Cold rads?

[joesoap13]

Hi Guys, need a bit of advice please.
I have two old rads that are not getting hot, barely warm.
I flushed one ages ago, Black,no change.
I suspected crud, but just drained the other one, and the water is crystal clear, could drink it!
Was going to flush it, but didn’t bother .
Can I just change the body of the trv, using the existing nuts on rad and pipe,as the trv gets hot, but not beyond it!
That seems the obvious problem, even though the pin is ok, springs back.
Means draining system.!
Theirs inhibitor in the system.

 

[picasso]

Might be a weak pump or balancing issue, try turning all the rads off except one of the problem rads and see if it heats up, post back what happens.

 

[joesoap13]

Hi Picasso, thanks for reply
I have got all rads off except the problem one and a small one in bathroom which gets red hot, for comparison,but problem rad still not getting hot.
I did the same the other day, to eliminate balance problem, although I have just rebalanced them again,rad got warmer, but not hot.
The pipe to the trv is red hot, so is trv body, but not the rad ,top gets tepid, bottoms and elsewhere are cold.

 

[JohnD]

I have got all rads off except the problem one and a small one in bathroom

... all the rads off except one of the problem rads...

"all" includes the bathroom rad.

 

[picasso]

You sure the lockshield valve is fully open ?

 

[joesoap13]

"all" includes the bathroom rad.

Just turned rad in bathroom off.
Didn, t want boiler blowing off!
Boiler just shut down, rad still not getting hot.

 

[joesoap13]

Had to reset the boiler

 

[joesoap13]

Lock shield fully open?
bathroom rad on again as it just shuts boiler down?

 

[ericmark]

9 times out of 10 not the fault of radiator not working.
With no wall thermostat as each TRV closes the water is pushed with more vigour through those which are still open so poorly set lock shield valves only cause a delay in radiator getting hot.

However with a wall thermostat the boiler can be turned off before all rooms are heated. We need a wall thermostat to stop cycling, but should be in coolest ground floor room without an outside door or other heating. In real terms such a room rarely exists, so we use a compromise. But that compromise should not allow boiler to turn off until all rooms are heated.

So we should measure the temp in and temp out on each radiator with all TRV's wide open and set so all show same temp drop normally around 15 to 20 degrees C. But having thermometers to do this before rooms get too hot is not so easy.

So starting at closest to boiler the one most likely to heat up first, I turn off lock shield valve, allow to cool, then turn it on 1/4 turn at a time until feel warmth in supply side pipe, then move to next, once all done, then may need a little trimming, but 9 times out of 10 that cures it.

With mothers house I looked at target and current temperatures shown on the PC for all the wifi TRV heads and if current below target opened lock shield a bit, and if current above target closed lock shield a little once of course it had been running for some time, and once set rooms were within 1 degree of set temperature within 2 hours of boiler running.

When I was selling house, all electronic TRV heads were replaced with old wax, and the rooms still kept to temperatures set.

The big problem as I see it is TRV heads marked *123456 that is about as much use as chocolate fire guard, the user simply does not know if lock shield or TRV needs altering.

 

[joesoap13]

Turned bathroom off again, rad just warmer, but not hot.
So trv is letting water through, but why not hot as the incoming pipe trv is on ?
Been like it a while.
Hasn’t shut down again yet!

 

[denso13]

So starting at closest to boiler the one most likely to heat up first

The OP's radiator isn't heating properly with all the others shut off. Balancing or the thermostat has nothing to do with it.

 

[picasso]

The valve on the other side of rad (ie the lockshield valve)

 

[ericmark]

The OP's radiator isn't heating properly with all the others shut off. Balancing or the thermostat has nothing to do with it.

Good point, so next idea I have is bleed both pipes, so turn off TRV and bleed with lock shield open, then turn off lock shield and bleed with TRV open so both feed and return both bled, and in doing so you have also checked neither pipe blocked, needs to be done when heating not running.

 

[joesoap13]

Hi.

This is what I did this morning, as I suspected rad was blocked with gunk as top was tepid and the rest stone cold.
Bled rad again.
Drained rad,from trv side, water clear as a bell.
Disconnected both trv and lock shield from empty rad.
Took top on trv so it should be open,but no water as such coming out, just a tiny trickle.
Presume this is what bleeding the pipes is ?
Cold !
Opened lock shield and plenty coming out.
So, presumed the trv was/is blocked, but not totally.
Reconnected both pipes to rad

Strange this.still got me baffled.
Whilst messing with trv, give it a clout or two, messing with pin,put bit of oil on pin.
The rad filled, I did not hear it, until I saw water coming out of bleed valve !
How did the rad fill from trv if blocked ?

Lockield was still closed .
Yet won’t allow hot water in now ?

Shut all rads down, except small bathroom one, problem rad now “slightly “warmer, inlet pipe to trv very hot, exit pipe from lock-shield cold.
Shut bathrad, so only problem rad open, rad still only tepid, hardly any change.
Still no top on trv, pin up, and springing up/down ok when pushed.
Assumed trv is practically blocked, and can I change it just using existing nuts on rad and inlet pipe,
are threads the same, ?
Change new lock shield at the same time, even though it’s working ok.
Got new ones on another rad, and size looks similar !
Are they a standard sized body ?
Old ones are Honeywell, 26 years old at least, but, still have them on another rad, working ok
Got three rads with them on, two with same problems as above, other ok.
All other rads are ok, but different types of rad, and trv’s

 

[jackthom]

What size are the pipes to the TRV? If much smaller than 15mm a pipe blockage becomes more of a possibility and the TRV could be OK.

If you don’t have white carpets nearby and aren’t afraid of some water spillage you could put some towels down and very cautiously slacken off the pipe connection to the TRV to see if much water starts to squirt out. Then you might learn where the blockage is.

Take care not to release the pipe connection totally though.