# Residential HVAC Systems



## rgrace (Jul 11, 2013)

Greetings. I would like to get some feedback from code officials in jurisdictions across the states as to how each handles the enforcement of M1401.3 of the International Residential Code, 2009 or 2012, heating and cooling equipment sizing. Examples: Do you require plans and calculations to be submitted and reviewed by plan review staff? Do you require a certification form filled out by the designer or contractor to be submitted and reviewed by plan review staff? Does your inspections staff require such information to be presented at the time of inspection? Are these methods of submission and compliance verification left up to the discretion of the plan review or inspection staff, such as when an inspector sees that an electrical service panel that is completely filled during the time of inspection, and requests a load calculation per IRC E3602.2? Any other methods?

Thank you all in advance for your feedback.


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## rgrace (Jul 18, 2013)

Wow, a week in queue, 90+ views, and no comments. Silence speaks volumes. We are re-evaluating the way we enforce this section, and your input is much appreciated. We have a very stringent way of doing this now, and are considering going to something as minimal as self-certification. I'll keep you updated


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## Gregg Harris (Jul 18, 2013)

You can not be serious!


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## Gregg Harris (Jul 19, 2013)

rgrace said:
			
		

> Greetings. I would like to get some feedback from code officials in jurisdictions across the states as to how each handles the enforcement of M1401.3 of the International Residential Code, 2009 or 2012, heating and cooling equipment sizing. Examples: Do you require plans and calculations to be submitted and reviewed by plan review staff? Do you require a certification form filled out by the designer or contractor to be submitted and reviewed by plan review staff? Does your inspections staff require such information to be presented at the time of inspection? Are these methods of submission and compliance verification left up to the discretion of the plan review or inspection staff, such as when an inspector sees that an electrical service panel that is completely filled during the time of inspection, and requests a load calculation per IRC E3602.2? Any other methods? Thank you all in advance for your feedback.


I would also like to here from other jurisdictions an the issue of sizing equipment and using proper load calculations and duct sizing.

Most contractors throughout the United States struggle with this issue due to lack of knowledge.

Most all contractors will oversize both gas furnaces and air conditioning. A lot of it is due to the lack of requirements in local and state codes, and lack of enforcement when it is an adopted code.

The other big issue with this subject is that there is rarely benchmarking at time of commissioning that confirms that the equipment is performing as designed by the manufacturer.

About three years ago the federal government along with states where offering tax rebates for high efficiency equipment that was installed. A tremendous amount of equipment was increased in size to mach the efficiency requirements to convince consumers to purchase.

The governments implemented the efficiency rating of the equipment but never implemented performance requirements to verify performance. This has led to high efficiency equipment to be installed not only over sized but installed on duct systems that will not deliver the proper amount of air with high static pressure leading to higher energy costs for the consumer. Thus the higher cost to and increased failure rate is a burden to the consumer of the product and every other consumer due to higher utility cost and increased carbon foot print.


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## Rick18071 (Jul 19, 2013)

we require plans and cals for plan review. None of us understands them. For all we know they could be using the same one over and over.


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## Gregg Harris (Jul 19, 2013)

Rick18071 said:
			
		

> we require plans and cals for plan review. None of us understands them. For all we know they could be using the same one over and over.


 In a lot of cases that is true especially on subdivisions for new construction even though the house has a higher or lower load calculation. Or a load calculation is done and equipment or modifications to structure are changed.


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## rgrace (Jul 19, 2013)

Gregg Harris said:
			
		

> You can not be serious!


Hahahaha, well at least THAT got things started


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## TimNY (Jul 20, 2013)

I ask for equipment specs, Manual J and D.  If I don't get the D I don't make a fuss.

I do look at the J.  It's not that difficult to figure out, provided the correct report are forwarded for review.  The software de jour appears to be Wrightsoft.  Wrightsoft has a bazillion reports, each with different bits of information on it.  I don't think it's difficult to understand, it's just figuring out the terminology on the report.

At a minimum:

-confirm outdoor design temp is correct

-confirm indoor design temp is correct

-look for anomalies the contractor has added, like fan/vent loads, and make sure they match the actual loads

-do a rough calc on the volume of the home and make sure the summary report reflects the actual volume

A big red flag are number is bold italics.  The program puts any variable that has been manually overridden in bold italics.

