/r/hvacadvice
A place for homeowners, renters, tenants, business owners or anyone with a general question about their HVAC system.
Please read rules before posting!
/r/HVACadvice exists to offer insight from people who are experienced in the HVAC field. If you are experiencing issues with your Heating, Air Conditioning, Ventilation and Refrigeration system PLEASE call a professional. While the mods do their best to make sure information is accurate, you should ALWAYS take internet advice with a grain of salt.
No advertising is permitted here - as in do not post links to your blog, specific products for sale on other websites, etc.
If you have an electrical question, feel free to ask over at r/askanelectrician !
Please do not crosspost to r/hvac or r/thermostats - pick one sub for your post.
Blacklisted topics:
- Disabling safety systems, even for just a minute to test or because you are very cold. Zero tolerance.
- DIY asbestos abatement
- Untrained work on three phase or electrical voltages higher than 240
- Venting refrigerant deliberately or advocating doing so.
- Uncertified refrigerant use (using gauges without proper certifications).
- Unlicensed or uncertified work on gas appliances directly affecting the flow of gas/exhaust, examples include: gas pressure adjustments, venting, gas pipe work.
An immediate ban will result for anyone giving unsafe or dangerous advice.
Related Subreddits:
/r/HVAC (mother and father to us all)
r/hvacporn (for those sweet, sexy mechanical rooms and installs)
r/askanelectrician (for basic electrical questions)
r/ProHVACR (questions about owning or operating a HVAC company)
r/refrigeration (commercial refrigeration stuff)
r/airbalance (for Test, Adjust and Balance professionals)
r/kitchensuppression (for commercial range hood/restaurant fire suppression)
r/airconditioners (window units, wall shakers and all related equipment)
r/construction (for the lols and the hahas)
There's also the HVAC discord that seems like a pretty chill place to hang out, but it isn't affiliated with Reddit. The mod crew is forever on call here.
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/r/hvacadvice
127,385 Subscribers
Noticeable difference in performance after maintenance
Had the furnace inspected/tuned up a month ago. It's noticeable how different it has been performing. Blower stays on longer after thermo kicks off. Takes a little bit to ignite as well. Also been noticing cooler air coming out on some cycles, warmer air on others.
Here's the invoice and scope of the last inspection. You guys seeing anything? I almost feel like callimg them back.
15:04 UTC
Can't figure out 7-wire furnace for smart thermostat
I would like to install a smart thermostat and can't figure out the wiring (apologies if I use incorrect terminology in comments to follow). Thermostat has RhWYG wiring with unused blue and brown wires and unused B, O, and Rc labeled connectors (no C). I installed a programmable thermostat years ago to replace a really old dial-type thermostat and followed the wiring that was already used, so maybe I didn't wire it correctly. I can't find any furnace configurations online that match mine. I thought I had a normal furnace/AC but unfortunately can't find the manual. There are 7 wires hooked up from two bundles, with an extra W and R from bundle 2. From bundle one, I have normal RWYG wires/connections, but then also brown wire to C (even though C/brown is unused at the thermostat) and an unused blue wire. From bundle two, I have white wire to Y and red wire to C. So C has both brown and red wires and Y has both yellow and white. Blue wire is unused and there are no unused slots/connectors.
I'm not sure what I'm supposed to do about the common wire that most smart thermostats need. Google searches say that blue is most common wiring for C at both at the thermostat and the furnace, but I have no extra space at the furnace. So 3 questions: 1 - can I use the brown wire as the common wire since it's already connected to C at the furnace but is unused at the thermostat? 2 - should I replace the brown wire at the furnace C with blue and then use blue as the common wire at the thermostat? 3 - is everything just f'd up?
15:03 UTC
What could be causing this noise and resulting vibration in a top floor apartment?
Currently dealing with this noise whenever the condensers on the roof kick in above our guest bathroom. This noise reverberates through the apartment and is making it unliveable.
We are dealing with a landlord through a property manager to solve the problem at the moment. They have tried padding and are now debating springs to elevate the units. Would this be the likely solution, or could this noise be a result of something faulty in the unit itself?
14:48 UTC
Goodman Natural gas furnace valve wont open .
My goodman furnace wont turn on . it was stop heating after 20-30 minutes but now it wont open the gas valve at all. when it was intermittent i was reading 15vac idle and 25vac when its triggered .What would be the cause my gas valve wont get 24v? TIA
14:43 UTC
One thermostat heats whole house despite other thermostats being off. Help!
