Subject: From: Date:

Re: [ECS] Need quick HVAC advice Steven Wegman Wed, 16 Jun 1999 09:02:34 -0400

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At 12:36 AM 6/16/99 -0400, you wrote:

>1) He has suggested a unit that is 90% efficient.  What does that mean, and
>do I care?  I know enough to know that 90% units are significantly more
>expensive that 80% ones.  BTW, currently, my electrical bills are around
>$400/mo. During the summer. The contractor thinks he can lower that a fair
>amount with this unit.

The efficiency rating indicates the amount of electricity that is wasted
(or used, depending how you look at it) to either heat or cool the house.
Usually heating raes are expressed as efficiency values; e.g., 90% percent
efficient means that 90 percent of the gas (oil, whatever the heating
source is) is converted to heat to heat the house, with the remaining 10
percent going out the flue.  Thus, the higher the heating efficiency, the
lower the cost to heat the house in the winter.  However, keep in mind that
the HVAC unit is just one component of a system.  There is also the
A-frame.  If you put in a high efficiency unit, the contractor may have to
also replace the A-frame unit in order to have the new unit operate
flawlessly.

	Cooling efficiency is expressed in EER (or SEER; SEER stands for seasonal
energy efficiency ratio).  SEER is always higher than EER, which is not
adjusted.  Typical high efficiency cooling units have SEER's between 12 and
16.  Again, the higher the better.

	Of course, it goes without saying, that the higher the efficiency, the
greater the initial (purchase) cost.

	For a frame of comparison, I built a 9000 sq. foot house in Maryland and
installed a geothermal HVAC system; heating efficiency of 93% and EER (not
SEER) of approx. 30.  Cost for system was approx. 30K.  My electric bill
ranges from a low of $100/month to a high of $280/month.  This includes
lights, tv, etc.  A friend of mind build a 10,000 sq foot home approx. 30
miles from me (thus, same climate) after I built my house.  He installed
90% efficient gas furnace and SEER 15 a/c units (cost was approx. 22k).
His bills in the summer are over $600.00/month.  Over the long run, I will
save much more than the 8K difference.


	In deciding what to install, you need to consider how long you intend to
remain in the house.  Also, certain systems could require larger ducts,
which is difficult in a retro-fit situation.



>3) Obviously, the proposed HVAC system will handle it's own logic, when it
>comes to managing the temperature in each zone.  Is that something I am
>better off letting ECS do?  Am I paying for a level of processing for the
>system that I don't need to because I use ECS?

	I recommend letting the HVAC electronics handle the logic, and just use
ECS to control setpoints.  This way, if ECS is down, the HVAC system will
still function on its own.  If everything is controlled by one processor,
the danger is that when the processor goes down, you will loss your HVAC.




>4) Am I better off having them install a one zone system, and trying to add
>the dampers and thermostats to make it a 4 zone system myself?  Or is that
>notion crazy?

>5) Am I nuts to try to do a 4 zone system? Here are my proposed zones:
>Z1: Most of the house, with the exception of the following;
>Z2: Den, which has a high heat load because of multiple computers, A/V
>equipment, Amps, monitors, etc;
>Z3: Sun/Family Room, which has a 20 foot wall of glass, 15 feet high at the
>peak;
>Z4: Basement (finished)


	Depends upon the size of the house and its openness.  For example, my
house is divided into 3 zones, using seperate HVAC units.  However, no zone
dampers are used because the house is an open design, meaning, for example,
that there are few rooms (on the first floor) that can closed off.  Thus,
there is no point in, for example, installing a damper for the dining room,
when air from the living room flows into the dining room (due to the lack
of a door between rooms).

		If the house is small the cost of the zoning will probably out weigh the
benefits.  Exception might be for a room that is rarely use.  In that case,
the zoning could cut off air flow into the room.

	On option is to have the contractor install the zone units in the ducts,
but not install the electronics.  The units in the ducts will run between
100 and 200 each.  This way, you can determine afteerward, whether you need
zoning.  If you do, you can use ECS to control the zoning units in the
ducts.  If ECS fails, the zone units would revert to a default state, the
HVAC units would still work, and the rooms would be heated/cooled.

steve wegman
swegman@erols.com

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