Emergency Procurement: Supply of boiler units with a built-in economizer and integrated modulated burner

New amendment added #1: Dear BiddersPlease be advised that the below changes are made to the RFQ requirements:The deadline for submissions is extended till December 18, 2025.Clause 1.4 of the Section II Schedule of Requirements is now amended to be read as follows: “The Bidder must have experience in supplying similar equipment in Ukraine or EU/EEA countries and must provide evidence (contracts, purchase orders, performance certificates, etc.) of the successful completion of at least 3 contracts for the supply of the proposed or equivalent equipment (at least one of the contracts must be for supply of gas boiler unit(s) with a unit capacity of at least 14 MW), implemented over the last 10 years.”Qualification criteria 3.2 (Criteria Tab of the RFQ) is now amended to be read as follows: “The Bidder must have experience in supplying similar equipment in Ukraine or EU/EEA countries and must provide evidence (contracts, purchase orders, performance certificates, etc.) of the successful completion of at least 3 contracts for the supply of the proposed or equivalent equipment (at least one of the contracts must be for supply of gas boiler unit(s) with a unit capacity of at least 14 MW), implemented over the last 10 years”.Clause 1.2 of the Section II Schedule of Requirements is now amended to be read as follows:“The main applicable regulatory acts and standards used in design, manufacture, control, and certification are as follows (provided for reference purpose)”.Clause 1.2.26 of the Section II Schedule of Requirements (“NPAOP 0.00-1.20-98 Safety rules for gas supply systems in Ukraine”) is now removed from the requirements.Clause 2.2.35 of the Section II Schedule of Requirements is now amended to be read as follows: “The type of flue gas heat exchanger: built-in stainless steel for condensing type, and built-in low-alloy steel for dry type.”Clause 2.2.38 of the Section II Schedule of Requirements is now amended to be read as follows: “Flue gas outlet from the economizer - vertically uphill, horizontal or vertically downward (depending on the mode)”.Please check the amended documents RFQ_Section_II_Schedule of requirements_Boiler units with a built-in economizer and integrated modulated burner_RFQ_2025_60436_rev1 and iRFQ_Section_III_Returnable Bidding Forms_Boiler units with a built-in economizer and integrated modulated burner_RFQ_2025_60436_rev1 in the Documents section.Thank you.

New clarification added: Do we understand correctly that the boilers must be equipped with boiler automation and cascade automation for 4 (four) boilers and that they must be included in the cost of the tender offer?Dear BidderThank you for your request. Please find the answers below.The minimum requirements to boiler units content configuration are reflected in the Section II Schedule of Requirements. The boiler units must be equipped with boiler automation. Cascade automation for all  boilers is not required according to the Section II Schedule of Requirements.Thank you.

New clarification added: Considering the important explanations and significant clarifications provided regarding the fact that economizers must still be condensing and there are strict requirements regarding the permissible materials / steel grades from which they must be made, we ask that you extend the deadline for submitting tender offers by +2..3 days.Dear BidderThank you for your request. Please find the answers below.The deadline for submissions will be extended for 2 days, till December 18, 2025.Thank you.

New clarification added: Subject: Request to Increase Maximum Dimensions (Clause 2.1.1) based on Economizer TypeReference: Section II, Clause 2.1.1 (Max dimensions 3910 mm x 11000 mm).Limiting the length of the boiler unit to no more than 11000 mm significantly limits the range of available technical solutions and suppliers of boiler equipment.According to public information available on the public procurement portal:https://prozorro.gov.ua/uk/tender/UA-2025-11-17-016933-a17.11.2025 a tender was announced for the construction of a boiler house using equipment that is the subject of the current tender RFQ/2025/604320.11.2025 tender UA-2025-11-17-016933-a for the construction of a boiler house was canceled.According to the information contained in the tender documentation UA-2025-11-17-016933-a, the sections of the project related to the construction part and equipment layout are:1.1.2. 307-24-GP. General plan;1.1.4. 307-24-AB. Architectural and construction solutions;1.1.5. 307-24-KB. Concrete (reinforced concrete) structures;1.1.6. 307-24-KM. Metal structures;1.1.7. 307-24-KM. Metal structures. Chimneys;1.1.8. 307-24-TMK. Thermomechanical solutions of the boiler house;1.1.20. 307-24-POB. Construction organization project;As boiler equipment, the boilers "High-temperature water-heating boiler UNIMAT UT-M 64 (thermal power 20235 kW, 10 bar)" are designedAs of now, the boiler room premises in accordance with the project and the terms of the tender have not yet been built.If the participant in the RFQ/2025/6043 tender proposes equipment other than those specified above and wins, the general designer, in accordance with Ukrainian legislation, as the author of the project, must make appropriate changes to the current version of the design documentation. In this case, all the features of the selected equipment according to the RFQ/2025/6043 tender procedure must be taken into account, including its geometric dimensions, type, brand, etc.Considering the above information and the fact that the boiler room has not yet been built, as well as the explanations you provided regarding the implementation of condensing economizers, we ask you to soften the very strict restriction on the overall dimensions of boiler units, namely to allow the following boiler unit dimensions "(Max dimensions 3910 mm x 12500 mm)".Dear Bidder,Thank you for your request. Please find the answers below.The size limitation has been carefully considered by the end user of the equipment and the maximum allowed tolerance was included in the tender requirements. The boilers procured under this RFQ must fit the existing and already built boiler house building which can not be rebuilt or extended. The provided dimensions are maximum allowed and can not be changed.Thank you.