The J almost always is inflated.  I don't blame them, on an 83 day the indoor design temp is 75.  That sucks, especially when it's been 90+ all week here.  My system is designed correctly and it's struggled at 76 a few times.  So, even though the calcs are reviewed, there has to be a little cushion to reflect that no owner of a 2M+ house wants to sit in 75 degrees.

The last bit is to confirm the units installed match the calcs.

Tim


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## Daddy-0- (Jul 21, 2013)

We require that they have the calcs but we only review them on a complaint basis. Most contractors do not have to file a manual j with us unless requested by us. Of course we are in ROVA not NOVA so I am sure we are missing something. Hahahaha


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## Gregg Harris (Jul 21, 2013)

Daddy-0- said:
			
		

> We require that they have the calcs but we only review them on a complaint basis. Most contractors do not have to file a manual j with us unless requested by us. Of course we are in ROVA not NOVA so I am sure we are missing something. Hahahaha


What do you do when the consumer complains and the contractor states " hey it past inspection its not our problem"?


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## peach (Jul 21, 2013)

In NOVA, we have to get car emissions inspections, too.. that's not a statewide requirement.

I work in DC, not VA (but I live in NOVA).. it's the plan reviewers' job to check the manual J and get the information on the plans; the inspectors don't have the time in the field to do the PR job.

Do we miss on it.. sure.


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## Daddy-0- (Jul 22, 2013)

Visual option on ductwork is still allowed for now and if there is an issue with equipment sizing we ask for the calcs and manual J. If it passes great if not the contractor has some explaining to do and some equipment to replace. For what it is worth, there is a wide variety of interpretation of the Virginia codes on this issue and the strict interpretations are mainly in northern Virginia near DC. It is not a perfect system and I have seen grown men screaming at each other about what interpretation is correct.


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## rgrace (Jul 22, 2013)

Daddy-0- said:
			
		

> I have seen grown men screaming at each other about what interpretation is correct.


Yea, me too.

And I especially like what TimNY says,

"The J almost always is inflated. I don't blame them, on an 83 day the indoor design temp is 75. That sucks, especially when it's been 90+ all week here. My system is designed correctly and it's struggled at 76 a few times. So, even though the calcs are reviewed, there has to be a little cushion to reflect that no owner of a 2M+ house wants to sit in 75 degrees."

The problem that I've seen is when no "cushion" has been permitted at all. The Manual J/S is informative guidelines in assisting to size HVAC equipment. Variables such as changing exterior envelope materials during construction can change the Manual J calculation (going from one brand and color of vinyl siding, changing from interior gypsum board to wood paneling), or any deviation from the duct design (branch takeoff fittings, supply air boot fittings, elbows and offsets), not to mention a contractor really has no idea what kind of interior shading is going to be installed by a homeowner (most will put "none"). Of course, none of these field changes are provided to the person who calculated the HVAC system design for their review so that they can make modifications to the Manual J calculation and system sizing. Given all the variables, if no "cushion" were permitted (as I have seen), the home would have to be constructed perfectly, without changes (materials, leakage, no window or door changes, no duct system deviations, etc., etc., etc.) for the system sizing to be perfect, but ONLY perfect on those few days that the outdoor air temperature matches exactly what was used to do the Manual J calculation in the first place. On all other days that either exceed or fall short of the design temperature, the system will be oversized or undersized. You cannot blame a homeowner for being highly upset (with county or contractor, depending on who didn't permit a "cushion") when they cannot cool their home at all when the outdoor temperature exceeds that of the design temperature.


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## jar546 (Jul 22, 2013)

We require a copy of the Manual J calcs for our file.  We only review basic information.  Just asking for them creates enough of a problem.  What we really see oversized are steam boilers being replaced.  We ask for a copy of the calcs they used to see if they actually measured lineal footage of pipe, radiators,etc.


