Dehumidify w/ Ductless Advice Needed

[Dayna]

Need Advice!

Building a home with one large room (19x41) and one smaller room (15x20) on ground level. Will have some living area in basement (unexposed) that doesn't need cooling but will need dehumidifying.
ENTIRE HOME (including basement) will have in-floor hot water radiant heat.

Looking at installing ductless mini in my two gound level rooms... or at least in main (larger) room. From other posts I read Mitsu, Sanyo, Daikin, & Fujitsu are the better manufacturers. Do these manufacturers have dehumidifiers on them? If so are they in the same wall mount or is there a "return"? Where does the condensation get discharged? Is there a way to "suck up" or have the "return" air come from the basement?

Thanks
Dayna

[barty]

This is the only split that controls (de) humidification

http://www.daikin.co.uk/aircondition...ra/default.jsp

However if you want a return air ducted from another room you need

http://www.daikin.co.uk/aircondition...ed/default.jsp

But these do not come with the sarara option.


All air conditioning dehums by default but most don't have any actual conteol over the humidity level




Cheers

Richard

[dcmcm5]

The Fujitsu units have what they call "dry mode" which is intended to help dehumidify when cooling is not required. I have not spent any time understanding the difference between this and what Daikin offers, so I don't know the difference.

[mchild]

I have been researching the various products of the mini/multi split market and from I have seen many have the "Dry" mode, but it is not a dehumidify on demand feature. It simply reduces the fan speed and cycles the refrigerant flow on and off to help with dehumidification with minimal over cooling. It does not do so by monitoring humidity, it must be turned on and off each time you want to dehumidify. I have not looked at the Daikin units barty linked, they may be different. Many manufacturers do not offer their full product line here in the US. If the units are available here they will likely have a different model number.

If the units are of the variable capacity type then they will do an overall better job at dehumidifying as they will adjust the refrigerant flow and fan speed during light loads and keep the refrigerant flowing longer which will provide better humidity control.

This is different than the on demand dehumidify feature of some of the US manufactured systems and controls (Honeywell IAQ and Carrier Infinity as an examples) that will call for the compressor to come on in low stage and reduce the blower speed (typically with a variable speed blower) when the humidity exceeds the set point on the control and cycle off when either the set point humidity has been reached or over cooling has occurred.

[teddy bear]

I have been researching the various products of the mini/multi split market and from I have seen many have the "Dry" mode, but it is not a dehumidify on demand feature. It simply reduces the fan speed and cycles the refrigerant flow on and off to help with dehumidification with minimal over cooling. It does not do so by monitoring humidity, it must be turned on and off each time you want to dehumidify. I have not looked at the Daikin units barty linked, they may be different. Many manufacturers do not offer their full product line here in the US. If the units are available here they will likely have a different model number.

If the units are of the variable capacity type then they will do an overall better job at dehumidifying as they will adjust the refrigerant flow and fan speed during light loads and keep the refrigerant flowing longer which will provide better humidity control.

This is different than the on demand dehumidify feature of some of the US manufactured systems and controls (Honeywell IAQ and Carrier Infinity as an examples) that will call for the compressor to come on in low stage and reduce the blower speed (typically with a variable speed blower) when the humidity exceeds the set point on the control and cycle off when either the set point humidity has been reached or over cooling has occurred.

Most of these systems operate at a lower cooling rate while over-cooling with a grossly over-sized coil. The sensible/latent ratios while using SER +13 coil at a reduced capacity tring to maintain <50%RH are at best 70/30. This means that 70% of the energy goes to over-cooling. Cooling coils are near freezing with <40^F cold air making ducts/grills sweat. Being near the cold air supply is not comfortable. Without cooling load, over-cooling is quick and dramatic. The moisture removed per kwh is <2 lbs. At the end of the drying cycle, the cooling coil retains 2-3 lbs. of water per ton of capacity. A 3 ton +13 SEER coil retains 6-8 lbs. water. The water slowly re-evaporates back to the home. Also the ducts are near 100%RH until the coil is dry. One lb. of water humidifies 1,000 sqft. of home 9%RH. With +70^F outdoor dew points, 100 cfm of natural infiltration/ventilation and 3 occupants, latent load is 100 lbs. per day.

Modern high efficiency dehumidifiers remove 4-8 lbs. of moisture per KWH, while generating a small amount heat. Some a/c designers are opting for designing systems to provide 45%RH without a/c operation. This includes typical natural infiltration/ventilation and normal number of occupants. With a 70^F outdoor dew point, 2 occupants, and 75 cfm of damp air infiltration, maintaining 50%RH while 75^H inside, requires +4 lbs/hour of dehumidification. Diffusion through structure from outside air/earth and other activities are additional loads. During this extreme moisture load, 75 lbs. of dehumidification maintains 45%RH in a 2,000 sqft. home. 15 kwh for a high eff. dehu or 45 kwh with an a/c while extreme over-cooling the home. Lowering the outside temp/dew point 5^F makes controlling inside %RH is easy with the dehu and impossibe with the a/c.

I suggest a high eff. dehu like Santa Fe Advance in the basement and a normal mini split a/c in the open space. The basement can be connected via the dehu to the open part of the home. Consider a small amount of fresh air to the dehu. With the dehu & a/c, you can have any temp-%RH combination for max comfort and minimum energy useage. Dehu TB

[Dayna]

I suggest a high eff. dehu like Santa Fe Advance in the basement and a normal mini split a/c in the open space. The basement can be connected via the dehu to the open part of the home. Consider a small amount of fresh air to the dehu. With the dehu & a/c, you can have any temp-%RH combination for max comfort and minimum energy useage. Dehu TB

First what mini-split system would you suggest?
Next, how do I get fresh air to the dehumidifier? Do I need to install ductwork -- if so, how large would you suggest?
Finally, the Santa Fe Advance (by Thermastor, correct?) is that a fixed dehumdifier or a portable that sits in the middle of the room?

Thanks for your input and anyone else who puts in their two cents.

[teddy bear]

SF Advance is connected to the outside via 6"insulated flex duct.
Regards the mini split, check with local a/c contractors. Regards TB

[kuryakin]

Fujitsu has a 'dry' function, which is essentially a dehumidifier. Push that button, and it runs at a fairly low speed and a REALLY low coil temperature to remove moisture. As I have had it explained to me, it runs an algorithm that detects latent load, and adjusts output accordingly. Got one in Mom's sunroom, and ran this mode only once, just to see what it did. Well, that room became VERY dry!

This is the only split that controls (de) humidification

http://www.daikin.co.uk/aircondition...ra/default.jsp

However if you want a return air ducted from another room you need

http://www.daikin.co.uk/aircondition...ed/default.jsp

But these do not come with the sarara option.


All air conditioning dehums by default but most don't have any actual conteol over the humidity level




Cheers

Richard