After reading of the problems with heat & cool distribution in well sealed and insulated houses and having a "boss" who dislikes the looks of mini split indoor units. But not needing more heat or cooling than a "Hyper heat" can provide. I'm thinking of locating a mini split's indoor unit in a closet with a small "air handler" ( like Electro Industries HE-N-00-21).  The closet would have a "return air" duct under the air handler and directly into it and an "outlet" duct through the floor under the mini split..The air handler's outlet would be pointed up while the closet outlet duct is in the floor so the air would be forced to reverse directions and flow down over and around the mini split   With the closet door closed the  the air handler draws air from the 'return air system (the basement in my situation) and forces it out the floor to a conventional forced air heating/cooling duct network.  The air handler's ECM motor would overcome the friction losses of the duct work and be controlled by a thermostat in a distant hallway and do it with very little power consumption.  With the closet door open the mini split would be 'programed' to about the same temperature as the remote thermostat.  Again with the closet door closed the mini split would heat, or cool some (as much as it's controls choose) of the air passing it   The air handler will also distribute other heat sources, such as the masonry heater I hope to also have.  I was going to try and use an over sized ERV but this solution is much more economical as I can "right size" the ERV and use "one sided" ducting from the bathrooms with the return into the basement.
 Has anyone done something similar?
 See any problems?

Posted By Liebler on 30 Jun 2013 11:33 PM
After reading of the problems with heat & cool distribution in well sealed and insulated houses and having a "boss" who dislikes the looks of mini split indoor units. But not needing more heat or cooling than a "Hyper heat" can provide. I'm thinking of locating a mini split's indoor unit in a closet with a small "air handler" ( like Electro Industries HE-N-00-21).  The closet would have a "return air" duct under the air handler and directly into it and an "outlet" duct through the floor under the mini split..The air handler's outlet would be pointed up while the closet outlet duct is in the floor so the air would be forced to reverse directions and flow down over and around the mini split   With the closet door closed the  the air handler draws air from the 'return air system (the basement in my situation) and forces it out the floor to a conventional forced air heating/cooling duct network.  The air handler's ECM motor would overcome the friction losses of the duct work and be controlled by a thermostat in a distant hallway and do it with very little power consumption.  With the closet door open the mini split would be 'programed' to about the same temperature as the remote thermostat.  Again with the closet door closed the mini split would heat, or cool some (as much as it's controls choose) of the air passing it   The air handler will also distribute other heat sources, such as the masonry heater I hope to also have.  I was going to try and use an over sized ERV but this solution is much more economical as I can "right size" the ERV and use "one sided" ducting from the bathrooms with the return into the basement.
 Has anyone done something similar?
 See any problems?

sounds a lot more compicated than simply doing central HVAC?

Chris,
The "standard" ducted heat pumps simply SUCK as heaters when outdoor temperatures are below zero f
While the Fujitsu RLS2H series of mini splits delivers rated heat output at -15fand Mitsubshi's Hyper heat units deliver 80% of rated output at -13f. What I'm proposing, is using a small modular air handler typical of a forced air HVAC system to even the heat/cool distribution and hide the ugly mini splt head. Definitely no more complex than a ducted central HVAC system.

Liebler,

Some mini-split manufacturers have ceiling mounted systems that show only the grill.  That type might also be a good way to avoid seeing the unit like the types that hang on a wall.  Most brands that I have seen require a condensate pump for ceiling mounted units.  See Daikin.

Posted By Liebler on 02 Jul 2013 09:59 PM
Chris,
The "standard" ducted heat pumps simply SUCK as heaters when outdoor temperatures are below zero f
While the Fujitsu RLS2H series of mini splits delivers rated heat output at -15fand Mitsubshi's Hyper heat units deliver 80% of rated output at -13f. What I'm proposing, is using a small modular air handler typical of a forced air HVAC system to even the heat/cool distribution and hide the ugly mini splt head. Definitely no more complex than a ducted central HVAC system.

thats why they come with a back up resistance heat strip

Posted By Liebler on 30 Jun 2013 11:33 PM
as I can "right size" the ERV and use "one sided" ducting from the bathrooms with the return into the basement.
 Has anyone done something similar?
 See any problems?

yes the problem is you are taking moist air from the bathrooms and putting into a basement that is typically damp anyway, you would be creating an unhealthy indoor air invironment, the ERV must be exhausted to the exterior of the home

Supply ducts in one area and returns in another doesn't mix well with closed doors. You don't want to pressurize or depressurize rooms.

Jump ducts over the doors could help equalize pressure.  If sound privacy is important, then duct openings can be offset from one side of the wall to the other.

Alton,
None of the ceiling mounted indoor units work with the low temperature heating systems.

Chris,
A heat pump delivers more heat than the energy it consumes, the ratio is called the coefficient of performance (COP). The best of the mini split have a COP of 1.5 at -15f resistance heat always has a COP of 1.
You are misunderstanding what I'm saying. There are 2 flow paths through an ERV. The one going to the outside will be fully ducted. The one bringing outside air in will end in the basement. And each bathroom will have duct to the basement. So the basement serves as a portion of the duct going back to the bathroom.

Jorr,
I agree. Each room that has a supply duct will have a return path into the basement.

If sound privacy is important, then duct openings can be offset from one side of the wall to the other.

Or top to bottom. But it takes a huge area to get pressure really low (say 1 pascal). See here where they couldn't achieve < 3 pascals @ 125 cfm when using a single hi/low transfer duct.

