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Modern gas boilers are good because, under normal operating conditions, they work completely autonomously. Human intervention is usually required only to adjust the parameters. But for stable operation, they need a certain pressure and quality of gas, as well as high-quality and constant power supply. The last task is handled by an uninterruptible power supply for a gas boiler. Their choice and parameters will be discussed.
What is a UPS for?
In our country, in winter, heating is indispensable. Moreover, heating is desirable without failures and stops – in severe frosts, the system can be defrosted. When organizing the system, it must be remembered that most modern boilers are controlled by automation, and the movement of the coolant in the system is provided by circulation pumps. All of this equipment is powered by electricity.
Given that power outages are not uncommon in winter, additional measures must be taken to create a redundant power supply. In most cases, they install a UPS – an uninterruptible power supply. Its task is to supply power from batteries in the event of a power outage or “sag” in the network.
Features of choice for gas boilers
An uninterruptible power supply for a gas boiler must be selected in such a way that it supplies voltage of the correct form – as close as possible to an ideal sinusoid. In this case, phase synchronization of the sinusoid is also important.
All these requirements are necessary to ensure the normal operation of the control unit. In most imported gas boilers, automation is assembled on the basis of electronics, and it is demanding on the quality of the power supply. To assess how important this requirement is, it is worth saying that, according to the statistics of service centers, about 40-55% of gas boiler breakdowns are associated with the failure of the control board. At the same time, boards are almost never repaired. They simply need to be replaced.
It is also worth remembering that the failure of the control board due to unstable power is a non-warranty case (almost all manufacturers). So the cost of the board and its replacement has to be paid out of your own pocket. Moreover, many boards are delivered “on order”, and this is a few weeks of waiting. How to heat the house at this time is an interesting question … If you also remember that the cost of the board is about 40-50% of the cost of the unit, you involuntarily think about purchasing a high-quality and reliable uninterruptible power supply for a gas boiler.
The good news is that you can “drive” the rest of the equipment that requires high-quality and guaranteed power supply to one UPS of sufficient power, or you just want to ensure its uninterrupted operation. Most often, these are computers, televisions and a couple of emergency lighting bulbs.
Types of uninterruptible devices
Today, the distribution network offers three types of UPS:
- off-line (on-line);
- on-line (off-line);
- Line-Interactive (line-interactive whether line-interactive).
Offline UPS (redundant type)
These are the simplest and cheapest uninterruptible power supplies. Off-line can be translated from English as “not in line”, which reflects the principle of operation of this device. In an uninterruptible device of this type, the upper and lower voltage limits are set, at which the boiler operates normally. As long as the network parameters are within these limits, power is supplied directly from the line.
If the voltage becomes more or less, the switching relay is activated, power is supplied through the UPS from the batteries. When the network parameters return to normal, the relay operates again, turning off the uninterruptible power supply. For a gas boiler, such protection is, of course, better than nothing, but when turned on / off, significant power surges are observed in the network. So the stabilization in this case is not complete – there are no big dips or peaks, but the supply voltage is far from ideal. The second disadvantage of offline uninterruptibles is that they cannot correct the shape of the sinusoid.
Therefore, off-line uninterruptible power supplies for gas boilers should be used only if you already have a stabilizer installed on a scrap or apartment. It produces an ideal voltage, and the UPS in this circuit simply connects the batteries in the absence of voltage. This scheme is expensive, but creates normal conditions for the operation of equipment that is demanding on the quality of the power supply.
On-line UPS (permanent type)
This type is also called uninterruptible power supply units with double conversion. All because of the principle of operation:
- The input AC voltage is converted to DC and used to charge the batteries connected to the device.
- The DC voltage is converted into AC with an ideal sine wave shape.
It turns out the power supply is converted twice. This guarantees voltage stabilization and an ideal sinusoid shape.
Online uninterruptible power supplies are connected to break the power circuit. While the voltage is normal, the linear power is converted, when the voltage is low, its deficiency is replenished by charging the batteries, in the absence of power supply is supplied from the battery.
The disadvantage of this equipment is the high price and rapid discharge of batteries, which is due to the fact that it is spent on straightening surges. However, if you need the best uninterruptible power supply for a gas boiler, buy online type equipment.
