Causes of the problem
Most often, “cold bottom” can be found in old radiators, but not only in them. If you install a bimetallic radiator, there is also a chance to detect such an ailment. There are quite a lot of reasons for the occurrence of a “cold bottom”, so you need to look at the main ones.
Human factor
A person can also become the direct cause of a non-heating radiator. And usually they are as follows:
- A riser that they simply forgot to turn on because “it was late and the plumbers were tired.”
- Closed valve of the automatic air vent system.
- Incorrect connection during installation.
- Child-closed three-way valve.
They can be solved by calling the appropriate support service, correctly connecting the battery (or bypass, see below), and carefully checking the taps.
Clogging
The most common reason for this phenomenon is clogged radiators. Here are other reasons why there is a strong temperature difference in the battery: low quality coolant and air getting inside.
This phenomenon can also be affected by the liquid inside the radiator, since it contains various solid particles. While the heating season is just beginning, excess elements may be present in the water, which makes its quality terrible.
If there is an individual heating circuit, then the water will not have such disadvantages.
Why can air affect the temperature at the top and bottom of the battery?
- Because special bacteria are involved that can only live in an environment saturated with oxygen.
- Such bacteria are also called anaerobic.
- Microorganisms themselves do not cause harm to the radiator.
- The damage is caused by their waste products, which settle at the bottom of the radiator as sediment.
Also, silt can settle at the bottom, which gets there from the entire heating main.
Another reason is the special design of the heat exchanger. Because of this, there are places in its shape where dirt accumulates.
Why doesn't half the battery heat up? Because it's clogged!
There are many reasons why the batteries are hot on top and cold on the bottom: the apartment is being renovated, and the craftsmen made mistakes during installation, the seal was broken due to work on the line. But the most common one is a blockage.
The coolant often contains impurities - sand, rusty flakes, remnants of gaskets and sealing rubber. Over time, sludge and deposits accumulate in batteries. As a result, they heat worse.
How to clean a clogged battery?
To do this you will have to remove it and wash it. Prepare a suitable location before starting work. It is better to do this in the bathroom or in the yard.
Procedure:
- Cover the surface of the bath with a thick cloth and install a protective mesh over the drain hole.
- Close the shut-off valves and disconnect the joints.
- Drain the liquid, remove the radiator, and transfer it to a work surface. Be careful not to get burned.
- Gently tap each section to remove any rusty residue.
- Pressure wash with a hose.
After this, reassemble in reverse order and reinstall.
Problems with shut-off valves
Shut-off valves can also affect the temperature difference at the top and bottom of the radiator. The function of this element is to shut off the working fluid.
What does the shut-off valve consist of? It consists of a ball valve, a cone valve and a thermal head.
- The bottom of the battery becomes cold if problems occur with the tap.
- You should pay attention to one small detail: all taps have an arrow that indicates the direction for the liquid so that it moves without causing breakdowns in the line.
- If the tap is initially installed incorrectly, then the position of the arrow can be any, it does not play any role. Thus, due to a broken faucet, the fluid does not circulate properly. Incorrect installation of fittings can also affect the temperature difference.
It is necessary to inspect the shut-off valves as a preventative measure. It happens that some of its types require a special valve position. Therefore, it will have to be reinstalled.
Bypass
The bypass is the same pipe that stands in front of the installed heating device. Everyone has one, it’s needed to bypass water past the battery. If installed incorrectly - too far from the radiator, or in line with the central riser, it does not allow water, which tends to travel along the shortest path, to circulate normally, heating the radiator sections. In this situation, they will either not heat at all or will be very bad. Check how your bypass is installed. Perhaps this is the direct reason why the batteries do not heat up
Lack of pressure
The circulation of fluid in the system may be disrupted if there is not enough pressure. This is another reason why the temperature at the bottom of the battery is lower than at the top. Therefore, you need to check if everything is normal with the pressure. In the USSR, batteries were made of cast iron.
Unlike today's models, in those days the passages were wider, which did not require much pressure.
The problem is that the pressure required for modern batteries is quite high, and the line is designed for old Soviet batteries, which cannot offer this pressure to users. Therefore, the working fluid cannot pass through the entire heat exchanger. However, the pressure may be insufficient not only because of the line.
- It happens that neighbors decide to experiment with heating.
- Among such experiments, we can highlight the connection of a heated floor, which takes water from centralized heating.
- Neighbors can also increase the volume of the heat exchanger and regulate their batteries.
- Therefore, a sufficient number of reasons for the temperature difference in the radiator come from neighbors. Moreover, connecting underfloor heating in apartment buildings and increasing the volume of the heat exchanger are prohibited by law.
- All of the above actions reduce the pressure in the line, which makes the bottom of the radiator cold.
