How To Make A MAU More Energy Efficient? - HVAC - DIY Chatroom Home Improvement Forum
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Like Tree2Likes
 
 
Thread Tools
Old 11-28-2019, 08:44 PM  
Newbie
 
Join Date: Nov 2019
Location: Calgary, Alberta, Canada
Posts: 16
Rewards Points: 32
Default

How to Make a MAU More Energy Efficient?


I live in a small condo building. Myself and some of the other owners are interested in improving the energy efficiency of the building. One of the things we are considering is adjusting the temperature and/or air flow rate from a make-up air unit (MAU) that supplies air to the building hallways.

With respect to this, the questions I have are:

1) Other than the comfort level of the temperature in the hallways, are there any other factors that we should be considering?

2) Is there a simple way to adjust the air flow rate from a MAU?

3) Are there any other common ways to make a standard MAU operate more energy efficiently?

Any suggestions would be appreciated.
nielkfj is offline  
Sponsored Links
Advertisement
 
Old 11-28-2019, 09:23 PM  
Member
 
david86camaro's Avatar
 
Join Date: Apr 2016
Posts: 31
Rewards Points: 4
Default

Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by nielkfj View Post
I live in a small condo building. Myself and some of the other owners are interested in improving the energy efficiency of the building. One of the things we are considering is adjusting the temperature and/or air flow rate from a make-up air unit (MAU) that supplies air to the building hallways.



With respect to this, the questions I have are:



1) Other than the comfort level of the temperature in the hallways, are there any other factors that we should be considering?



2) Is there a simple way to adjust the air flow rate from a MAU?



3) Are there any other common ways to make a standard MAU operate more energy efficiently?



Any suggestions would be appreciated.


Code probably would dictate the amount of airflow of the unit. So the only way to save money with the existing unit would be to lower the temp, but would cost comfort. If your replacing the unit there are different options that can make it more efficient but mostly it costs more up front to save efficiency.


Sent from my iPhone using Tapatalk
david86camaro is offline  
Sponsored Links
Advertisement
 
Old 11-28-2019, 09:27 PM  
83yr old neophyte retired
 
Join Date: Nov 2019
Location: Mousetown, southern Illinois, USA
Posts: 222
Rewards Points: 444
Default

Re: How to Make a MAU More Energy Efficient?


We'd need to know what is being used to supply the MUA and whether it is with or without a heating or cooling method.

I've put several MUA unit in commercial buildings and usually they were simple swamp coolers (evaporative coolers). Fine tuning the flow rate to achieve an air balance with the outgoing air was as simple as selecting the motor pulley size. The initial unit size was critical and had to be close enough that a motor pulley change would do the job.

You'll not be able to change the efficiency much since whatever motors are involved pretty much tell the tale on that since fan laws are exactly what the term implies, it's a physical law and not subject to user discretion.

The concept of MUA is inherently inefficient since you are throwing away as much as you input and any energy expended doing that is lost along with any temperature tweaking you are doing in the process. Recapturing that energy is possible but neither easy or cheap.
__________________
Timing has a lot to do with the outcome of a rain dance.
surferdude2 is offline  
Sponsored Links
Advertisement
 
Old 11-28-2019, 09:58 PM  
Newbie
 
Join Date: Nov 2019
Location: Calgary, Alberta, Canada
Posts: 16
Rewards Points: 32
Default

Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by david86camaro View Post
Code probably would dictate the amount of airflow of the unit. So the only way to save money with the existing unit would be to lower the temp, but would cost comfort. If your replacing the unit there are different options that can make it more efficient but mostly it costs more up front to save efficiency.


Sent from my iPhone using Tapatalk
I would prefer to set the MAU at the minimum flow rate allowed by code to save heating costs. I imagine the flow rate was set up when the building was constructed 40 years ago, but I would like to have it checked. Do you know if this is easy or difficult to do?

The MAU was replaced 12 years ago, so there could have been a change to the system that increased to the airflow at that time.

