[beenthere]

Hey Beenthere,

How do you know your load is 50,000? You Don't. It could be 60,000 or it could be 40,000 depending on how you guessed on you Manual J. You don't know.

The point is you don't know the load, just a range at best. In the example you present the range is +-20%. Still does not matter what it is just that it changes. Put in a 60k.

Does not change the fact that the J provides no value in sizing if we need it only to differentiate between a 50,000 but heater and a 100,000 but heater.
I think you are making my point. It's a bit silly.

Peace

ACBD

Why sell a furnace twice the size that is needed? Is it just to make more money?

The load at design doesn't change. Unless the customer makes changes to the home or their lifestyle.

 

[AC Bad Dog]

Thanks for helping with this.

Why sell a furnace twice the size that is needed? Is it just to make more money?

The load at design doesn't change. Unless the customer makes changes to the home or their lifestyle.

Beenthere,

You would not.

Your manual J will tell you 40k with one set of guesses and 60k with another. Hardly a science project. You are guessing. You do not that @ 0 outside the load is 50,000. You cannot say that. Since these are your ranges of your guesses you make my point, it is not about the totals, only that loads change. Furnaces come in 20K increments so this is silliness.

Point is you do not know the load at any outside temp on an old house. You are guessing. Best I'll give you a range in your guess. 50,000 +- 20%. The tool you are using to get the number is not precise at all.

As discussed our industry is not held in high regard overall.

I hate contractors who rip off consumers, please don't go there.

AC BAD DOG

 

[ga-hvac-tech]

I guess someone needs to step in here, in defense of load calcs... since Seaton is gone...

Yes, there are lots of subjective things in a load calc... and yes, IMO there is really NO way to be absolutely accurate. However:

The house I am doing currently:
Roughly 7000 ft not including the basement
3 systems
3 VS furnaces (2-95%, 1-80%)
3 16 SEER 2 stage AC's
(Ruud equipment BTW)

I ran load calcs on each level... and found all three furnaces grossly too big. The AC loads were not too far off... and we did go a little large fort the main level AC on purpose because they entertain a lot. Also, there are 3 grade-school aged kids there (can you say in and out, leaving the door open... ).

IMO load calcs can give one a good idea, something maybe as close as within 10% of actual needs. The problem with load calcs is one cannot really know what is hidden in the walls... and that is significant... one can only guess.

After one has run dozens of load calcs, and seen the results of systems installed... and talked to the HO's after 6 mos, 1 year, etc... one can get a feel for what to look for, to make one's load calcs more accurate.

Still though... within 10% is about as accurate as they come IMO.

Thoughts?

 

[beenthere]

Beenthere,

You would not.

Your manual J will tell you 40k with one set of guesses and 60k with another. Hardly a science project. You are guessing. You do not that @ 0 outside the load is 50,000. You cannot say that. Since these are your ranges of your guesses you make my point, it is not about the totals, only that loads change. Furnaces come in 20K increments so this is silliness.

Point is you do not know the load at any outside temp on an old house. You are guessing. Best I'll give you a range in your guess. 50,000 +- 20%. The tool you are using to get the number is not precise at all.

As discussed our industry is not held in high regard overall.

I hate contractors who rip off consumers, please don't go there.

AC BAD DOG

The rip off is telling people to just get what ever size furnace like you suggest.

While furnaces come in 20,000 increments in a brand. By using 2 different brands, you have one in even inputs, and the other in odd inputs. Which gives you a much better selection. So that a house that needs a 62,000 BTU output, can have a furnace installed closest to that output.

If you don't want customers ripped off. Then they need a load calc done. And they'll get the comfort and savings they paid for.

 

[AC Bad Dog]

They should get a modulating furnace, because your loads are guesses at best

The rip off is telling people to just get what ever size furnace like you suggest.

While furnaces come in 20,000 increments in a brand. By using 2 different brands, you have one in even inputs, and the other in odd inputs. Which gives you a much better selection. So that a house that needs a 62,000 BTU output, can have a furnace installed closest to that output.

