV is fully open. The flow will depend on the size of rad;a 2kw rad will require twice the flow of a 1kW, assuming the temp drop across each rad is the same.

Your a pedantic soul did you really think I meant the same flow to each rad no matter how big it is ? 300 single to a 2 metre double

 

[EFLImpudence]

Sorry.. I think what i am trying to say is that when the TRV is on the flow side and the TRV reaches its set temperature then the flow of water to the radiator is restricted thus cooling the room down.

Yes.

If the TRV is on the return side then the water to the radiator (via the flow) is not restricted, it is still coming through at the same rate

Where do think it is going?

- so how does this cause the temperature of that room to drop and the radiator "closed off"? All that i can think is happening now, is that the TRV is restricting the flow of water going into the return?

Yes - so, what happens then on the flow side?

I may have this wrong, i am only a DIYer I thought that the water gets pumped through the flow side, then circulates around the radiator then out the return side back to the boiler.

So, what happens when you close the return side?

When using a garden hose, what happens if you turn off the tap on the wall?
What happens when you turn off the hand-held valve on the end of the hose?

 

[SkipFeeney]

Yes - so, what happens then on the flow side?

I wrongly thought that the water would circulate around the radiator then go back down the flow thus the radiator will always have a supply of newly heated water coming into it. Live and Learn!

From moggets response i now know what happens:

Water is (very nearly) not compressible. So if you block the return, no more can come in the flow. Thus the radiator cools down.

Thanks for all your help.

 

[D_Hailsham]

The lock shield valve is to even out the flow to each rad

Nor strictly true. The LS ensures that each rad gets the correct flow when the TRV is fully open. The flow will depend on the size of rad;a 2kw rad will require twice the flow of a 1kW, assuming the temp drop across each rad is the same.

Your a pedantic soul did you really think I meant the same flow to each rad no matter how big it is ?

Of course not, but some less knowledgeable readers might think that "even out" meant getting the flows approximately the same.