Comparison Novator LK-20H vs Novator LK-15H

The nominal diameter of the pipes for which the water metre is designed. It is indicated in millimetres, but the addition of "mm" in the record is usually not indicated.

In the most general terms, DN can be described as the internal diameter of the inlet and outlet of the water metre. However, the actual inner diameter may differ from the nominal one by several millimetres. It is because the inner diameter is indicated by a number from the standard list, and in case of discrepancy, it is rounded up to the standard value: for example, diameters of 23 mm and 26 mm will both correspond to DN 25. This technique is used for both metres and pipes; however, in most cases, the differences from the standard are not significant enough to affect connectivity. Therefore, when choosing, it is quite possible to proceed from the fact that the nominal diameter of the metre must correspond to the nominal diameter of the pipe — especially since the diameters of the fasteners (thread or flange; see below for details) also depend on this size.

The list of nominal diameters that are most common in modern water metres looks like this: 15, 20, 25, 32, 40, 50, 65, 80, 100..., 150 and 200 mm.

Minimum water flow for this metre model.

The minimum flow rate is the smallest flow rate at which the counting mechanism can provide measurement with an acceptable error of ±5%. This deviation is higher than the counter error in the standard mode (from Qt to Qn, see below for details), it is considered undesirable, but generally acceptable. But when the flow rate drops below Qmin, the error increases to unacceptable values, and there is no question of acceptable measurement accuracy. So, ideally, it is worth choosing a metre in such a way that its Qmin is not higher than the water consumption at the minimum intensity of consumption. Detailed recommendations for estimating the actual water consumption for different water supply systems can be found in special sources.

Transitional water consumption for water metre model.

The transitional flow rate is the flow rate at which the maximum measurement error changes — namely, decreases: in the range from Qmin (see above) to Qt it is ±5%, and at the Qt level and above it drops to ±2%. In other words, Qt is the smallest flow rate at which the device gives not just an acceptable, but a minimum error. Thus, the optimal consumption intensity for any metre is in the range between Qt and Qn (see below), and it is this range that is best to focus on when choosing.

Detailed methods and recommendations for estimating water consumption for a particular water supply system can be found in special sources.

Nominal flow rate for this metre model.

It is the highest flow rate at which the device can work indefinitely (during the entire service life) without failures, malfunctions and exceeding the maximum allowable error (± 2%). For a short time, a higher flow rate is also allowed (for more details, see “Maximum water flow (Qmax)”), however, the regular mode is still the mode in which this rate does not exceed Qn. So this parameter is the main one when choosing a device. Ideally, the actual water flow should always be in the range between the nominal and transitional (see above) flow.

Maximum water flow for water metre .

The maximum flow rate is considered to be the highest flow rate at which the device can operate for a short time (less than 1 hour per day and less than 200 hours per year) without failures, malfunctions and exceeding the maximum allowable error (± 2%). For several reasons, this figure is usually twice the nominal flow rate Qn (see above). When choosing a metre for maximum flow, you need to take into account the peak consumption of the system that it serves — that is, the flow rate when all consumers are turned on maximum at the same time: this rate should not exceed Qmax, otherwise the metre will not be able to cope with its task normally. If the system is constantly operated in the maximum consumption mode, then it is worth choosing not by Qmax, but by Qn.

Sensitivity threshold for this water metre model.

The sensitivity threshold is the lowest flow rate at which the device begins to respond to the movement of water and record the flow; at a lower speed, the measuring mechanism simply does not distinguish between flow and still water. The lower this indicator, the less likely it is that, at low consumption, water will be consumed without accounting. In household models (see "Type") the sensitivity threshold does not exceed 40 L/h, there are also much lower figures — 10 L/h, or even 5 L/h. In industrial metres designed for large industries, there are values of hundreds of litres per hour.

The size of the threaded connection provided in the metre with the corresponding type of installation (see "Connection type").

Ideally, the metre itself, other components of the metering system (such as a filter and a check valve) and water pipes should have the same threaded connection diameter — this eliminates fuss with adapters and problems associated with speed drops due to uneven internal diameters. However, in some cases, you can use adapters. These situations are described in more detail in special sources.

Traditionally, water pipe thread sizes are indicated in inches and fractions of an inch. In modern water metres, the following sizes are mainly found: 1/2 ", 3/4", 1", 1 1/4", 1 1/2", 2", 2 1/2". In this case, the thread diameter is associated with diameter DN (see above): larger DN requires larger fasteners. However, there is no rigid dependence here — for example, a metre with DN 20 can be equipped with both 3/4 "and 1" threads.

General water metre dimensions in length, depth and height. Sometimes only one size can be indicated in this paragraph — the length: it is most important during installation, it is the length that is taken into account when choosing the required distance between the ends of the pipes. At the same time, it is worth remembering that between these ends, not only the metre itself is most often located, but also other devices and parts: connecting fittings, a valve, a coarse filter, a check valve, etc. Details on this can be found in special sources; here we note that for some models, the specifications separately indicate the length with complete mounting fittings (see below). Without fittings, the length can be from 80 – 100 mm in the most compact devices to 250 mm or more in the largest.

Depth and height, in turn, allow you to estimate how much free space around the pipe is needed for the normal placement of the metre.

The length of the water metre with complete mounting fittings installed on it.

The fittings are used when installing models with a threaded connection (see "Connection"). They are short pipes screwed onto the inlet and outlet of the metre and play the role of a kind of adapter between the device and other elements of the system (for example, a coarse filter and a check valve for a traditional household metre). Knowing the length with fittings installed, it is easier to calculate the required distance between the ends of the pipes: when calculating, you do not need to separately take into account the length of the fittings, they are already taken into account in this size.