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It is practically impossible to survive in winter without heating in our country, because a lot of time, effort and money are devoted to its device. The most common type of heating we have is water (liquid) heating. Its component is a coolant. How to choose a coolant for a heating system, how to download it – in the article.
What is a coolant and what should it be
The heat carrier in a liquid heating system is the substance by which heat is transferred from the boiler to the radiators. Our systems use water or special antifreeze liquids as a heat carrier. When choosing, you must be guided by several criteria:
- Safety. From time to time, heating leaks or they require maintenance and repair. In order for the repair work not to be dangerous, the coolant must be harmless.
- Harmless to components of the heating system.
- Must have a high heat capacity to transfer heat efficiently.
- Have a long service life.
The coolant for heating systems is selected according to operating conditions
Given these requirements, the most suitable liquid for the heating system is water. It is safe, harmless, has a high heat capacity, and the lines of operation are unlimited. But in those heating systems where there is a high probability of downtime in winter, water can do a disservice. If it freezes, it will burst pipes and/or radiators. Therefore, antifreeze is used in such systems. At negative temperatures, they lose their fluidity, but the equipment does not tear. So it is easy to choose a coolant for a heating system from this point of view: if the system is always under supervision and in working condition, you can use water. If a temporary residence (dacha) or it can be left unattended for a long time (business trips, winter holidays), if frequent and / or long power outages are possible in the region, it is better to fill in antifreeze into the system.
Features of using water as a heat carrier
From the point of view of the efficiency of heat transfer, water is an ideal heat carrier. It has a very high heat capacity and fluidity, which allows it to deliver heat to the radiators in the required volume. What kind of water to fill? If the system is of a closed type, you can fill in water directly from the tap.
Yes, tap water is not ideal in composition, it contains salts, a certain amount of mechanical impurities. And yes, they will settle on the elements of the heating system. But this will happen once: in a closed system, the coolant circulates for years, a small amount of replenishment is very rarely required. Therefore, a certain amount of sediment will not bring any tangible harm.
If the heating is open, the requirements for water quality, as a heat carrier, are much higher. Here there is a gradual evaporation of water, which is periodically replenished – water is added. Thus, it turns out that the concentration of salts in the liquid increases all the time. And this means that the sediment on the elements also accumulates. That is why purified or distilled water is poured into open-type heating systems (with an open expansion tank in the attic).
In this case, it is better to use distillate, but it can be problematic and expensive to get it in the required volume. Then you can fill in the purified water, which is passed through the filters. The most critical is the presence of a large amount of iron and hardness salts. Mechanical impurities are also useless, but it is easiest to deal with them – several mesh filters with a cell of different sizes will help to catch most of them.
In order not to buy purified water or distillate, you can prepare it yourself. First, pour and stand to settle most of the iron. Carefully pour the settled water into a large container and boil (do not close the lid). This removes hardness salts (potassium and magnesium). In principle, such water is already well prepared and can be poured into the system. And then top up with either distilled water or purified drinking water. This is no longer as costly as the initial fill.
Antifreeze for heating
In heating systems, in addition to water, special non-freezing liquids are poured – antifreezes. Usually these are aqueous solutions of polyhydric alcohols. Not so long ago, glycerin-based antifreeze appeared on our market. So now there are three types of antifreeze liquids for heating systems.
Types of antifreeze liquids and their properties
Antifreezes are based on two substances: ethylene glycol and propylene glycol. The first is cheaper, freezes at lower temperatures, but is very toxic. You can get poisoned not only by drinking, but even by simply soaking your hands or breathing in fumes. The second non-freezing coolant for the heating system is based on propylene glycol. It is more expensive, but safer. Sometimes it is even used as a dietary supplement. Its minus (except for the price) is that it loses fluidity at higher temperatures than propylene glycol.
