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  1. #14
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    Quote Originally Posted by dan sw fl View Post
    HUMIDITY CONTROL
    I'll keep humidity control in mind. But Calgary is fairly dry, if anything we could probably use higher humidity.

    __ AUTO ADJUST DAMPER would be standard on MAU.
    Damper would be controlled by providing ~ 0.05" W.C. Positive Pressure
    Interesting. I didn't know that. If it has an auto damper that controls the air pressure that would be ideal. I'll ask the manufacturer.

    Is there some sort of small compressor built into the MAU that provides the air pressure to control the damper?

    CO2 Controller may be an alternative in a few situations.
    Not sure what you mean here. The MAU only supplies air to hallways (and the boiler room), not a garage, if that's what you mean.

    _ Might wish to think about manually opening window during Clothes Air Dryer use.
    I guess that would reduce the amount of air going through the MAU. But I imagine the amount of energy savings would be minimal, and people are unlikely to do this in the winter when the weather is cold.

    Control the TIMING AND AMOUNT of exhaust air from EACH Condo.

    ASHRAE STD. 62.2 - 2013
    ___ Understand & Use the INFILTRATION CREDIT _ _ from data provided by a BLOWER DOOR TEST

    For example,
    _ 30 CONDOS * ~ 40 CFM / CONDO = 1,200 CFM Total Continuous ( weekends )
    __________ 40 CFM Could be less than a Continuous flow rate.
    ______ No one home during the day _ _ Reduce exhaust air flow rate for upto 12 hours
    A lot of information to absorb here, but at first glance it looks like an interesting possibility - beyond what I had in mind, but perhaps a re-think of the ventilation system for the whole building would be worth it if the energy savings are large.

    According to some old drawings that I have, the original MAU (replaced 12 years ago) was rated for 1,500 cfm. The square footage of the entire building, 12 apartments and all common areas, is roughly 18,000 sqft (not all areas are ventilated by the MAU). Assuming the current MAU has the same flow rate, does 1,500 cfm seem excessive?

  2. #15
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    Quote Originally Posted by pecmsg View Post
    You need a Mechanical Engineer. There are several factors involved, Building code and Fire Codes. Residential building Common areas are Positive pressure. Hallways, Emergency stairs Etc. Air changes per hour requirements need to be meet!
    I see. I was kinda thinking it would require an engineer if the air flows are changed.

    However, I think the first thing that needs to be done is to find out if the current MAU system is operating as intended. Perhaps it is providing too much flow rate. Do you know how this would be checked? Would this typically be done by a maintenance technician?

  3. #16
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    Quote Originally Posted by buford View Post
    Is the MAU using gas for fuel? And do each units have a gas fireplace? I have seen condos where the gas is on a common meter and during the winter, the fire places are on and drives up usage.
    The MAU is indeed gas fired, but there are no gas fireplaces in the building.

    However, the boiler and hot water heater are also gas fired and there is only one meter for the whole building, as far as I know. So we don't actually know how much gas the MAU uses. But I think it will be much more than the boiler and water heater combined, since the MAU runs continuously 24/7 and heats air from sometimes sub-zero temperatures to room temperature. Whereas the boiler is normally only maintaining room temperature in each zone.

  4. #17
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    Quote Originally Posted by nielkfj View Post
    I'll keep humidity control in mind. But Calgary is fairly dry, if anything we could probably use higher humidity.



    Interesting. I didn't know that. If it has an auto damper that controls the air pressure that would be ideal. I'll ask the manufacturer.

    Is there some sort of small compressor built into the MAU that provides the air pressure to control the damper?



    Not sure what you mean here. The MAU only supplies air to hallways (and the boiler room), not a garage, if that's what you mean.



    I guess that would reduce the amount of air going through the MAU. But I imagine the amount of energy savings would be minimal, and people are unlikely to do this in the winter when the weather is cold.



