[tinmarine]

OH boy, this thread is fun again...

Amen brother.

 

[ga-hvac-tech]

Beenthere and I will be here all week for your entertainment. Just remember to tip your waitresses and buy us a drink once in a while to whet our whistles.

If it were live, I would buy you two drinks to watch and enjoy the evening...

 

[tedkidd]

I just wanted to see what Robin had to say about it.

lmao right now!

 

[RandomNick]

Why would a contractor ask you those specifically personal questions? Contractors primarily look to condition a house according to the needs of the house. That way, if you move next year, the system is still appropriate for the house and the new occupants.

I accept that a house can be considered to have generic requirements and I welcome contractors who point out potential resale issues. However, future homeowners aren't a party to the transaction. Assuming that no law or code is violated and there are no safety or neighboring property damage type issues, the only requirements that matter are those of the current homeowner. Those requirements are, by definition, a function of how they use the home and what their preferences are regarding temperatures. A contractor simply cannot make an appropriate recommendation until after they have identified those requirements.

Those questions I quickly thew out were only meant to communicate the idea. Obviously, a contractor does NOT need to know what hours the homeowner keeps. However, they DO need to know what temperatures the client wants at various times of day.

If you have temperature sensitive pets, don't you think that it is your responsibility to address that? Are you going to have a system installed to maintain 78 degrees because you have an exotic bird or are you going to provide a temperature controlled room with no deadly drafts for that bird? Old people die off and infants grow up. We turn our thermostats up or down to accomodate these needs or we put a supplemental heater in certain rooms requiring a higher temperature. This is not a contractors primary concern and is something that needs to be addressed by the consumer if there is a specific concern.

This isn't about who is ultimately responsible for what. It is about professionalism and quality of work... recommendations and solutions which best satisfy a client's requirements. Theoretically at least, the contractor is the professional in the relationship and he/she knows what information should be factored into calculations and decisions so that false assumptions (like: they'll be asleep and won't care if the temp drops a bit, they'd prefer a smaller system supplemented with a space heater) aren't made and potentially important information (like: small basement office with four extra people during the week, large appliance loads from computer/theater gear, exotic pet heaters) aren't overlooked. Thus the contractor is in the best position to assure proper communication. Nevertheless, I do believe consumers must make an effort to educate themselves and surface issues they are aware of. Which I why I encouraged "contractors and homeowners to make sure that adequate information is exchanged".

 

[RoBoTeq]

As far as larger furnaces isn't there also loses on the start up and cool down?

As far as I know blower does not start until heat exchanger is hot enough, nearly all heat to get to that point is going out the flew, so more starts more energy wasted.

Seems logical to me.

Jim

Yes, the larger capacity the furnace, the more start up and cool down waste there is. Add this to the fact that there are going to be more start ups and cool downs and you can be wasting quite a bit of energy. Like I've stated before, I've had several HO's complain that there new 95% efficient 2 stage furnace uses more fuel then their old standing pilot furnace did.

 

[RoBoTeq]

I accept that a house can be considered to have generic requirements and I welcome contractors who point out potential resale issues. However, future homeowners aren't a party to the transaction. Assuming that no law or code is violated and there are no safety or neighboring property damage type issues, the only requirements that matter are those of the current homeowner. Those requirements are, by definition, a function of how they use the home and what their preferences are regarding temperatures. A contractor simply cannot make an appropriate recommendation until after they have identified those requirements.

Those questions I quickly thew out were only meant to communicate the idea. Obviously, a contractor does NOT need to know what hours the homeowner keeps. However, they DO need to know what temperatures the client wants at various times of day.



