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National Wood Burner Performance Review: Phase 2

Executive Summary

1 Introduction

2 Methodology

3 Test Results

4 Conclusions

Appendix 1: Review Protocol

2 Methodology

The project methodology involved a number of discrete processes, including:

• random selection of wood burners to test

• development of a protocol for verifying wood burner compliance

• communication with interested parties

• purchasing the 10 wood burners

• testing design, emissions and efficiency.

Burner selection, protocol development, and project communication are discussed in more detail below.

2.1 Random selection of wood burners

Wood burners randomly selected for inclusion in the performance review were sourced from the lists of ‘authorised’ and ‘tested’ wood burners published on the Ministry website.⁴

At the time the review began these lists contained 66 authorised and 44 tested wood burners, respectively. There were some wood burners on both lists that were identical, and these duplicates were removed before the random sampling took place. Where there were any doubts as to whether the same wood burner was on both lists (ie, if they had only slightly different names) it was initially assumed they were different.

The objective of the sampling process was to randomly select two lists of wood burners to include in the performance review. One list was to comprise 40 wood burners for the design verification testing and the other list to comprise 10 wood burners for the full emissions testing process.

2.2 Protocol for determining compliance

The review protocol is the agreed process by which the design verification testing was carried out and the classification of failures undertaken. This protocol was developed by John Yolland, an independent engineer with many years experience with wood burners, in association with the project partners. Technical input was also provided by industry representatives.

The objectives of the protocol are to:

• introduce the rationale for determining compliance

• specify the basis for selecting wood burners for inclusion in the review

• specify the dimensions that will be measured and the allowable tolerances

• provide examples of verification failure

• provide classifications of failure and recommended remedial actions.

Given the potentially sensitive nature of this work it was considered to be important to have the support of the industry. The design protocol was reviewed by a working group of the New Zealand Home Heating Association before being finalised. A copy of the protocol is attached as Appendix 1.

The failure classifications according to measured outcomes are provided in Table 1.

For Phase 2, in which both design verification and emissions and efficiency testing were carried out, there arises the possibility of conflicting outcomes. For example, a burner may suffer a ‘minor’ failure in the design verification but have resulting emissions that would be classified as a ‘moderate’ failure in accordance with the review protocol. It is further important to acknowledge the limits of accuracy of the test methods AS/NZS 4012:1999 and AS/NZS 4013:1999.

Table 1: Failure classification

Note: Because the limits of accuracy are substantial, there is no ‘minor’ category for efficiency failures.

Overall classification of failure was determined on a case-by-case basis. In general, however, priority was afforded to results of actual performance (ie, emissions and efficiency testing). For example, a burner that suffered a serious failure in the design verification but only a minor failure for actual efficiency, would be classified as a minor failure.

Whilst unlikely, it is conceivable that a burner could suffer a failure in design verification and still pass the emissions and efficiency standards. This occurred for the Lady Kitchener. The approach in this instance was to notify the failure but not to request any remedial action.

2.3 Communication with interested parties

As mentioned above, it was important to carry out this project in consultation and co-operation with interested parties. The prime concern for the main project partners was to determine whether wood burners offered for sale match the wood burners for which approvals had been granted and/or test reports issued. However, it is also important for retailers to know they are selling wood burners that are legally able to be installed in the various regions around New Zealand. It is further necessary to inform potential consumers about the status of burners in the review – particularly in the case of burners suspended from the list.

The results of the review were published in two reports – Phase 1 in June 2007 and Phase 2 in this report. In addition to this the Ministry made detailed review information to interested parties upon direct request. For example, consumers wishing to purchase a burner that was temporarily suspended from the authorised list were informed of the reasons behind the suspension and the status of the burner. Similarly, full technical information was provided to councils considering consent applications and retailers querying burner status. The commercial considerations of manufacturers subject to requested remedial actions were not ignored; such information was only provided verbally and upon direct request.

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