Day & Night builds central ducted heating and cooling equipment: gas furnaces, air conditioners, heat pumps, air handlers and packaged units. In a typical foothill home, those pieces combine into one of three systems: a furnace with an air conditioner, an air handler with a heat pump, or a dual-fuel pairing of a furnace and heat pump.
Foothill Air Systems is an authorized Day & Night dealer, and it is the line we recommend when a house has workable ductwork and wants one central system. This guide explains what each component does, how they fit together, and what matters more than the name on the cabinet.
What is in a central ducted system?
A central system has an indoor unit, usually an outdoor unit, and the ducts that connect the indoor unit to every room.
- The indoor unit holds the blower that moves air through the ducts. It is either a furnace, which also makes heat, or an air handler, which pairs with a heat pump.
- The indoor coil sits on or inside the indoor unit. In cooling, it absorbs heat from house air. With a heat pump, it also releases heat in winter.
- The outdoor unit is either an air conditioner, which only cools, or a heat pump, which cools and heats.
- The line set is the pair of copper refrigerant lines that connect the indoor coil to the outdoor unit.
- The ducts, filter and thermostat complete the system. The ducts often determine comfort more than any other piece.
The HVAC glossary defines each of these parts in a sentence or two.
What does a Day & Night gas furnace do?
A furnace burns natural gas or propane inside a sealed heat exchanger. The blower pushes house air across the hot metal and out through the ducts, while combustion gases vent outdoors through a flue. Furnace efficiency is expressed as AFUE, the share of fuel energy that becomes usable heat over a season.
Day & Night offers furnaces at more than one efficiency and staging level, including condensing furnaces that extract extra heat from the exhaust and drain the resulting condensate. Multi-stage and variable-speed models can run at lower output most of the time, which usually means steadier temperatures and quieter operation during a long foothill heating season.
At elevation, furnace installation has to follow the manufacturer's high-altitude guidance, because thinner air affects combustion. A furnace set up for altitude typically fires at a reduced input, so its delivered capacity is lower than its sea-level rating. That is one reason we run a combustion analysis at startup.
What does a Day & Night heat pump do?
A heat pump uses refrigerant to move heat. In summer it moves heat out of the house like any air conditioner. In winter it reverses and moves heat from outdoor air into the house. Its capacity falls as outdoor temperatures fall, so selection has to account for your local design temperature.
A heat pump is usually paired with an air handler, which often includes electric resistance strips as auxiliary heat for the coldest hours and during defrost. It can also be paired with a gas furnace in a dual-fuel system, where the furnace takes over below a set outdoor temperature. For the tradeoffs, see heat pump vs. furnace in the Sierra foothills.
What is an air handler, and when do you need one?
An air handler is an indoor unit with a blower and coil but no burner. You need one when the outdoor unit is a heat pump and there is no furnace. Air handlers commonly sit in a garage, closet, attic or crawlspace. Because a heat pump system relies entirely on the air handler for airflow, duct sizing and static pressure matter even more than with a furnace.
What about packaged units?
A packaged unit puts every component in one outdoor cabinet, typically on a pad or roof, with ducts running into the building. They are common on light commercial buildings and in homes without room indoors for equipment. Day & Night builds packaged units in gas-electric and heat pump versions. Our article on commercial HVAC in the foothills covers rooftop units in more depth.
When is Day & Night the right choice?
Day & Night equipment tends to fit best when:
- The home has existing ductwork that tests well or can be corrected.
- You are replacing a furnace and air conditioner and want a matched pair from one manufacturer.
- You want a dual-fuel system that combines a heat pump with a furnace.
- You want whole-home filtration and humidification built into a central air handler.
If the house has rooms the ducts do not reach, a zoned or ductless system may be the better answer, alone or alongside central equipment. Our Mitsubishi vs. Day & Night comparison explains how we choose.
What goes wrong with central ducted systems?
Most problems with central equipment, from any brand, come from design and installation:
- Sizing off the old nameplate. The old unit may have been oversized, or the house may have changed since it went in.
- Ducts that cannot carry the airflow. Undersized returns and crushed flex duct raise static pressure, which reduces capacity and strains the blower motor.
- Refrigerant charge never verified. An incorrect charge reduces capacity and efficiency and can shorten compressor life.
- Furnaces not set up for altitude. Combustion that was not checked can waste fuel or create unsafe conditions.
- Condensate lines that freeze or clog. Condensing furnaces and cooling coils both produce water that needs a reliable drain path, including in cold crawlspaces.
What do we look for when installing Day & Night equipment?
Our process for a central system usually includes:
- A Manual J load calculation using your elevation's design temperature, rather than copying the old equipment size.
- A duct inspection and static pressure test before equipment is chosen, so any duct correction is part of the plan.
- Electrical checks for the outdoor unit and any auxiliary heat.
- A combustion analysis at furnace startup, including a look at venting and combustion air.
- Commissioning measurements such as airflow, temperature rise or split, and refrigerant charge, recorded for your file.
If your current system is aging, our repair or replace framework is a useful first read.
How long does a Day & Night installation take?
A straightforward equipment replacement is typically one day. Adding a heat pump where there was only a furnace, changing fuel type, correcting ductwork or working in a tight crawlspace or attic can extend it to two or three days. We give you a realistic schedule up front, so you can plan around it.
Do you service Day & Night equipment you did not install?
Yes. We diagnose, maintain and repair existing Day & Night systems regardless of who installed them. Sending us the model and serial numbers ahead of time helps us arrive prepared. For older systems, a service visit is also a good time to get a clear picture of the equipment's condition before a failure forces a decision.
What is the next step?
To talk through a furnace, heat pump or dual-fuel system, see our Day & Night systems page and HVAC replacement process, browse the repair and replacement guides, or contact us. You can also call (530) 212-0057, Monday through Friday, 8 to 5.