Despite the high toxicity, ethylene-glycol coolants are more often bought. This is most likely due to the price – propylene glycol is twice as expensive. But ethylene-glycol antifreezes in their pure form are also chemically active, can foam, and have increased fluidity. Additives fight foam and activity, and increased fluidity is not corrected in any way. Paired with toxicity, it is a dangerous combination. If there is the slightest possibility somewhere, this antifreeze will leak. And since its vapors are poisonous, this will not lead to anything good. Therefore, if possible, use propylene glycol.
| Name | Substance | The weight | Operating temperature range | Beginning of crystallization | Thermal decomposition temperature | Life time | Possibility of dilution with water | Price |
|---|---|---|---|---|---|---|---|---|
| Dixis (Dixis) 65 | monoethylene glycol | 10 kg | -65°C ~ +95°C | -66 ° C | + 111 ° C | 10 years | Yes | 850 rub |
| Warm House – Eco | propylene glycol | 10 kg | -30 ° С to + 106 ° С | -30 ° C | + 170 ° C | 5 years | Yes | 1050 rub |
| Dixis TOP (Dixis TOP) -30 | propylene glycol | 10 kg | -30 ° С to + 100 ° С | – 31 ° C | + 106 ° C | 3 years | Yes | 960 rub |
| ANTIFROST based on glycerine | glycerol | 10 kg | -30 ° С to + 105 ° С | 4 years | no | 700 rub | ||
| PRIMOCLIMA ANTIFROST based on propylene glycol | propylene glycol | 10 kg | -30 ° С to + 106 ° С | -30 ° C | + 120 ° C | 5 years | Yes | 762 rub |
| TERMAGENT 30 | ethylene glycol | 10 kg | -20 ° С to + 90 ° С | -30 ° C | + 170 ° C | 10 years | no | 650 rub |
| Teplocom (glycerine) | glycerol | 10 kg | – 30°С to +105°С | 8 years | no | 780 rub |
Another important drawback is that ethylene glycol reacts very poorly to overheating, and overheating occurs at a fairly low temperature. Already at +70°C, a large amount of sediment is formed, which settles on the elements of the heating system. Deposits reduce heat transfer, which again leads to overheating. In this regard, such antifreezes are not used in systems with solid fuel boilers.
Propylene glycol, on the other hand, is almost chemically neutral. It reacts less than all coolants with other substances, overheating occurs at higher temperatures and does not lead to such consequences.
At the end of the last century, antifreeze for heating systems based on glycerin was developed. It is a cross between ethylene and propylene coolants. It is safe for humans, but does not have a very good effect on gaskets, and also reacts poorly to overheating. In terms of price and temperature characteristics, it is approximately in the same range as propylene coolants (see table).
Features of systems with antifreeze as a coolant
When designing a heating system, it is necessary to initially take into account the coolant. This is due to the lower heat capacity of non-freezing liquids, as well as their other properties. If all the equipment was designed for water, and antifreeze is poured into it, the following problems may arise:
- Not enough power and the house will be cold. This is due to the lower thermal conductivity of antifreezes. This problem can be solved with little bloodshed – to increase the speed of the coolant by installing a more powerful circulation pump. But in a good way, an increase in the number of radiator sections is required.
- In closed systems, the volume of the expansion tank may not be sufficient. This is due to the fact that when heated, antifreeze expands more than water. The way out is to put another tank. The total volume should be slightly more than required (the volume can be taken from the table).
The volume of the expansion tank for different types of coolant - If ordinary rubber gaskets are used, when using ethylene glycol or glycerin, they will break down and leak after a short time. Therefore, before pouring antifreeze in all detachable joints, the gaskets are replaced with paronite or teflon.
As you understand, the best coolant for a heating system is water. It is better in terms of performance and much cheaper. If the heating is threatened with defrosting, it is necessary to fill in antifreezes, but not for automobiles, but special ones for heating. In this case, if there is a sufficient amount of funds, it is better to use propylene glycol. Ethylene antifreeze is an extreme case. They are suitable for closed systems with special gaskets and automated boilers to prevent overheating.
