fan speed and refrigerant charge

[rcamner]

In the "good old days" (which not only means "20 years ago with simple equipment" but also "I didn't know squat about HVAC"...), my furnace (paired with an A/C condensor) had 4 speed taps on the fan, and when the weather got hot, I'd move the tap from medium-low for heating to medium-high for cooling and was happy as a clam!

So, today, 20 years later, I have a fancy A/S Heritage 16 heat pump paired with a York 95%+ variable speed blower gas furnace. And, thanks to the folks here, I now know about squat+2% about HVAC.

Because my family likes not to hear too much blower, during the heating season (when the stuff was installed), we asked the contractor to set the stage 1/stage 2 HP heating fan speed reasonably low (as low as possible consistent with comfort) and the "when the t-stat isn't calling for heat" fan speed (there's got to be a word for that..."continuous fan" setting?) setting set to medium low (2nd lowest of 4 speeds). So, when no heat was called for, the fan speed was whisper quiet, and when heat was being delivered, the fan speed ramped up somewhat.

When the contractor came out for the "before A/C season tuneup", he advised setting the "continuous fan" setting up a notch so that we'd have more continuous air flow when the t-stat wasn't calling for cool. We said "sure."

Now, interestingly, when the t-stat calls for cool, the fan speed actually DECREASES from the "continuous fan" setting of medium-high in stage 1 cooling! Seems a bit weird.

We don't get great cooling, particularly on the second floor, and I was thinking maybe a greater fan speed would help (humidity control is not an issue because I'm in the Pacific Northwest where it simply isn't humid).

The tech also said that one can't go mucking around with the fan speed because different fan speeds require a different amount of refrigerant charge, so if I wanted the fan speed changed, they would do so but also adjust the refrigerant charge.

So, a few questions...


How important is matching fan speed with refrigerant charge, and why is that?
Does it make sense for the (stage 1) cooling fan speed to be lower than continuous fan speed?
Would greater fan speed result in better cooling?
Can heating fan speed and cooling fan speed be set separately, or must it be the same because of the refrigerant charge issue?
I have 2 main duct trunks, both with dampers, one for each floor. Could I help my second floor/first floor issue a bit by dampering down the 1st floor trunk, or is that a lousy idea for some other reason related to the 98% of HVAC knowledge I still don't have?

[Ti Llaves]

In the "good old days" (which not only means "20 years ago with simple equipment" but also "I didn't know squat about HVAC"...), my furnace (paired with an A/C condensor) had 4 speed taps on the fan, and when the weather got hot, I'd move the tap from medium-low for heating to medium-high for cooling and was happy as a clam!

So, today, 20 years later, I have a fancy A/S Heritage 16 heat pump paired with a York 95%+ variable speed blower gas furnace. And, thanks to the folks here, I now know about squat+2% about HVAC.

Because my family likes not to hear too much blower, during the heating season (when the stuff was installed), we asked the contractor to set the stage 1/stage 2 HP heating fan speed reasonably low (as low as possible consistent with comfort) and the "when the t-stat isn't calling for heat" fan speed (there's got to be a word for that..."continuous fan" setting?) setting set to medium low (2nd lowest of 4 speeds). So, when no heat was called for, the fan speed was whisper quiet, and when heat was being delivered, the fan speed ramped up somewhat.

When the contractor came out for the "before A/C season tuneup", he advised setting the "continuous fan" setting up a notch so that we'd have more continuous air flow when the t-stat wasn't calling for cool. We said "sure."

Now, interestingly, when the t-stat calls for cool, the fan speed actually DECREASES from the "continuous fan" setting of medium-high in stage 1 cooling! Seems a bit weird.

We don't get great cooling, particularly on the second floor, and I was thinking maybe a greater fan speed would help (humidity control is not an issue because I'm in the Pacific Northwest where it simply isn't humid).

The tech also said that one can't go mucking around with the fan speed because different fan speeds require a different amount of refrigerant charge, so if I wanted the fan speed changed, they would do so but also adjust the refrigerant charge.

So, a few questions...


How important is matching fan speed with refrigerant charge, and why is that?
Does it make sense for the (stage 1) cooling fan speed to be lower than continuous fan speed?
Would greater fan speed result in better cooling?
Can heating fan speed and cooling fan speed be set separately, or must it be the same because of the refrigerant charge issue?
I have 2 main duct trunks, both with dampers, one for each floor. Could I help my second floor/first floor issue a bit by dampering down the 1st floor trunk, or is that a lousy idea for some other reason related to the 98% of HVAC knowledge I still don't have?

