Page 1 of 2 12 LastLast
Results 1 to 13 of 15
  1. #1
    Join Date
    Jul 2009
    Posts
    247

    Question about potential energy savings

    I'm looking at possible energy savings when it comes time to start replacing equipment. Here is a short list of the rooftops I have to work with:

    Trane SFCA -753-2b type 268-532-1-8
    Trane SACA (cant read entire model number) Type 263-531-1A (10 ton?, unit cooling only, no heat)
    Carrier 48dd008a

    Units I believe are 220v 3 phase. I'm wondering what kind of energy savings can be realized by going to newer multistaged equipment such as the lennox strategos, compared to the current units and compared to units such as the lennox landmark series (this building is locked to lennox equip for all intents and purposes). A couple other tidbits of info: Elec cost is roughly $.066 per kwh, and the building has a demand charge of $7 per KW (figured on 15min intervals) in the summer and $3.5 per KW in the winter.

    Also, it appears the SFCA units are 150k btu in, 112k btu out at approx $5.5/MCF. Can you foresee any savings in the heating side with the multistage equip.

    One final point to mention. I have one banquet room that is approx 2,500 sq ft. that uses 2 of the SFCA units and 1 of the SACA units. Only the 2 SFCA units provide heating to the space during the winter.

  2. #2
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190

    Potential Energy savings more than the "BOX"

    I understand your question and finding out how much electric power is needed per ton of cooling is a straightforward lookup. The real question is what reductions of power are possible if you look at the SYSTEM. For instance say you have 30 tons now and it is an east west office building with 3 constant volume rooftops. Perhaps a single 25 ton unit( already with 2 or more compressors) with VAV dampers could replace the 3 units since the sun is not an the east at the same time it is on the west face.
    Another question is How well is the equipment maintained? Same as residential, if refrigerant charge is not correct, you're wasting energy.
    And finally the biggest opportunity is demand ventilation vs some outside air damper unless someone has already closed the damper because they thought it was just eating up the power.
    So your question only scratches the surface of what you need to ask your contractor, although this would take a first class commercial contractor to get good answers, probably with the support of an engineers block loads at the very least
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  3. #3
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190

    PS from your question I thought you were the consumer

    I didn't look at your profile until after I posted. Perhaps the mods could make your contractor minus * clear or just blame it on me for not looking first
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  4. #4
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,670
    Best that I can do is to move this to Tech to tech forum.

    stebs,

    You should consider Professional Membership.

  5. #5
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    Besides the equipment enhancement, why not consider a control system to boot?

  6. #6
    Join Date
    Jul 2009
    Posts
    247
    I'm a facility manager, and have a decent understanding of HVAC equipment and how to maintain it. I refuse to go anywhere near refrigerant piping, system charging, or heat exchanger issues. Had one of the SFCA units throw a fan belt last winter and had the business manager have the service company change it as I was afraid the heat exchanger may have been compromised as the heat ran for some time without the fan running and it was a liability issue I didnt want on my shoulders. I'd apply for pro if I could, but doubt I would have it granted as I dont work for an HVAC company.

    Anywho, I posted this question as you guys would be far more knowledgable with potential savings between the different units. The previous trend has been to replace the aging units with landmark units, and I cannot see how these would be very effecient as they are single stage cool. It makes way more sense to me to have units that can match the building's load rather than cycling between off and full capacity. I can figure gas costs and electrical costs all day long, but I dont have the real world experiences with these various units that you guys do. I realize improving the building envelope would be a very wise choice, but getting the business to spend the money for that would be practically impossible.

    As for the control system, I have been looking at the lennox L connection network system. Do I understand correctly that if I had a room with multiple RTU's serving it, that the control system would stage those units better and more efficiently than a couple of T-stats in the room controlling units individually? Would this system also help keep demand charges down during setback recovery and during the day?

    One final thing, this building has a dining room that i'm guessing is approx 1200 sq ft that has 2 ancient carrier air handlers with i'm assuming 15kw heat strips in each of them (have not had a chance to verify). One of my suggestions to management is going to be to replace those with a couple of G61v's to help reduce energy costs. Would the L connection network system be able to treat this room as having 4 stages of heat/cool rather than 2 seperate 2 stage systems?

  7. #7
    Stebs, I wanted to ask you about your FM career is there a way I can private message you?

  8. #8
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    969
    Why do you care about energy savings when the cost is passed through to the tenants?

    But lets say just because it makes sense. your question is broad and you can go into many directions. I think what it will boil down to is how much Capital your owners are willing to spend on improvements and what the ROI will be and that will help you decide what you can and cant do.

    anyway, depending on the use of the building signal tenant or multi-tenant many company's and engineers are leaning towards LEED standards or at the least trying to achieve ASHRAE standards like the ones below. how does you building compare to today's standards? You may find your not and the cost to get it up to the standard will cost to much in time and money. So if your looking to change out a unit to a more efficient unit, that's easy. If you looking to make a plan effect the total energy savings for the whole building with a 5 year plan then you will need to do more home work.