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## Gregg Harris (Jul 22, 2013)

rgrace said:
			
		

> Yea, me too.And I especially like what TimNY says,
> 
> "The J almost always is inflated. I don't blame them, on an 83 day the indoor design temp is 75. That sucks, especially when it's been 90+ all week here. My system is designed correctly and it's struggled at 76 a few times. So, even though the calcs are reviewed, there has to be a little cushion to reflect that no owner of a 2M+ house wants to sit in 75 degrees."
> 
> The problem that I've seen is when no "cushion" has been permitted at all. The Manual J/S is informative guidelines in assisting to size HVAC equipment. Variables such as changing exterior envelope materials during construction can change the Manual J calculation (going from one brand and color of vinyl siding, changing from interior gypsum board to wood paneling), or any deviation from the duct design (branch takeoff fittings, supply air boot fittings, elbows and offsets), not to mention a contractor really has no idea what kind of interior shading is going to be installed by a homeowner (most will put "none"). Of course, none of these field changes are provided to the person who calculated the HVAC system design for their review so that they can make modifications to the Manual J calculation and system sizing. Given all the variables, if no "cushion" were permitted (as I have seen), the home would have to be constructed perfectly, without changes (materials, leakage, no window or door changes, no duct system deviations, etc., etc., etc.) for the system sizing to be perfect, but ONLY perfect on those few days that the outdoor air temperature matches exactly what was used to do the Manual J calculation in the first place. On all other days that either exceed or fall short of the design temperature, the system will be oversized or undersized. You cannot blame a homeowner for being highly upset (with county or contractor, depending on who didn't permit a "cushion") when they cannot cool their home at all when the outdoor temperature exceeds that of the design temperature.


There is already a cushion built into Manual J. If the system is designed and installed properly in a house with a reasonable envelope, and the system is commissioned with benchmarks to prove the performance of the equipment there should be no problem in maintaining a 20 degree differential from outdoors to indoors.

It is all about air, the properties of air and the distribution of air.

For comfort cooling the first factor to consider is to control the latent heat in the space, "humidity"

Depending on the humidity in the conditioned space, the system must first remove the latent heat before you see a temperature drop. When a system is oversize with a "cushion" added" it will cool rapidly with no moisture removal leaving the humidity to be high and the occupants of the space to be uncomfortable, and mold growth to take place inside the air distribution system and the conditioned space and walls.

If design temperatures are used the system is already over sized 80% of the cycle use.


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## rgrace (Jul 22, 2013)

I totally understand the concept. In the past decade, I am aware of only one home owner complaint of high humidity levels, and that was due to a 6" round duct tied to the return air duct without any regulating means. Our most recent complaints have not been related to comfort levels due to humidity, but rather the inability of the selected, approved, equipment to cool the home. -sigh-


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## rgrace (Jul 22, 2013)

. . . 6" round OUTDOOR AIR duct . . .


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## Gregg Harris (Jul 22, 2013)

rgrace said:
			
		

> I totally understand the concept. In the past decade, I am aware of only one home owner complaint of high humidity levels, and that was due to a 6" round duct tied to the return air duct without any regulating means. Our most recent complaints have not been related to comfort levels due to humidity, but rather the inability of the selected, approved, equipment to cool the home. -sigh-


[/COLOThe complaints related to the equipments inability to perform is directly related to the equipment selection, and the lack of performance set up and testing after installed.

When selecting equipment it is not just a matter of picking a furnace, evaporator coil, and condensing unit. "other accessories we can discuss down the line as to how they effect the performance of the equipment"

Once the load calculation "Manual J" has been properly performed, and the air distribution "Manual D"  by using Manual "S" for equipment selection to match what is required to heat and cool the occupied space. There should be no problem.

The problem is that 90% of all HVAC contractors have a limited knowledge as to how these applications relate to the structure. 

You can go to HARI website and for one 3 ton condensing unit of one brand you can choose multiple furnaces or air handlers along with multiple evaporator coils to choose from.

Most contractors will select the equipment to match a SEER rating "Seasonal Energy Efficiency Ratio" generally the highest "meaning the most expensive combination" irregardless of what the Manual J tells them. The evaporator coil is selected according to the latent and sensible heat ratio determined by the Manual J. Thus you might have 10 coil choices to accomplish that any where from a three ton coil to a 5 ton coil. Once the Sensible Heat Ratio is determined, the CFM "Cubic Feet Per Minute" can be determined for setting the airflow requirements.

If all of the parameters are used and applied properly the system will perform as the manufacture has designed it and the structure will cool. 

If the consumer states " my upstairs bedroom over the garage never cools" the first suggestion by the contractor is " well you have a 3 ton system we can give you a 4, of five ton and that will take care of the problem." "This happens frequently by the way" Now the contractor installs a larger unit on a duct system that more than likely was installed to deliver less than 3 tons and we have another problem introduced to the equation. Excess static pressure due to the increased volume of air that is required to be delivered, the new system will deliver less than the required volume of air so the problem is now compounded.

