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Old 12-01-2019, 08:44 PM   #16
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by surferdude2 View Post
WOW! That's a lot of air infiltration or should I say injection. Even if you can get better control of the temperature, you still need to find a way to throttle that air flow without affecting any other area that may require it. You need professional help and will likely have to re-duct the system. You're living in a wind tunnel!
OK, that gives me some idea about whether or not the air-flow coming into my apartment is normal or not.

Perhaps the video of the door makes it look worse than it is. It doesn't take much air to blow out a match. When I feel around the door with my hand it feels like light blowing, about as strong as blowing with your mouth on a spoonful of hot soup to cool it off. Also, the air velocity is higher coming underneath the door, than around the sides and top, probably because the gap beneath the door is much larger than the gap between the door and frame.
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Old 12-01-2019, 09:05 PM   #17
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Re: How to Make a MAU More Energy Efficient?


By those simple tests, it's clear that you are well above any desirable air exchange that is normal. If you can't get the system changed, put weatherstrip at the door jamb and get one of the door bottom cozies, maybe one of the slider type that allows for opening and closing the door. Don't worry, normal infiltration and any leaks you get around your work will still provide enough air exchange.
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Old 12-01-2019, 09:46 PM   #18
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by surferdude2 View Post
By those simple tests, it's clear that you are well above any desirable air exchange that is normal. If you can't get the system changed, put weatherstrip at the door jamb and get one of the door bottom cozies, maybe one of the slider type that allows for opening and closing the door. Don't worry, normal infiltration and any leaks you get around your work will still provide enough air exchange.
OK, thanks. It's good to have somebody with experience give their impression.

I was thinking about the weatherstripping and a door cozie. I figure the door cozie is the better option for the bottom of the door because I can regulate the amount of ventilation by simply sliding the cozie to the side to leave part of the door bottom open.
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Old 12-01-2019, 10:42 PM   #19
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Re: How to Make a MAU More Energy Efficient?


a few questions:

have you considered an energy audit? there are firms that will do "blower door tests" of your building and help you find and control leaks. hallway door gaskets aren't going to do much here if the units are leaking lots of air and pulling it in from the MAU.

is the MAU over-pressurizing the hallway? if yes, then you're just throwing away money for no reason.

what kind of exhaust fans do you have for the condos? standard fart fans? if so, have you considered replacing them with an HRV?

what kind of MAU do you have? direct fire? 80%? 95%? hot water? does it have an economizer of any kind?

what kind of controls does the MAU have? does it take "demand" into account, or does it just push a set CFM/temperature?

Last edited by u3b3rg33k; 12-01-2019 at 10:44 PM.
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Old Yesterday, 12:20 AM   #20
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by u3b3rg33k View Post
a few questions:

have you considered an energy audit? there are firms that will do "blower door tests" of your building and help you find and control leaks.
I have been thinking about something like that - possibly the government has a free service. But, right now I am just gathering information. Next I will try to find out if the MAU is pushing the correct flow rate, and if it can be modified.

Quote:
hallway door gaskets aren't going to do much here if the units are leaking lots of air and pulling it in from the MAU.
The units don't have any ventilation system that continuously sucks air out of the units. Just an electric "fart" (haha) fan, stove hood fan and a dryer.

Quote:
is the MAU over-pressurizing the hallway? if yes, then you're just throwing away money for no reason.
Some other people have commented that they think this is the case. I made some videos demonstrating the air coming in to my unit around the entrance door, and air exiting out an exterior window. You should be able to view them here:

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

All other windows in the unit were closed and no fans turned on.

What do you think? Does this look like excessive air flow coming around the door?

Quote:
what kind of exhaust fans do you have for the condos? standard fart fans? if so, have you considered replacing them with an HRV?
HRV (heat recovery ventilation?) is likely going to be expensive, and so beyond what we want to do. Right now I'm just looking at having the temperature and/or flow rate from the MAU adjusted so that we aren't using any more energy than is necessary.

So I guess it isn't the MAU that I want to make more efficient, but the MAU and building 'system' that I want to make more efficient.

Quote:
what kind of MAU do you have? direct fire? 80%? 95%? hot water? does it have an economizer of any kind?
It's an Engineered Air Model S225/O/R. It is natural gas burning, not hot water. I believe it is indirect fired because it supplies air to the interior of the building. I don't know about the percentage or economizer.

Quote:
what kind of controls does the MAU have? does it take "demand" into account, or does it just push a set CFM/temperature?
I'm pretty sure it doesn't take demand into account, but rather a set CFM and temperature is more likely, although the temperature set point is adjustable.

It's only as small condo building. 12 units, four level walk-up, wood structure, built in 1979. Nothing fancy. The building architect's drawings that we have, specified the original MAU to have a flow rate of 1,500 cfm. That MAU was replaced with the current MAU 12 years ago, which I assume has a similar flow rate.
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Old Yesterday, 01:28 AM   #21
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Re: How to Make a MAU More Energy Efficient?


