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PNM Responses to Joe Kordzi’s email of November 1, 2010 

Question 1: 

The revised costs include a correction to the air heater modifications for Units 3 and 4, 

which were inadvertently double counted in prior estimates. The record so far does not 

contain the vendor quote on which the air heater costs are based, or any other support. In 

response to our previous request, B&V responded that the information is not in the public 

record. As these costs are large, we need the supporting vendor proposal for the air 

heater modifications. 

 

Response: 

Please refer to PNM response to EPA’s other email from November 1, 2010. 

Question 2: 

We cannot confirm B&V's costs for electrical equipment. The original cost estimate 

includes $484,000 per unit for an "electrical system upgrade." We cannot confirm this 

cost, using the SJRPP proposals that were provided or the cost excerpt in the OAQPS 

Commentary, Appx. B, Section 4.11: Electrical Upgrades. Please provide a calculation 

cited to specific pages/line items of the supplied quotes and identify each item that is 

included. 

 

Response: 

The following items were taken from the SJRPP quotation and included in the San Juan 

estimate: 

• 480 volt feeder breakers – budget price of $69,200 for 2 units 

• Low voltage switchgear (for small electrical loads like the ammonia 

system) – budget price of $248,000 for 2 units 

• 480 volt motor control centers (MCC’s) (for small electrical loads like the 

ammonia system) – budget price of $500,000 for 2 units 

• Secondary Unit Substation Transformer – budget price $180,000 for two 

units 

The total budgetary cost for all of these items was $1,065,100 for two units ($532,550 per 

unit). These costs are shown in the budgetary estimate build up for SJRPP, previously 

supplied to the EPA. The actual costs were somewhat different, but in the same range. 

The actual quotations were provided to the EPA last week. 

This budgetary cost was then scaled using the following equation: 

cos $484,000

670

544

cos _ _ 3 1.03 $532,550

_

_ _ cos _ _ cos

0.6

0.6

=

⎟

⎠

⎞ ⎜

⎝

⎛ = × ×

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = × ×

PNM t

PNM t Unit

SJRPP MW

PNM unit MW PNM t escalation rate SJRPP t
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The electrical modifications discussed above are independent of B&V’s updated auxiliary 

power assessment (submitted to the EPA on October 22, 2010) because these are the low 

voltage requirements and do not support the additional power requirements for the draft 

fans. The auxiliary power assessment performed by B&V (and submitted to the EPA on 

October 22, 2010) was performed to assess the auxiliary power needs of the draft fans. 

In addition to the costs above, which were all used for supplying power to the small SCR 

loads (dilution air fans, NOx monitoring systems, elevator, seal air fans, etc.), a 

$1,000,000 allowance (per unit) was included in the original balance draft conversion 

estimate to cover modification associated with the new fans. This $1,000,000 was an 

allowance and was not based on any quotations or detailed estimating. It was simply an 

allowance. 

When B&V performed a detailed assessment of the auxiliary power needs, the 

$1,000,000 allowance was removed from the balance draft conversion estimate to ensure 

that auxiliary power costs were not being double counted. This is explained in Table 4 

and Table 5 of PNM’s cost estimate update, submitted to the EPA on October 22, 2010. 

Question 3: 

You have added a new cost item, entitled "auxiliary electric system requirements," 

amounting to $6,400,000 for each of Units 1 and 2 and $8,350,000 for each of Units 3 

and 4. These additions are based on "minimum" load changes totalling 25,594 kw. An 

SCR typically uses about 0.3% of a plant's electric output. In the original B&V cost 

estimate, the annual auxiliary and ID fan power was calculated assuming 4,881 kW, 

which is equal to about 0.3% of the plant output. We do not understand the basis for 

ascribing 100% of the cost for upgrading auxiliary electrical equipment to support 

increases in load that are five times greater than the demand of the SCR alone. We feel 

that if any of these costs are warranted, they should be proportioned among the various 

Consent Decree modifications. To make this calculation, we will need a list of the 

Consent Decree modifications, the cost of each project, and the load change for each. 