    ASHRAE Standard 55, “Thermal Environmental Conditions for Human Occupancy”
    ASHRAE Standard 62, “Ventilation for Acceptable Indoor Air Quality”
    ASHRAE Standard 90.1, “Energy Standards for Building Except Low-Rise
    Residential Buildings”

  9. #9
    Join Date
    Feb 2012
    Location
    Upstate SC
    Posts
    84
    I would keep the comparison as simple as I could looking at EER ratings and deferred maintenance costs. If you are going from single stage to two, use the the integrated part load values which should make it more attractive. Also, I'm not sure what you meant by BTU's in and out. Total vs. latent?

  10. #10
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by stebs View Post
    I'm a facility manager, and have a decent understanding of HVAC equipment and how to maintain it. I refuse to go anywhere near refrigerant piping, system charging, or heat exchanger issues. Had one of the SFCA units throw a fan belt last winter and had the business manager have the service company change it as I was afraid the heat exchanger may have been compromised as the heat ran for some time without the fan running and it was a liability issue I didnt want on my shoulders. I'd apply for pro if I could, but doubt I would have it granted as I dont work for an HVAC company.

    Anywho, I posted this question as you guys would be far more knowledgable with potential savings between the different units. The previous trend has been to replace the aging units with landmark units, and I cannot see how these would be very effecient as they are single stage cool. It makes way more sense to me to have units that can match the building's load rather than cycling between off and full capacity. I can figure gas costs and electrical costs all day long, but I dont have the real world experiences with these various units that you guys do. I realize improving the building envelope would be a very wise choice, but getting the business to spend the money for that would be practically impossible.

    As for the control system, I have been looking at the lennox L connection network system. Do I understand correctly that if I had a room with multiple RTU's serving it, that the control system would stage those units better and more efficiently than a couple of T-stats in the room controlling units individually? Would this system also help keep demand charges down during setback recovery and during the day?

    One final thing, this building has a dining room that i'm guessing is approx 1200 sq ft that has 2 ancient carrier air handlers with i'm assuming 15kw heat strips in each of them (have not had a chance to verify). One of my suggestions to management is going to be to replace those with a couple of G61v's to help reduce energy costs. Would the L connection network system be able to treat this room as having 4 stages of heat/cool rather than 2 seperate 2 stage systems?
    Ultimately you have to look at yoru return on investment. You best bet is first look at properly sizing the equipment and making sure you have adequate airflow so to can opperate efficienctly as well as regular PM even jsut for simple things like checking belt tension & condition and filter changes. Finally, a good control package that properly designed and configured can go a long way. Jsut having thermostats in the wrong location, not managing humidity levels can kill delivered efficiency.

    In a office area, as facility manager, IMO, you first goal is occupant comfort, then system reliability and erviceability (can I get parts easily and do I have an installer that knows thsi system) then finally efficiency. If you cover the first two, the 3rd will often fall inline.

    I'm sure almost every pro would agree that a 30 year old outdated lower effciency system that well maintained, properly sized and controlled, is far better than a brand new system that isn't designed or installed correctly.


    On a side note, I too am in the facility manager role, but I've proven knowledgeable, particularly on the residential side to be granted the priveledge of pro status. I'm careful only to respond to subjects that I'm familiar with technically. I think it's healthy and helpful to have some professionals on this site on both sides of the "fence". This site is an amazing resource.


    On your final question. One option is using a lead lag controller. This could provide you with 4 stages of capacity with some models of controllers. It also gives you equal run time and if both blowers need ot keep running for adequate airflow or fresh air (you are bringing in fresh outdoor air into the lunchroom aren't you?)

  11. #11
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    969
    G61v's residential units in a commercial building? do you have gas in place? you need to consider existing duct size and know the design of the AH's to see what replacement options you will have

  12. #12
    Join Date
    Jul 2001
    Location
    Canada
    Posts
    1,813
    Why do you care about energy savings when the cost is passed through to the tenants?

    Like because he wants a building that has tenants in it. Tenants do look at their operating costs when deciding to renew a lease or move to newer more efficent buildings.

  13. #13
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    969
    Quote Originally Posted by Control Man View Post
    Why do you care about energy savings when the cost is passed through to the tenants?

    Like because he wants a building that has tenants in it. Tenants do look at their operating costs when deciding to renew a lease or move to newer more efficent buildings.
    Yes, true. But you will get a different answer depending on who you ask.

    Plus depending on how the lease is written. if your billing back for electrical use then the price per KW in negligible, if the cost is built into the lease then the owner or the tenant don't care. The only time energy savings will be a benefit to owner or new tenant, IF the the total energy saving for the whole building will lower the rental rate per sq ft a few cents. 50 cents a sqft will either make a deal or lose a deal. If the electrical cost is passed through to the tenant, the Owner sees no benefit for spending tens of thousands for up grades to save the tenants money. when they have a 10 year lease. Owners will only upgrade if they have too, one unit at a time.

    Thats very basic for how i can explain it here. But again this relates to how the building is occupied, by one tenant or its Mutli-tenant and how the lease is written.


    Plus if the local rental rates are xx per sqft and you charge xx per hour for overtime electrical and that's the local average. Lower your overtime rate a few cents if you want to attract people . Its all about money. Tenants will stay where they like to work 90% of the time. and owners will give free rent to keep them. money money

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event