If I had a conventional air handler I'd agree. But my Unico air handler is a "high velocity" design that's supposed to output higher temp air through 2 inch diameter ducts that mixes with room air. The new heat pump is a 3 ton 14 SEER Carrier unit (very simple). The existing (2005 vintage) air handler is rated at 3-3.5 tons and only the leaky coil (and TXV) were replaced. I am at the low end of the spec CFM range but I am within the spec air flow range. The blower speed is not adjustable but it has a restrictor plate to throttle air flow. This house was built in 1850 something and there was no good way to retrofit full size ducts so we went with this oddball high velocity system. It actually works well except in one room where the mini ducts are too long. The old R22 heat pump which was replaced was also 3 tons.
> -----Original Message----- > From: Mercedes [mailto:mercedes-boun...@okiebenz.com] On Behalf Of > Mitch Haley via Mercedes > Sent: Thursday, January 17, 2019 10:02 AM > To: Mercedes Discussion List <mercedes@okiebenz.com> > Cc: Mitch Haley <mi...@mitchellhaley.com> > Subject: Re: [MBZ] OT: Heat Pump Demand Defrost? > > Sounds like your brand new system is too big for the available airflow. > Refrigeration units are more efficient at lower temperature rise. > If you're seeing more than a 20-25° rise from return to supply temp you need > more air. > (like 68° thermostat setting and 88° supply outlet temps) It might be because > the installer didn't set the blower speed right or it might be because your > ducts > are too small. > I'd check the static pressure (pressure in the supply duct minus pressure > going > into the air handler) and find out if you're overworking the new blower. If > you > have the install book it should have some pressure info, but IIRC anything > over > one inch is considered bad. > > Luckily my house had a 100,000 btu furnace in it, so although the ducts were > marginal for the original design they're oversized for the 46k furnace and 1.5 > ton AC I put in. > > > On January 16, 2019 at 11:40 PM Scott Ritchey via Mercedes > <mercedes@okiebenz.com> wrote: > > > > My other system is a new (week-old) Carrier R410 heat pump so I'm a little > reluctant to start hacking it just yet. That new R410a Carrier heat pump > with a > Unico air handler really puts out heat; I get 110+ degree source air when > it's 50 > degrees outside and still 100+ degree source air when it's 25-30 degrees > outside. > > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
