# FACSIMILE TRANSMISSION

TO:
Name: Larry Wethje Company: ARI Telephone: 703 524-8800 

### Fax No: 703 528-3816
FROM: Name: Ed Pollock Company: DOE 

### Telephone: 202 586-5778 Fax No: 202 586-4617
Larry, Date: July 27, 1995

I am sending you some figures that Greg Rosenquest put together for us which summarize the results of the calibration he did of the MODCON model using data and guidelines provided by members of the committee. The "before" results were generated using the test measurements. "After" results represent the model output when guidelines recommended by the committee were used to restrict certain parameters. The bars represent the model deviation from measured values. Greg noted that the accuracy of the predicted values were proportional to the completeness of the input values. The predictions for heat pumps are not quite as good as for AC only systems. However, in all cases there seems to be pretty good correlation. More important, there does not appear to be any larger disagreement at the 12 and 13 SEER levels than there were at the 10 SEER level. This makes me think that the model is not too bad. As I told you on the phone, if the companies are willing to provide the data, I would like to have Greg do this same type of analysis at higher levels of SEER to see how the model does when we have more design option combinations. Also, you said there were concerns about performance improvements not being as large as predicted with certain combinations (time delay and TXV being the best known). If you could provide the necessary data, we would be glad to investigate the ability of the model to handle these combinations. As I have indicated to you and others on the committee, DOE cannot just drop the MODCON/life cycle cost analysis approach. Since this analysis is a part of the public record, we must be able to explain why we could not use this approach in a way that would hold up in court. Based on the results shown in the attached graphs, I don't see how we can say the model is not usable. Thus we will need to look for other areas where corrections need to be made. We are will to discuss any approach you might recommend, but in the end we have to address this TO: Name: Company: Telephone: Fax No: FROM: Name: Company: Telephone: Fax No: Larry, 

# FACSIMILE TRANSMISSION

LanyWethje 

### ARI 703 524-8800 703528-3816

EdPollock DOE 202 586-5778 202586-4617 Date: July 27, 1995

I am sending you some figures that Greg Rosenquestputtogetherfor us which st;lmmarize the results ofthe calibration he did ofthe.MODCON model using data and guidelines provided by members ofthe committee. The "before" results were generated using the test measurements. "After" results represent the model output when guidelines recommended by the committee**wen~** used to restrictcertain parameters. The bars represent the model deviation from measured values. Greg noted thatthe accuracy ofthe predicted values were proportional to the completeness ofthe inputvalues. The predictions for heatpumps are not quite as good as for AC only systems. However, in all cases there seems to be pretty good correlation. More important, there does not appearto be any larger disagreement at the 12 and 13 SEERlevels than there were at the 10 SEERleveL This makes me think thatthe model is nottoo bad. As I told you on the phone, ifthe companies are willing to provide the data, I would like to have Greg do this same type ofanalysis at higher levels ofSEERto see howthe model does when we have more design option combinations. Also, you said there were concerns aboutperformance improvements notbeing as**larg~** as predicted with certain combinations (time delay and TXVbeing the bestknown). Ifyou could provide the necessary data, we would be glad to investigate the ability ofthe model to handle these combinations. As I have indicated to you and others on the committee, DOE cannotjustdrop the MODCON/life cycle cost analysis approach. Since this analysis is a part ofthe public record, we must be able to explain why we could not use this approach in a way that would hold up in court. Based on the results shown in the attached graphs, I don'tsee how we can say the model is notusable. Thus we will need to look for other areas where .corrections need to be made. We are will to discuss any approach you might recommend, butin the end we have to address thisissue. My feeling is that results will be more satisfactory if we hit it straight on and continue

with the current approach, since both DOE and the MODCON group have already invested a lot of time in it. I suggest the following approach for your consideration: 1. Check the MODCON model at higher values of SEER 2. Review the design options being considered for technical problems such as combinations where the effects are not cumulative, too large a credit has been allow, etc. 3. Evaluate the costs being used for inconsistencies and to ensure price/volume values seem reasonable. (Based on my review of the analysis to date, I suspect this is where we will find the major problems if any exist.) 4. If the industry wants to follow a track similar to the ASHRAE 90.1 method, we would encourage them to do this. I believe it may be a useful way to identify abnormalities in the current approach. Hopefully at some point we will be able to make the two methods converge. We look forward to meeting with you on Wednesday. We appreciate the assistance ARI and its members have given us and we want to continue the spirit of cooperation. We are aware that the issue of having to deal with a change in,refrigerants at the same time changes in efficiency are being considered is still of concern to many of the manufacturers and we invite continuation of discussions on ways to minimize the impact of the two. issue. My feeling is thatresults will be more satisfactory if we hitit straight on and continue with the current approach, since both DOE and the MODCONgroup have already invested a lot oftime in it. I suggest the following approach for your consideration: 1. Check the MODCON model at higher values ofSEER 2. Review the design options being considered for technical problems such as combinations where the effects are not cumulative, too large a credithas been allow, etc. 3. Evaluate the costs being used for inconsistencies and to ensure price/volume values seem reasonable. (Based on myreview ofthe analysis to date, I suspect this is where we will find the majorproblems ifany exist.) 4. If the industry wants to follow a track similarto the ASHRAE 90.1 method, we would encourage them to do this. I believe itmay be a useful way to identify abnormalities in the current approach. Hopefully at some pointwe will be able to make the two methods converge. We look forward to meeting with you on Wednesday. We appreciate the assistance ARI and its members have given us and we want to continue the spirit ofcooperation. We are aware that the issue ofhaving to deal with a change inrefrigetants at the same time changes in efficiency are being considered is still ofconcern to many ofthe manufacturers and we invite continuation of discussions on ways to minimize the impact ofthe two.