Do you know what temperature range is typically used for building hallways?
nielkfj is offline  
Old 11-28-2019, 10:15 PM  
Member
 
Join Date: Nov 2015
Location: Maine
Posts: 8,440
Rewards Points: 7,000
Default

Re: How to Make a MAU More Energy Efficient?


Your local building department or a local engineer should know what levels of fresh air were necessary by code 40 years ago, 15 years ago, and if you make any changes today. Air quality requirements have changed a lot over the past 40 years and not necessarily in your favor.

Canada is a cold climate and they do have some strict regulations. We have some members here from Canada so may be able to get some specifics.

Do you know if the fresh air unit is dealing solely with air quality or also combustion air?

Bud
__________________
I volunteer my help and opinions, but you are responsible for what YOU choose to do with that information.
Bud9051 is online now  
Old 11-28-2019, 10:54 PM  
Newbie
 
Join Date: Nov 2019
Location: Calgary, Alberta, Canada
Posts: 16
Rewards Points: 32
Default

Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by surferdude2 View Post
We'd need to know what is being used to supply the MUA and whether it is with or without a heating or cooling method.
The MAU sits on the roof of the building and draws 100% of its intake air from outside. The air is pushed into ducting that travels vertically straight down the building with vent outlets to three hallways. It's a pretty simple system as far as I know.

It has a natural gas fired heat exchanger inside, no cooling.

Quote:
I've put several MUA unit in commercial buildings and usually they were simple swamp coolers (evaporative coolers). Fine tuning the flow rate to achieve an air balance with the outgoing air was as simple as selecting the motor pulley size. The initial unit size was critical and had to be close enough that a motor pulley change would do the job.
Motor pulley ... didn't think of that. I was hoping there is a baffle plate or similar that can simply be adjusted to restrict the flow rate out of the blower. But I guess that would be a waste of electricity since the blower would be pushing more air than it needs to. So it would probably be worth changing the pulley instead.

Do you know how difficult or easy it is to check the air flow rate?

Quote:
You'll not be able to change the efficiency much since whatever motors are involved pretty much tell the tale on that since fan laws are exactly what the term implies, it's a physical law and not subject to user discretion.
It's the natural gas heating costs that we are trying to impact. We don't know how much the MAU consumes during the year, but we suspect it is considerable. It draws unheated air (sometimes very cold) continuously 24/7, and brings it up to room temperature whenever the outside air temperature is below room temperature. So up here in Canada it will even be burning natural gas in the summer during cool nights, which are the norm.

Quote:
The concept of MUA is inherently inefficient since you are throwing away as much as you input and any energy expended doing that is lost along with any temperature tweaking you are doing in the process.
I think I see what you're saying - even if we tweak the temperature downwards on the MAU, the air will be heated to room temperature in the apartments by other means such as the building hot water heating system. The air then leaks out the exterior windows and doors at the same temperature as before the MAU temperature tweek and in the end the same amount of heat is lost.

However, part of what I would like to achieve is better control of the temperature in my apartment. I think that with the MAU constantly pushing room temperature air under the entrance door to my apartment I am not able to cool my apartment at night below room temperature as much as I would like to.

I figure if the MAU temperature was set lower, any air that blows under the door of my apartment, can be 'topped-up' to whatever temperature I prefer using the building hot water heating system. Do you think this would work?

Quote:
Recapturing that energy is possible but neither easy or cheap.
I can't see how an energy repaturing system could be implemented. If the same positive pressure is supplied to the hallways it will be pushed under the doors of all the apartments and leak out the exterior windows and doors just the same.
nielkfj is offline  
Old 11-28-2019, 11:24 PM  
83yr old neophyte retired
 
Join Date: Nov 2019
Location: Mousetown, southern Illinois, USA
Posts: 222
Rewards Points: 444
Default

Re: How to Make a MAU More Energy Efficient?