If you don't want customers ripped off. Then they need a load calc done. And they'll get the comfort and savings they paid for.

Hey Beenthere,

I just ran a Manual J on my house twice.

Once with a tight set of assumptions and one with loose. First time R30 in my attic next R19.

Depending on my guesses my heat loss is somewhere between 35,000 and 60,000 BTU/h. This is what I get with a manual J.What is "correct"?

So I just got a load done, two of them,now what?

What is right? How is the manual J science if this is the spread.

I have seen contractors using manual J come up with guesses of 3-5 tons on the same 2500 sq. ft house. Again, only your loads are right? what about the guy who did the same manual J and came up 1.5 tons higher?

Science? Come on,,witchcraft at best!

Thanks for playing.


Good luck,

AC BAD DOG

 

[ga-hvac-tech]

Hey Beenthere,

I just ran a Manual J on my house twice.

Once with a tight set of assumptions and one with loose. First time R30 in my attic next R19.

Depending on my guesses my heat loss is somewhere between 35,000 and 60,000 BTU/h. This is what I get with a manual J.What is "correct"?

So I just got a load done, two of them,now what?

What is right? How is the manual J science if this is the spread.

I have seen contractors using manual J come up with guesses of 3-5 tons on the same 2500 sq. ft house. Again, only your loads are right? what about the guy who did the same manual J and came up 1.5 tons higher?

Science? Come on,,witchcraft at best!

Thanks for playing.


Good luck,

AC BAD DOG

Just a thought there AC...

If the house currently has a 135,000 BTU natural draft furnace... a 70K or 75K or 80K furnace would be a HUGE savings.

On the AC side... a VS drive furnace with humidity control option set up will absorb some over-sizing.

 

[beenthere]

Hey Beenthere,

I just ran a Manual J on my house twice.

Once with a tight set of assumptions and one with loose. First time R30 in my attic next R19.

Depending on my guesses my heat loss is somewhere between 35,000 and 60,000 BTU/h. This is what I get with a manual J.What is "correct"?

So I just got a load done, two of them,now what?

What is right? How is the manual J science if this is the spread.

I have seen contractors using manual J come up with guesses of 3-5 tons on the same 2500 sq. ft house. Again, only your loads are right? what about the guy who did the same manual J and came up 1.5 tons higher?

Science? Come on,,witchcraft at best!

Thanks for playing.


Good luck,

AC BAD DOG

Maybe you wanna get away from the keyboard and go and see what you have in the attic.

Yep, I've seen Manual J's that are 5 tons for 2400 sq ft homes. the guy uses 1.2 for infiltration, and R9 for walls, and what ever low value for the attic. Too bad he didn't really check anything.

A load calc is like most anything else. if no real effort is put into it, then its results/benefits are just about useless.

 

[AC Bad Dog]

Thanks GA, Hey Beenthere help me here.

Just a thought there AC...

If the house currently has a 135,000 BTU natural draft furnace... a 70K or 75K or 80K furnace would be a HUGE savings.

On the AC side... a VS drive furnace with humidity control option set up will absorb some over-sizing.

Hey GA,

1.My house currently has a 4 ton WF geo unit, 2 Stage.(provided free from WF)

2.Prior to this it had a 3 ton Lennox XP19 with a 60k G61MVP VS gas Backup(provided free by Lennox)

3. Prior to this it had a 2.5 Ton Steller AC and a 80,000 P1UDD Furnace (provided free by York)

4. Prior to that house was built with 4 ton Rheem and 100,000 BTU Furnace

So, Four systems 4 different sizes all were correct, put in by the absolute best in the business, yet none of them did a load. Why is that Beenthere?

Repeat, Best designers there are in HVAC did the work. None did a Load! Why?

The guys who did my last 3 systems were hand picked by the manufacturers who gave me the systems. All three designers worked for the Manufacturer.

Maybe they know something!

AC BAD DOG

 

[ga-hvac-tech]

I cannot comment on what other shops do...