I think that "leave room doors open whenever possible" is good energy advice for any ducted house. On the other hand, leaving doors separating upstairs from downstairs closed should be beneficial in reducing winter stack effect driven flow. But maybe it would need assistance from an active system.

Posted By Liebler on 03 Jul 2013 12:36 PM

Chris,
A heat pump delivers more heat than the energy it consumes, the ratio is called the coefficient of performance (COP). The best of the mini split have a COP of 1.5 at -15f resistance heat always has a COP of 1.
You are misunderstanding what I'm saying. There are 2 flow paths through an ERV. The one going to the outside will be fully ,ducted. The one bringing outside air in will end in the basement. And each bathroom will have duct to the basement. So the basement serves as a portion of the duct going back to the bathroom.

Jorr,
I agree. Each room that has a supply duct will have a return path into the basement.

Liebler,
Yes I understand the advantages of heat pumps, but how often is it going to dip below zero?what part of the country are you in?
I also understand the workings of ERV's I have installed many.............. so you intend to draw the fresh air thru the damp basement into the bathroom?

Here are some ducted mini-split units. But I don't know if they work in cold climates.

http://www.greendroplet.com/index.php/duct-less-mini-split-systems/concealed-ducted.html

In general, it would be nice to know whether the various outdoor units could be used with various indoor units. Including refrigerant to water heat exchangers. Since some of the outdoor units work with several indoor units, my guess is that the outdoor unit has some of the intelligence in it. Who knows, it might not care what type of head/coil/heat exchanger it is driving.

Chris,
I'll be building on the northern edge of Michigan's lower peninsula which has over a month of sub zero nigh time lows in a typical year. "so you intend to draw the fresh air thru the damp basement into the bathroom?" Yes I intend to draw fresh air through the basement but I hardly think it'll be damp because of r40 walls and r24 below the slab and following the best practices for drainage of PWF structures.

Posted By Liebler on 03 Jul 2013 10:18 PM
I hardly think it'll be damp because of r40 walls and r24 below the slab and following the best practices for drainage of PWF structures.

Liebler,
I hope for your sake your set up works, I have personally never seen a basement that was not damp,
I still maintain that it is a bad idea to bring fresh air thru a basement area

Even if the basement is not damp, I think it is a bad idea to free flow air through the basement. It means the basement has to stay at the same conditioned state as the rest of the house. If the basement is not used the same as the main floor, why would you keep it at the same temperature as the main? That is a lot of cubic feet to condition as well as a lot of building envelope for heat loss or gain. Apart from the inefficiencies, it means the time it takes to change the condition of the air on the main almost doubles.

If the basement is not used the same as the main floor

It's a good question, but it may bring up "why have a basement at all".

There are two ways to control humidity in underground (or other high mass) spaces (basement, garage, crawlspace, etc). Either a) insulation + lots of continuous ventilation to keep it approximately the same temp and humidity as the other space or b) seal it up and dehumidify it. Liebler's ventilation may not meet the "continuous" spec and an exposed slab (the top surface, not the bottom) may not meet the insulated spec (if it is ever allowed to get cool).

As a rule PWF and ICF basements do not have the same humidity issues as cip basement. Liebler's is PWF. This is not an endorsement for PWF.

"It means the basement has to stay at the same conditioned state as the rest of the house."

Not at all! During the heating season, this is the fresh air from outside that has been " warmed" by cooling the air being ventilated. It is COOLER than the indoor air temperature which was ventilated. There will be no deliberate attempt to heat the basement. It will however be heated by the uninsulated floor that is it's ceiling.

Anyway I'm thinking of changing "the plan" and eliminating the basement as the cold air return plenum.
The new plan would exploit my ceiling service cavity and use it to return air to the closet (containing the mini split and air handler). I would switch to a down flow air handler, sitting on the closet floor below the mini split which would push it's output through metal ducts in the basement. The ducts would go to floor registers in each room located along outside walls. Each room would have one, or more, return air grill(s) located high on interior wall(s). The stud spaces with return grills would have no top plates allowing flow into the ceiling service cavity.

After some more thought I've abandoned the air handler in favor of several Panasonic fans. I'll use 5 of the PV 13 VKS3 units which have switch selectable air delivery with 50, 70, 90, 110 CFM selectable on the internal switch. Each fan has a 6" duct outlet. The top walls of the closet will have 'return air' grills and all the rooms will have return air grills into the hallway above their doors. I'll control the fans with a current sensing relay sensing current in the power line to the mini split. The 'automatic' control can be overridden by a switch for continuous fan operation. The fans will be installed near the bottom of the closet's walls and their ducts will start out downward but turn horizontal below the floor and each fan will serve about the same heat loss through 2 or 3 floor registers along outside walls. I'll initially set the mini split's fan speed to 'low' which delivers 336CFM and maxes out at 11,400 BTU/h. and the fans to 70 CFM each. With the initial setup the fans add about 28 watts when running. Should I need more heat or cool power, I'll select a higher fan speed on the mini split and change the switch settings on all 5 fans, which of course takes more power. But 35 watts of fan power will support 14,800 Btu/h or 46 watts to support the full, 18000BTU/h,  output of the 15RLS2H.   I checked with Fujitsu and yes the warranty is void if the unit is closer than 6 feet from an opposite wall so closing the closet door voids the warranty, so be it! BTW the person I spoke to liked the idea and even said it should work fine.

While I haven't done the calculations with your figures, most passive returns short of an open door cause enough room pressurization to effect infiltration and wall moisture (summer). Consider a supply and return duct to each room so that you can balance room pressures (wrt the outside) to zero.