You should be wary of “masters” who, having read the forums, advise installing shut-off valves on the bypass. You can't do that. If the authorities find out about such manipulations, they will have to bring everything back to the original fine and pay a fine. If the authorities find out about the installation of heated floors in an apartment building, they may even give a real deadline.
Basic malfunctions of heating systems and their elimination
Air jams
Air pockets occur in radiators and pipes and interfere with the normal circulation of water in the heating system. They appear for various reasons:
- violation of the technology for filling the system with water after the summer period;
- non-compliance with water deaeration regime;
- performing repairs with disassembling pipelines;
- failure to observe slopes when installing the heating system;
- air leakage through leaky joints.
To remove air from the system, use a Mayevsky valve installed on the radiator. You should open it, wait until the air comes out, the hissing stops, and the water begins to pour out calmly without bubbles. After this, the valve is closed. Don't forget to provide a container or towel to drain the water.
Old cast iron batteries do not have Mayevsky taps. The air is released without completely unscrewing the plugs at the ends of the radiators. It is better to entrust this operation to plumbers - if you unscrew the plug completely, you can flood the apartment.
In the cold season, the main thing is good heating. Unfortunately, not all houses in winter remain at a comfortable level.
This applies to both multi-apartment housing and the private sector. Why is this situation happening and what to do?
Not enough coolant speed
If the speed of movement of the working fluid is low, this will lead to its cooling.
The bottom of the battery will be especially cold. Why can water move slowly?
- At some point in the pipeline there is a narrow cross-section (most likely, the polypropylene pipes are poorly soldered).
- The liquid initially moves slowly (most likely due to insufficient power of the circulation pump or due to its breakdown, or if there is no circulation pump at all).
- Old pipes can accumulate deposits that impede the normal flow of fluid.
Flow extender
A typical problem for a two-pipe system. Is it possible to make any number of sections? It is possible, but the very last sections of the battery will not warm up. Cause? Water, like a person, looks for “where it’s easier” and follows the shortest path. In order to “teach order” to the lazy one - water, a flow extender is required. Factory-made, or made independently from a piece of pipe. By directing the fluid to the middle of the structure, it will force the flow to circulate correctly, reaching the farthest ends of the heat exchanger.
Interesting fact: the same problem can be solved by connecting the heating device “diagonally”. But this is rarely used, due to the lack of aesthetics of this solution on ready-made systems.
Cold
The radiator may have a cold bottom if it is installed in a room with low temperatures. Or if it is installed on a loggia or veranda. In cold weather, the liquid in the batteries cools much faster.
Three way valve
Such a tap is required to switch the bypass-battery direction. If this is the reason that the radiator does not heat, then the problem can be eliminated in 3 ways:
- No disassembly. In cases where the tap turns easily, but switching does not occur at all (neither one nor the other works), you can try to develop the device using multiple turning movements. In this case, blockages, as a rule, are washed away by the flow, going into the riser. The operation of shut-off valves is restored in full.
- With partial disassembly. There's no way to turn the tap? We're not trying to break it. Carefully unscrew the locking screw of the handle, remove it, place the screw back in order to prevent deformation of the part during further work. Further actions are carried out with a wrench. It is not recommended to use round nose pliers, pliers, etc. The reason is the same as with the screw - not to damage the rod. Holding the rod with a wrench, we smoothly rock it back and forth, starting with minimal vibrations. If you cannot make minimal movements, slightly loosen the large hex nut that presses the stuffing box seal. If it starts to dig in, place a small container. Continuing the work, moving the rod, press the seal into place, turning the large nut back accordingly. We unscrew the screw, install the handle, screw in the screw, and rejoice.
- In rare cases, when the internal stop is simply torn off, the crane has the ability to “spun in a circle” endlessly - we simply select the position of the handle in which normal operation is ensured.
Fixing the problem
Is it possible to somehow eliminate this shortcoming? First of all, you should check whether the supply and return are not confused.
Perhaps the root of the problem lies in a bad faucet.
- It should be replaced with a new one, which will have a wider longitudinal section.
- If the problem persists, replacing the heating pipes with new ones with a larger diameter will help.
You can also increase the speed of movement of the working fluid by installing a circulation pump in the line.
By following these tips, you will be able to get rid of the temperature difference in the battery.
Silt at the bottom
The water in central heating systems is of poor quality. Sediment falls out of it, forming a layer of sludge at the bottom of the radiator. When using low-quality or incorrectly selected coolants, the same thing happens.
As sediment accumulates, the throughput of the lower collector decreases. Less coolant passes through the heating radiator, it cools down quickly. Heat transfer decreases.
The problem can only be solved by flushing the radiator. To do this you need:
- Shut off the supply and return;
- Unscrew the radiator from the incoming and outgoing pipes;
- Wash it with special means.
