Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [hvac]

18 questions
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2 answers

How to average two 0-10 V signals?

For an HVAC application I'm searching for a way to average two 0-10 V signals with the ability to give a "weight" to one or another. Example: I have input A at 10 V and input B at 5 V. If I make a dumb average I get 7.5 V. I want to be able to…
Nicobzh
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RS485 Protocol Reverse Engineering & Replay Challenges

I'm trying to reverse engineer the RS485 protocol used by my home heater/AC. This protocol handles communications between the wired remote control (WRC)/thermostat and the main heater/ac indoor unit (IU). My goal is to eventually be able to mock the…
adamz
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5 answers

Would retro-fitting a DC motor as the blower motor in a residential furnace be more efficient than existing 1/2 hp AC motor?

There exists DC motors of various voltages (12, 24, 48, etc) and various powers (1/2 hp, 1 hp, etc). They seem to have the necessary power and RPM to operate the blower in a conventional residential furnace. During a power outage a 12 V DC motor…
Peggy Schafer
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2
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2 answers

Current Transformer in power meter

How to measure the total power in a 3 phase electrical system with one current transformer?
Arceus
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1 answer

Can a 10uf Capacitor be used in place of a 15uf capacitor temporarily?

I am in Phoenix and it's hot. The indoor blower motor just went out on our AC unit and the wife and kids are not happy. It is just a bad capacitor. Original capacitor is 15uf 440v. I was able to get one on Amazon that will be here in two days but it…
Matt Cashatt
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What is a Fast-Stat Commonmaker actually doing?

Trying to get an Ecobee thermostat to work in my old house where I only have two wires going to my thermostat. Ecobee needs a common, and the remedy they suggest is a Fast-Stat Commonmaker, which has two parts - one that lives up near the thermostat…
vicatcu
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Start heat pump (HVAC) from electric generator: AVR voltage surge issue

I'm trying to start the heat pump from the generator, and it turns out successfully...for an hour. First of all, mandatory specs and preconditions: heat pump: Mitsubishi Electric PUHZ-SHW140YHA electric generator: Foro FV 20000 TRA 14 KW…
Alex
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1 answer

HVAC 24VAC backfeed prevention

I have an HVAC system with a powered open/powered closed supply damper, Ultra-aire 120 V dehumidifier and ventilation damper that is powered to open. I have everything wired up and it is working, however, since I have two 24 V signals going to open…
micron
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2 answers

How to divide 24VAC to 24VDC for use with GPIO

I'm working on a project to gather metrics from my HVAC. I need to detect the presence or absence of 24vAC on two different wires (Y/yellow/cooler, W/white/heater) relative to common - either of which will be periodically pulled to 24vAC by a relay…
Brad Hein
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Could someone help me identify a part number/brand for this surface mount diode?

I’m repairing the main control board for a HVAC unit that was damaged in a power surge. Nothing too complex, just a diode that was blown and needs to be replaced. The problem is I’m not exactly sure what part number the diode has and I want to make…
Chase Grochett
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1 answer

Different fan size in same duct

Im trying to build pc cabinet such that there is 3 fan input to cabinet, and just one output which is the smps inbuilt fan. Then seal off all other air gaps. Q. Will the smps fan break due to receiving 3x its capability? Or reprase as, Will using…
iuofk
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Can I replace two run capacitors with a dual run capacitor?

In this unit https://ameristarhvac.com/wp-content/uploads/pdf/M4AC3-Air-Conditioner-Installation-Manual.pdf Can I replace the 35 uF capacitor and the 6 uF capacitor with a 35/5 uF dual capacitor? If so, how do I wire it up. Here is the wiring…
tsdexter
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What kind of component is this, and is it damaged?

My central heating controller stopped working. It's essentially an AA battery powered device with a thermistor, some buttons, and an LCD screen, which lets me program desired temperatures for various day/time periods. When the controller decides…
Chris
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What are these electric components?

This is a snapshot from a single-line diagram of emergency switchboard drawn in 1984 for an oil & gas project. What are these two components next to the motor symbol? What could CP stand for? What is the rectangle with a black dot? The * note…
Corentin Pane
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Where do I measure the Amp draw of my motor which is connected to a centrifugal fan?

I just started my job as an apprentice technician. For the longest time, my supervisor have always been measuring the amp draws of my motor from the outgoing cable from the motor to the electric panel (which is below the full load amperage stated on…
Hanif Shidki
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