Comparison Novator LK-15G vs Gross ETR-UA 15/80 cold

The purpose is indicated by the temperature of the water with which the metre can be used.

— For cold water. Metres intended for use in cold water supply systems and not designed for hot water. They are blue in colour as standard. In most of these models, the maximum water temperature (Tmax) is from 30 to 40 °C — this is quite enough for traditional water supply systems. However, there are also higher rates — up to 50 °C inclusive. Such metres will be useful where the cold pipeline may be subjected to additional heating and quite warm water may flow through it. An example is a stand-alone water supply system, some of the pipes of which are exposed to direct sunlight and can become very hot.

— For hot water. Metres intended for use in hot water supply systems; traditionally painted red. The standard temperature in DHW systems with centralized water supply is 65 °C, but higher values are possible. Therefore, in such metres, the maximum water temperature (Tmax) is not lower than 90 °C, and in the most advanced models — 95 °C. Note that such devices can easily cope with cold water, so technically it is quite possible to put a hot water metre in the cold water system; however, this is not justified in fact, since constant operation in abnormal mode adversely affects accuracy. And for water supply with a very unstable temperature, it is better to use universal metres (see below).

...— For cold/hot water. Metres that are equally well suited for both hot and cold water. Like specialized models for hot water supply, they have a maximum allowable temperature of at least 90 °C; the main difference is that this variety provides almost the same accuracy at any water temperature. Such properties are useful, first of all, if the temperature in the water supply is not constant, especially if the "hot" and "cold" periods take approximately the same time intervals. However, nothing prevents the use of such metres even at a stable temperature — except that the cost of universal models will be somewhat more expensive than specialized devices of similar quality.

The highest water temperature allowed for water metre.

This parameter is directly related to the purpose (see above): in devices only for cold water, Tmax is usually in the range of 30...40 °C heating water in a pipeline exposed to the sun). For metres that can be used with hot water, this figure is 90...95 °C.

Of course, in no case should the maximum water temperature be exceeded — this can lead to damage to the metre and even an accident with a flood” Putting a metre with Tmax at a level of 90 °C and above in a cold water supply system makes sense only if the device was originally designed for both hot and cold water; see "Suitable for" for details.

The division value on the measuring scale of the water metre.

The division price is the minimum measurement step, the difference between two adjacent smallest units, in other words, the smallest difference in readings that the metre can display. The smaller this difference, the more detailed data the device produces. For example, a value of 0.01 m³ allows you to display data with an accuracy of the second decimal place — that is, such a metre will show, for example, a change in the amount of water consumed from 0.02 m³ to 0.03 m³, but will not perceive the difference between 0.022 m³ and 0.028 m³ (readings will remain at the level of 0.02 m³). However, modern water metres — even household ones — for the most part, have a lower division price, from 0.001 m³ and below.

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.

The presence of a special protective cover on the water metre scale. Usually, such a cover is closed, it is opened only to check the readings. Such a detail protects, first of all, the transparent plastic with which the scale is covered — from bumps, scratches and dirt; thanks to this, the plastic remains transparent for a long time, does not become foggy and does not interfere with reading data from the scale. However, the role of the cover is not limited to this, it often provides additional protection for the case as a whole; and in some models, sensors are mounted in the cover to transmit data from the metre, used in remote control systems. Note that all these functions can be provided both in industrial and household metres (see "Type").