Radiator Heats Only Halfway: Top Warm, Bottom Cold - Thermostat & Return Pipe Solutions

Question

Hello. As in the topic, the radiator only heats up to half, i.e. the top heats and the bottom is cold. The return pipe is also cold. A thermoregulator is installed on the supply pipe. All radiators in the whole apartment heat up the entire apartment, but in one room it only heats up to half. I am asking for some advice because there are already quite severe frosts and the room is cold. I attach photos of the radiator. The installation is airless.

k0s10r · Accepted Answer

If it was air-tight, it would not heat up all or from half to the side of the vent. and my colleague does not heat in from the middle down, as my colleague saskia wrote too little water he gets.

piotrkk · Accepted Answer

Pull the thermostatic head itself off the valve, as a rule, it is screwed onto the valve. The head is responsible for closing and opening the valve itself. Maybe there is something wrong with her and not working properly. Curtains also do their job, if you cover the thermostatic valve, the head closes the flow and the effect is just like you have. If you take the heads off, move the protruding pin in the form of a sticking rod about 2mm towards you and away from you to facilitate or move it. The heater typically has too little flow (it can also be the farthest radiator) and there is no air in it. Check how it works without a head and let me know. Greetings Peter

EkoGrzew · Accepted Answer

ooh ... I'm starting to fear if you can handle it.
First of all, disconnect the pump from the electricity supply.
Close both valves with the red handle below the pump and above. at the bottom between the pump and the valve is this brass oblique filter. unscrew the plug at the end of this end. be careful water drips. remove the mesh inside and clean it. then proceed in reverse order. start the pump as soon as you are sure that you open the valves.
good luck.

EkoGrzew · Accepted Answer

Unscrew the valves first the bottom then the top

EkoGrzew · Accepted Answer

at this time, turn off those radiators and let only this one heat up. it doesn't hurt Added after 24 : at most, more f ... s for the filter will go

EkoGrzew · Accepted Answer

As I read it, it still occurred to me that you have swapped the power supply back, but it's probably impossible because the installation is still intact. only the heater replaced. also clogs on the return. gently tap on the return near the heater. the worst-case dirt will stay on the filter, so you'll just clean it again or twice. you already know how to do it I wish warmth

claddagh ring · Answer

First of all - vent at the valve built into the radiator.
Second - one of the valves (inlet or outlet) may need to be replaced.
Third - you may need to unplug the heater and drain the water - sediment may have accumulated at the bottom of the system and you should rinse the water several times.

wojtik4444 · Answer

The heater was vented several times with no effect. Maybe something is wrong with this thermoregulator? There is a circulation pump next to the stove and regardless of whether it is on 1 or 3, the effect is the same - only half of it heats up. I doubt that there is sediment on the bottom because the heater is only in the third heating season.

claddagh ring · Answer

The drain tube may be cold as there is poor flow and the water is releasing heat from the radiator. A circulation pump, if not diesel, it's cold all over the cottage

Valve replacement - low cost and approximately 10 minutes of work.

Added after 1 [minutes]:

And one more thing - what is the pressure in the system?

wojtik4444 · Answer

Even if the pump is not working, the radiators are still warm . How can this pressure be checked? : p

claddagh ring · Answer

There is a timer on the boiler. The radiators are warm after the pump has pumped hot water into them. Then the pump goes off until the thermostat wakes it up again. If the pump does not work at all, the radiators are cold.

Cowboy zagrabie · Answer

And this radiator is not accidentally dropped on the right side? This is how it looks to me in the middle photo. The side to the valve should be slightly higher.

saskia · Answer

Too small passage on the valve (orifice), or it is the farthest (last) radiator in the circuit and the boiler switches off (return temperature from other radiators) before it heats up.
If the pump is circulating, the slight air lock caused by tilting the radiator in the wrong direction should not make such a difference.

EkoGrzew · Answer

wojtik4444.
You say that the heaters are in the third season ... Do you have a filter-filter or any other filtering device installed on the boiler room return? it's once. Now, to find out what's going on, just do one thing:
Turn off all the heaters you have at home, leave the problematic one open (actually remove the heads as your friend advises here) in the boiler room on the central heating pump, put the highest level of overrun (3 usually) and let the boiler heat up during this time. (and at what level of the rundown is it currently set?) how do you do it, check how the radiator behaves. and describe it.
greetings
radoslav

wojtik4444 · Answer

I don't know if it's this boiler because there are two. One is connected to the furnace horizontally and there is no indicator there, but there is one more vertical and it shows 300 kPa at least. So the radiator is lowered on the right side and the left side is higher on this occasion that there is a vent. I just thought that I should take this head off, but I'm afraid that something will break off right now how does this plastic pull? There are no filters, because this installation is over 25 years old and also has an old structure I'll try to turn these radiators off as you advise The pump is constantly running in top gear (i.e. 3). Just advise me how to remove this plastic from the thermoregulator?