If it were me, I'd stop the air infiltration under the door as a first step. Then you should be able to control you living space temperature if you have a thermostat that controls a valve for the heat.

Lowering the temperature of the MUA might save some money but perhaps not since any gain may be countered by the hot water heating system. I think you may have too much incoming air and and since it is at a fairly constant temperature, it will make it hard to control your living space much lower... it's acting to swamp out any influence you try to set lower than it.

If you only wanted lower temperature at night, which I can appreciate, you could possibly modify the existing system with a dual thermostat and a timer to get nightly setback.

Anyway, try one of the long tubular draft stops that are available for placing at the bottom of a door... they look like long stockings filled with sand or maybe dry beans. That may be enough to isolate your living space enough so you can have better control.
__________________
Timing has a lot to do with the outcome of a rain dance.
surferdude2 is offline  
Old 11-28-2019, 11:50 PM  
83yr old neophyte retired
 
Join Date: Nov 2019
Location: Mousetown, southern Illinois, USA
Posts: 222
Rewards Points: 444
Default

Re: How to Make a MAU More Energy Efficient?


Oh, and to answer your other question, no, there is no easy simple way to measure air flow volume. You have to know the velocity of the air, the cross sectional area of the duct and the static pressure. Another method is to measure the fan dimensions, the speed of rotation and the static pressure of the duct. Then you check those parameters against the a table based on fan laws to arrive at an estimated volume.

Far easier is to rely on the manufacturer to tell you what his product will deliver under specific static pressure. Most tradesmen do it that way and trust that it's as close as needed. They (manufacturer) can also advise you as to if and how the volume can be reduced.
__________________
Timing has a lot to do with the outcome of a rain dance.

Last edited by surferdude2; 11-28-2019 at 11:54 PM.
surferdude2 is offline  
Old 11-29-2019, 12:06 AM  
Newbie
 
Join Date: Nov 2019
Location: Calgary, Alberta, Canada
Posts: 16
Rewards Points: 32
Default

Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by Bud9051 View Post
Your local building department or a local engineer should know what levels of fresh air were necessary by code 40 years ago, 15 years ago, and if you make any changes today. Air quality requirements have changed a lot over the past 40 years and not necessarily in your favor.

Canada is a cold climate and they do have some strict regulations. We have some members here from Canada so may be able to get some specifics.
So are you saying that if we we make any change to the MAU flow rate the code might only allow increased flow not decreased flow?

Quote:
Do you know if the fresh air unit is dealing solely with air quality or also combustion air?

Bud
If I understand correctly you are asking if the MAU supplies air to the "mechanical room", which has a natural gas fired boiler and a water heater, to make up for the air lost to combustion. Now that I think about it, I believe it does. So it supplies air to three hallways and the "mechanical room" in the basement.
nielkfj is offline  
Old 11-29-2019, 12:42 AM  
Newbie
 
Join Date: Nov 2019
Location: Calgary, Alberta, Canada
Posts: 16
Rewards Points: 32
Default

Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by surferdude2 View Post
If it were me, I'd stop the air infiltration under the door as a first step. Then you should be able to control you living space temperature if you have a thermostat that controls a valve for the heat.

Lowering the temperature of the MUA might save some money but perhaps not since any gain may be countered by the hot water heating system. I think you may have too much incoming air and and since it is at a fairly constant temperature, it will make it hard to control your living space much lower... it's acting to swamp out any influence you try to set lower than it.
That is also what I am thinking - maybe not completely swamping out my efforts to control the temperature, but having too much of an impact in counteracting my efforts.

Quote:
If you only wanted lower temperature at night, which I can appreciate, you could possibly modify the existing system with a dual thermostat and a timer to get nightly setback.
The MAU was replaced 12 years ago. Unfortunately when this was done, the installers disconnected the hallway thermostat that was hooked up to the original system. So now the MAU outlet temperature is set with a dial on the unit itself (with a temperature sensor about five feet downstream).

