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mchild
12-01-2008, 06:34 PM
I am considering installing the Sanyo Eco-i Mini in my home. It has a nominal heat rating of 60,000 BTU’s. The installation will include two indoor ducted air handlers, one on each of the two levels of my home.

Through careful study of my existing heating and cooling systems I have determined about 75% of the heat load is carried by the first floor indoor unit and the remaining 25% is carried by the second floor unit. In the summer, when the system is in cooling mode, about 60% of the cooling load is carried by the second floor unit. I have monitored this when outdoor conditions are at or near design conditions.

Because of this I will need to size the first floor indoor unit for its need to provide the majority of the heating load and the second floor indoor unit for the majority of the cooling load. Thus, they are each over sized when in use for the non-majority function. That is, the first floor cooling capacity of the unit will be much larger than needed and the second floor heating capacity will be more than needed.

At about 20*F (-6.6*C) the heat loss of the home is about 50,000 BTU and the output capacity of the outdoor unit is the same. Therefore, the first floor unit will need to provide about 38,000 BTU (75% of 50,0000) and the second floor unit about 12,000. I have sized the first floor unit to have cool/heat capacities of 36,000/39,000 and the second floor unit to have 24,000/27,000.

This brings me to my question. When in heat mode and the outdoor temps drop to the point that the outdoor unit is constantly running at full capacity in order to maintain the indoor temp, how is the amount of refrigerant divided between the two indoor units? Are the wired remote controls capable of determining that the actual load in the home is 38,000 on the first floor and 12,000 on the second floor?

Many thanks.

Gary
12-01-2008, 08:18 PM
You may be able to compensate for this with fan speeds. For example, in heating mode put the first floor unit in high speed and the second floor unit in medium or low speed. Vice versa for the cooling mode. In the cooling mode, be careful that the first floor airflow is sufficient to keep the coil from freezing. And of course you will want TXV metering devices.

nike123
12-01-2008, 09:59 PM
This brings me to my question. When in heat mode and the outdoor temps drop to the point that the outdoor unit is constantly running at full capacity in order to maintain the indoor temp, how is the amount of refrigerant divided between the two indoor units? Are the wired remote controls capable of determining that the actual load in the home is 38,000 on the first floor and 12,000 on the second floor? Both indoor units have Electronic Expansion Valve (EEV) in them, and adjustment of unit capacity is done by sensing temperature of return air. When return air become close to set value then EEV start to decrease capacity of related unit. That reduced capacity indoor unit converts in numerical value and sends information to outdoor unit which adjust compressor speed in order to match outdoor unit capacity to that of sum of indoor unit really needed capacities.

mchild
14-01-2008, 04:15 AM
Both indoor units have Electronic Expansion Valve (EEV) in them, and adjustment of unit capacity is done by sensing temperature of return air. When return air become close to set value then EEV start to decrease capacity of related unit. That reduced capacity indoor unit converts in numerical value and sends information to outdoor unit which adjust compressor speed in order to match outdoor unit capacity to that of sum of indoor unit really needed capacities.

Thank you nike123.

That is how I had interpreted the technical manual but I wanted to make sure I was correct.

May I ask another question? When in cooling mode and an indoor unit is not operating at full capacity, I believe the latent cooling capacity would be greatly reduced due to the relatively large indoor coil surface area. A larger coil would mean it is operating at a relatively warmer temp and thus the latent removal would be less. Is there method to determine the latent capacity when in partial mode?

Many thanks.

nike123
14-01-2008, 04:31 AM
Thank you nike123.

That is how I had interpreted the technical manual but I wanted to make sure I was correct.

May I ask another question? When in cooling mode and an indoor unit is not operating at full capacity, I believe the latent cooling capacity would be greatly reduced due to the relatively large indoor coil surface area. A larger coil would mean it is operating at a relatively warmer temp and thus the latent removal would be less. Is there method to determine the latent capacity when in partial mode?

Many thanks.

I will check literature on this mater and see what I could find.

techguy
14-01-2008, 06:34 PM
Hi Michild,

Eacjh Sanyo indoor unit will give a demand to the outdoor of between 2.2 kw min and its max rated operating out put maximium.
This is demand is determined by the indoor PCB after it looks at set point / return air or space temperature, coil temperatures both refrigerant on and off and supply temperature.