New clarification added: The provided answer places a special emphasis on operation in condensing mode on diesel fuel.Taking into account the provided answers, please confirm for clarity whether we have understood everything correctly:- all four boiler units must be able to operate in condensing economizer mode;- accordingly, economizers for boilers with gas and combined burners (gas/diesel) must be condensing and made of stainless steel of appropriate quality.Please confirm this.Dear BidderThank you for your request. Please find the answers below.The boiler units with combined (gas/diesel) burners must be able to operate in condensing economizer mode.Economizers for boilers with combined burners (gas/diesel) must be condensing and made of stainless steel of appropriate quality (as clarified in the previous clarifications).Thank you.

New clarification added: Subject: Request to Remove Irrelevant and Redundant Regulatory Requirements (Section 1.2)Reference: Section 1.2, Items 1.2.1, 1.2.3, 1.2.14, 1.2.15, 1.2.23, 1.2.26, 1.2.27.Question: We respectfully request a review of the list of regulatory documents in Section 1.2 to ensure they are legally valid and relevant to the subject of procurement (Supply of Goods). We identified three categories of requirements that create ambiguity or excessive administrative burden:Irrelevant Building/Operational Codes:Item 1.2.1 (DBN V.2.5-77:2014 "Boiler-rooms") and Item 1.2.27 (DBN V.2.5-56:2014 "Fire protection systems") are building codes for facility design, not product manufacturing standards.Item 1.2.23 (NAPB A 01.001-2014) relates to operational fire safety rules for personnel, which cannot be certified for equipment.Redundant Welding Certification:Items 1.2.14 and 1.2.15 require specific separate certification for DSTU EN ISO 3834-2/5.However, Item 1.2.3 mandates compliance with PED 2014/68/EU. Compliance with PED (especially for Category IV pressure equipment) already inherently covers strict welding quality assurance requirements. Demanding a separate ISO 3834 certificate duplicates the PED conformity assessment and imposes an unnecessary administrative burden on European manufacturers.Expired Regulation:Item 1.2.26 (NPAOP 0.00-1.20-98) has been repealed and replaced by NPAOP 0.00-1.76-15 (correctly listed in Item 1.2.28 ).Request: To ensure clear compliance requirements:Confirm that Items 1.2.1, 1.2.23, and 1.2.27 are for reference only and do not require specific product certification.Confirm that a valid PED 2014/68/EU certificate (or Module H/H1) is sufficient proof of welding quality, satisfying the intent of Items 1.2.14/1.2.15 without separate submission.Remove the expired Item 1.2.26.Dear bidderThank you for your inquiry. Please find the answers below.The certificates that must be provided by the bidders together with the tender offer are reflected in clauses 1.10.2, 1.10.3, 1.10.4, 1.10.5, 1.10.6 of the Section II Schedule of Requirements.Subsection 1.2 lists the main applicable regulations and standards used in the design, manufacture, inspection and certification of the equipment for reference purposes. The requirements of subsection 1.2 will be amended.Clause 1.2.26 (“NPAOP 0.00-1.20-98 Safety rules for gas supply systems in Ukraine”) will be removed from the requirements.Regarding the confirmation of welding quality - providing only the H1 PED 2014/68/EU certificate is not sufficient evidence, as it does not allow us to assess the welding quality of the manufacturer. Together with the H1 PED 2014/68/EU certificate, a copy of the certificate of conformity of production to the requirements of DSTU EN ISO 3834-2:2022 (EN ISO 3834-2:2021, IDT; ISO 3834-2:2021, IDT) must be provided.Thank you.