The thermostat is still on the wall and apparently the severed wiring is still up on the roof, so I am thinking about having it hooked up again so that we can have a thermostat with setback as you suggested.

Quote:
Anyway, try one of the long tubular draft stops that are available for placing at the bottom of a door... they look like long stockings filled with sand or maybe dry beans. That may be enough to isolate your living space enough so you can have better control.
My neighbour has one of those. I have just been using a small rug. It is effective at stopping the flow under the door. However the air also comes around the sides and top of the door. I can feel it lightly blowing in with my fingers. So I am thinking about installing some thin weatherstripping (fits between the door and the frame) to completely seal the door.
nielkfj is offline  
Old 11-29-2019, 01:10 AM  
Newbie
 
Join Date: Nov 2019
Location: Calgary, Alberta, Canada
Posts: 16
Rewards Points: 32
Default

Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by surferdude2 View Post
Oh, and to answer your other question, no, there is no easy simple way to measure air flow volume. You have to know the velocity of the air, the cross sectional area of the duct and the static pressure. Another method is to measure the fan dimensions, the speed of rotation and the static pressure of the duct. Then you check those parameters against the a table based on fan laws to arrive at an estimated volume.

Far easier is to rely on the manufacturer to tell you what his product will deliver under specific static pressure. Most tradesmen do it that way and trust that it's as close as needed. They (manufacturer) can also advise you as to if and how the volume can be reduced.
OK. I was intending to contact the manufacturer anyway to ask if they have an operating manual.

If we do need to get an HVAC expert in to calculate the required airflow and measure the actual air flow do you know where we should look for one - a maintenance company, installer, manufacturer etc.?
nielkfj is offline  
Old 11-29-2019, 06:30 AM  
An old Tradesmen
 
Join Date: Oct 2008
Location: Somewhere
Posts: 38,169
Rewards Points: 8,116
Default

Re: How to Make a MAU More Energy Efficient?


Many MAUs have a thermostat in them that can be set so the burners don't come on, if the temp is below X degrees outside. So it may be possible to set yours not to heat the air unless its below 60 or 55F outside.

You should be able to download a manual from the manufacturer.
__________________
When posting in certain forums, knowing your location will help others give better feedback/advice/solutions to your questions.
beenthere is offline  
Old 11-30-2019, 09:44 PM  
Newbie
 
Join Date: Nov 2019
Location: Calgary, Alberta, Canada
Posts: 16
Rewards Points: 32
Default

Re: How to Make a MAU More Energy Efficient?


Quote:
Originally Posted by beenthere View Post
Many MAUs have a thermostat in them that can be set so the burners don't come on, if the temp is below X degrees outside. So it may be possible to set yours not to heat the air unless its below 60 or 55F outside.
OK, thanks, would be good if it had this function.

I'm also considering installing a thermostat with nighttime temperature set back. Only problem is the old thermostat in the hallway was disconnected when the MAU was replaced 12 years ago. So would have to get that reconnected first.

Quote:
You should be able to download a manual from the manufacturer.
Ya, I've been meaning to try and get a manual for the MAU so I can understand what features it has.
nielkfj is offline  
Old 11-30-2019, 09:50 PM  
Newbie
 
Join Date: Nov 2019
Location: Calgary, Alberta, Canada
Posts: 16
Rewards Points: 32
Default

Re: How to Make a MAU More Energy Efficient?


I've made a couple videos showing the amount of air coming around the entrance door to my apartment from the hallway, and air leaving my apartment through a cracked-open window. It should be possible to view them here:

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?
nielkfj is offline  
Old 11-30-2019, 10:21 PM  
83yr old neophyte retired
 
Join Date: Nov 2019
Location: Mousetown, southern Illinois, USA
Posts: 222
Rewards Points: 444
Default

Re: How to Make a MAU More Energy Efficient?


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!
__________________
Timing has a lot to do with the outcome of a rain dance.
surferdude2 is offline  
Sponsored Links
Advertisement
 
 

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Top of Page | View New Posts