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sorry for the late response, I was away for awhile. quark - i would think the mcpdt equation can still describe an aspect of the situaion - the heat rejection stays the same then the mass flow increases(corresponding pressure increase)and refer DT decreases due to higher refregerant velocity...

We're considering some work to reduce the condenser approach temp. e.g 6°F to 1.6°F. In order to move forward I need to calculate the cost savings. The system has a water-cooled centrifugal chiller. Can the cost savings be calculated by using site data e.g. gpm, temperatures, power cost...

sridhar1312 - . WB depression seems to make sense, but unfortunetly, i don't have the exact temps during the summer months. CTDon - Thanks for the link - good info. Equalizer lines have been an issue in the past as well e.g. two cell towers -- 10"-10" into 10" then into 10" common equalizer...

HVAC68 - the design WB is 68°F. At 95°F DB and above the CWS temp starts to increase. I'm not sure of the WB temp but "typical" WB temps at 95°+ DB for our area. I think the issue is really a load based problem (need more heat rejection area as you indicated) at the towers and not so much...

Thanks HVAC68 for the spreadsheet cdxx139 - no problem with topic. this is good info and could figure into the decision in the long run (not to mention other projects!). for a little more info: we ended up adding louvers in adjacent walls and velocity stacks just to maximize performance of...

The desert would be nice! We inherited the site so had to make do with what was installed. Good point-will look into this as an option as well.

thanks everyone, i'll try to summarize: the plant is less thatn 10years old and is a total of 2000 tons (3+1 with 500T chillers/towers). The cooling towers are sized for 68°F WB (a little undersized). maintenance is good and the plant is running well, the CWS temp starts to rise when OAT rises...

We're considering two options for additional heat rejection. The problem is that on a design day our cooling towers run at their limits and we lose redundancy with them. The thought is to either add a 1000ton cooling tower to the existing ones (largest we can fit); or, add a 350 nominal ton...

quark - DETAILS!! :) I appreciate your input and follow up. Thanks all.

MintJulep - I agree it is best to fix or replace the dampers. There are multiple 130ton units and the cost would be signifcant and potentially disrupt operations. This calc may assist in quantifying the energy waste etc to present a case to fix, replace or seal them off. Quark - After I...

Thanks all for the input. marc/utility/mint -- Damper Specs: I need to dig up the specs but I believe design should be less than 2 cfm/sqft leakage. In this case, we know they leak and are trying to determine if leakage is excessive and could potentially de-rate the unit on a design day e.g 105...

Hello All, I was trying to figure out the amount (CFM) of outside air leaking through a closed control damper. After some thought it seems the best method is to calcualte the outside air percentage based on temperatures per the following: x% = outside air percentage (OA%) Ta = outside air temp...

Thank you both very much for the response. GMcD...these are flooded batteries. we have proper ventilation rates and have not had any problems with static discharge and no humidification for the last five years i.e no explosions. gepman...To control the battery environment to a minimum of 30%...

I've searched for a design guidline for humiditiy requirement in battery rooms but have not had any luck. There is quite a lot of info regarding ventilation but not humidification. What is a typical guidline or reference for humidity in battery rooms?

mintjulep I'd have to verify the accumulator-I think it would be integral to the chiller. also, if the heater came on as soon as the generators kicked in (15seconds?) then we shouldn't have a problem with oil migration to the crankcase (although we would still have a longer reboot time for the...

we would have a restart sequence to avoid overloading the electrical busses. I think it would take at least 4-5 minutes for the chillers to get back to 100% load.

The operating condition is: chiller is at full load, utility outage and chillers shut down, generators quickly start and power is restored to restart the chillers. If the generators start quickly and power is restored would you really need to have the crankcase heaters and associated...

rbulsara i'm not specific because i haven't yet read the material! my point was to take an idea (fire alarm systems) from concept(nebulous)to concrete (less nebulous) i.e. presentation to quiz on presentation. Why am i getting reprimanded?

rbulsara i suppose going from nebulous to less nebulous is part of the learning process...FWIW, i am learning about fire alarm systems. DavidCR i appreaciate your comments. i did find some manufacturer's data and a NFPA Fire Alarm Systems Workbook. The workbook includes info on...

I figured that there must have been a reason for the tongue lashing I received, but I can take it. I can understand both of your frustrations and appreciate your comments. This type of forum is great, but sometimes the intent is hard to discern from an email. Again, just looking for info.