We described this in more detail in the articles How to flush a heating radiator and How to remove a heating radiator without consequences.
Photos of the best heating radiators
Low temperature
If the difference in the temperature conditions of the bottom and top of the batteries is not too significant, then there is no need to worry. This arrangement of radiators is quite natural. The circulating coolant always has time to cool down a little, which is due to fairly high heat output rates. Very large discrepancies may require system intervention.
If the water temperature in the heating system is low, then it will be necessary to increase the heating of the coolant by increasing the power of the operating heater. A good result is also achieved by using a special heat-reflecting screen. For this purpose, it is recommended to use traditional aluminum foil or modern and reliable material such as penofol.
An important point with a two-pipe connection is the ability to regulate the temperature in a separate battery using special fittings, represented by a conventional shut-off valve. This ensures an increase or decrease in the volume of coolant in each radiator by adjusting the shut-off valves.
Read also: What to do when you run out of money
Briefly about the heat supply of an apartment building
If you have the courage to figure out on your own why the batteries do not heat well, it would be a good idea to familiarize yourself with the basic concepts associated with heating a residential apartment building.
Most high-rise buildings use a single-pipe system equipped with U-shaped risers. Let us show a conditional diagram of the heat supply of three floors.
Hot water (red in the diagram) rises through one riser and passes, for example, through the bedrooms, to the top floor, where, in a loop, it goes down through other rooms (blue). This scheme has been designed since Soviet times for the use of cast iron radiators. Hot water enters the lower radiator manifold and, after passing through all sections, leaves the battery through the upper manifold.
A special role was given to jumpers (bypasses). They maintained general forced circulation throughout the entire pipeline of the U-shaped riser (in the diagram - for the six radiators shown), acting as a safety net in cases of radiator clogging with liquid technical dirt that accumulates during many years of operation. When passing through the riser, some part of the total displacement of hot water supplied from below turned to the radiator on one floor, and the rest passed by unhindered, delivering heat to the apartments adjacent to the riser.
The aluminum heating radiators that have appeared are designed for two-pipe systems with hot water supplied through the upper collector and its output from the lower collector. They have a completely different design of the internal cavity, and accordingly, different hydraulics. When they began to indiscriminately replace obsolete cast iron radiators with modern aluminum ones, but maintaining a single-pipe design, the heat flow from hot water inside the radiators began to weaken due to the divergent directions of convection heat flows from the cooling water and the hot water pumped by an external pump.
Concerned that the heating radiator was not heating up, residents began to resort to various technical tricks, not caring at all about their freezing law-abiding neighbors. This inconsistency between the types of structures and the decrease in the speed of water passing through the radiator led to dirt deposits in the sections. Every year more and more sludge is deposited, and now the last battery, completely clogged with sludge, no longer heats. This epidemic then covers the entire radiator.
Battery not connected correctly
Another very common situation of cold bottom and hot top of the battery is its incorrect (unprofessional) connection. Particular attention when organizing a heating system will require the installation of a bypass in front of the heaters, the correct choice of connection diagram and proper installation of all shut-off valves.
The best option would be a parallel (diagonal) connection with a coolant supply at the top and a “return” at the bottom. In addition, it must be remembered that there must be the necessary space at the top and bottom of the battery to ensure normal and stable air exchange. Otherwise, the operation of such a device will be completely ineffective and problematic.
Large heat losses
Checking heat losses in the heating system is easily carried out using a special high-precision measuring device - a thermal imager. Such a device makes visible the infrared radiation emitted by surrounding objects and helps to measure temperature in a non-contact way with an accuracy of 0.1 ° C or better. The device display reflects the data of the measurements performed in the form of a color image, in which each shade corresponds to a strictly defined temperature range.
One of the time-tested and effective options for increasing the thermal output of the battery and reducing heat loss is to install a special reflector or screen made of aluminum foil behind the radiator. This very simple and cheap device will ensure that thermal energy is directed from the wall of the house directly into the room. As practice shows, the use of such a reflective screen can increase the thermal efficiency of the heating system by 12-15%. Among other things, it is strictly not recommended to cover the radiator with several layers of paint. In this case, heat loss often reaches the same 10-12% and with hot radiators you feel cold in the apartment.
The windows are “phoning”
Even the most modern and expensive plastic windows can cause heat loss as a result of improper glazing. Particular attention is required to improperly sealed joints that form between the window sill or wall and the window frame. All problem areas must be treated with silicone sealants or special polyurethane foam.
Problems with new windows are rather an exception to the rule. Most often, drafts occur when there are old windows with wooden frames in the room. And no matter how hot you make the radiators, it will still be cold in the apartment. In this case, the only way to get rid of heat loss through window openings once and for all is to install new multi-chamber plastic windows produced by well-established manufacturers.