It is all about air.


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## zigmark (Oct 22, 2013)

In Washington State the heating system sizing forms are provided for use by the state through a Washington State University program started many years back.  Just recently this State has started moving toward using the IECC by incorporating the States' amendments into that document.  Here is a link to the excel program that is used; www.energy.wsu.edu/Documents/Prescriptive%20Worksheet%20Both%20Zones.xlsx

www.energy.wsu.edu/Documents/2012%20Glazing%20Schedule.xlsx

www.energy.wsu.edu/Documents/Heat_Sizing_code%20specs_final.xls

www.energy.wsu.edu/Documents/Table_406_2_Energy_Credits_2012_WSEC.pdf

The last link is to the explanation of required energy credits a home owner must incorporate into their building.  So depending upon the size of the proposed construction they are required to obtain between 1.0-2.5 credits from the options listed.

We require them to submit this information at plan review.  As previously stated the systems were often oversized prior to this being implemented.  We still occasionally get a heating contractor that wants to argue about a systems ability not being able to heat the proposed structure so they don't have to sell a less expensive model.

ZIG


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## Gregg Harris (Oct 23, 2013)

zigmark said:
			
		

> In Washington State the heating system sizing forms are provided for use by the state through a Washington State University program started many years back.  Just recently this State has started moving toward using the IECC by incorporating the States' amendments into that document.  Here is a link to the excel program that is used; www.energy.wsu.edu/Documents/Prescriptive%20Worksheet%20Both%20Zones.xlsxwww.energy.wsu.edu/Documents/2012%20Glazing%20Schedule.xlsx
> 
> www.energy.wsu.edu/Documents/Heat_Sizing_code%20specs_final.xls
> 
> ...


Unfortunately not only do the contractors in the HVAC industry not have the knowledge base to properly design install and commission heating and air conditioning equipment, it appears that individuals in the code enforcement industry also have a long way to go in understanding and implementing good industry practice.

A code proposal was presented to change the criteria for load calculations for comfort cooling that was rejected numerous  times and at different state and national levels. It was again rejected at the code hearings recently held in New Jersey, and put up for a floor vote and passed.

This is a clear indication that enough people where gathered to vote on something that they had no competent knowledge about the subject matter.

If this code change is not one reversed, "this will take time but will happen" it should be rejected at every state level and not adopted. This is only going to lead to worse situations than are already becoming apparent to consumers on the performance of there heating and cooling systems, not to mention the excess wear and tear and increased maintenance of the equipment and the excess electricity that will need to be produced to satisfy the demand.

RM9 – 13

M1401.3

Proponent:

Richard Grace, Fairfax County VA,

representing

The Virginia Plumbing and Mechanical

Inspectors Association and the Virginia Building and Code Officials Association

Revise

as follows:

M1401.3

Equipment/

appliance

Sizing

.

Hea

ting and cooling equipment and appliances shall be sized in

accordance with ACCA Manual S based on building loads calculated in accordance with ACCA Manual J

or other approved heating and cooling calculation methodologies.

Exception:

Heating and cooling equipment and appliances shall not be limited to the capacities

determined in accordance with Manual S where any of the following conditions apply:

1.

The specified equipment or appliance utilizes multi

-

stage technology or variable refrigerant flow

te

chnology and the loads calculated in accordance with Manual J fall within the range of the

manufacturer’s published capacities for

that equipment or appliance.

2.

The specified equipment or appliance manufacturer’s published capacities cannot satisfy

both

the total and sensible heat gains calculated in accordance with Manual J and the

manufacturer’s next larger standard size unit is specified.

3.

The specified equipment or appliance is the lowest capacity unit available from the specified

manufactu

rer.

Reason:

Item 1

-

Current technology is widely available that incorporates multi

-

stage or VRF systems for increased efficiency.

Some of these appliances have such a wide span of functionality that they extend beyond the allowable requirements outlined

in

Manual S. However, this technology allows the appliance to operate between minimum and maximum capacities, based on loads

imposed, thus eliminating the problems associated with single

-

stage, oversized appliances. Additionally, the appliance will operat

e

efficiently during times where outdoor air temperatures exceed those used to calculate the loads in Manual J.