    A lot of information to absorb here, but at first glance it looks like an interesting possibility - beyond what I had in mind, but perhaps a re-think of the ventilation system for the whole building would be worth it if the energy savings are large.

    According to some old drawings that I have, the original MAU (replaced 12 years ago) was rated for 1,500 cfm. The square footage of the entire building, 12 apartments and all common areas, is roughly 18,000 sqft (not all areas are ventilated by the MAU). Assuming the current MAU has the same flow rate, does 1,500 cfm seem excessive?
    That's a tiny MUA.
    Probably everyone was thinking at least 6-12000 cfm.
    Also, are you sure it doesnt use some return air?
    Altho 1500 18 is only about 80cfm per apartment, so it's probably sized to make up the exhaust air.

    Sent from my SM-G950U using Tapatalk

  5. #18
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    Quote Originally Posted by Juan Madera View Post
    Big capital expense, but might consider an air-to-air heat exchanger that takes all the exhaust air (bath vents) from the building in a common duct and transfers the recovered heat into the supply air. Supply air will be cooler than what you have now, but economy of operation is worth the look.. All the new hotels I've seen use these.

    As to efficiency of MAU, if it is a direct fired type, it is 100% efficient. Engineer is recommended in any case, one that has actually worked hands on in the field is preferable..
    Ya, probably a big capital expense and unlikely to be accepted by other owners. What I'm focussing on is trying to optimize the efficiency of the existing equipment. I figure that means reducing the supply temperature from the MAU, and reducing the flow rate if possible. It seems like there is no code restriction on the supply temperature. However, reducing the flow rate is restricted by code. That's where the engineer would be needed I assume.

    Another option mentioned is installing a programmable thermostat that will set the hallway temperature back during the night.

    I sure hope the MAU isn't direct fired. I'm pretty sure it is indirect, otherwise we would smell natural gas from time to time I would think.

  6. #19
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    Quote Originally Posted by icy78 View Post
    That's a tiny MUA.
    Probably everyone was thinking at least 6-12000 cfm.
    Also, are you sure it doesnt use some return air?
    Altho 1500 18 is only about 80cfm per apartment, so it's probably sized to make up the exhaust air.

    Sent from my SM-G950U using Tapatalk
    I'm quite sure there is no return air going into the unit. I've been up on the roof and took photos. Just checked the photos now and there is definitely no ducting going into the unit upstream of the fan.

    There's only 12 apartments. So 1,500 12 = 125cfm per apartment.

    For some reason the hallways for the two basement apartments do not have any make-up air. I might be because both of these apartments have their own hallway with no other apartments sharing that hallway.

  7. #20
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    Quote Originally Posted by nielkfj View Post
    I'll keep humidity control in mind. But Calgary is fairly dry, if anything we could probably use higher humidity.

    Interesting. I didn't know that. If it has an auto damper that controls the air pressure that would be ideal. I'll ask the manufacturer.

    ___________
    _______ I suspect damper may have electrical controller. ___ ie.. Belimo or similar

    Is there some sort of small compressor built into the MAU that provides
    the air pressure to control the damper?
    ___________

    Not sure what you mean here.
    The MAU only supplies air to hallways (and the boiler room), not a garage, if that's what you mean.

    I guess that would reduce the amount of air going through the MAU.
    But I imagine the amount of energy savings would be minimal, and
    people are unlikely to do this in the winter when the weather is cold.

    A lot of information to absorb here, but at first glance it looks like an interesting possibility -
    beyond what I had in mind, but perhaps a re-think of the ventilation system
    for the whole building would be worth it if the energy savings are large.

    According to some old drawings that I have, the original MAU (replaced 12 years ago)
    was rated for 1,500 cfm.
    __ Actual set-up and rating would not necessarily be the same.

    The square footage of the entire building, 12 apartments and all common areas,
    is roughly 18,000 SqFt (not all areas are ventilated by the MAU).

