High velocity questions

[teigo]

In the process of having a home built. The architect had mechanical engineer spec. the mechanicals. Calls for radiant heating and high velocity air conditioning(unico). The plans call for six separate zones with separate air handlers and condensers. The local installers want to reduce to four air handlers and zone with dampers. Also want to use conventional air conditioning in some of the zones. Can high velocity and conventional be mixed. Any recommendations. Also want to know if whole house filtration can be utilized with unico system. Engineer calls for hepa on all units. Finally can humidification be utilized with unico system. Calls for drysteam. Thanks

[karsthuntr]

Unico is very pricey compared to conventional. I don't think you can zone Unico's, but zoning is a good option if you have a small area to cool.

There is no problem with Unico in one part of a house and conventional in another part.

[teigo]

Thanks, I was woundering because the literature states high V's works by air currents and conventional doesn't work in the same manner. The other question was regarding humidification, I can't seem to get an answer. I think the installers want to use conventional for this reason. But will it humidify the whole house, if it's only on certain zones

[karsthuntr]

Humidity will travel to the driest point. It will work if you have enough.

[gillman-air]

I just finished a 14000 sq. ft. house. It has five systems, three of them are high velocity. they work great but unico says not to zone.

[teigo]

How about filtration, hepa or april air, will they work with High velocity and is it possible to add humidification to high velocity duct work.

[BaldLoonie]

Why high velocity in new construction? Great when you don't have the room to snake ducts in an old house but starting from scratch, why do it.

For the price of a Unico air handler which cuts SEER & capacity, you can buy a nice variable speed air handler from any brand which improves SEER, maintains capacity, has low speed fan for filtration & circulation, easy to zone, easy to add humidification.

I don't see how you can add extra filtration to HV. They move so little air to begin with. Probably could rig up some kind of fan powered hum or a steam model, sure couldn't do a bypass.

[rsmith46]

Originally posted by BaldLoonie
Why high velocity in new construction? Great when you don't have the room to snake ducts in an old house but starting from scratch, why do it.

Because the architect and mechanical engineer think it would be neat, their worried about being cool.
The HVA/C contractor wants to use conventional where posable. They want to make the house cool.

[GradyWhite244]

I've delt with too many architects & mechanical engineers. Tell them to take a hike. Listen to your HVAC contractor. He makes his living doing HVAC. All architects know is "looks good". Mechanical engingeers often have no real world experience on HVAC, especially residential. The Bald One is wise in these matters.

[teigo]

Thanks for the info. I'm not sure why High Vel. was spec'ed. I'm trying to recollect conversations with architect. But maybe your right it was their preference. Our interest were filtration due to allergies of the kids and humdification for the northeast winters that are extremely dry. From what i can decifer from the hvac tech. Plans to run separate plenum for a heat recovery unit and fitration and humidification, which may be necessary to add humidification and whole house filtration. Nice boat and thanks for the imput. Any imput on indirect water heaters super stor vs vaughn

[cafocker]

If I were you I would research high velocity and humidity. the high velocity system if I'm correct uses 300 cfms. they use this low cfm rate and large evap. coils to extract as much humidity as possible(for comfort). Their claim to fame is to cool and heat a space without creating any draft(asperation). I've also seen large 4" filters used on their returns; they didn't work because the filters restricted too much of the air flow; the contractors needed to change to 2" media filters. The high velocity system works great in spaces only rats can fit in. I would do as much research as possible before installing this system in new construction; it could be a nightmare in the long run. Go conventional or walk away. But what do I know?

[hvac-tech-lane]

Opinions vary I consider unico a superior system for comfort, properly installed will have a very low space temprature gradient among other positives.
check out this thread ;http://hvac-talk.com/vbb/showthread.php?threadid=72064
In regards to humidification the answer is yes
From unico web site:
Power Humidifiers. Several manufacturers make a
humidifier that mounts on the supply plenum and
pulls air into the unit past a wetted pad and discharges
the moistened air back into the supply air
stream at the same location. These humidifiers depend
on the heated air to evaporate the moisture so
installation on the return where air is about room
temperature would significantly degrade performance.
While some manufacturers have indicated using
hot water will increase the evaporation rate, other
manufacturers that indicate their testing shows that
using hot water does very little to boost evaporation
rates contest this. Having this information Unico, Inc.
is recommending that power humidifiers be installed
on the return side only when there is no other viable
option because of the likelihood of capacity reduction.
No power humidifier manufacturer had any performance
data for normal return air temperatures,
such as 21°C [70°F] but capacity was estimated at
50% of the rated performance at 49°C [120°F] air
temperature.
Since the static pressure in the Unico System supply
plenum is typically 373 Pa [1.50 I.W.C.] the power
humidifier must withstand this static pressure to operate
properly. The first two power humidifiers listed
in Table 3 are not recommended for installation on
the supply plenum of the Unico System; the manufacturers
have indicated these units should not be operated
at static pressures over 75-100 Pa [0.30 to .40
I.W.C.]. The manufacturer of the third power humidifier
listed, Trion Model G100, has indicated that their
unit will operate satisfactorily at the higher static
Hope this helps.

[teigo]

The plan spec'ed Dri Srteam VLC 3-1 Humidifiers on two of the six air handlers(550cfm and 800 cfm respectfully). These air handlers service the first floor. There is one other air handler in the basement that services the masterbed. Other three air handlers service bedrooms on second floor, large rec. room with high ceiling and small loft area. My concerns, are will the steam humidification reach bedrooms since they are on air handlers of communal spaces. Also has hepa filters spec'd for all air handlers. Which from what I been reading will restrict the flow and may not work. thanks