May you send me the make and model plus serial numbers of both the indoor and outdoor units? I may be able to help answer your questions. In response to question #5 be careful damping down your airflow for this action could cause your evaporator to freeze the required airflow per ton of a/c is 400 cfm per ton. And word require an air flow meter. It's best in your case to try and adjust your diffusers in areas in your home to obtain the proper airflow in accordance to area size.

[amd]

How important is matching fan speed with refrigerant charge, and why is that?

Without explaining the refrigerant cycle and charging techniques in great detail I can't really answer your question. Your contractor is correct - listen to what he has to say.

Does it make sense for the (stage 1) cooling fan speed to be lower than continuous fan speed?

Depends on how york's board works - the continuous fan speed is irrelevant to heating/cooling operation.

Would greater fan speed result in better cooling?

It would result is greater sensible capacity (ability to reduce the temperature), lower latent capacity (ability to remove humidity), and better distribution. Most systems should be set up for 400 CFM per done; a variable speed blower can be used in conjunction with a humidistat to reduce airflow when greater dehumidification is required.

Can heating fan speed and cooling fan speed be set separately, or must it be the same because of the refrigerant charge issue?

For heatpump operation, no.
For furnace operation, yes.

[rcamner]

May you send me the make and model plus serial numbers of both the indoor and outdoor units? I may be able to help answer your questions.
I'll do so later today when I get home. Thank you.

[rcamner]

How important is matching fan speed with refrigerant charge, and why is that?

Your contractor is correct - listen to what he has to say.I wasn't really doubting what my contractor had to say..I just like to understand (and, I have to say, that not EVERYTHING I've ever had a contractor say to me turned out to be correct, though I do have a lot of confidence in this particular one).


Does it make sense for the (stage 1) cooling fan speed to be lower than continuous fan speed?

Depends on how york's board works - the continuous fan speed is irrelevant to heating/cooling operation.

Would greater fan speed result in better cooling?

It would result is greater sensible capacity (ability to reduce the temperature), lower latent capacity (ability to remove humidity), and better distribution. Most systems should be set up for 400 CFM per ton; a variable speed blower can be used in conjunction with a humidistat to reduce airflow when greater dehumidification is required.

Ha! Are the terms "sensible" and "latent" just set up so us poor HOs don't have the faintest idea of what people are talking about? :D


Can heating fan speed and cooling fan speed be set separately, or must it be the same because of the refrigerant charge issue?

For heatpump operation, no.
For furnace operation, yes.

Thanks for your complete answers.

Is the 400CFM/ton figure you give for stage 1 or stage 2 cooling/heating? There's quite a difference, in my (limited) experience.

[Ti Llaves]

I wasn't really doubting what my contractor had to say..I just like to understand (and, I have to say, that not EVERYTHING I've ever had a contractor say to me turned out to be correct, though I do have a lot of confidence in this particular one).



Ha! Are the terms "sensible" and "latent" just set up so us poor HOs don't have the faintest idea of what people are talking about? :D


Thanks for your complete answers.

Is the 400CFM/ton figure you give for stage 1 or stage 2 cooling/heating? There's quite a difference, in my (limited) experience.


For your review, Hope info is helpful see link below.

http://contractingbusiness.com/enewsletters/cb_imp_78220/

I'm concerned about the duct work in your home is it compatible with your blower?

[amd]

Is the 400CFM/ton figure you give for stage 1 or stage 2 cooling/heating? There's quite a difference, in my (limited) experience.

That figure is for full cooling capacity.

Variable speed blowers move less air on low than high cooling to keep the evaporator coil cold and remove humidity properly.

[Ti Llaves]

For your review, Hope info is helpful see link below.

http://contractingbusiness.com/enewsletters/cb_imp_78220/

I'm concerned about the duct work in your home is it compatible with your blower?
For your review.
http://contractingbusiness.com/enewsletters/cb_imp_78220/

http://en.wikipedia.org/wiki/Sensible_heat

[beenthere]

May or may not need to adjust charge with a blower speed change. Depends on how much of a change.

That furnace can have the continuos speed set higher then low cool if you want. No harm.

Adjusting the damers will help. Make small adjustments though.

Heating and cooling speeds are set seperately on that furnace.