New clarification added: Subject: Clarification on Clause 2.2.38 – Flue Gas Outlet Direction vs. Operational ModeReference: Section II, Clause 2.2.38 ("vertically uphill") and Clause 2.2.40 (Inlet Temperature).Question: We request clarification on whether the requirement in Clause 2.2.38 for the flue gas outlet to be "vertically uphill" is a technical error, as its feasibility depends strictly on the economizer type:Non-Condensing (Dry) Operation: If the economizer is intended to operate dry (above dew point), a vertical uphill outlet is technically possible.Condensing Operation: If the economizer operates in condensing mode (which is indicated by the specified inlet water temperature of 60°C in Clause 2.2.40), a vertical uphill outlet is technically incorrect. In this configuration, condensate would flow downward against the upward gas stream, leading to flooding and backflow.Request: Please clarify the intended operational mode. If the system is condensing (due to the 60°C inlet), we request that Clause 2.2.38 be revised to allow for "horizontal" or "vertical downflow" outlets to ensure proper condensate drainage.Dear Bidder,Thank you for your request. Please find the answer below.The EN 12953 series of standards does not contain a direct requirement for a fixed direction of flue gas outlet ("vertically upwards"). The direction of the outlet is determined by the design of the equipment and the operating mode.EN 12953 requires that in the presence of condensation, the possibility of gravity drainage of condensate is ensured, and its accumulation and flooding of gas ducts and reverse flow are excluded.In non-condensing (dry) mode, a vertical upward outlet is allowed;In condensing mode, a vertical upward outlet does not meet the requirements of EN 12953 and must be replaced by a horizontal or vertically downward outlet with organized drainage.The requirement of clause 2.2.38 will be amended to be read as follows: “Flue gas outlet from the economizer - vertically uphill, horizontal or vertically downward (depending on the mode).Thank you.

New clarification added: Considering the tender documentation and the provided explanations:"(A) All 4 boilers are required to be of the same brand and manufacturer.(B)All burners specified under 1.1.9 (Gas) must be of the same brand and model, and all burners specified under 1.1.11 (Dual-Fuel) must be of the same brand and model. Gas burners and Dual-fuel burners can be from different manufacturers but all gas burners must be of the same brand and model and all dual-fuel burners must be of the same brand and model."Do we understand correctly that boilers equipped with gas burners may differ somewhat from boilers equipped with combined burners, namely, have slightly different geometric dimensions of the boiler unit and combustion chamber (taking into account the fact that the boilers are equipped with different burner devices). At the same time, they must be of the same brand and manufacturer and meet the rest of the key tender requirements (such as effective thermal capacity, thermal efficiency, NOx and CO emissions, etc.)?Dear BidderThank you for your request. Please find the answers below.As specified in the RFQ requirements and the clarification provided before all boilers must be from the same manufacturer and of the same brand and meet all the requirements as specified in the Section II Schedule of Requirements. Maximum allowed boiler dimensions for all 4 boilers are provided in the clause 2.1.1 of the Section II Schedule of Requirements.Thank you.

