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

EE-RM-93-801 COMMENT 0II

TO: 

Name: 

Company: 

Telephone: 

Fax No: 

FROM: 

Name: 

Company: 

Telephone: 

Fax No: 

Larry, 

FACSIMILE TRANSMISSION 

LanyWethje 

ARI 

703 524-8800 

703528-3816 

Ed Pollock 

DOE 

202 586-5778 

202586-4617 

Date: July 27, 1995 

I am sending you some figures that Greg Rosenquest put together for us which st;lmmarize 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 wen~ 

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 larg~ 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 
issue. 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.

EE-RM-93-801 COMMENT 0II

issue. 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 inrefrigetants 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.