(Heating, Ventilating, and Air Conditioning) For questions about installing, repairing, and troubleshooting HVAC systems.

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2answers
56 views

Installing Honeywell Wifi on Ruud Furnace with G wire replacement

trying to install RTH9580. My thermostat has only 4 wires so I am trying to substitute the G wire instead of C wire. On the furnace I put a jumper between Y and G wires and moved G wire to C wire ...
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1answer
4k views

why does my heat pump wiring diagram show 7 wires going to the thermostat but the thermostat only says it needs 5?

Here is a link to the wiring diagram for my heat pump. The thermostat that I am planning on buying has the following terminals C, G, Y, O/B, RC, R, Aux, E, and L. The instructions say to jump the RC ...
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1answer
763 views

How can I add a C-wire to a Venstar T5800 thermostat?

I am trying to replace my existing thermostat. My old thermostat has: Rh, W (coming from the heating unit). Rc, Y, G (coming from the AC unit). On the Venstar T5800, I can map as follows: Rh+Rc -...
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9answers
97k views

Why won't my A/C turn on after I replaced the thermostat batteries?

Our thermostat died yesterday, but after replacing the dead batteries with fresh batteries, and confirming the LCD screen was operable, our AC no longer turns on. I have attempted a factory reset on ...
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1answer
78 views

Wiring for New Thermostat

I just bought new programmable z-wave thermostats (Honeywell TH8320ZW). I thought I had the wired correctly, but I woke up to a pretty chilly house this morning. The fan is working, but it seems to ...
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1answer
779 views

Correct Wiring for Furnace Blower Motor

After getting my furnace blower motor replaced, it now runs only in the following scenarios: 1. Mode "Cool" Fan "Auto" 2. Mode "Cool" Fan "On" 3. Mode "Heat" Fan "On" In other words it will not run ...
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1answer
29 views

What kind of system carries both hot and cool water to my condominium?

I have an ancient furnace and air conditioner in my condo. Basically the building supplies water to every unit. In the winter it is warm water, the summer cool water. Every condo has a blower unit ...
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3answers
6k views

Can I sense filter replacement need based on filter pressure drop?

I should first point out that the system I'm referring to will be a self build DIY project. Fan and Filters being the only items purchased complete, And I'm still in the design phase but I'm not a ...
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1answer
29 views

Stack Effect and an open top floor window

I have recently had an energy audit for my home and discovered a large amount of air leakage. As a result I have learned about Stack Effect, and how it impacts a home's ability to retain warm or cool ...
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0answers
47 views

temperature on thermostat not going down with fan running

I just had a new ac unit installed but it does not blow cold air. the techs have checked it 5 + times and have said that all the numbers and stuff check out. so while i have it on auto fan cold, i ...
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0answers
7 views

HE furnace exhaust vent termination in non-freezing location

we are installing a HE 100k btu gas furnace. our contractor is installing the exhaust side vent under the cantilevered section of the house that we believe is not ok. we have a cantilevered section ...
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2answers
6k views

Is a lip necessary on an HVAC ceiling register boot for use with flexible ducting?

I've installed some new ceiling register boots to use with flexible ducting and realized after install that they have a smooth connection with no lip. I'm assuming they are made for metal ducting, as ...
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1answer
43 views

electric heater keeps needing to be reset by turning fan on and off atleast every 1-2 days

My electric furnace is about 23 years old, it quits working but does not trip a breaker. It feels warm to hot at furnace and just kind of clicks occasionaly when I turn thermostat up to 90 to try and ...
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2answers
1k views

How do I cut a straight line in an installed wood floor for a flush mount HVAC vent?

At some point a previous owner installed hardwood flooring in my house. Nice. They did not however make a hole for the front entryway heating vent. The duct and duct outlet exists in the crawlspace ...
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2answers
39 views

AC tripping power breaker

My central AC is dripping power breaker What I have checked Filters are clean I cleaned outside unit with water I put in a new capacitor It cools fine it just trips middle of night like 4am
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1answer
41 views

Oil furnace fan won't shut off when “heat” plug is connected to control board

I was changing my thermostat and I attempted to make the swap live without turning power off. When I connected new thermostat, the fan kept running. Ruled out bad thermostat and wire short by ...
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1answer
26 views

I have an electric furnace that sometimes blows cold air

I have an electric furnace that blow cold air sometimes. I replaced the thermostat and that did not fix it. The fan blows fine. If I shut if off for a few minutes and then try again, about half the ...
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0answers
24 views

A/C board is bad…is this from previous poor repair?

