1.1 Scope
Gas-fired condensing water heaters are used to provide hot water for domestic purposes or process heating, and offer an energy efficient method of generating hot water. They can be installed close to the point of use, or in a central plant room.
Gas-fired condensing water heaters are described as ‘storage’ type products if they generate hot water by heating water stored within the product itself. Other types of gas-fired condensing water heaters are described as ‘non-storage’ type products, and can be divided into continuous flow type products that are designed to instantaneously generate hot water directly from cold water, and those that heat water as it is circulated round a loop (which may also include buffer vessels).
Gas-fired condensing water heaters are available in a range of different efficiencies. The Energy Technology List (ETL) Scheme aims to encourage the purchase of higher efficiency products.
The ETL Scheme covers three categories of gas-fired condensing water heaters:
- Storage type, gas-fired condensing water heaters not exceeding 150kW
- Non- storage, instantaneous (or continuous flow) type, gas-fired condensing water heaters
- Non-storage, circulator (or multi-pass) type, gas-fired condensing water heaters.
To be eligible for inclusion on the ETL, products shall meet the requirements as set out below.
1.2 Definitions
Gas-fired condensing water heaters are products that are specifically designed to continuously provide hot water either by the direct heating of water as it passes through the product, or the heating of water contained in an integral storage vessel.
1.3 Requirements
1.3.1 Eligibility requirements
To be eligible products, shall:
- Be gas-fired.
- Be a condensing gas-fired water heater.
- Comply with the requirements of the Water Supply (Water Fittings) Regulations 1999, the Water Byelaws 2000 Scotland and the Water Regulations in Northern Ireland (for example, by inclusion in the Water Regulations Advisory Scheme’s Water Fittings and Materials Directory, or equivalent schemes, such as KIWA and NSF).
- Have an appropriate Conformity Assessment mark
In addition, non-storage – circulator type, gas-fired condensing water heaters shall:
- Use fully premixed burners or an appropriately matched forced draught burner (or burners).
- Automatically respond to changes in hot water demand by modulating their output in a continuous manner across a minimum turndown ratio of 5:1, without initiating a purge cycle.
- Products with a thermal output in excess of 400kW shall either use burners from the “burners with controls” list on the ETL or:
- Incorporate a microprocessor based burner control system.
- Use a variable speed motor controller (or Variable Speed Drive) to operate each forced draught fan incorporated into the product.
- Where mechanical dampers are used to modulate the air flow to the burners, they shall be operated by a precision servomotor. The servomotor shall be controlled by a positional or flow-based feedback mechanism that automatically adjusts its operation to correct for mechanical wear, valve stiction and hysteresis.
- Where control valves are used to modulate the fuel flow to the burners, they shall be operated by a precision servomotor. The servomotor shall be controlled by a positional or flow-based feedback mechanism that automatically adjusts its operation to correct for mechanical wear, valve stiction and hysteresis (this requirement shall not apply to pneumatically operated modulating gas valves).
In addition, non-storage – instantaneous type, gas-fired condensing water heaters exceeding 70kW shall be fitted with an integral, fully pre-mixed, modulating burner.
1.3.2 Performance requirements
Eligible products shall meet or exceed the appropriate performance criteria:
- Products with a rated heat output <= 400kW, shall meet or exceed the gross water heating energy efficiency ηwh thresholds shown in Table 1.1 at the declared load profile.
- Products with a rated heat output > 400kW, shall meet or exceed the gross thermal efficiency thresholds shown in Table 1.2.
Table 1.1 Minimum gross water heating energy efficiency (ηwh) for gas-fired condensing water heaters with a rated heat output of 400kW or less (all product categories)
|
Declared load profile |
3XS |
XXS |
XS |
S |
M |
L |
XL |
XXL |
3XL |
4XL |
|
|
Water Heating Energy Efficiency (ηwh) |
≥ 70.0% |
≥ 80.0% |
≥ 85.0% |
|
|||||||
Where:
- Water Heating Energy Efficiency (ηwh) is the ratio between the useful energy in the water provided and the energy required for its generation, expressed as a percentage.
- Load profile is a given sequence of water draw-offs, as specified in in Annex III, Table 1 of Commission Regulation (EU) No 814/2013 “Ecodesign requirements for water heaters and hot water storage tanks”.
Table 1.2 Minimum gross thermal efficiency for gas-fired condensing water heaters with a rated heat output of over 400kW
|
Product category |
Nominal heat input (kW) |
Test conditions |
Gross thermal efficiency % |
|
Non storage – instantaneous type |
> 400kW |
At 100% load, flow/return temperatures of 80/60ºC |
≥ 85.6% |
|
At 30% load, return temperature of 30ºC |
≥ 93.7% |
||
|
Non storage - circulator type |
> 400kW |
At 100% load, flow/return temperatures of 80/60ºC |
≥ 85.6%
|
|
At 30% load, return temperature of 30ºC |
≥ 93.7% |
“≥” means “greater than or equal to”
For products with a rated heat output <= 400kW, the load profile used for the test shall be declared by the manufacturer and shall be the maximum load profile or the load profile one below the maximum load profile for the product.