Item 2

-

Often times, the appliance manufacturer’s published total and sensible capacities are at odds with the requirements of

Manual S. There

are many cases where the total capacity of the appliance will fall within the parameters of Manual S in relation to

the calculated total gain, however the sensible capacity of the appliance may fall short of the calculated sensible gain, thus unable to

pr

ovide efficient sensible cooling for the space. When the manufacturer’s next standard size larger is chosen to meet the sensi

ble

gain, the total capacity of the appliance may then exceed the requirements of Manual S. Choosing the larger appliance will en

ab

le a

more efficient and effective system.

Item 3

-

The current code language does not have provisions for sizing appliances for minimal dwelling unit or dwelling addition

loads, other than forcing owners and contractors to change appliances to less desirable systems. For example; a 2 story townhouse,

in climate zone 4, with 600 square feet per floor wants to utilize a two

-

zone system, or a separate heat pump system for each floor.

A 1.5 ton unit per floor would exceed the requirements of Manual S, however

a 1.5 ton unit could be the smallest available appliance

made by the desired manufacturer. Current language would require a complete design change, such as utilizing a single applian

ce

to serve the entire dwelling rather than the more desirable two

-

zone system, or requiring a system that utilizes electric baseboard

heating and window

-

mounted air conditioning units. This is absurd, and an unfair to an owner that desires to reduce energy costs.

Cost Impact:

none

RM

9-

13

Public Hearing:

Committee:

AS

AM


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## markw (Oct 23, 2013)

You could always install a 3 ton/vari speed and add a 2 zone control for each level. More efficient, less energy used, less maintenance.lower

installation cost, I have installed a bunch of em. Greg, just my 2, the overall requirement for man J + S is LONG overdue and the systems you speak of are a small % of the total installed. Its not that hard to learn the correct sizing methods, in fact,the absence of codes/enforcement has enabled those "HVAC" contractors to continue to install oversized,underducted,leaky sytems.


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## Gregg Harris (Oct 23, 2013)

markw said:
			
		

> You could always install a 3 ton/vari speed and add a 2 zone control for each level. More efficient, less energy used, less maintenance.lowerinstallation cost, I have installed a bunch of em. Greg, just my 2, the overall requirement for man J + S is LONG overdue and the systems you speak of are a small % of the total installed. Its not that hard to learn the correct sizing methods, in fact,the absence of codes/enforcement has enabled those "HVAC" contractors to continue to install oversized,underducted,leaky sytems.


The requirement for popper sizing has always been a code requirement what this new article will allow is disregarding of correct sizing of the equipment rather to jump to the next size. In the case where a 4 ton system selection would work the next size equipment is a 5 ton, allowing to oversize in excess of a whole ton.

There are multiple combinations in each tonnage that allows for adjusting the latent and sensible load capacity to match the structure.

This code proposal is to quell the complaints of consumers when they complain that there systems will not cool, when the contractor is required to follow proper sizing criteria.

It is rare that a contractor will install a system and commission it to perform as the manufacturer has designed it to perform with the proper set up and adjustments to prove the capacity of the system.

This is where the problem resides is with the lack of competence of the HVAC contractor.


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## markw (Oct 23, 2013)

Agree on all points,code change included.

After 20+ yrs in the business I have never been ask by any AHJ for load calcs.


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## Gregg Harris (Oct 24, 2013)

markw said:
			
		

> Agree on all points,code change included. After 20+ yrs in the business I have never been ask by any AHJ for load calcs.


Some jurisdictions have started requesting them and the contractor stands there like a deer in the headlights. They begin guessing at information submitting it and being rejected, as they should.

There is not a single air-conditioning manufacturer that does not require you to size the equipment according to the design load of the structure.

One of the points made by the submitter is that "ACCA manual J is not the only sizing method that can be used, ASHREA can also be used" This in itself is a true statement, the ironic part is that if you open the ASHREA Handbook for HVAC Application under Equipment sizing in the first paragraph it states,

"With this information, heat loss and gain can be calculated using the Air-conditioning Contractors of America (ACCA) manual J or similar calculation procedures."

The majority of the substantiation statement in the proposal is bogus and has no validity.


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## markw (Oct 25, 2013)

QUOTE=Gregg Harris;117596]Some jurisdictions have started requesting them and the contractor stands there like a deer in the headlights. They begin guessing at information submitting it and being rejected, as they should.

Oh yea, I have seen a few of those looks. The old squirrel cage starts running when, after years installing whatever/however, we learn of an inspection that will require us to become accountable.


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