HVAC and Multi-Family
Buildings
Five minute History of HVAC
• Discovery of fire – open combustion.
• 1735 – First enclosed stove in France
• 1742 – Benjamin Franklin patented his all
metal stove with closing doors
• 1796 – Benjamin Thompson “Count
Rumford” detailed his efficient fireplace.
• 1830s – Perkins patents “steam tube”
The Steam Era
• Water Tube boiler – 1867
• Cast Iron Sectional Boiler – 1880’s
allowed for modularity
• 1880 New York Cities Steam system is
underway.
• 750 patents awarded between 1870 -1930
for steam related products and technology.
After WWII, Age of electricity
• Companies like TACO, B&G and others
start producing low cost circulators
• Furnaces and Fan coils standardize and
become available.
• Piping and ducting systems are introduced
by B & G and Carrier.
• 1965 on one out of ten homes have AC
The age of electronics:80s – 90s
• Inexpensive relays, proportional
controllers, and sensors became available
• Building Automation systems piggyback
onto fire and security alarm systems.
• Mass produced electronics displaces
electro-mechanical controls.
Age of the computer: 2000s
• The personal computer drives the cost of
computing down.
• Mini-computers or controllers are available
to drive power electronics and process
control.
• VFDs, advanced boiler controls, ECM,
ICM and other variable speed motors
So why are we here?
Hasn’t someone figured out
the perfect system yet?
HVAC goals:
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Comfortable temperature
Humidity control
Building Durability
And of course to be as:
Cheap as Possible
Types of Heating Systems
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2.
3.
4.
5.
Forced Hot water
Forced Hot Air
Water Sourced Heat Pumps
Air Sourced Heat Pumps
Straight Resistance heat
Electricity as a percentage:
• Forced hot water:
– 5% electricity, 95 % fossil fuel
• Forced hot air
– 10% electricity, 90% fossil fuel
• WSHP COP – 4
– 25% electricity, 75% fossil fuel (heating mode)
• ASHP + Electrical resistance
– 100% electricity
Forced Hot Water
The Classic.
Balanced Distribution
How we balance circuits:
Terminal Unit:
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Fin Tube Baseboard – 500 btus/lnft/hr
Radiant infloor – 35 btus/sq/ft/hr
Radiant panel – varies up to 13,000 btu/hr
Fan Coil – varies to MMbtu/hr
Every Terminal Unit is low temp compatible.
Not all are high temperature compatible.
Fin Tube Baseboard:
Most Common Terminal Unit:
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CHEAP: $6 a foot in Material.
Well established and easily understood.
Never lasts its expected lifespan.
Does not perform if furniture is crammed
against it.
• Freeze potential is high.
Radiant Panel:
More Costly but Durable:
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Radiant Panel, $20 a lineal foot.
Less well known, some early adopters.
Much more durable construction.
More compatible with lower temp supply.
Less prone to freezing due to higher
radiant portion.
It doesn’t have to burn to be hot!
Radiant In floor- Wet system
Radiant In floor – Dry System
Radiant In floor – Dry System
Radiant In floor
• Expensive retrofit, limits floor systems /
covering options.
• Can utilize lower temperature water
• Has long lifespan, life of Pex?
• Requires educating tenants about thermal
mass, the thermostat as an accelerator.
• Not necessarily more efficient
Air handlers
Air handlers:
• Less common in residential property in
Vermont.
• Offers opportunities to do ventilation along
with heating / cooling.
• Often causes over / under pressure zones.
• And….
One zone for all…
Controls:
• Controls are often thought about as wires,
signals and relays. It is better to think
about controls as processing information.
• What do we know?
• What do we do with what we know?
Classic system:
Classic System:
• No real information is transferred from
zone to boiler.
• We are always heating as if it is the
coldest day of the year
• Maybe, just maybe, we shut down in the
summer.
• Look for open windows in this
arrangement.
A little better:
A little better:
• We modulate supply water temperature to
match heat loss (Outdoor Air Reset
Control)
• Staging is available for multiple boilers.
• Cycle rate can be managed better.
• WWSD might occur, just might as long as
we don’t do dumb things like this….
Almost idiot proof:
But the display says it works:
Controls can only work when
properly installed:
What is OAR
Tekmar installation
A lot better:
• Mod/con boiler or two staged boilers sized
at 60% of true load no DHW
• OAR control, DHW priority, WWSD using
an ECM based primary pump.
• Wall panels radiators, mechanical zone
valves at each radiator, no electric zone
valves.
How I would do my own house:
• Mod/con boiler with buffer tank – I will
probably have <2000 btu/hr loads.
• Lower coil connected to solar DHW
system
• ECM primary pump, radiant panel
• Ability to tie in wood boiler in future.
Water Sourced Heat Pumps:
• All heat pumps are air conditioners with
reversing valves.
• COP is only the efficiency of the unit, not
of the system, don’t be fooled
• Water side delta T is king, keep strainers
clean, stock freeze stats
• Watch out for simultaneous heating and
cooling, three way valve leaking, etc.
WSHP Hook up
Dirty strainer & leaky three way
Domestic How Water Production
• Usually forgotten about, can account for
40% of fuel used in very efficient buildings.
• In some situations, should be separated
from space heating system.
• Is often overlooked as an easy upgrade.
DHW - Types
• Stand alone appliance – gas, oil or electric
• Indirect fired tank
– Coil
– Tank in a tank
• On demand – this is more single family.
• Solar
Its all about the GPM
• Gallons per minute – Peak loads.
– Storage + production or the first hour rating.
• In directs offer the best of both worlds,
however not always the most efficient.
• A tank in a tank can produce 10 gpm all
day long.
• Tank standby losses are pretty much the
same regardless of size.
Least tanks to do the job:
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Remember, boilers losses count
Its not a chimney, it’s a Straw!
DHW calls come almost every hour
Never fire two boilers to do DHW
Think about your situation, are firing a 2.5
million btu boiler to heat 80 gallon tank?
Tank in a tank:
Use Dielectric fittings:
Coil in a tank:
Solar
• About 185,000 btu/yr per square foot of
array
• Size for people, 10 sq/ft per BD, 50% load
• Size storage for array 1.5 to 2.0 gallons
per sq/ft of array.
• Do not recirc through your storage tanks.
• Do not forget about expansion!
Flat panel – industry standare
The evacuated tube
How they compare
Closed loop system
Yes, we can make it complicated
ECM pumps:
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Essentially a brushless dc motor
Can run at variable speeds
Can be 20 to 65% more efficient.
Is the only legal pump in Germany after
2011
Highgate Apartments
More to come on ECM
• Just starting to look at the data
• Will have more installed for next winter.
• More companies are seeking UL listing.