Questions tagged [hvac]

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Wiring a 120 V device to a HVAC thermostat? [migrated]

I'm looking control a 120 V device with an HVAC thermostat. The device is a scrubber that cleans air and should\must only run when the HVAC is running (running in the cool state, heat state, or just ...
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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 ...
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HVAC 24VAC backfeed prevention [closed]

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, ...
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Would there be any safety issues if the input voltage on the primary coil is bigger than what the rated voltage is?

I have a neon sign transformer that converts 120 V to 12 kV which is the rated voltage. Using the 1:100 ratio would it be safe to have the input voltage be 140 V converted to 14 kV when the specified ...
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2 answers
130 views

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 ...
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5 answers
2k views

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 ...
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3 votes
0 answers
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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 (...
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1 answer
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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 ...
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2 answers
159 views

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 ...
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2 votes
2 answers
167 views

Current Transformer in power meter

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

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 ...
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1 answer
142 views

Do 0-10V proportional valves and dampers require a sourcing or sinking controller?

A 0-10V controller can use either sourcing or sinking to set the control voltage (see Wikipedia 0-10V Lighting Control, for example). For sinking control, the controlled device provides a high ...
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