EkoGrzew · Answer

now it turns out that the installation is 25 years ... and the radiators are for the third season ...
you have to wash it .. but after the season maintenance is necessary - rinsing the installation. and installation of the filter on the return from the installation (larger than the central heating pump wheel) and check in general - clean the oblique filter at the central heating pump
and as for the head, it's not any plastic, just set it on a five and unscrew (it can be possible by hand) this hexagonal nut at the head.
and do what I wrote above.
greetings

wojtik4444 · Answer

and when I unscrew this cap, nothing will start to drip?

Added after 11 [minutes]:

I unscrewed this thermoregulator and I have this view

and I was moving this tiny pin back and forth

we'll see if it helps. And behind the spindle there is a nut with some numbers only in the picture are invisible. What are these numbers on this cap for?

EkoGrzew · Answer

leave the rest alone and do what I wrote about above Added after 1 [minutes]: these are the hydraulic settings of the valve

wojtik4444 · Answer

so far I was moving this mandrel and I was just burning in the furnace. Napal up to 70 degrees and wait a moment. Oh, so you'd better not touch it because you can still adjust something

EkoGrzew · Answer

do you smoke already ?? And you checked the skew filter at the pump ????? work for the railroad. Then light up, turn the heaters off without that one, set the pump to 3 and see the radiator.

wojtik4444 · Answer

and how does this filter look like? Added after 5 [minutes]: Because I don't know where he is. I enclose a photo of the pump circuit in the boiler room

wojtik4444 · Answer

Thanks now I have to wait for the temperature to drop before we can start working; D

wojtik4444 · Answer

ok thanks i will remember

wojtik4444 · Answer

I cleaned this filter (it was a bit of shit in a minute, as if someone poured oil there) . The pump turned on, the heater got a little warmer downstairs but still lukewarm. I vented it upstairs and nothing. So I turned it on and unscrewed it at the bottom under the vent and a little cold water (about 4 liters) flew and then I unscrewed the butterfly from the return and, surprisingly, the tube started to be hot at the bottom but when I turned the radiator on the back, it started to be colder and it is lukewarm again.

EkoGrzew · Answer

did you turn off the other radiators during this time? Added after 42 : lukewarm is not cold anymore

wojtik4444 · Answer

i.e. I only turned 2 because the rest do not have these thermoregulators, i.e. kitchen, 2 rooms and bathroom do not have it

qusha · Answer

Hello. I have a similar problem
I have had heaters in my new single-family house for 3 years. This season, however, some heaters only heat up to 50% of the surface, i.e. where there is a hot water inlet, the circulation pump runs at maximum speed, temperature in the water in the boiler 75 degrees 24 hours a day. I have PurmoVentil compact heaters with bottom feed from one-right side. The heaters were vented and filled with water by an experienced plumber. The larger heaters have the desired temperature on almost the entire surface, and the smaller ones, especially only half or less, ie the left side does not heat up. I have a flow regulator that is fully unscrewed. Heating is NOT gravity.
What's the cause! ???

szymonjasiu · Answer

It is possible that the radiator is connected inversely.
Check the tubes under the heater. The hotter one should be the one closer to the center of the radiator (power supply), and the one closer to the edge of the radiator should be cooler.

zybie · Answer

Start by cleaning the filter as previously described.

Radiator Heats Only Halfway: Top Warm, Bottom Cold - Thermostat & Return Pipe Solutions

How do I fix a radiator that only heats the top half while the bottom and return pipe stay cold, even after venting it and with a thermostatic valve on the supply pipe?

Topic summary

FAQ

Quick Facts

Why is my radiator hot at the top but cold at the bottom?

How do I know if air or sludge is the problem?

What quick test confirms poor flow?

How do I clean the oblique (slanted) filter near the pump?

Will removing the thermostatic head cause leaks?

How can I free a stuck valve pin?

What lockshield setting balances flow?

Could reversed supply and return pipes cause half-heating?

Should I drain the system after every heating season?

What additives prevent future sludge?

Why do radiators stay warm even when the pump is off?

How much energy can sludge waste?