New clarification added: The requirement "2.2.13 Min. permissible temperature of the boiler return line is 50°C (without the use of mixing elements)." describes a unique feature of BOSCH Unimat UT-M boilers.Regardless of the boiler manufacturer, there is physics: the dew point when the boiler is operating on natural gas is approx. 57°C, which at a return temperature of 50°C will require recirculation (admixture of hot water from the supply to the return), otherwise there will be corrosion of the boiler heating surfaces. BOSCH Uniman UT-M provides for the use of internal recirculation, when hot boiler water is mixed into the cold return flow (ejection effect) in order to avoid low-temperature corrosion. So, in order to avoid condensation, in any case, recirculation is required, whether it is external, internal or combined (internal + external), and for the recirculation to work, a certain flow rate must be ensured - either by a boiler circuit pump or a recirculation pump. It turns out that BOSCH boilers use mixing elements, but only external, not internal. In addition, the tender documentation states that the return line temperature is 60°C, which is significantly higher than the boiler return line temperature requirement of 50°C. The boiler room is high-temperature with a schedule of 130/80oC in the boiler circuit - so the operating temperatures of the return line will be significantly higher than 50oC.Therefore, we ask you to exclude the strict requirement "2.2.13" or change the permissible temperature (increase by +5-10K) and state in the next edition "2.2.13 Min. permissible temperature of the boiler return line is 50-60°C (without the use of mixing elements). Without this, the number of tender participants may be reduced to one product "BOSCH Unimat UT-M". Dear BidderThank you for your request. Please find the answer below.The value of the minimum permissible temperature specified in clause 2.2.13 provides that the temperature in the return line before the boiler should not be less than 50 degrees. Temperatures of 55 or 60 (the values ​​to which it is proposed to increase) already meet the requirements, namely, already more than 50 degrees.Thank you.

New clarification added: Subject: Technical Clarification on Clause 2.2.35 – Carbon Steel Suitability for Non-Condensing OperationReference: Section II, Clause 2.2.35 ("steel with anti-corrosion coating") and Clause 2.2.40 (Inlet Temperature).Question: We request clarification on the necessity of the "anti-corrosion coating" specified in Clause 2.2.35.From an engineering perspective:If the economizer is designed for Non-Condensing (Dry) operation (where flue gas temperature is maintained above the dew point), the industry standard is the use of high-quality unalloyed carbon steel (without galvanization or special internal coatings). In a dry environment, carbon steel is sufficient to ensure the required service life, and additional coatings (like zinc) provide no technical benefit and may degrade at high temperatures.If the economizer operates in a Condensing mode, coatings on carbon steel are unreliable for a 20-year lifespan, and Stainless Steel is required.Using carbon steel with generic "anti-corrosion coating" (such as galvanization) for economizers is not a widely accepted standard in the global industrial boiler market for condensing applications.The industry standard for ensuring a 20-year lifespan (Clause 1.1.2) in condensing conditions is the use of solid corrosion-resistant materials (Stainless Steel or Al-Si alloys), not coated carbon steel, which is prone to coating failure and rapid acid corrosion.More than 90% of the solutions on the market for economizers for industrial boilers are as follows:1) Dry mode (Non-condensing):Inlet water temperature > 60-70°C (above dew point).Material: Ordinary carbon boiler steel (Carbon Steel).Coating: None (or light preservation for transportation). In dry gas, steel does not corrode, protection is not required. Galvanizing here is an unnecessary expense.2) Condensing mode (Condensing):Inlet water temperature < 60°C (below dew point).Material: Stainless steel only.Coating: Not required, as the material itself is resistant to acids.Request: If the system is intended to operate in a Non-Condensing mode, please confirm that unalloyed carbon steel (without additional anti-corrosion coating) is acceptable, as per standard international engineering practice for dry flue gas heat recovery.Dear Bidder,Thank you for your request. Please find the answer below.For the manufacture of elements of the boiler unit, namely the economizer, it is necessary to use steels specified in EN 12953-2, sub-section 1.2 of the Section II Schedule of Requirements.When using liquid fuel (diesel fuel) as a reserve, there is a high probability of condensation processes.Therefore, it is required to use corrosion-resistant steels that are stable in an acidic environment.Thank you.