[Ti Llaves]

That figure is for full cooling capacity.

Variable speed blowers move less air on low than high cooling to keep the evaporator coil cold and remove humidity properly.
HIP HIP HURAY FOR YOU!

[Ti Llaves]

May or may not need to adjust charge with a blower speed change. Depends on how much of a change.

That furnace can have the continuos speed set higher then low cool if you want. No harm.

Adjusting the damers will help. Make small adjustments though.

Heating and cooling speeds are set seperately on that furnace.
Just my personal opinion, I find it wise to have the manufacturer specs when I'm troubleshooting, plus I'm confident that the problem is analyzed correctly. Please understand that I'm not trying to say that your opinion is incorrect. It's just the way I operate.

[jerryd_2008]

How important is matching fan speed with refrigerant charge, and why is that?

Without explaining the refrigerant cycle and charging techniques in great detail I can't really answer your question. Your contractor is correct - listen to what he has to say.

Really! So if my 4-ton York DFHP was installed with stage 2 blower at 1900 CFM and I want the contractor to decrease the speed to the 1700 CFM setting (close to 400 CFM/ton) to increase humidity control and reduce power usage, the contractor would need to adjust the refrigerant level?:eek:


Does it make sense for the (stage 1) cooling fan speed to be lower than continuous fan speed?

Depends on how york's board works - the continuous fan speed is irrelevant to heating/cooling operation.

...[/B]

Think he said he has an A/S but on my York the Fan On or Circulating Fan settings can be set at 100%, 70% or I believe 40% of the (stage 2) blower speed. The 100% setting isn't comfortable for us with it blowing at us all night. I settled at 70%.

[amd]

Really! So if my 4-ton York DFHP was installed with stage 2 blower at 1900 CFM and I want the contractor to decrease the speed to the 1700 CFM setting (close to 400 CFM/ton) to

Any good contractor will check the charge after making adjustments.


increase humidity control and reduce power usage, the contractor would need to adjust the refrigerant level?

Reducing the blower speed improves dehumidification but it reduces overall capacity and efficiency.

[jerryd_2008]

Any good contractor will check the charge after making adjustments.

Doesn't really answer my question. My contractor seems reluctant to mess with the charge. Need something to go on here.:confused:


Reducing the blower speed improves dehumidification but it reduces overall capacity and efficiency.

Yeah, maybe. But Brian K, I believe, in another thread provided a link to an article of studies done by or for the big companies that says lower CFM can save some serious electriityc costs and raises EER (think that means it's a good thing). So efficiency doesn't seem to be an issue in terms of cost. In terms of capacity, I believe going from a 10 SEER to an 18 SEER 2 stage DFHP with a coil that is 1 ton larger makes my capacity a non-issue. Is that another way of saying that I think my new system is over sized?;)

[rcamner]

May you send me the make and model plus serial numbers of both the indoor and outdoor units? I may be able to help answer your questions.

York furnace model YPC080C16MP11/Serial W0A9571343
American Standard Heritage 16 Heat Pump Model 4A6G6036B10000A/Serial 83054KU1F

(I hope I transcribed all that correctly...I got them off the handwritten contractor warranty document...if they're wrong, I'll go look at the plates)

Thanks.

[rcamner]

For your review, Hope info is helpful see link below.

http://contractingbusiness.com/enewsletters/cb_imp_78220/

I'm concerned about the duct work in your home is it compatible with your blower?

Well, I wouldn't know, of course. However, when the contractor installed the new system he told me that the return air duct was grossly insufficient for the old system (let alone the new one!) and at his recommendation I had him double the capacity of the return air. Is that what you mean, or are you concerned about the supply ducts?

[amd]

for the big companies that says lower CFM can save some serious electriityc costs and raises EER (think that means it's a good thing). So efficiency doesn't seem to be an issue in terms of cost.

I would like the see that study, because that's counter-intuitive and contradicts every performance data spec sheet I've seen.

If reducing the blower speed improves efficiency, so does running a system with a plugged filter; the effect is the same on systems with multi-speed blower motors.

Note that efficiency, capacity, and power are different. Insufficient airflow can reduce instantaneous energy use yet still have a negative effect on efficiency. Read some detailed spec sheets - goodman has them available to the general public.

[Ti Llaves]

York furnace model YPC080C16MP11/Serial W0A9571343
American Standard Heritage 16 Heat Pump Model 4A6G6036B10000A/Serial 83054KU1F

(I hope I transcribed all that correctly...I got them off the handwritten contractor warranty document...if they're wrong, I'll go look at the plates)

Thanks.
Thanks for sending the info, I will review you system and get back to you.