This isn't about who is ultimately responsible for what. It is about professionalism and quality of work... recommendations and solutions which best satisfy a client's requirements. Theoretically at least, the contractor is the professional in the relationship and he/she knows what information should be factored into calculations and decisions so that false assumptions (like: they'll be asleep and won't care if the temp drops a bit, they'd prefer a smaller system supplemented with a space heater) aren't made and potentially important information (like: small basement office with four extra people during the week, large appliance loads from computer/theater gear, exotic pet heaters) aren't overlooked. Thus the contractor is in the best position to assure proper communication. Nevertheless, I do believe consumers must make an effort to educate themselves and surface issues they are aware of. Which I why I encouraged "contractors and homeowners to make sure that adequate information is exchanged".

No doubt about it, communication is key to a comfortable system. When I was contracting, I would ask generic questions such as; "Are there any special needs your family has?" or "Do you have any specific complaints about the current system that you would like to be different?"

I've installed a cooling system for a woman, elderly at the time, who wanted her system to maintain 65 degrees. It was a challenge with the existing ducting, but we did it. I'm sure whoever moved into that home after she left has been cold and clammy in the summer.

 

[RandomNick]

No doubt about it, communication is key to a comfortable system. When I was contracting, I would ask generic questions such as; "Are there any special needs your family has?" or "Do you have any specific complaints about the current system that you would like to be different?"

Complements to you for doing that, and to others who do that.

I've installed a cooling system for a woman, elderly at the time, who wanted her system to maintain 65 degrees. It was a challenge with the existing ducting, but we did it. I'm sure whoever moved into that home after she left has been cold and clammy in the summer.

Old and wanted it cold? That seems unusual to me, but there are all sorts of folks out there. I once new a guy who had some disorder (can't remember what it was called) that caused him to perceive temperatures as being significantly colder than they actually are. So for example, 74F felt like 64F to him. He wasn't faking it either... he moved his work area to the unconditioned loading dock during the summer and to the boiler room during the winter. I've heard of others who experience that sort of thing but the difference between actual and perceived shifts from time to time. That could really suck.

 

[commerce48]

You are both talking at cross purposes and confusing the basics of motor sizing. You size a motor for a rated work range, not efficiency. Back to fundamental physics: work done. If you are pushing a constant CFM with a fixed blower size at a fixed static, you will perform the exact same work with any size motor that is within its rated work range.

For example, you have a furnace with a 1/3 HP motor pushing 1000 CFM against 0.5" static. Replace that motor with a 1/2 HP motor pushing 1000 CFM against 0.5" static (same air handler, ducts, and fan), you still have exactly the same work done. Thus identical energy usage. Beenthere is dead right there without having to look up fan laws.

However, bigger motors will have slightly larger energy use. This is only because they have larger mass. Larger mass requires more energy to accelerate (start up) and ever so slightly more to maintain speed outside of a vacuum and absolute zero). But unless you are starting up every 5 minutes, this is a very small amount. It is very possible that sample to sample variance (perhaps a slight bearing tolerance difference) will make more of a difference to energy use than a small size difference.

By the way, I'm talking about modern brushless ECM motors. Not much in the way of frictional losses.

The design engineers could care less about the energy cost difference between a 1/3 and 1/2 HP motor, it is trivial. They only care that the motor is within the overall design work range, and secondarily will choose the smaller motor with a reasonable work life because it costs less to manufacture.

Both Beenthere and RoBoTeq are right, but Beenthere is more right. And he doesn't argue like a woman (not that I'm suggesting anyone is - that would be wrong).

 

[RoBoTeq]

Complements to you for doing that, and to others who do that.



Old and wanted it cold? That seems unusual to me, but there are all sorts of folks out there. I once new a guy who had some disorder (can't remember what it was called) that caused him to perceive temperatures as being significantly colder than they actually are. So for example, 74F felt like 64F to him. He wasn't faking it either... he moved his work area to the unconditioned loading dock during the summer and to the boiler room during the winter. I've heard of others who experience that sort of thing but the difference between actual and perceived shifts from time to time. That could really suck.

This lady was a feisty one. She was a slim woman, very energetic, so I suppose her metabolism must have just been running hot all of the time. I wound up getting work from three of her children including some work at the family business.