The indoor unit will look at the differance between the setpoint and the space/return air temperature. . Then at the coil temperatures and will try to maintain a set supply air temperature of 12 degrees C in cooling mode and 38 degrees C in heating mode.

The electronic expansion valve will modulate to maintain these temperatures and the Compressor speed will be adjust to proivide the required refrigerant flow rate which would be required to maintain the correct indoor coil temperatures.

There should be no problem operating the system as you describe in your first post.

Regards

T

mchild
14-01-2008, 08:05 PM
Hi Michild,

Eacjh Sanyo indoor unit will give a demand to the outdoor of between 2.2 kw min and its max rated operating out put maximium.
This is demand is determined by the indoor PCB after it looks at set point / return air or space temperature, coil temperatures both refrigerant on and off and supply temperature.

The indoor unit will look at the differance between the setpoint and the space/return air temperature. . Then at the coil temperatures and will try to maintain a set supply air temperature of 12 degrees C in cooling mode and 38 degrees C in heating mode.

The electronic expansion valve will modulate to maintain these temperatures and the Compressor speed will be adjust to proivide the required refrigerant flow rate which would be required to maintain the correct indoor coil temperatures.

There should be no problem operating the system as you describe in your first post.

Regards

T

Thank you techguy. Very informative answer.

Seems like my heating will work well. My thoughts are now on the cooling side as we live in a humid area and latent removal is important.

Let us say the system is in cooling mode and the load is very light, say 2.2 to 2.3kw. One indoor unit is running and trying to maintain 12C supply air with the setpoint at 26C and supply air just a little warmer than that. With a delta between the return and supply of about 14C, the space would over cool unless the fan speed is very, very low.

From this I conclude the indoor PCB must be able to run the fan at much lower speeds than the low setting that is selectable from the remote. I must assume there is a desired air volume per kw produced so that the 12C can be maintained and over cooling is minimal?

Thank you again for your help.

techguy
15-01-2008, 11:42 AM
HI Michild,

The cooling supply air temperature of 12 C is only when on full load the closer you getto setpoint and the lower load or demand the indoor gives to the outdoor . |The actual supply air temperature will drift up to 14- 16 degrees C and the electronic expansion valve will close down .

Basically the further you are off setpoint the more work the system does the closer you get to setpoint the less work it does the setting of 12 C + or - 2 is a that the unit will supply duiring cooling. The actual can be much higher depending on how close to setpoint you are. If you are 1 degree off setpoint the unit could be supplying 15-16 degrees C.

It is possible to adjust these supply setpoints or to switch off the supply air control if the client finds this necessary. This is done by entering an engineers code into the remote and adjusting the code number item data as necessary.

Fan speed can be controlled automatically in fan auto mode 3 degrees off setpoint high speed/ 2 degrees off setpoint medium speed/ 1 degree off setpoint low speed.

Hope this helps

T

Gary
15-01-2008, 04:22 PM
Here is a psychrometric chart:

http://www.owlnet.rice.edu/~phys203/handouts/Nautica_SI.pdf

Assuming the supply air is near 100% humidity:

Find on the chart 16C @ 100%RH, plot horizontally to 26C for a RH of about 55%.

Find on the chart 12C @ 100%RH, plot horizontally to 26C for RH of about 40%.

Given enough run time, the system should be able to achieve these RH levels.

Supply air humidity levels (measured close to the coil) tend to be a little under 100%, so we can expect the resulting average RH to be towards the lower end of the 40-55% range, all within acceptable limits.

mchild
15-01-2008, 05:24 PM
HI Michild,

The cooling supply air temperature of 12 C is only when on full load the closer you getto setpoint and the lower load or demand the indoor gives to the outdoor . |The actual supply air temperature will drift up to 14- 16 degrees C and the electronic expansion valve will close down .

Basically the further you are off setpoint the more work the system does the closer you get to setpoint the less work it does the setting of 12 C + or - 2 is a that the unit will supply duiring cooling. The actual can be much higher depending on how close to setpoint you are. If you are 1 degree off setpoint the unit could be supplying 15-16 degrees C.