All I know is my customers are VERY satisfied and happy with my work. How happy: I literally do not advertise at all (I am not even in the YP), I have SO much referrals I sometimes cannot take care of them all. I also get to fire the worst few customers every year.

In over 30 years of running a small business, I have never had a BBB complaint, never had a bounced check, and never had a customer that wanted their $$$ back.

Can any of the folks who did your house truly say this...

 

[AC Bad Dog]

Now I see only your guesses are correct?

Maybe you wanna get away from the keyboard and go and see what you have in the attic.

Yep, I've seen Manual J's that are 5 tons for 2400 sq ft homes. the guy uses 1.2 for infiltration, and R9 for walls, and what ever low value for the attic. Too bad he didn't really check anything.

A load calc is like most anything else. if no real effort is put into it, then its results/benefits are just about useless.

I am happy to see you are so certain of uncertainty, it must be nice to know you are the one guy who's loads are correct, when all around you get different numbers. I wish i could feel that way. Unfortunately I have been ruined by hanging out with the best of the best. The top designers in HVAc have much less certainty in their answers than you do. I'll let these guys know, you duh man!

It must be nice to be able to know infiltration rates on old houses with such certainty when no one else can.

It must be great to know duct leakage rates without testing.

Can you see into walls?

Can you see dead people?

Thanks,

ACBD

 

[AC Bad Dog]

Hey GA

I cannot comment on what other shops do...

All I know is my customers are VERY satisfied and happy with my work. How happy: I literally do not advertise at all (I am not even in the YP), I have SO much referrals I sometimes cannot take care of them all. I also get to fire the worst few customers every year.

In over 30 years of running a small business, I have never had a BBB complaint, never had a bounced check, and never had a customer that wanted their $$$ back.

Can any of the folks who did your house truly say this...

Both my WF and Lennox provide incredible comfort.

Hard to get you money back when equipment and installs were free

AC BAD DOG

 

[kayjh]

My opinion differs from TB's. Most houses don't need a whole house dehumidifier.

With the over sized units you have now, your running in the 60s as far as humidity. Correctly sized units will bring that down into the 50s. And if they are single stage units with VS blowers, you will probably be able to get to the low 50s. 2 stage should be able to get you into the 40s, but obviously not that low every day.

Its also a falsehood that an A/C must move 400CFM per ton. My own is only moving 280 CFM per ton(don't ask your contractor to set your this low). Yes, I can only run it for about 20 minutes when its 70 outside. But in that 20 minutes, I can drop my indoor RH between 6 to 10% depending on outdoor conditions. I generally set my stat to 72, and run 48 to 50% RH.

If you want true comfort from your A/C, a 2 stage with VS blower, and a thermostat that can do cool to dehumidify, and slow the blower when the humidity is above set point during a normal cooling call..

AC Bad Dog, Beenthere,

Thanks for your posts. As you can tell, I'm just trying to educate myself a bit more this time around. Hopefully by doing so, I'll have a better dialog and better chance for success with the new AC system.

The 2 stage system seems like it does what our 5 year old Weil McLain modulating boiler does, combined with the Tekmar control system. We have a complicated system with 6 zones in our house, but each room is the same temperature and we never have an actual roomheat to thermostat variance of more than 1 degree Celsius in any room. In the shoulder season, we seen the boiler modulating at 10 - 20%. We have 230,000 BTU capacity which is a bit more than we ned, but we plan to in floor heat some additional 3 season rooms in the future.

As for the AC, I expect as you say that a whole house humidifier will not be necessary in our climate if we can just size the unit correctly and be able to have it operate for longer periods of time in "stage 1". This will lower our humidity, while at the same time remove the stuffiness in the air that seems to creep up when the system is between cooling cycles.

Does anyone ever mix some outside fresh air into a system (without the use of an HRV)? We have an "economizer" on our packaged unit at our ofice which will mix cool outside air into the system in the morning and late evenings to reduce compressor run times. I think it also adds fresh air into the office. I was just wondering whether it would be common to add a fresh air intake to our system. I'm assuming that if you want outside air to come in you'd need a way to get inside air to the outside?

Thanks for your posts.