Response: 

Attachment 1 is being provided to give information on the latest fan sizing calculation. 

We continue to update and revise the fan sizing calculation and improve it as we gain 

more knowledge about the plant operation. B&V’s estimate assumes that the existing 

fans would be replaced with larger fans to handle the new system pressure requirements 

from SCR installation. This is especially required for Units 3 and 4 ID fans, which are 

already running at their maximum capacity with no margin left for nominal ash fouling of 

convective heat transfer surfaces or leakage that is expected to increase between major 

unit maintenance outages. The new fans would be sized to operate normally at the full 

load conditions of the modified units, as well as 20 percent margin on pressure on the 

maximum continuous rating. Maximum Continuous Rating (MCR) refers to the 

equipment design values. This is where B&V predicts the equipment will be operating at 

full load without margin. Test Block (TB) refers to the maximum capability of the draft 

fan equipment and includes margin for nominal fouling and system leakage. The margin 

allows for some operating and maintenance flexibility to allow the unit to continue to 
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meet full load if, for example, boiler convection pass surfaces are fouled with ash 

deposits and the air heater has worn seals which results in additional leakage beyond asnew conditions. The electrical system has to be sized to allow starting of the new larger 

fan motors as well as continuously operate at the test block conditions, but this is not 

necessarily where the unit will be continuously operating. 

For the sizing of ID fans for new generating units, the standard B&V fan sizing 

philosophy for developing test block (TB) conditions is recommended. This philosophy 

includes the application of the following items to the required MCR conditions for the 

new fans: 

• 10 percent margin on flue gas exiting the boiler 

• 50 percent margin on leakages throughout the draft system 

• 50 percent margin on air heater differential pressure 

• 25°F temperature increase at the fan inlet 

• Adjustments of draft system pressure drops to correspond with increased TB flow 

rates 

• 1.0 inch of water gauge (in w.g.) control allowance 

The application of these items typically results in flow margins in the range of 15 to 20 

percent and pressure margins in the range of 35 to 45 percent. Compared to normal fan 

margins for new units, the fan margins for retrofit AQCS modifications are normally less, 

as is the case for the ID fan sizing used for the conceptual design for the SJGS. 

This calculation shows that for Units 1 and 2, approximately 2,200 kW (3,000 hp) 

additional fan capacity is required per unit to add the SCR. For Units 3 and 4, 8,600 kW 

(11,600 hp) additional fan capacity is required. 

For the consent decree, the following auxiliary electric work was performed: 

• New control system for the Unit 1 and 2 startup transformer to prevent both units 

from starting up at the same time. 

• New 480 v motor control centers for the fabric filter loads 

No new transformers or switchgear were added to the station for the new fan impacts that 

resulted from the recent consent decree work. Instead, the spare capacity of the plant 

auxiliary electric system was used towards supplying power to the fans. There is no 

spare capacity left at the plant for additional power consumption that would result with 

the addition of SCR. The additional electrical load requirements are based on the 

modifications needed to support the draft equipment impacts of SCR operation and are 

not considered current constraints as the SJGS is operating as intended utilizing the air 

pollution control systems installed to comply with the consent decree. 

When sizing the auxiliary electric system, it is recommended that the fans run off of a 

dedicated transformer. There are two options for providing this transformer. First, is to 

provide a new, dedicated transformer and associated equipment to power the new fans. 

The other option would be to clear off an existing transformer and move smaller loads 

from an existing transformer to a new, smaller transformer. In this second approach, the 

new fans could be run off of the old transformer (once it has been cleared off). This 
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option may sound less expensive because the transformer being purchased would be 

smaller. However, the difference in cost is typically made up be the labor associated in 

re-routing all the smaller, non fan loads to the new transformer. It increases the retrofit 

difficulty of the project and the uncertainty for additional costs resulting from 

complications in this option. Therefore, the first option was selected by B&V and was 

described in the updated cost estimate submitted to the EPA on October 22, 2010. 
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Attachment 1 

Fan Sizing Calculation 
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