It is possible to adjust these supply setpoints or to switch off the supply air control if the client finds this necessary. This is done by entering an engineers code into the remote and adjusting the code number item data as necessary.

Fan speed can be controlled automatically in fan auto mode 3 degrees off setpoint high speed/ 2 degrees off setpoint medium speed/ 1 degree off setpoint low speed.

Hope this helps

T

Thanks again techguy for much information.

I must be missing a point though. If the indoor unit can operate as low as 2.2kw then the larger capacity ducted air handlers must be able to run at lower fan volume than the published tech data.

As an example the Sanyo UR364 ducted air handler which is rated at 10.6kw cooling has a high fan speed of 1,800. This is air volume of 170 per kw - the air volume I would expect to find. The low fan volume is rated 1,260 which would be 572 per kw if the indoor unit was operating at the low 2.2kw starting level capacity. That is extremely high air volume. Therefore, I had thought the PCB must be able to run at a lower volume than the low setting when operating in the 2.2kw range in order to maintain a reasonable balance between air volume and cooling capacity. What am I missing here?

Gary
15-01-2008, 05:53 PM
Thanks again techguy for much information.

I must be missing a point though. If the indoor unit can operate as low as 2.2kw then the larger capacity ducted air handlers must be able to run at lower fan volume than the published tech data.

As an example the Sanyo UR364 ducted air handler which is rated at 10.6kw cooling has a high fan speed of 1,800. This is air volume of 170 per kw - the air volume I would expect to find. The low fan volume is rated 1,260 which would be 572 per kw if the indoor unit was operating at the low 2.2kw starting level capacity. That is extremely high air volume.

I assume you meant to say, "That is extremely high air volume per kw". Or another way to say this would be, "That is extremely low kw per air volume". Not much cooling is being done because not much cooling is needed. Why is this a problem?

Gary
15-01-2008, 06:01 PM
Ahhh... you are saying indoor unit kw. The kw is provided by the outdoor unit, not the indoor unit.

mchild
15-01-2008, 06:52 PM
I assume you meant to say, "That is extremely high air volume per kw". Or another way to say this would be, "That is extremely low kw per air volume". Not much cooling is being done because not much cooling is needed. Why is this a problem?

Gary,

Yes, you are correct in the way you have completed my sentence. My finger and brain are sometimes detached.

My concern is the latent capacity would be virtually nothing with that high of air volume to the kw of cooling. In fact, with that volume of air I would expect the indoor cooling would be about 8kw. Seems the PCB must be able to run the fan at lower volumes when the load is very light and the indoor unit is only delivering 2.2kw of cooling.

Gary
15-01-2008, 07:29 PM
Gary,

Yes, you are correct in the way you have completed my sentence. My finger and brain are sometimes detached.

My concern is the latent capacity would be virtually nothing with that high of air volume to the kw of cooling. In fact, with that volume of air I would expect the indoor cooling would be about 8kw. Seems the PCB must be able to run the fan at lower volumes when the load is very light and the indoor unit is only delivering 2.2kw of cooling.

If the kw is being adjusted to maintain 12C supply air, then the needed balance between air volume and kw is achieved, as is the target humidity.

Gary
15-01-2008, 07:51 PM
My concern is the latent capacity would be virtually nothing with that high of air volume to the kw of cooling. In fact, with that volume of air I would expect the indoor cooling would be about 8kw. Seems the PCB must be able to run the fan at lower volumes when the load is very light and the indoor unit is only delivering 2.2kw of cooling.

If the outdoor unit (not indoor unit) is delivering 2.2kw to match the fan speed and 8kw is needed, then the temperature will rise above setpoint, the fan will go to a higher speed and the outdoor unit must then deliver more kw in order to maintain the 12C supply air temp at the current fan speed.

nike123
16-01-2008, 12:42 AM
This is from Fujitsu VRF and I think that others use same control logic.
http://www.mediafire.com/?3nkxkyteis2

Gary (or anyone else), what you think about this in respect of humidity control?

techguy
16-01-2008, 02:07 AM
Hi Michild.
Sanyo systems do not have humidity control any DEhum is as a result of cooling. You are quite correct to point out the ineffiency of low cooling demand versus airflow.

However at low demand and high air volume the room temperatures will rise and demand and cooling output will increase.