 

[captube]

AC Bad Dog, Beenthere,

Thanks for your posts. As you can tell, I'm just trying to educate myself a bit more this time around. Hopefully by doing so, I'll have a better dialog and better chance for success with the new AC system.

The 2 stage system seems like it does what our 5 year old Weil McLain modulating boiler does, combined with the Tekmar control system. We have a complicated system with 6 zones in our house, but each room is the same temperature and we never have an actual roomheat to thermostat variance of more than 1 degree Celsius in any room. In the shoulder season, we seen the boiler modulating at 10 - 20%. We have 230,000 BTU capacity which is a bit more than we ned, but we plan to in floor heat some additional 3 season rooms in the future.

As for the AC, I expect as you say that a whole house humidifier will not be necessary in our climate if we can just size the unit correctly and be able to have it operate for longer periods of time in "stage 1". This will lower our humidity, while at the same time remove the stuffiness in the air that seems to creep up when the system is between cooling cycles.

Does anyone ever mix some outside fresh air into a system (without the use of an HRV)? We have an "economizer" on our packaged unit at our ofice which will mix cool outside air into the system in the morning and late evenings to reduce compressor run times. I think it also adds fresh air into the office. I was just wondering whether it would be common to add a fresh air intake to our system. I'm assuming that if you want outside air to come in you'd need a way to get inside air to the outside?

Thanks for your posts.

As far as the outside air there is discussion going on here..http://hvac-talk.com/vbb/showthread.php?t=828042

 

[teddy bear]

My opinion differs from TB's. Most houses don't need a whole house dehumidifier.

With the over sized units you have now, your running in the 60s as far as humidity. Correctly sized units will bring that down into the 50s. And if they are single stage units with VS blowers, you will probably be able to get to the low 50s. 2 stage should be able to get you into the 40s, but obviously not that low every day.

Its also a falsehood that an A/C must move 400CFM per ton. My own is only moving 280 CFM per ton(don't ask your contractor to set your this low). Yes, I can only run it for about 20 minutes when its 70 outside. But in that 20 minutes, I can drop my indoor RH between 6 to 10% depending on outdoor conditions. I generally set my stat to 72, and run 48 to 50% RH.

If you want true comfort from your A/C, a 2 stage with VS blower, and a thermostat that can do cool to dehumidify, and slow the blower when the humidity is above set point during a normal cooling call..

It takes 30 minutes to load a dry coil with enough mositure to start dripping down the drain. Roughly 1 lb. of moisture per ton of SEER 13 coils to load the coil. Yes the indoor %RH drops, but as the moisture left on the coil re-evaporates back into the home the %RH rises. If the dew point of the outside air is +60^F without a real cooling load, your indoor dew point will be as high as outside plus the moisture from the occupants. You have many hours of low/no cooling loads with high outdoor dew points.
Hope your customers do not get a fresh air change every 4-5 hours as recommended.
If your customers are fussy, they will not be happy depending on the weather they are exposed to. A good dehumidifier will maintain <50%RH regardless of the cooling load or the methically perfect sized a/c. I am currently removing 20 gals of moisture per week without any cooling while maintaining <50%RH in my finished basement. Hang on, you will be ok most of the time.
Regards TB

 

[beenthere]

Hey GA,

1.My house currently has a 4 ton WF geo unit, 2 Stage.(provided free from WF)

2.Prior to this it had a 3 ton Lennox XP19 with a 60k G61MVP VS gas Backup(provided free by Lennox)

3. Prior to this it had a 2.5 Ton Steller AC and a 80,000 P1UDD Furnace (provided free by York)

4. Prior to that house was built with 4 ton Rheem and 100,000 BTU Furnace

So, Four systems 4 different sizes all were correct, put in by the absolute best in the business, yet none of them did a load. Why is that Beenthere?

Repeat, Best designers there are in HVAC did the work. None did a Load! Why?

The guys who did my last 3 systems were hand picked by the manufacturers who gave me the systems. All three designers worked for the Manufacturer.

Maybe they know something!