Products with a rated heat output > 400kW shall meet or exceed the minimum gross thermal efficiencies at both full load and part load test conditions, as specified in Table 1.2.
Suppliers shall report the following, which will be published on the ETL Product Search:
- The model’s NOx emissions (mg/kWh) when the measured efficiency value in conformity with Table 1.1 or Table 1.2 was recorded.
1.4 Measurement and Calculations
1.4.1 Measurement standards
All products shall be tested in accordance with the procedures set out in one of the test standards recognised by the ETL as set out below, or in accordance with equivalent procedures for assessing thermal efficiency within applicable British Standards.
Tests to determine gross water heating energy efficiency (products <= 400kW) shall be carried out at the conditions specified in BS EN 13203-2:2015.
Tests to determine gross thermal efficiency (products > 400kW) shall be carried out at the test conditions specified in an appropriate test standard named in Table 1.3.
Table 1.3 ETL recognised test standards to determine gross thermal efficiency
|
Test standard |
Applicable product categories |
|||
|
|
1 |
2 |
3 |
|
|
BS EN 89:2015 Gas-fired storage water heaters for the production of domestic hot water |
✔ |
|
|
|
|
BS EN 303-3:1999 Heating boilers — Part 3: Gas-fired central heating boilers — Assembly comprising a boiler body and a forced draught burner‘. |
|
|
✔ | |
|
BS EN 303-7:2006 Heating boilers — Part 7: Gas-fired central heating boilers equipped with a forced draught burner of nominal heat output not exceeding 1,000kW‘. |
|
|
✔ | |
|
BS EN 15502-1:2012+A1:2015 Gas-fired heating boilers. General requirements and tests BS EN 15502-2-1:2012+A1:2016 Gas-fired central heating boilers. Specific standard for type C appliances and type B2, B3 and B5 appliances of a nominal heat input not exceeding 1 000 kW |
|
|
✔ | |
|
BS EN 26:2015 Gas-fired instantaneous water heaters for the production of domestic hot water |
|
✔ | ✔ | |
1.4.2 Rounding
For the avoidance of doubt, all efficiency test data should be presented to one decimal place. As an example, a 500kW non storage, instantaneous, gas fired condensing water heater with a gross thermal efficiency of 85.5% at the full load condition would be deemed to be a fail.
1.5 Verification for ETL Listing
Any of the following testing routes may be used to demonstrate the conformity of products against the requirements:
- In-house testing – Self-certified
- In-house testing – Self-tested and verified or cross-checked by an independent body
- Witnessed testing
- Independent testing
- Representative testing (see clause 1.5.1)
Further information regarding the first three routes can be found in the ETL Testing Framework.
1.5.1 Representative testing
Where applications are being made for gas fired condensing water heaters that are variants of the same constructional design and rated outputs up to and including 400 kW to be included on the ETL, test data may be submitted for a representative selection of models. The representative models shall be selected by dividing the range of products into groups of models with similar design characteristics, and testing a model in the lowest quartile of predicted performance in each group. The performance of each model in the group shall be predicted using a validated mathematical model. As a minimum, at least one model shall be tested in each range of products.
Where applications are being made for products of the same constructional design and rated outputs greater than 400 kW to be included on the ETL, test data may be submitted for a single representative model provided that the maximum rated output of the products being applied for is not more than twice, or less than half, the maximum rated output of the product tested. Where the range of rated outputs exceeds these limits, products should be grouped into size ranges that comply with these rules, and test data submitted for one representative model for each group.
It should be noted that:
- If a manufacturer voluntarily removes a representative model from the ETL then other products linked with that representative model may or may not be permitted to remain on the ETL.
- If any product submitted under these representative model rules is later found not to meet the performance criteria when independently tested, then all products based on the same representative models will be removed from the ETL.
1.6 Conformity testing
Products listed on the ETL may be subject to the scheme’s conformity testing programme in order to ensure listed models continue to meet the ETL requirements.
1.7 Review
1.7.1 Indicative review date
This specification is scheduled for review during the 2024/25 review cycle.
1.7.2 Illustrative future direction of the requirements
The next technical review will consider how renewable technology and smart capability could be integrated into this category, as well as potentially setting emissions performance thresholds. The review will also consider further uplifting the turndown ratio for non-storage water heaters, consider the efficiency thresholds in light of any regulatory changes (e.g., Part L of the Building Regulations) and consider the case for hydrogen ready appliances.