I can't find that model number at the Engineered Air site. You may just have to get a pro to measure the flow of that unit

Since the engineered drawings called for 1500 cfm and the unit has been changed and the new unit model number has a 225 in it... it might justify having a pro measure the air flow of the system. Simple math 1500cfm /12 units = 125 cfm each. That's about what a small fart fan delivers. You're getting much more than that from what your smoke tests indicates. Something is wrong and the energy loss savings by fixing the system could pay for the repairs pretty fast.
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Old Yesterday, 02:57 AM   #22
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by nielkfj View Post
I have been thinking about something like that - possibly the government has a free service. But, right now I am just gathering information. Next I will try to find out if the MAU is pushing the correct flow rate, and if it can be modified.
I think it would be worth your time - it can be used as a tool to verify before/after air sealing work as well
Quote:
Originally Posted by nielkfj View Post



The units don't have any ventilation system that continuously sucks air out of the units. Just an electric "fart" (haha) fan, stove hood fan and a dryer.
you can do energy recovery from general areas and bathrooms, but NOT directly from range hoods. code says no, likely because of grease fouling/fire hazard risks. it COULD be done, but what homeowner is going to keep up on the maintenance? i assume a single digit percentage, hence the code prohibition
Quote:
Originally Posted by nielkfj View Post


Some other people have commented that they think this is the case. I made some videos demonstrating the air coming in to my unit around the entrance door, and air exiting out an exterior window. You should be able to view them here:

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

All other windows in the unit were closed and no fans turned on.

What do you think? Does this look like excessive air flow coming around the door?
yes i think that looks wrong, but looks != data

Quote:
Originally Posted by nielkfj View Post
HRV (heat recovery ventilation?) is likely going to be expensive, and so beyond what we want to do. Right now I'm just looking at having the temperature and/or flow rate from the MAU adjusted so that we aren't using any more energy than is necessary.
a big HRV isn't that expensive (fantech has a 1400cfm unit for $3800). you will spend more money on labor getting it installed and commissioned properly than the equipment itself.

Quote:
Originally Posted by nielkfj View Post
So I guess it isn't the MAU that I want to make more efficient, but the MAU and building 'system' that I want to make more efficient.
yep. the building is a system and should be looked at as such. where do you want the air to go in/out? is it going there? if it's going in, it IS going out, so might as well have it controlled instead of uncontrolled.

Quote:
Originally Posted by nielkfj View Post
It's an Engineered Air Model S225/O/R. It is natural gas burning, not hot water. I believe it is indirect fired because it supplies air to the interior of the building. I don't know about the percentage or economizer.



I'm pretty sure it doesn't take demand into account, but rather a set CFM and temperature is more likely, although the temperature set point is adjustable.
that sounds like a system that makes sense in a restaurant/commercial building, not one that makes sense in a building with significantly lower air exchange requirements.

in new construction, individual HRV/ERVs might make sense for the units, and one for the common areas (with demand sensors if significant energy savings are possible). with a retrofit you may find it more economical to supply to the common areas and exhaust through the units. I have seen plenty of apartment buildings with centralized exhaust out of the bathrooms, and fresh air supplied to the hallways. it helps keep individual tenant odors contained to their units.

Quote:
Originally Posted by nielkfj View Post
It's only as small condo building. 12 units, four level walk-up, wood structure, built in 1979. Nothing fancy. The building architect's drawings that we have, specified the original MAU to have a flow rate of 1,500 cfm. That MAU was replaced with the current MAU 12 years ago, which I assume has a similar flow rate.
if that's the case, you should have 1500cfm of centralized exhaust. mind you 1500cfm is around 4 tons of cooling/ 50kBTU heating (based on 400cfm/ton sizing, may vary on outdoor conditions). having an HRV with reheat in the system could cut that in half. for continuous operation the savings add up fast.

Last edited by u3b3rg33k; Yesterday at 03:01 AM.
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Old Yesterday, 04:03 PM   #23
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by u3b3rg33k View Post
if that's the case, you should have 1500cfm of centralized exhaust. mind you 1500cfm is around 4 tons of cooling/ 50kBTU heating (based on 400cfm/ton sizing, may vary on outdoor conditions). having an HRV with reheat in the system could cut that in half. for continuous operation the savings add up fast.

1500 CFM with an outdoor temp of -20F and an air discharge temp of 70F would be roughly 150,000 BTUs. 180,000 BTUs if the OPs outside Temps reach -40F.


If the unit had cooling, it would be closer to 12.5 tons of cooling, unless the OPs area reaches Temps exceeding 90F outside, then it would be 20 to 25 tons of cooling.
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Old Yesterday, 05:33 PM   #24
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Re: How to Make a MAU More Energy Efficient?


Nothing like cooling and heating the great outdoors!

Makeup air is inherently energy wasteful, even more so if an excessive amount is used... then it becomes like infiltration on steroids or the wolf of infiltration in sheep's clothing, if you will.

I remain of the mind that this system needs checking by a pro.
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Old Yesterday, 06:42 PM   #25
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Re: How to Make a MAU More Energy Efficient?


I agree with surfer dude. The necessary air exchange volume is separate from the efficiency of that process and any excess is wasteful from the start. Measure what is needed THEN make that exchange as efficient as possible.