To make it easier for customers to navigate, dyes are added to coolants. In ethylene – red or pink, in propylene – green, in glycerin – blue. After a while, the color may not become so intense or disappear altogether. This is due to the thermal destruction of dyes, but does not affect the properties of the antifreeze itself.
How to download coolant
Problems usually arise only with closed systems, since open ones are filled through an expansion tank. The coolant for the heating system is simply poured into it. It spreads through the system under the influence of gravitational force. It is important that when filling the system, all air vents are open.
There are several ways to fill a closed heating system with coolant. There is a way to fill without the use of technology – by gravity, there is a submersible pump of the “Kid” type or a special one, with which the system is pressure tested.
Fill by gravity
This method of pumping coolant for a heating system, although it does not require equipment, takes a lot of time. It takes a long time to squeeze out the air and just as long to gain the desired pressure. By the way, we pump it up with a car pump. So the equipment is still required.
We find the highest point. Usually this is one of the gas vents (we remove it). When filling, open the tap to drain the coolant (the lowest point). When water runs through it, the system is full.
With this method, you can connect the hose from the water supply, you can pour the prepared water into the barrel, raise it above the entry point and so pour it into the system. Antifreeze is also poured in, but when working with ethylene glycol, you will need a respirator, protective rubber gloves and clothing. If a substance gets on a fabric or other material, it also becomes toxic and must be destroyed.
When the system is full (water ran out of the drain tap), we take a rubber hose about 1,5 meters long and attach it to the entrance to the system. Select the input so that the pressure gauge is visible. At this point, install a check valve and a ball valve. We attach an easily removable adapter for connecting a car pump to the free end of the hose. After removing the adapter, pour the coolant into the hose (keep it up). After filling the hose, using the adapter, we connect the pump, open the ball valve and pump the liquid into the system with the pump. You have to be careful not to let air in. When almost all the water contained in the hose has been pumped in, the valve closes and the operation is repeated. On small systems, to get 1,5 bar, you will have to repeat it 5-7 times, with large ones you will have to fiddle longer.
Filling with a submersible pump
To create a working pressure, the coolant for the heating system can be pumped with a low-power submersible pump of the Malysh type. We connect it to the lowest point (not the system drain point). We connect the pump through a ball valve and a check valve, we put a ball valve at the drain point of the system.
Pour the coolant into the container, lower the pump, turn it on. During operation, we constantly add coolant – the pump should not drive air.
In the process, we monitor the manometer. As soon as its arrow has moved from zero, the system is full. Up to this point, the manual air vents on the radiators can be open – air will escape through them. As soon as the system is full, they must be closed.
Next, we begin to raise the pressure – we continue to pump the coolant for the heating system with a pump. When it reaches the required mark, we stop the pump, close the ball valve. We open all air vents (on radiators too). Air escapes, pressure drops. We turn on the pump again, pump a little coolant until the pressure reaches the design value. Let’s blow the air again. So we repeat until their air vents stop air coming out.
Then you can start the circulation pump, bleed the air again. If at the same time the pressure remains within the normal range, the coolant for the heating system is pumped. You can put it to work.
Using a pressure pump
The system is filled in the same way as in the case described above. In this case, a special pump is used. It is usually manual, with a container into which the coolant for the heating system is poured. From this container, liquid is pumped through a hose into the system. You can rent it from companies that sell pipes for plumbing. In principle, it makes sense to buy it – if you use antifreeze, you will have to change it periodically, that is, you will need to fill the system again.
When filling the system, the lever goes more or less easily, when the pressure rises, it is already harder to work. There is a pressure gauge on both the pump and the system. You can follow where it is more convenient. Further, the sequence is the same as described above: pumped up to the required pressure, bled air, repeated again. So until there is no air left in the system. After – we also start the circulator for five minutes (or the entire system, if the pump is in the boiler), bleed the air. We also repeat several times.