Good afternoon, dear guests and subscribers of the "Build for Myself" channel!
In the process of writing an article, in order to clearly present information, I took as an exampletwo-storey house 150 sq.m. and in some cases, referred to it.
I think every homeowner has a task to make a reliable home heating system that would compensate for the heat loss of the house and warm the residents without any hassle.
And, when we rely on a seller or an unscrupulous specialist in the design and installation of heating systems, here they can write us an invoice for a standard set: hydraulic arrow, underfloor heating collector, on the collector for the radiator network and a couple of pumping groups: one for the warm floor, the rest for the radiator collectors systems.
All this is certainly good. But, only for the seller. And we will overpay 40-50 thousand, because the house is up to 200 sq.m. in most cases, one ordinary pump built into a wall-mounted boiler will also pull.
The maximum that you need to buy is only a set for underfloor heating, and then only if the entire first and / or second floor is mounted with this system.
But, if the underfloor heating is only 30 - 50 sq.m., then even without additional sets, be sure, even pump 25-40 will pull freely. I wrote an article about the construction of such warm floors: Hot water floor with temperature control without mixing unit. Decent and beautiful solution!
So, about the labeling of circulation pumps:
For example: UPS 25-40
First digit - 25 - thread size for connection to the system (nuts supplied in the kit (mm.))
Second digit - 40 - the amount of head (dm.), sometimes called the height of rise - but this is an insidious word, it is better to use "head".
In other words, the head is the maximum value of the hydraulic resistance of the system to the movement of the coolant that the pump can pump.
Thus, the UPS 25-40 marking indicates a product with thread 25 mm (1 inch) and head 40 dm. or 4 meters or the maximum overpressure generated by the pump 0.4 atm.
For a circulation pump, the number of storeys of a building is completely unimportant, since this equipment has at the inlet (on the suction side) exactly the same column of liquid as at the outlet. Thus, both columns are balanced according to the principle of communicating vessels, and the pump only needs to circulate, and not increase the pressure (this is not a booster pump).
Therefore, the characteristic of the head of the circulation pump does not relate to overcoming the volume of liquid, but to the hydraulic the resistance of the heating system, which consists of all its elements: valves, radiators, corners, constrictions fittings, etc.
The choice of a pump needs to be made only by two parameters: based on heat needs of the room and overcoming resistance in the system. Therefore, to begin with, we must understand the heat loss at home, which occurs through the roof, walls, windows, doors and floors.
There is a lot of information on this topic on the net: corner rooms with two windows lose more heat than rooms with one wall bordering the street. The area of the glazing is also important, if it is panoramic glazing, the heat loss there increases up to 30%. But, on average in the house - specific heat losses are taken as 100-110 W per 1 sq. M.
Thus, for example at home 150 sq.m. is 15 kW. And, knowing the heat loss, it is required to find the performance of the circulation pump. And the performance just corresponds to the volume of water that needs to be distilled through the system for the necessary heat transfer to the room through the radiators. This is what is called - consumption.
So, the performance is calculated like this: Q = (0.86 * P) / TF
- Q - productivity (m³ / h);
- Р - power level of the heating system (kW);
- TF is the temperature difference of the heating medium between the inlet and outlet.
At the second stage, we calculate the required head according to the formula that specialists use in practice: H = Z * R * L, Where:
- H-required head;
- Z-hydraulic resistance of elements;
- R-resistance of the pipeline;
- L is the length of the pipeline.
I would not like to overload this article with figures and calculations, and will limit myself only to formulas. But, according to the calculation, a separate article will definitely be released!
Based on the results of the calculation, we get Q and H, productivity and head, respectively. This is precisely the basis when choosing a pump, and experts collectively call these parameters - operating point of the pump.
The pump is selected according to the pump performance curves, where:
- abscissa (X) - productivity Q,
- along the ordinate (Y) - head H.
Almost all pumps have 3 operating modes, just those are plotted on the graph (bold lines) in the manual for each pump. Their dependence is as follows: the higher the performance, the lower the head.
By projecting our obtained Q and H values onto the graph, we get the operating point, according to the position which - we will be able to assess whether the pump suits us or not, as well as the high-speed mode of its operation in our system. If the operating point is outside the graph of the 3rd mode, then it is better to go to the selection of another pump with higher characteristics and project your point on its graphs.
In the figure - I marked the field in which the operating points of various systems are most often located.
From the author
I have worked in sales for a long time. The sales system is built in such a way that employees are trained by marketers and prepared for how to do it right from the context pull out information and manipulate the characteristics of the equipment, which sometimes even experienced and knowledgeable specialists begin doubt.
Friends, the calculations do not take much time or effort, since there is a lot of information on the Internet. The fact is that for the most part the seller will offer us to buy a pump that is an order of magnitude more efficient than required, and, accordingly, its cost will be several thousand more.
For a house heating system 100 - 200 sq.m. usually one pump from an inexpensive household line is enough "with a head".
I hope you enjoyed the article and found it useful. Thanks for attention!
Operation of the circulating pump with all closed radiators (operation with a "closed valve")
Installation of a circulation pump: supply or return?