Do not get to hung up on the fact that the demand varies on the indoor this is only in response to room conditions. The indoor unit will always try to achieve adquate coil temperatures to satisfy the room requirements. The figure of 2.2 kilowatts is the min demand possible to achieve wether this is actually achieved duiring operation would depend on the conditions specific to the actual site. Also 12 degrees C for supply air is a factory setting and can easily be adjusted on site in a range of 5-17 degrees C to suit the endusers personal preferences.

If the latent load and the supply air temperature starts to rise then the demand on the outdoor will increase to match this within a relativley short period of time.

At the end of the day this is a comfort A/C system and will be more that adquate for your home.

The indoor fan will not drop below minimum speed on cooling . It only does this on heating thermo off to avoid cold draughts being experienced by the homeowner/end user.

I have a Sanyo system in my own home and have no problems with it at all.

Mind you I live in Ireland dont laugh the weather over here is absimal if a Sanyo system can operate here it can operate anywhere.

T

mchild
16-01-2008, 04:10 PM
This is from Fujitsu VRF and I think that others use same control logic.
http://www.mediafire.com/?3nkxkyteis2

Gary, what you think about this in respect of humidity control?

nije123,

Thank you for that link.

That is a better explanation of the operation than found in the Sanyo manual. I hope the Sanyo system operates in the same manner. The difference I noticed from the Sanyo explanation was the auto switch over to DRY mode when at the lower limits of cooling demand. If the Sanyo unit operates the same way it should help with the overall operation to maintain comfort. Maybe techguy can comment on that.

mchild
16-01-2008, 05:13 PM
Hi Michild.
Sanyo systems do not have humidity control any DEhum is as a result of cooling. You are quite correct to point out the ineffiency of low cooling demand versus airflow.

However at low demand and high air volume the room temperatures will rise and demand and cooling output will increase.

Do not get to hung up on the fact that the demand varies on the indoor this is only in response to room conditions. The indoor unit will always try to achieve adquate coil temperatures to satisfy the room requirements. The figure of 2.2 kilowatts is the min demand possible to achieve wether this is actually achieved duiring operation would depend on the conditions specific to the actual site. Also 12 degrees C for supply air is a factory setting and can easily be adjusted on site in a range of 5-17 degrees C to suit the endusers personal preferences.

If the latent load and the supply air temperature starts to rise then the demand on the outdoor will increase to match this within a relativley short period of time.

At the end of the day this is a comfort A/C system and will be more that adquate for your home.

The indoor fan will not drop below minimum speed on cooling . It only does this on heating thermo off to avoid cold draughts being experienced by the homeowner/end user.

I have a Sanyo system in my own home and have no problems with it at all.

Mind you I live in Ireland dont laugh the weather over here is absimal if a Sanyo system can operate here it can operate anywhere.

T

techguy,

The concern I have is with the indoor unit that will be on the first floor of my home. As I mentioned in my original post, I had thought it would be the U36 size. That size was chosen to provide sufficient heating, but will be rather over sized in the cooling mode.

The maximum cooling load of the first floor is about 15,000 BTU (4.4kw), thus much of time the indoor unit will have a much lighter load than this. My concern is the U36 indoor unit is just too large for the cooling load and will end up cycling off much of the time. And, of course if it is off it will not dehumidify.

I agree the system is an advance comfort system and I do not want to end up compromising it by oversizing the indoor unit and creating a problem.

nike123
16-01-2008, 05:50 PM
techguy,

The concern I have is with the indoor unit that will be on the first floor of my home. As I mentioned in my original post, I had thought it would be the U36 size. That size was chosen to provide sufficient heating, but will be rather over sized in the cooling mode.

The maximum cooling load of the first floor is about 15,000 BTU (4.4kw), thus much of time the indoor unit will have a much lighter load than this. My concern is the U36 indoor unit is just too large for the cooling load and will end up cycling off much of the time. And, of course if it is off it will not dehumidify.

I agree the system is an advance comfort system and I do not want to end up compromising it by oversizing the indoor unit and creating a problem.