AC BAD DOG

I met more then 1 factory guy that sized by sq ft. Doesn't make it or them right.

All 4 systems were not right, unless your house was added on to and or improvements made each time.

Doubt they all flew in the "best" designers in HVAC to do your units, and duct work.

 

[beenthere]

I am happy to see you are so certain of uncertainty, it must be nice to know you are the one guy who's loads are correct, when all around you get different numbers. I wish i could feel that way. Unfortunately I have been ruined by hanging out with the best of the best. The top designers in HVAc have much less certainty in their answers than you do. I'll let these guys know, you duh man!

It must be nice to be able to know infiltration rates on old houses with such certainty when no one else can.

It must be great to know duct leakage rates without testing.

Can you see into walls?

Can you see dead people?

Thanks,

ACBD

I can see why your an out of work comedian.

Duct leakage rate is easy to check in many homes, not all though.

Infiltration a bit harder.

Walls can be tested. If the customer wants to pay for the added time.

My on average 40% smaller then what was originally installed load calcs hasn't left a customer with poor heating or cooling. And has provided long run times like it should. Decreased energy bills in line with my estimate(not just 20% of my estimated savings, of course I don't tell them they are going to save a hundred bucks a month on cooling).

 

[beenthere]

AC Bad Dog, Beenthere,

Thanks for your posts. As you can tell, I'm just trying to educate myself a bit more this time around. Hopefully by doing so, I'll have a better dialog and better chance for success with the new AC system.

The 2 stage system seems like it does what our 5 year old Weil McLain modulating boiler does, combined with the Tekmar control system. We have a complicated system with 6 zones in our house, but each room is the same temperature and we never have an actual roomheat to thermostat variance of more than 1 degree Celsius in any room. In the shoulder season, we seen the boiler modulating at 10 - 20%. We have 230,000 BTU capacity which is a bit more than we ned, but we plan to in floor heat some additional 3 season rooms in the future.

As for the AC, I expect as you say that a whole house humidifier will not be necessary in our climate if we can just size the unit correctly and be able to have it operate for longer periods of time in "stage 1". This will lower our humidity, while at the same time remove the stuffiness in the air that seems to creep up when the system is between cooling cycles.

Does anyone ever mix some outside fresh air into a system (without the use of an HRV)? We have an "economizer" on our packaged unit at our ofice which will mix cool outside air into the system in the morning and late evenings to reduce compressor run times. I think it also adds fresh air into the office. I was just wondering whether it would be common to add a fresh air intake to our system. I'm assuming that if you want outside air to come in you'd need a way to get inside air to the outside?

Thanks for your posts.

I installed a few fresh air intakes on resi systems. I generally use an IAQ stat to control the damper for the intake. Aprilaire has a nice damper unit with its own control for this also.

 

[dan sw fl]

REASONABLE Use of Load Calcs

I guess someone needs to step in here, in defense of load calcs... since Seaton is gone...

Yes, there are lots of subjective things in a load calc... and yes, IMO there is really NO way to be absolutely accurate.

IMO load calcs can give one a good idea, something maybe as close as within 10% of actual needs. The problem with load calcs is one cannot really know what is hidden in the walls... and that is significant... one can only guess.

After one has run dozens of load calcs, and seen the results of systems installed... and talked to the HO's after 6 mos, 1 year, etc... one can get a feel for what to look for, to make one's load calcs more accurate.

Still though... within 10% is about as accurate as they come IMO.

Thoughts?

KISS - LOAD CALC ADDRESSES DESIGN CONDITION.


Design conditions exist for ~2% of the year.
9,000 ( 8,760 = 365 * 24) * 2% = 180 hours / year

So for maybe 5 hours a day 35 days a year, the load calcs give a representative idea of the capacity that is needed. ~ 12% accuracy in a load calc should be more than sufficent to make a satisfactory equipment selection.

:.02:
Loads probably change upto 30% in ~ 6 hours twice each day.
In other words, loads are CONSTANTLY Changing.

The remaining 8,400 ( 8,760 - 2* 180) hours a year the heating and cooling equipment may be in some sort of modulation or on-off mode.

