Cool Twin Rad - on a Single Pipe System

[Beano1967]

Further to my previous tale from the River Bank

//www.diynot.com/forums/viewtopic.php?t=18782&highlight=A

I opted for a professional power flush and am now living in Central Heating and Hot water Paradise .... almost.

However, there has always been one particular Double Panel Radiator on circuit that never, never gets hot just warm. The Rads been flushed independantly and the pipe 'single pipe system' that runs under the rad is piping hot. The pipe into the TRV is 'piping hot'. The nearest portion of the Rad is hot'ish but fades to cool very rapidly over the radiator until; it exits via the lock shield cold?? Its Been bled, its been flushed so whats the problem? have discounted system balancing because the temperature in the single pipe below, before and after the Rad is piping

Cheers

 

[doitall]

Valve problem

questions are the valves tboe or boe, is the thermostatic valve for single pipe system, is the valve actually opening or is the pin stuck, and is the return fully open, what size pipe the main run and the branch into the rad, were injector or tounge tees used, or were sweep tees used,

that should for now

 

[Bahco]

the temperature in the single pipe below, before and after the Rad is piping

Earlier in your thread you say the water enters rad hot and exits cold and then in the qoute you say temp after rad is piping
As the water gives up some heat to the rad, it then leaves to heat the next one albeit a little cooler. The single pipe acts as flow and return.
Post back with your findings but you should find the exit will be approx 12 degrees cooler.

 

[Beano1967]

Many thanks for the responses. Here we go.

tboe or boe? sorry confused by this one.
The pin has been fully exercised (head off and manually exercised)
The pipe size on the run is 15mm, red hot, and tee'd off into the rad 15mm (I know not conventional).
TRV open MAX, lock shield Fully Open.
Yorkshire tee fittings intersecting the single pipe run to the rads.
Regarding the temperature. The Heat in the single pipe system running below the Rad is Red Hot. The spur off the tee into the TRV is piping hot but the spur from the Lock Shield back to the Tee on the single pipe system is cold.
Don't have clip on thermometers. But seems a lot less than 12 degrees.
All the other Rads on the circuit pipes to the TRVs Hot, from the Lock Shield Hot.

Hope these answer some questions.

 

[Bahco]

TBOE -Top ,bottom opposite ends. To help flow the hot water enters the top of rad and exits at the bottom.
Why not try changing the valves, maybe blocked as you have already flushed your rad

 

[doitall]

Is the yorkshire fitting brass or copper, and can you see the numer on it.

15mm pipe is ok, but as I first said the thermostatic valve should be for a one pipe system, it has a bigger hole for reference, which allows the water to enter the radiator without going straight passed, it should still work though which suggest one or the other valves is not fully open.

Is the ciruit pipe hot past the lockshield valve

 

[Beano1967]

Valves BOE.
The Y'fitting is copper.
Don't know if the TRV is Single Pipe Specific.
The return pipe from the Lock Shield (back to the single pipe run) is cold, as is the area of the rad next ot the lock shield.
Lock Shield is fully open.
TRV is set to MAX

 

[doitall]

Have you checked the pin on the valve isn't stuck.

 

[ChrisR]

R U sure the lockshield isn't stuck shut?

 

[Beano1967]

I've exercised the pin on the TRV, even put a different head on the TRV just in case the head was faulty. As for the Lock Shield, the spigot does rise and fall as you screw/unscrew it. However, it does leave a tiny amount of brass swarf on the surface each time its done. But I can onlt physically check it with the rad off and thats going to be a weekend job.

Is the general consensus its 'probably' a valve-related issue?

 

[PTH]

To find out if it is a valve problem - prepare for a bit of a mess, and I would suggest you do this with system fairly cool. Turn off both radiator valves, open the air vent, then open each valve in turn. You should get an idea of the flow rate through each valve from the amount of water coming out of the air vent. The lockshield should pass more than the TRV when fully open but both should make a reasonable mess on the wallpaper.

 

[doitall]

For the sake of £20 or less fit two new valves, preferably tboe, flow to the top that is.