    Assuming the current MAU has the same flow rate,
    does 1,500 cfm seem excessive?
    12 CONDOS _ 2 BEDROOMS _ ~ 1,200 SQ FT EACH

    ASHRAE 62.2 -2013

    Required Make-Up air flow rate would be in the Ball park of 30 CFM
    after an Infiltration Credit of 30 CFM is used.

    The existing Infiltration amount must be verified by an actual Blower Door Test.

    EXAMPLE WORK SCOPE:
    _________ One OPTION

    Hallways = 0.03 * ~ 3,000 = ~ 90 CFM

    12 * 30 CFM = 360 CFM
    ____________+ 90 CFM
    ___________+ ___ ___ any Make-up Air for any other COMMON Areas
    _____ Total < ~ 600 CFM.

    POSITIVE PRESSURE MUST BE MAINTAINED in Hallways.

    It appears that 1,500 CFM is excessive IMO.
    However, your local requirements may be based on
    a Canadian IAQ standard that I am not familiar with.

    NOTE: Hallways are not considered to have Occupants.

    AHJ in applicable Calgary Building Department / Disciplines
    should review your proposed MAU plans.

    AUTHORITY HAVING JURISDICTION

    ANY STRUCTURAL CHANGES WOULD BE SUBJECT TO LOCAL PERMITING PROCESS IMO.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  8. #21
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    If you are thinking of changing the design you will need engineer designed drawings and permits pulled. Keep in mind the building and each HVAC system in the individual unit are designed for certain conditions. If you change the temp of the hallway, you are changing the conditions the individual units are designed for.

  9. #22
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    Quote Originally Posted by ammoniadog View Post
    Ha, I was waiting for someone to say this! It don't get more efficient than 100%, well unless it's a heat pump, but I've gotten into some heated arguments about how it's impossible for heat pumps to defy the laws of physics, so I'm not going to go there.

    With that being said, I believe direct fired units are banned from areas where people sleep, so I'm guessing it has heat exchangers.



    This doesn't prove anything other than that your apartment is at more of a negative pressure than the hallway is. A better test would be to go down near the water heaters/boilers when they're not running and hold a match near the flue pipe and see which direction the flame goes (assuming that they're natural draft with no dampers), or go near an outside door to the building and do the same thing with the door slightly cracked.
    OK, I did the match flame test on the door to my apartment and on an exterior window to my apartment. I made a video of each test which you can watch from this drop box:

    https://drive.google.com/drive/folde...ED?usp=sharing

    All other windows in my apartment and the balcony door were closed, and all forced ventilation devices (bathroom fan, range hood fan, dryer) were turned off.

    From the videos it shows that the velocity of air coming around the door is quite a bit higher than exiting through the window opening. In fact it looks like there is barely any air flowing out the window at all. I guess the air coming in around the door is mostly exiting out the bathroom, range hood and dryer ducts even though they aren't turned on.

    Does this look like normal air flow into and out of an apartment in a building with a MAU?

  10. #23
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    Quote Originally Posted by dan sw fl View Post

    ___________
    _______ I suspect damper may have electrical controller. ___ ie.. Belimo or similar

    __ Actual set-up and rating would not necessarily be the same.
    The figure of 1,500 cfm comes from a mechanical drawing by the architect who designed the building and is an "Issued for Building Permit and Tender" revision, not "As Built". So 1,500 cfm could be totally wrong.

    12 CONDOS _ 2 BEDROOMS _ ~ 1,200 SQ FT EACH
    Actually all 12 condos are only about 1,000 sq ft each.

    ASHRAE 62.2 -2013

    Required Make-Up air flow rate would be in the Ball park of 30 CFM
    after an Infiltration Credit of 30 CFM is used.

    The existing Infiltration amount must be verified by an actual Blower Door Test.

    EXAMPLE WORK SCOPE:
    _________ One OPTION

    Hallways = 0.03 * ~ 3,000 = ~ 90 CFM

    12 * 30 CFM = 360 CFM
    ____________+ 90 CFM
    ___________+ ___ ___ any Make-up Air for any other COMMON Areas
    _____ Total < ~ 600 CFM.