THEREFORE, 2 stage seems to be an EXCELLENT idea for many climates.

I would Not be Strongly recommending 2-stage cooling for climates with < 1,000 Cooling Degree Days or MOD furnaces in the less demanding Southern climates.
... K.I.S.S.

NOW GO SELL YOUR 2-STAGE + VARIABLE SPEED EQUIPMENT to the CustOMers who wish to have C O M F O R T in ' their FORT'. ! !!

USE detailed Load Calcs without adding more margin to size equipment.

Only add margin for the customers who wish to address PARTY Time ( > 10 people )

 

[AC Bad Dog]

Two Guys go to the house...

KISS - LOAD CALC ADDRESSES DESIGN CONDITION.


Design conditions exist for ~2% of the year.
9,000 ( 8,760 = 365 * 24) * 2% = 180 hours / year

So for maybe 5 hours a day 35 days a year, the load calcs give a representative idea of the capacity that is needed. ~ 12% accuracy in a load calc should be more than sufficent to make a satisfactory equipment selection.

:.02:
Loads probably change upto 30% in ~ 6 hours twice each day.
In other words, loads are CONSTANTLY Changing.

The remaining 8,400 ( 8,760 - 2* 180) hours a year the heating and cooling equipment may be in some sort of modulation or on-off mode.

THEREFORE, 2 stage seems to be an EXCELLENT idea for many climates.

I would Not be Strongly recommending 2-stage cooling for climates with < 1,000 Cooling Degree Days or MOD furnaces in the less demanding Southern climates.
... K.I.S.S.

NOW GO SELL YOUR 2-STAGE + VARIABLE SPEED EQUIPMENT to the CustOMers who wish to have C O M F O R T in ' their FORT'. ! !!

USE detailed Load Calcs without adding more margin to size equipment.

Only add margin for the customers who wish to address PARTY Time ( > 10 people )

Hey Dan,

Two guys go to visit a nice lady living in a 2400 sq. ft 2 story colonial house built in 1971 facing east/west currently with a broken 4 ton AC.

1st guy
Does the whole dog and pony show with his tape measurer, Wright=soft draw board, or maybe even his new Wrightsoft hand thing.
After 2 hours he has come up with a requirement of exactly 3.43785697312 tons. So he sells the nice lady a new 3.5 ton AC.

2nd Guy
Takes out a simple compass and shows the lady how the sun moves over her house and, my my, how she must have quite a bit of cooling around 4 pm when the sun is peaking on the back of her house.She explains to him that she already knows that because she lives there. He explains that loads are always changing and that is why he will replace her 4 ton with a new 4 ton two stage.


Which lady is Happier and More Comfortable?

Thanks,

ACBD

 

[kayjh]

Hey Dan,

Two guys go to visit a nice lady living in a 2400 sq. ft 2 story colonial house built in 1971 facing east/west currently with a broken 4 ton AC.

1st guy
Does the whole dog and pony show with his tape measurer, Wright=soft draw board, or maybe even his new Wrightsoft hand thing.
After 2 hours he has come up with a requirement of exactly 3.43785697312 tons. So he sells the nice lady a new 3.5 ton AC.

2nd Guy
Takes out a simple compass and shows the lady how the sun moves over her house and, my my, how she must have quite a bit of cooling around 4 pm when the sun is peaking on the back of her house.She explains to him that she already knows that because she lives there. He explains that loads are always changing and that is why he will replace her 4 ton with a new 4 ton two stage.


Which lady is Happier and More Comfortable?

Thanks,

ACBD

My question is if she had 4 ton and the calculation showed she needs 3.5 Ton, can you just put a 2 stage 4 Ton in and then if she had a bit too much cooling the system will operate in stage 1 most of the time and stage 2 when she is having a party or on an unusually hot day?

I'm curious to know if there is a tonnage equivalence that shows a 4 Ton operating a stage 2 is 4Ton and at stage one is ? Ton (is it 2 ton, 2.5 ton, 3 ton, etc.).