Bud

Note, here is some background on the debate among the experts regarding how much air is needed.
https://www.energyvanguard.com/blog/...-Not-Be-Futile
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Old Yesterday, 08:16 PM   #26
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by beenthere View Post
1500 CFM with an outdoor temp of -20F and an air discharge temp of 70F would be roughly 150,000 BTUs. 180,000 BTUs if the OPs outside Temps reach -40F.


If the unit had cooling, it would be closer to 12.5 tons of cooling, unless the OPs area reaches Temps exceeding 90F outside, then it would be 20 to 25 tons of cooling.
I was bad and didn't do any maths, just based on standard cfm/ton. sorry.

1500cfm of makeup air sounds like a restaurant/kitchen.
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Old Yesterday, 09:42 PM   #27
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by surferdude2 View Post
I can't find that model number at the Engineered Air site. You may just have to get a pro to measure the flow of that unit

Since the engineered drawings called for 1500 cfm and the unit has been changed and the new unit model number has a 225 in it... it might justify having a pro measure the air flow of the system. Simple math 1500cfm /12 units = 125 cfm each. That's about what a small fart fan delivers. You're getting much more than that from what your smoke tests indicates. Something is wrong and the energy loss savings by fixing the system could pay for the repairs pretty fast.
Hmm, did a quick check of Home Depot, confirming 125 cfm is a fart fan. It does seem like I'm getting more that what a fart fan would push coming around my door.

Ya, maybe 225 means 2,250 cfm. That's the first thing to find out. After that, I guess I'll discuss with the other owners about bringing in an energy auditor or an HVAC engineer to specify the correct flow rate.
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Old Yesterday, 11:42 PM   #28
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by u3b3rg33k View Post
I think it would be worth your time - it can be used as a tool to verify before/after air sealing work as wellyou can do energy recovery from general areas and bathrooms, but NOT directly from range hoods. code says no, likely because of grease fouling/fire hazard risks. it COULD be done, but what homeowner is going to keep up on the maintenance? i assume a single digit percentage, hence the code prohibition yes i think that looks wrong, but looks != data

a big HRV isn't that expensive (fantech has a 1400cfm unit for $3800). you will spend more money on labor getting it installed and commissioned properly than the equipment itself.
I think it would likely be over $10k, so probably very few of the owners will want to do this. Maybe if we had an energy audit that showed huge savings it might fly.

Quote:
yep. the building is a system and should be looked at as such. where do you want the air to go in/out? is it going there? if it's going in, it IS going out, so might as well have it controlled instead of uncontrolled.

that sounds like a system that makes sense in a restaurant/commercial building, not one that makes sense in a building with significantly lower air exchange requirements.

in new construction, individual HRV/ERVs might make sense for the units, and one for the common areas (with demand sensors if significant energy savings are possible). with a retrofit you may find it more economical to supply to the common areas and exhaust through the units. I have seen plenty of apartment buildings with centralized exhaust out of the bathrooms, and fresh air supplied to the hallways. it helps keep individual tenant odors contained to their units.
Our building has supply to the hallways and exhaust out of the units, which would be the bathrooms, range hoods and dryers. I believe the range hoods have a flapper on a spring, so they are normally closed when off. The bathroom fans and dryers I don't know if they have a flapper.

Quote:
if that's the case, you should have 1500cfm of centralized exhaust. mind you 1500cfm is around 4 tons of cooling/ 50kBTU heating (based on 400cfm/ton sizing, may vary on outdoor conditions). having an HRV with reheat in the system could cut that in half. for continuous operation the savings add up fast.
We don't have any cooling (don't need it here) just heating.
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Old Yesterday, 11:51 PM   #29
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by beenthere View Post
1500 CFM with an outdoor temp of -20F and an air discharge temp of 70F would be roughly 150,000 BTUs. 180,000 BTUs if the OPs outside Temps reach -40F.
We don't get to -40 here. 30-40 years ago we could get close once in a while, but nowadays there are maybe only a few days per year where it gets below -30 C (-22 F) for a daily low temperature.

Quote:
If the unit had cooling, it would be closer to 12.5 tons of cooling, unless the OPs area reaches Temps exceeding 90F outside, then it would be 20 to 25 tons of cooling.
We don't need cooling here, only gets about 90 F 3-4 days per year. Although last year we set an all time record high at 36 C (97 F) on one day.
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Old Today, 12:05 AM   #30
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Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by surferdude2 View Post
Nothing like cooling and heating the great outdoors!

Makeup air is inherently energy wasteful, even more so if an excessive amount is used... then it becomes like infiltration on steroids or the wolf of infiltration in sheep's clothing, if you will.
I'm starting to understand this. We are essentially pumping cold outdoor air into our building continuously, and paying for the energy costs to counteract it and maintain a comfortable indoor temperature. With no heat recovery it really must be minimized or we are wasting a lot of money.

Quote:
I remain of the mind that this system needs checking by a pro.
If I was the only person paying for it, I would hire an HVAC engineer and get a full evaluation of the building, without hesitation.
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