how do i know which is which?

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Hi i had a new system boiler and tank fitted a couple of years ago with an eye to an extension i was planning. I had the supply and return pipes to the future extension radiators terminated with gate valves(22mm pipe) under the floor. I plan to run in the two radiators for the extension myself so heres my question.

How do i find out which is radiator supply and which is return?

Also should i run in a single copper supply(10MM) pipe from the supply gate valve to close to the radiators and T off to both thermostats from there or run in two seperate pipes from the gate valve to each radiator(same question for the return pipe).

At the moment i can only see me putting the heating on and see which gate valve is hotter to decide which is supply and which is return.

Thanks for any help.
 
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Why should it make any difference which is flow and which return? As for pipe size, that depends on the size of the rads and the length of the run, but 10mm may be adequate for both.
 
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Its always better to fit TRVs on the flow.

The flow is always the hotter of the two.

Tony
 
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Why should it be better to fit TRVs on the flow? I would have thought that if anything the return would be better because there would be less heat from the valve body affecting the sensor head.
 
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With agile on this...Chris do you honestly think a trv is not designed to take into account water passing through it at 80 odd degrees . On proper designed system lockshield should always be on the return
 
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Ok thanks guys so if if follow this correctly i should run the heating for a while and see which of the gate valves/pipe sections are hotter to the touch. This will indicate hot water supply from the boiler, run 2 10 mm lines T'd off close to the 22mm pipe/gate valve, run these two line to the radiators, these two lines will have the thermostatic control valves on them and then connect the isolation valves to the return side of the radiator run the return lines from the 2 radiators back to the return gate valve T them in bled and voila an extended system!

The run from the gate valves(22mm pipe) to the radiators is approx 20 feet. Thanks for any help. I assumed that it mattered which way i hook the pipes up as the return line which the rest of the system is hooked to would be cooler since that water has radiated a percentage of its heat to air through the panels? Again i am trying to find my way through and am open to any suggestions.
 
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With agile on this...Chris do you honestly think a trv is not designed to take into account water passing through it at 80 odd degrees . On proper designed system lockshield should always be on the return
TRVs should operate reasonably accurately over the full range of flow and return temperatures (not just 80°C), but the UK practice of mounting them vertically so that the sensing head is immediately above the valve body and pipework (as opposed to normal European practice of having the head sticking out horizontally) means that the temperature sensed by the head will be higher than ambient. Mounting on the return will slightly reduce this effect.
 
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the UK practice of mounting them vertically so that the sensing head is immediately above the valve body and pipework (as opposed to normal European practice of having the head sticking out horizontally) means that the temperature sensed by the head will be higher than ambient. Mounting on the return will slightly reduce this effect.

With modern bi-directional TRVs you can have them horizontal or vertical on the flow or the return.

In theory the sensor should be horizontal as it senses the air flow better.


But then, in theory the flow should be connected to the top of the radiator and the return to the bottom, or your rad output will be down about 2% :!:
 
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Your making it more difficult than it is.Get your rads and hang them up,get your valves on and run your pipework to the rads t off for your trv then for your l/shield carry on to rad 2 and connect into valves ,and trvs why make bi/directional if there not doing the job properley, cant be just to make sure they dont chatter
 
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Personally i would use 15mm unless you are running 2 small rads.but thats a personal dislike of smaller pipework

Someone do a sketch as it allways helps to see a diagram(i would but dont know how to)
 
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