Back in May our A/C and heat would not kick on. Tech came out and replaced the A/C fuse box and everything was fine. Last week the coils froze up (has never happened before) and tech said the board ...
4
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4answers
6k views

How freely should a central A/C condenser fan spin?

Last year my home's central air condenser fan motor stopped working. When I noticed the house wasn't cooling down I went outside to investigate and found there was a humming sound coming from the unit,...
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1answer
110 views

New Thermostat installed but compressor comes on immediately

I have a new Insteon Thermostat that I'm using to replace my prior Honeywell t-stat. This is installed to a relatively new HVAC system (both AC and Heat) that DOES have a "c" wire. I've attached the ...
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2answers
112 views

Furnace fan works properly intermittently

My furnace fan sometimes stays on and runs continuously. I can stop it by flipping the breaker for the furnace on and off. It then stays off. When heat is called for, the fan comes on again and ...
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2answers
39 views

What would make my ac unit hiss

I live in a mobile home and my central ac unit starting hissing pretty loud 3 days ago and tday it is blowing only warm air. There is no water or ice inside or out. The outside unit is running but it ...
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1answer
1k views

What could be causing my Lennox furnace to blow cool air?

My Lennox outside furnace is blowing cool air, not hot even when the burner is lit. It takes 3 times longer to heat the house than it should. I just had the draft motor replace about a month ago and ...
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0answers
15 views

Central Air Conditioner coil cleaner

What is the best way to clean Air Conditioner could I bought two cans of web cool cleaner foamy thing http://m.homedepot.com/p/14-oz-Condenser-Coil-Cleaner-WCOIL/100351663 So I ended up using two ...
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1answer
23 views

RESIDENTIAL HEAT PUMP - HOW MANY TONS IS NEEDED?

Residential A/C unit question: What size Heat Pump is needed for a 1,924 sq.ft. home 35 miles northwest of Phoenix, Arizona? The home has 6" insulated exterior walls, stucco exterior, 10' ceilings, ...
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1answer
103 views

Less than 24 volts on the thermostat C wire

We have a brand new air handler at work, but the thermostat is mounted on a wall next to a server/computer room which is always warmer than the rest of the office. I want to install a thermostat that ...
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1answer
3k views

Blower fan works w/ heat “auto”, not with a/c “auto” or on “on”

I've read the posts with the opposite issue, which have been helpful (you guys are amazing!) but still no solution. Problem is that the blower fan does not come on when system is on "Cool" and fan is ...
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0answers
21 views

HVAC wiring White Rodgers 90-113 fan center with fan limit on RUUD gas furnace and AC

Need wiring diagram how the White Rodgers 90-113 fan center and fan limit, which are wired for heat and cooling in a gas furnace. It has following components: fan control center. fan limit. gas ...
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1answer
36 views

How long should a heat pump last before needing repairs?

We have a Goodman heatpump Model: SSZ140601 Model Desc.: 14 SEER HP, 5 TON Mfg Date: 6/3/2010 First of all, we did not register the unit so that cut our warranty in half. Two weeks ago, our ...
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0answers
26 views

What caused this motor to short?

These pics are from my ECM motor in my air handler. I knew the motor was my problem when it failed a phase-resistance test between the windings. The new motor passed the test and works great. I ...
4
votes
2answers
105 views

How can I check the refrigerant level in my air conditioner?

What kind of device do I need to check the refrigerant level in my home AC? Can I buy something like Mountain MTN8205 R134a Brass Manifold Gauge Set With Couplers? Please suggest if I am on the ...
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2answers
298 views

Trane xv80 3 blinks

Trying to be as thorough and concise as I can, zero experience with hvac. I have a year 2002 Trane xv80 that is giving me the three blink code, which indicates a pressure switch issue. I ...
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1answer
43 views

Why might a thermostat refuse to switch from Heat mode to Cool mode?