New clarification added: Subject: Critical Clarification: Condensing vs. Non-Condensing Operation & Material RequirementsReference: Section II, Clauses 2.2.40 / 2.2.41 (Inlet Temperatures), 2.2.27 (Efficiency), and 2.2.35 (Materials).Question: We request urgent clarification regarding the operational mode of the economizer to determine the correct design and materials.The tender specifies an inlet water temperature of 60°C (Clauses 2.2.40, 2.2.41).This temperature is at or below the flue gas dew point (especially for liquid fuel containing sulfur), which inevitably leads to the formation of acidic condensate on heat exchange surfaces.Operation in this range classifies the equipment as a Condensing (or partial condensing) Economizer.However, Clause 2.2.35 permits "steel with anti-corrosion coating," which is generally suitable only for Non-Condensing (Dry) operation. Using coated carbon steel in a condensing environment poses a severe risk of rapid corrosion and failure, contradicting the 20-year lifespan requirement.Request: Please clearly define the requirement:Is the Economizer required to be of the CONDENSING type?If YES: Please explicitly mandate the use of Stainless Steel for all wetted parts and prohibit carbon steel/coatings to ensure durability against acidic condensate.Is the Economizer required to be of the NON-CONDENSING (Dry) type?If YES: Please confirm that the system design includes measures (e.g., recirculation pumps/bypass) to maintain the inlet temperature consistently above the dew point (e.g., >65°C-70°C) to prevent corrosion of coated steel surfaces. Note that this may affect the stated efficiency values.Dear Bidder,Thank you for your request. Please find the answer below.According to the Requirements, sub-section 1.2 of the Section II Schedule of Requirements, manufacturers must use the standards given in this sub-section for the manufacture of economizers. In accordance with the requirements of EN 12953-2, as specified in clause 1.2.4 of the Requirements, the manufacturer may use only corrosion-resistant materials for operation in condensing mode, in particular stainless steel not lower than 1.4404 (AISI 316L) or equivalent in corrosion resistance.Galvanized low-alloy or carbon steel is not a corrosion-resistant material in an acidic environment, since the zinc coating is chemically destroyed by acids, which leads to rapid corrosion of the base metal. In this regard, EN 12953-2 does not allow the use of galvanized steel as an equivalent of stainless steel for wetted parts of the condensing economizer. For operation in condensing mode (on diesel fuel), only corrosion-resistant materials are allowed, in particular stainless steel not lower than EN 1.4404 (AISI 316L) or equivalent in corrosion resistance. Application galvanized low-alloy steel for wetted surfaces will not meet the requirements for durability and safe operation of the equipment.The economizer must be of the condensing type. Therefore the corrosion-resistant steels that meet the requirements of EN 12953-2 must be used for economizer manufacturing.Thank you.

New clarification added: Subject: Technical Revision of Clause 2.2.47.1 – Liquid Fuel Modulation RatioReference: Section II, Clause 2.2.47.1 and Clause 3.3 (Emission Standards)Question: Clause 2.2.47.1 requires a modulation ratio of 1:4 for liquid fuel. We request a revision of this parameter to 1:3 based on the following technical grounds:Atomization Physics: Leading global burner manufacturers utilize mechanical pressure atomization nozzles. For these systems, the technically proven modulation limit for stable operation is typically 1:3. Forcing a 1:4 ratio results in critically low fuel pressure at the burner tip, leading to poor atomization (larger droplet size).Conflict with Emission Standards: Poor atomization at high turndown ratios (1:4) directly compromises combustion quality, significantly increasing the risk of soot formation and high CO emissions. This would make it technically difficult to guarantee compliance with the strict environmental standards set forth in Clause 3.3 (CO < 150 mg/m³ for liquid fuel).Operational Reliability: Given that diesel is intended as a backup/emergency fuel, a 1:3 ratio provides the optimal balance between operational flexibility and flame stability.Request: To ensure the supply of reliable equipment that meets the strict environmental criteria, please revise Clause 2.2.47.1 to read as follows:"The burner must ensure a stable modulation ratio of at least 1:7 for natural gas and 1:3 for liquid fuel across the full operating range."Dear BidderThank you for your request. Please find the answers below.The technical requirements for the boilers were established based on the exact needs and technical requirements of the end users of the equipment. The requirements can not be changed.Thank you.

New clarification added: Subject: Clarification on Clause 1.4 – Qualification of Authorized RepresentativesReference: Section II, Clause 1.4 Question: Clause 1.4 requires the Bidder to have completed 3 similar contracts. This excludes authorized local representatives or subsidiaries of major European manufacturers who possess the necessary technical capacity and factory support but may not hold 3 historical contracts under their specific local legal entity name. Request: To ensure Best Value for Money and allow participation of official factory representatives, please confirm that the experience of the Equipment Manufacturer (or the Bidder’s Parent Company) will be accepted as proof of qualification, provided a valid Manufacturer’s Authorization is submitted.Dear Bidder,Thank you for your request. Please find the answers below.Please note that if the bidder wants to use the manufacturer’s previous experience the only authorisation is not enough and the bidder should submit a bid in Joint Venture with the manufacturer providing duly signed Form A: Joint Venture Partner Information Form. And all the required documents (including but not limited to Certificate of Incorporation, Scheme of the ownership of the company including disclosing the ultimate beneficiaries) must be submitted for all Join Venture members.Thank you.