[Ti Llaves]

York furnace model YPC080C16MP11/Serial W0A9571343
American Standard Heritage 16 Heat Pump Model 4A6G6036B10000A/Serial 83054KU1F

(I hope I transcribed all that correctly...I got them off the handwritten contractor warranty document...if they're wrong, I'll go look at the plates)

Thanks.
May you get the info on the equipment information plates. Having trouble with info given.

[rcamner]

Sorry for the delay...

York furnace: Model= YP9C080C16MP11A Serial= W0A9571343
American Standard HP: Model: 4A6H6036B1000AA Serial = 83054KU1F

Looks as if I had the model #s wrong. Hopefully this provides the info you need.

Thanks very much for your help.

[Ti Llaves]

Sorry for the delay...

York furnace: Model= YP9C080C16MP11A Serial= W0A9571343
American Standard HP: Model: 4A6H6036B1000AA Serial = 83054KU1F

Looks as if I had the model #s wrong. Hopefully this provides the info you need.

Thanks very much for your help.
Your welcome. Just allow me time to study your situation.

Thanks!

[Ti Llaves]

Your welcome. Just allow me time to study your situation.

Thanks!
Is this the correct outdoor unit info? See link below.

https://www.asdealernet.com/Resources/Literature/pdf/4a6h6036.pdf

[Ti Llaves]

Is this the correct outdoor unit info. See link below.

https://www.asdealernet.com/Resources/Literature/pdf/4a6h6036.pdf
And is this the correct furnace that you have? See link below.


http://www.yorkupg.com/PDFFiles/035-22091-001-D-0908.pdf

[Ti Llaves]

Is this the correct outdoor unit info? See link below.

https://www.asdealernet.com/Resources/Literature/pdf/4a6h6036.pdf
FYI see link below.


https://www.asdealernet.com/Resources/Literature/pdf/4A6.pdf


http://www.munchsupply.com/UserFiles/File/4A6H6%203%20Ton.pdf

[rcamner]

Yes, I'm pretty sure those are the correct indoor and outdoor units.

[Ti Llaves]

Yes, I'm pretty sure those are the correct indoor and outdoor units.
Thanks! will start the research on your questions.

[Ti Llaves]

Thanks! will start the research on your questions.
I have not forgotten you!!!!!!!

[rcamner]

No problem...I imagine this isn't the only thing you're working on in your life! ;)

[jerryd_2008]

I would like the see that study, because that's counter-intuitive and contradicts every performance data spec sheet I've seen.

If reducing the blower speed improves efficiency, so does running a system with a plugged filter; the effect is the same on systems with multi-speed blower motors.

Note that efficiency, capacity, and power are different. Insufficient airflow can reduce instantaneous energy use yet still have a negative effect on efficiency. Read some detailed spec sheets - goodman has them available to the general public.

Sorry for not answering quicker. Been on a road trip. Here is the article from briank101 in the thread "How do AC CFMs affect sensible and latent BTU output? ": https://www.ideals.uiuc.edu/bitstream/handle/2142/11894/TR151.pdf

I believe that I misspoke concerning EER. The article makes the following statement (my bold emphasis) about average power usage:

"The most noticeable effect of slowing the compressor and the evaporator blower speed is the increase in runtimes (Figure 4.3.3), and accompanying decrease in power consumption. Combining these two effects, Figure 4.3.6 shows a 32% reduction in average power."

Can't say I understand all of this article but it sounds good and comes from an organization supported by many of the big HVAC manufacturers. And as a HO, I don't care so much about EER, SEER, etc. It's what it costs to operate!

[richvacr]

it's all about energy transfer
I have not seen anyone mention temperatures only pressure
If the system set to what ever fan speed had a delta t of 20-25 degrees and 8-10 degrees superheat then this is where it should be
By lower fan speed without checking superheat liquid could flood back
If in a high humidity a lower fan speed would result in a colder coil and increase dehumidification and the condensing water would transfer heat/energy to the refrigerant
Simply but fan speed so SST is 36-40 dgrees with sufficent superheat according to manufacturer or if not known 8-10 degrees at evaporator would be good
another thing has anyone ran their hands over the evaporator to feel the liguid boiling off or is the system sized for the duct work?