I have this Honeywell RTHL2410C programmable thermostat and typical Florida electric AC system. Starting this Spring, it has started behaving strangely when switching from Heat to Cool mode. The ...
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0answers
205 views

Yellow wire connected to C terminal, blue wire connected to Y terminal at furnace

I'm trying to install a new smart thermostat the requires a C wire. My old thermostat operated on batteries. The pre-existing wiring system of the old thermostat looked normal (ie. red wire to Rc, ...
1
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2answers
9k views

How do I replace a condenser fan motor in a central air unit?

The condenser fan motor on my central air unit has seized up (tried like crazy to turn it it, but no go). I'm not sure how old the motor is but I'm guessing it's original, so about 12 years old. I ...
1
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1answer
1k views

Inverter air-conditioning units or non-inverter air-conditioning units?

I want to purchase new 8-9 units of air-conditioning for my new house. For the hall, kitchen and all the bedrooms. Some people say inverter air-conditioning is only suitable if you are using more ...
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1answer
23 views

Brown Spots Above Ceiling/Ductwork

Any idea what these spots might be? They're isolated to just one spots on my ceiling. My ductwork is right above this area. Thanks!
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0answers
23 views

ac high suction pressure 95 psi, 55 degree vsat temp.

ac,high suction pressure on trane 2.5 ton heat pump replaced reversing valve no help ,normal high pressure, super heat 12,subcooling 9 supposed to be 12,weighed r22 back in system. why high suction ...
1
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1answer
498 views

Why does the blower in the attic vibrate during heating when it is really cold?

We have a Carrier heat pump system in our home, and the blower is located in the attic. When it is especially cold, the blower runs on high (there are three levels: high, medium, low). During this ...
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0answers
27 views

New AC unit - condenser line freezing up

Last summer I had my entire HVAC system replaced, outside condenser, inside coil. The old system needed to have the some coolant added each summer as there was a small leak and the lines would ...
0
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2answers
44 views

A/C unit cycles on and off

My outside compressor / condenser is cycling on and off, even though the thermostat is calling for A/C. The blower in the house still runs, and the thermostat is working properly. ( I opened up the ...
0
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0answers
15 views

New thermostat wifi Honeywell need 5 wires

We purchased a new thermostat and it needs 5 wires, old one only has 4, but when we looked in furnace it has a 5th wire on a connection marked C but the bundle coming from wall behind thermostat only ...
1
vote
3answers
80 views

What's the most cost effective way of ventilation automation given no prior knowledge in the field

I have 3 fans for air inflow, and 3 fans for extract, all in one big hall. Currently I set the power of their motors with dimmers myself, looking at CO2 and temperature readings. I want to replace ...
1
vote
1answer
139 views

How to Change Chinese HVAC Thermostat

I am looking to put Nest thermostats in the house, I have now found out my entire house (one in each room, 6 of them) has been wired with HVAC Chinese U12A UNIVERSAL A/C CONTROL SYSTEM urrgh – they ...
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1answer
224 views

Why would only 1/3 of my registers be blowing warm air?

I have a Coleman gas furnace in a wall space in my house which somehow shares the blower on my a/c unit on the roof because it turns on when furnace is called to start, though it does bump up after a ...
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1answer
48 views

Could a leaking boiler be fixed?

I'm having a leaking hole in the cast iron boiler tube so does it mean that its time for a new boiler or is there any way it could be permanently fixed?
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1answer
45 views

My Air conditioner suddenly became defective after a power outage

So, these are the symptoms: 1] The big fan outside is taking a lot longer to start. 2] Within 2 minutes of start-up and cooling, it makes a growling/ rattling sound and 3] The power switch to start ...
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1answer
43 views

Can AC fan or motor be upgraded?

My AC blows cold air, so I assume my compressor outside works OK. Please correct if that's an incorrect assumption. The problem is, there is very little cold airflow that comes out of the floor ducts....
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2answers
159 views

How can I determine what grade air filter is appropriate?

I'm trying to figure out what kind of air filter is appropriate for my house. My local home warehouse store stocks over a dozen options. The primary difference between them seems to be Microparticle ...
1
vote
1answer
146 views

How to connect thermostat to newly-installed condenser/evaporator unit

I installed a furnace evaporator and condenser brand goodman 4 ton unit but need to know how to connect thermostat from condenser to the furnace to the thermostat if any suggestion.