Line-Interactive (line-interactive)
The properties and characteristics of uninterruptible power supplies of this type are not as good as those of online models, but not as bad as those of offline units. There are all the same batteries and a switch that, when the voltage drops, connects the UPS. But to stabilize the voltage, there is a special unit – an automatic voltage regulator (AVR in the figure above).
The disadvantage of line-interactive uninterruptible power supplies for a gas boiler is the non-instantaneous switching when the voltage changes. But it is much less than in offline devices, but the voltage is maintained constant (within certain limits). This equipment is the best choice, as it guarantees good results at a relatively low price.
UPS sizing
Determining what type of uninterruptible power supply for a gas boiler you need is not all. You need to know at least two more parameters: the power of the UPS and the capacity of the batteries that it can charge.
How to determine the power of an uninterruptible
To determine what power you need an uninterruptible power supply, look for the line “power consumption” in the gas boiler passport. On average, it is 150-170 watts. If there is a second circulation pump in the system, its power consumption must be added to this figure.
In order for everything to work without problems, a power margin of at least 20-30% is required. If possible, when choosing a UPS, the result can be doubled – just in case. Sooner or later, you will want to add a couple of devices to the load, as it is really convenient – when at least something works for you in the absence of electricity. This will be the minimum power of an uninterruptible power supply for a gas boiler.
Determining battery capacity
Many models of uninterruptible power supplies have built-in batteries. In this case, you don’t need to count anything. If the batteries are connected separately, you need to find the line “maximum charge current” in the technical specifications. We multiply this figure not by 10, we get the capacity of the battery that this UPS can charge. You can connect larger batteries, but in this case they will not be fully charged, which reduces their service life.
How to choose a UPS with built-in batteries? By the battery life you need. The dependence of the operating time on the battery capacity and power consumption is shown in the table. According to it, it is not difficult to select an uninterruptible power supply for a gas boiler.
Criteria for choosing a UPS for a gas boiler
From all of the above, we can deduce the following requirements for an uninterruptible power supply for a gas-fired boiler:
- Special UPS with sine wave output is required. Uninterruptibles for computers are unsuitable. At the output, they give out not a sinusoid, but a meander – the voltage is also variable, but not round, like a sinusoid, but with a cut off top. For computers, such a voltage is not a hindrance, but for a heating system – what else. Such voltage has a bad effect on the circulation pumps – they are buzzing, jerky. As a result, the impeller wears out quickly, the pump has to be changed.
- UPS power is selected with a margin. If possible, double the power consumption is necessary.
- It is advisable to choose the online type, a good option is the interactive type.
- The capacity of the batteries must be selected so that when the power supply is turned off, the heating can work for several hours (at least). This requirement is not critical if there is a generator. In this case, the batteries should last long enough for it to start. By the way, this is another reason why computer uninterruptibles should not be installed for the boiler – they are designed to operate the equipment for 10-15 minutes. During this time, you can correctly shut down all programs and turn off the equipment. For the boiler, these minutes are too short a time.
- It is desirable that it be possible to connect additional external batteries (there must be connectors). This is useful if you decide to increase the heating time from a backup power source or when connecting other equipment.
Scheme of connecting a gas boiler to an uninterruptible power supply (UPS)
The requirements are not the most stringent, but it is desirable to adhere to them. When connecting an uninterruptible power supply, observe the phasing (the UPS phase must be connected to the boiler phase, zero and minus to the corresponding conductors). Otherwise, the boiler will not work. Checking the correctness of the phasing is simple: pull the boiler plug out of the network. The boiler must continue to operate. If the flame goes out – check the correct connection, the operability of the ground. If everything is normal, but the boiler still does not work, then your UPS is built without a “through zero”. To start the boiler, you need to connect the N (zero) neutral terminals on the uninterruptible power supply at the input and output. For most boilers, this alteration solves the problem. But there are some brands of boilers, for example – Buderus (Buderus), which need to install resistance between the PE and N (ground and zero) inputs with a nominal value of 1 to 10 MΩ (Buderus even offers to buy their proprietary resistor).
Actually, this is all about choosing and even connecting an uninterruptible power supply for a gas boiler.