Is it possible to change the pump in a wall-mounted boiler to a non-standard one?

Hello! As I understand it, this is a gas wall-mounted boiler. Russian law does not contain a clear answer to your question. Therefore, I ask you to pay attention to two aspects:

1) According to the Decree of the Government of Russia No. 410 dated 05/14/2013, “Rules for the use of gas in terms of ensuring safety during operation and maintenance of gas equipment at home ...” independent replacement of gas equipment or its structural parts without involvement of employees by a specialized organization is not allowed. The document says that if a fact of unauthorized design change of an internal house boiler is discovered, the employees of the controlling organization are obliged to turn off the gas equipment and report this fact to Rostekhnadzor. Meanwhile, neither the Criminal Code nor the Administrative Code contain articles that would stipulate liability for unauthorized changes to the design of the boiler.

Practice shows that in normal use, the owner is almost never held liable after the completion of work on the replacement of structural parts. However, if any accident occurs (gas leak, explosion, fire), then with a high degree of probability the responsibility may be laid on you, including criminal.

2) Most gas boiler manufacturers attribute pump replacement to technical re-equipment, and not to structural changes. At the same time, the installed pump must be functional in accordance with the factory principle. In Federal Law No. 117 of 08/05/2000, technical re-equipment is understood as a set of measures to increase the technical and economic indicators of equipment by introducing or replacing obsolete, worn-out elements with more modern, efficient and safe ones. The law states that technical re-equipment does not require clearance.

Good luck