    POSITIVE PRESSURE MUST BE MAINTAINED in Hallways.

    It appears that 1,500 CFM is excessive IMO.
    However, your local requirements may be based on
    a Canadian IAQ standard that I am not familiar with.

    NOTE: Hallways are not considered to have Occupants.

    AHJ in applicable Calgary Building Department / Disciplines
    should review your proposed MAU plans.

    AUTHORITY HAVING JURISDICTION

    ANY STRUCTURAL CHANGES WOULD BE SUBJECT TO LOCAL PERMITING PROCESS IMO.
    I made some videos of a lit match held next to the gap in the door to the hallway, and next to an exterior window that is cracked open. You should be able to view them from this drop box:

    https://drive.google.com/open?id=1eg...H1MCsNRcUBThED

    From the videos, does it look like excessive air flow is coming around the door?

    One other question. I have been assuming that the codes don't have any requirements for the temperature of the make-up air entering the hallways, just the pressure or flow rate of the air. Is this correct?

  11. #24
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    Quote Originally Posted by comfortdoc View Post
    If you are thinking of changing the design you will need engineer designed drawings and permits pulled.
    OK, thanks.

    I think my first step will be to verify that the MAU is rated for an appropriate flow rate.

    Second step would be to bring somebody in to check the flow rate, and adjust it if it is not what the building was designed for.

    Third step, if needed, would be to get an engineer to change the design to a lower rate if possible.

    Keep in mind the building and each HVAC system in the individual unit are designed for certain conditions. If you change the temp of the hallway, you are changing the conditions the individual units are designed for.
    OK, that's what I was starting to gather, that the MAU and the boiler water heating systems affect each other. If one provides more heating the other should provide less heating, and vice versa.

    From an energy efficiency standpoint it seems the optimal set-up would be to minimize the flow rate and temperature from the MAU. Then each resident can use the boiler water heating system to 'top-up' the temperature to their own liking.

    Also, possibly a temperature setback controller can be used for the MAU to lower the supply temperature at night.

  12. #25
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    MAU N.G. Operating Cost

    __ BALL PARK SAVINGS

    ___ EXAMPLE CALC
    ___________________ Presume:
    ………….. 1. Existing air flow =~ Rated for MAU
    ………….. 2. Supply Temp from MAU = 70'F // feed to Hallways

    _______ $ 21.14 / month Savings
    ___ $ 130 PER YEAR per Condo
    ____ based on $ 0.90/ THERM Natural Gas

    ___ ___ … … ___ ___
    Attached Images Attached Images  
    Last edited by dan sw fl; 12-01-2019 at 06:59 AM.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  13. #26
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    Quote Originally Posted by dan sw fl View Post
    __ BALL PARK SAVINGS

    ___ EXAMPLE CALC
    ___________________ Presume:
    .. 1. Existing air flow =~ Rated for MAU
    .. 2. Supply Temp from MAU = 70'F // feed to Hallways

    _______ $ 21.14 / month Savings
    ___ $ 130 PER YEAR per Condo
    ____ based on $ 0.90/ THERM Natural Gas

    ___ ___ ___ ___

    So if I understand you correctly, you figure the building only needs about 780cfm - 12units*30cfm/unit (infiltration credit) = 420 cfm of forced ventilation. Is this correct?

    In Canada we might have tighter windows and doors than in Florida. So assuming there is no infiltration credit then the MAU would need to supply 780cfm. Is this correct?

    Did you check out the videos I made of the airflow into and out of my apartment? If so, do you think it looks like excessive airflow?

    Here in Alberta we have pretty cheap gas. Currently it costs only about CA$3.80/GJ ≈ US$0.30/therm. So I imagine the only economical way to reduce the flow rate would be to use the existing MAU and modify it for reduced flow in some way.

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