New clarification added: Subject: Request for review of qualification criteria (Section 1.4) due to market stagnationSubject: The requirement to provide 3 contracts and one of them for 14 MW in the last 5 years creates an insurmountable barrier for most Ukrainian companies. It is important to consider the context: due to the COVID-19 pandemic and the subsequent full-scale war, the market for construction of powerful boiler houses in Ukraine was effectively frozen. According to our data, this UNOPS project is the second such project of this scale in Ukraine (boilers with a capacity of more than 14 MW in the last 5 years). Requiring participants to have experience in implementing three similar projects at a time when such projects were not physically implemented in Ukraine means automatically disqualifying national Ukrainian suppliers and bidders. This contradicts the goals of Ukraine's recovery and local business development. Request: extend the period to 8-10 years (pre-COVID/pre-war period).Dear Bidder,Thank you for your request. Please find the answers below.The requirement of the clause 1.4 of the Section II Schedule of Requirements (as well as respective RFQ criteria) will be amended to be read as follows: “The Bidder must have experience in supplying similar equipment in Ukraine or EU/EEA countries and must provide evidence (contracts, purchase orders, performance certificates, etc.) of the successful completion of at least 3 contracts for the supply of the proposed or equivalent equipment (at least one of the contracts must be for supply of gas boiler unit(s) with a unit capacity of at least 14 MW), implemented over the last 10 years.”Thank you.

New clarification added: Question Regarding Burner Specification and Consistency (Clauses 1.1.9 and 1.1.11)Given that the tender specifies a total of four (4) boilers, comprising two (2) units with gas-only burners and two (2) units with dual-fuel (gas/diesel) burners, clarification is required regarding the scope of the "same brand/manufacturer" requirement in Clauses 1.1.9 and 1.1.11:Clause 1.1.9 refers to "Burners operating on gaseous fuel."Clause 1.1.11 refers to "Burners operating on gaseous and liquid fuel."Please clarify the intended scope of the consistency requirement:A) Project-Wide Consistency: Are all four (4) boiler units (i.e., both the gas-only burners and the dual-fuel burners) required to be of the same brand and manufacturer?B) Category Consistency: Does the requirement mean that all burners specified under 1.1.9 (Gas) must be of one brand, and all burners specified under 1.1.11 (Dual-Fuel) must be of one brand, potentially allowing for two different burner manufacturers across the project?Dear BidderThank you for your request. Please find the answers below.(A) All 4 boilers are required to be of the same brand and manufacturer.(B)All burners specified under 1.1.9 (Gas) must be of the same brand and model, and all burners specified under 1.1.11 (Dual-Fuel) must be of the same brand and model. Gas burners and Dual-fuel burners can be from different manufacturers but all gas burners must be of the same brand and model and all dual-fuel burners must be of the same brand and model.Thank you.

New clarification added: Text from the tender documentation:"аSection II: Schedule of requirementsB. Technical specifications for Goods – Comparative Data Tables1.1.5 Boiler units with economizers in accordance with this tender documentation must be of the same brand and be designed and manufactured by the same manufacturer."Question regarding Clause 1.1.5 – Restrictive Sourcing Requirement:We seek clarification on Clause 1.1.5 requiring Boiler and Economizer units to be manufactured by the same entity. This condition is contrary to international industry practice where combining components from specialized manufacturers often yields superior technical and economic efficiency. For instance, the tender documents do not impose a similar requirement for the Boiler and Burner units to be from the same manufacturer, which is often standard practice in the industry. Insisting on a single source for the Boiler/Economizer severely limits competition and may prevent the Procuring Entity from accessing the best available technology and most competitive pricing. Could this requirement be revised to ensure broader competition, provided the successful bidder provides a comprehensive warranty and performance guarantee for the integrated system?Dear BidderThank you for your request. Please find the answer below.Clause 1.1.5. “Boiler units with economizers in accordance with this tender documentation must be of the same brand and be designed and manufactured by the same manufacturer.” means that all the 4 boilers must be produced by the one manufacturer (be of the same brand) and also all the economizers must be produced by one manufacturer - be of the same brand (it may be different from the boilers manufacturer but all economizers must be from one manufacturer for consistency).Thank you.