 

[RoBoTeq]

HUH?!

Thus identical energy usage. Beenthere is dead right there without having to look up fan laws.

However, bigger motors will have slightly larger energy use.

So, by the new definition, identical and larger now mean the same thing?:spam:

Interesting to be proven correct and then deemed wrong in the same sentence:anyone:

Design engineer's actually care very much about the trivial differences in energy usage of motors. One way to gain needed fractions of a point SEER rating is to use the smallest motor that will do the job.

 

[commerce48]

HUH?! So, by the new definition, identical and larger now mean the same thing?:spam:

OK, so your ability to comprehend two simple concepts is quite limited.

That said, I could have worded it slightly better by talking about a motor's overhead to achieve and maintain a given RPM with a given change in mass. The energy usage for a given workload is the same, as Beenthere said. The overhead for a few more ounces of rotating mass is negligible. If such amounts were that important for SEER, fan blades would be carbon fiber, not steel.

 

[beenthere]

As far as larger furnaces isn't there also loses on the start up and cool down?

As far as I know blower does not start until heat exchanger is hot enough, nearly all heat to get to that point is going out the flew, so more starts more energy wasted.

Seems logical to me.

Jim

Modern furnaces use a timer to start the fan. So the blower will come on at the same time for a 60,000 as it does for an 80,000.

Your assuming the larger furnace will have more starts. In the posted example. Since the duct work is the correct size for the larger furnace. It won't have more starts then the smaller furnace. The furnace its self doesn't determine when to come back on.

If an 80,000 BTU and a 60,000 furnace both started 1000 times in a heating season. The 80,000 would use 5.55 CF more gas in those 1000 start ups before the blower started.

The amount of heat needed to satisfy the thermostat is the same from either furnace. So the 80,000 would shut off a little sooner. But have used as much gas as the smaller would with its longer run time.

If you triple the start up lost I posted. To include waste from cool down, then the 80,000 would use/waste 16.1 CF of gas in a year more then the 60,000. Spread that across a 5 month heating season, and you will never notice it.

 

[beenthere]

So now you're just going to go for the personal attacks? Real nice....


In a personal attack. i would have finished the sentence with a derogative word.

I'm sorry I can't find what I don't believe exists. Since it is your argument, it would be better if you found the support you need.

If all I was interested in was selling boxes, I wouldn't care if the equipment were oversized. I have taken more money out of my own pocket by talking contractors into smaller equipment then I care to think about. And I have never...EVER...had equipment returned for larger because of my recommendations. I have however seen more then a few units tossed in the junk pile after they were replaced by less capacity equipment.

I never sold a unit that was twice the size needed either. But you assume I did.

 

[beenthere]

Beenthere and I will be here all week for your entertainment. Just remember to tip your waitresses and buy us a drink once in a while to whet our whistles.

We might be able to get this thread up to the top 10 longest threads.

 

[RandomNick]

We might be able to get this thread up to the top 10 longest threads.

Oooooh! What does the starter of a top 10 thread win?!

Please let it be a new system... please let it be a new system...

 

[Airmechanical]

*

What I don't understand is: when I downsize a furnace the energy bill goes down so much more than anticipated. My wording may not have been perfect, but shall we talk about glass houses?

Not sure what "guess" I made in that statement. While I've learned from you in the past, it seems I get more and more bun, and less and less beef. If you don't learn from me either, not much point in going back and forth any more.

everything about sizing that you spew is a guess on your part, you are BPI, what the hell do you know about real world HVAC

get over the fact that less than 1% of the public plans on sealing their house, this means you need to study another subject

we know what would happen if you sized up a job

the job would be undersized, hopefully you would learn after a few undersized systems how to properly interpret a heat load calc

right now thekid you have no idea, your not in the same glass house as us pros

therefore, we can throw rocks at your personal glass house and not worry about breaking ours




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