If you fit 2 indoor unit on first floor instead of one, you could keep one switched of during low load conditions and have humidity properly controlled.

mchild
16-01-2008, 06:13 PM
If you fit 2 indoor unit on first floor instead of one, you could keep one switched of during low load conditions and have humidity properly controlled.

nike123,

I would like to think that great minds think alike. I have just started considering two units on the first floor as a possibility.

Seems as though two smaller units should handle the load with greater ease. Using ducted units, I will have to determine how to get a second air return back for the second unit. Space for such is very, very limited.

Thank you.

Gary
17-01-2008, 12:14 AM
In cooling mode, running the first floor fan at low speed continuously would reduce its maximum output from 36,000btu to about 24,000btu.

Lowering the supply air temp setting would increase its latent to sensible ratio, thus pulling more moisture out of the air while it is running.

mchild
17-01-2008, 07:10 PM
In cooling mode, running the first floor fan at low speed continuously would reduce its maximum output from 36,000btu to about 24,000btu.

Lowering the supply air temp setting would increase its latent to sensible ratio, thus pulling more moisture out of the air while it is running.

Gary,

Yes, you seem to be correct in that. Interesting enough the next smaller unit, rated at 19,000 BTU has much less air flow on a relative basis as it has a high fan CFM of 420. At the low fan setting (320 CFM) it seems as though it would be about 15,000 BTU.

So, if I can find a way to get a return air duct back for two of units (maybe an 18k and 12K or two 18k) and then set the fan speed on low and also set the cooling supply air temp lower, if needed, I would have a better overall setup.

Gary
17-01-2008, 07:43 PM
Here's another thought: You could connect the first and second floor return air ducts.

In cooling mode under light load, the first floor unit shuts off and the second floor unit continues running, pulling a portion of first floor air and drying it. The excess (dried) second floor air drifts down the stairwell.

In heating mode under light load, the second floor unit shuts off, the first floor unit continues to run, drawing a portion of second floor air and sending the excess back up the stairwell.

The connecting duct should be relatively small, say about 25% of the return duct size. Let's say the return duct is 20" X 20", or 400 square inches. The connecting duct should be 100 square inches.

mchild
17-01-2008, 10:13 PM
Here's another thought: You could connect the first and second floor return air ducts.

In cooling mode under light load, the first floor unit shuts off and the second floor unit continues running, pulling a portion of first floor air and drying it. The excess (dried) second floor air drifts down the stairwell.

In heating mode under light load, the second floor unit shuts off, the first floor unit continues to run, drawing a portion of second floor air and sending the excess back up the stairwell.

The connecting duct should be relatively small, say about 25% of the return duct size. Let's say the return duct is 20" X 20", or 400 square inches. The connecting duct should be 100 square inches.

Gary,

Good thought. May work, but getting a return from the second floor down to the first floor may be a bigger challenge than finding a way to get a second return air on the first floor. House was built 120 years ago and has had multiple add ons and renovations. But, something to consider. Thanks

Gary
17-01-2008, 10:53 PM
Gary,

Good thought. May work, but getting a return from the second floor down to the first floor may be a bigger challenge than finding a way to get a second return air on the first floor. House was built 120 years ago and has had multiple add ons and renovations. But, something to consider. Thanks

The connection wouldn't necessarily have to be between the main return ducts. Any returns in close proximity to each other could be connected, although connecting large returns would be more effective than connecting small returns.

The house being 120 years old, I would assume that it originally had a single heating system and common returns between upstairs and downstairs. On the other hand, maybe it started out with hydronic or steam heat... or a heating system on each floor.

mchild
17-01-2008, 11:30 PM
The connection wouldn't necessarily have to be between the main return ducts. Any returns in close proximity to each other could be connected, although connecting large returns would be more effective than connecting small returns.

The house being 120 years old, I would assume that it originally had a single heating system and common returns between upstairs and downstairs. On the other hand, maybe it started out with hydronic or steam heat... or a heating system on each floor.


Originally, the house was heated by the two fireplaces. At some point it looks like it had some type hydronic heat, and then, in the last 12 years of so, supply ducting was added for the first floor and in the attic for two separate systems. They do not connect in any way.

Returns are simply through the wall and second floor ceiling with short ducting tying the return filter grill to the respective air handler.

There is no basement, only a very shallow crawl space. What stands now is a "H" shaped structure that was built in several stages and using different building techniques.