I recently moved into a new home and I am trying to figure things out in regard to AC/Heating. It's a 5-zone heating and 2-zone cooling. All work well, except that when I turn on the heating on the top floor (gas furnace, heating only, baseboard), ALL other zones are also heating (despite their respective thermostats being OFF).
Cooling of top floor is controlled by thermostat on floor just below.
I checked top-floor thermostat wiring, which looks like this:
There seems to be two cable coming out of the wall, and a jump between R and RC. Why two set of cables? What is the R-Rc jump for?
Any thoughts that could help me not warm the whole house when we only need top floor heating?
Thank you!
14:39 UTC
Any Downside to steam humidifiers?
So due to the layout of my ducting, zone takeoffs, UV light, etc, I can’t easily fit a bypass humidifier on my furnace. But, my wife keeps asking me to install a humidifier….so, any downside to the Aprilaire steam humidifiers? Looking at this one specifically.
https://www.supplyhouse.com/Aprilaire-800-Series-800-Steam-Humidifier
14:27 UTC
High Boiler Pressure Troubleshooting
Hi everyone and thanks in advance for any pointers.
I have a Rennai E110 Boiler and am experiencing high system pressure when the heat is on. This is not an issue for hot water, only for running the heat. With the heat off, the system pressure is sitting at 13 psi. When the heat turns on the pressure builds to about 35 and trips the pressure relief valve. This will happen continually with the heat on with the pressure relief valve reducing pressure every 5-10 minutes.
I reviewed the instruction manual and confirmed the plumbing is consistent with the manual slide 19.
I think there may be an issue with the autofill valve but I am unsure how to troubleshoot it. My understanding is that this valve will let water into the "closed" (semi-closed?) loop but that valve should be limiting the amount of flow into the system. Clearly too much water is getting in since the pressure relief valve is having to reduce pressure and water in the system.
The autofill valve is a Watts 1156F valve. Any pointers on how to troubleshoot this or if any adjustments can be made?
https://www.watts.com/dfsmedia/0533dbba17714b1ab581ab07a4cbb521/20196-source/es-1156f-pdf
Any other advise as to what I should be looking at?
14:24 UTC
No air flow to 2nd Story: ducts too small?
We have a new furnace with plenty of power, but a couple of rooms on the second floor never get any airflow.
The two air ducts indicated feed the two rooms. I drilled pilot holes in them at a couple of points to check for blockages using an endoscope camera, but everything was clear. We've blocked any other pipes feeding off the truck that lead to other rooms. They have LOTS of airflow from the furnace. Still no change to the airflow to the 2nd-floor rooms
One AC person mentioned that the pipes feeding the rooms are too small (which they do look) but it was a fairly new install when an extension was built on the house.
Any thoughts? Or do we have to get that main trunk upgraded.
14:22 UTC
Auto filler / LWCO wiring issue on single pipe steam boiler
Hi all,
I'm a homeowner, DIY so please have your pitchforks at the ready lol.
New-to-me, old house built in 1900. Weil-McClain boiler installed in 2008 by previous owners, for the single pipe steam system. Previous owner told me auto filler didn't auto fill, and he called and it was too expensive to replace it so he just refilled it every few days in the thick of the wintertime here in southern New England.
My gf is pregnant, and I figured I'd rather have the auto filler do its thing as designed so I don't have to remember to fill the boiler. I've done some pretty extensive electrical, plumbing and other projects so after doing the research I wanted to try replacing the auto filler (Unimatch WFE-24v equivalent from supplyhouse.com). Bough the new part, wired it dry to test and it seemed to work as best as I knew. Plumbed it in and wired it up - no power to the boiler. Did the usual tests and determined the transformer died, via my multimeter as well as the smell of the burnt transformer.
Got a new generic 24v transformer (it was later on a Saturday, so no supplyhouse.com overnight or local supply houses were open) and wired it in. Everything works. Got cocky and wanted to make sure EVERYTHING works, including the damper control, LWCO (Safgard 400) and auto filler (WFE-24V, Uni-Match). Damper and LWCO seemed just fine. LWCO probe is crusty as all hell but it does work when the water level is lowered (LED illuminates).
The issue is the auto filler will slow blink green indicating a dwell period, then the LWCO will kick on calling for water, which causes the Auto filler to brown out...? I tested with my multimeter and I'm getting 24v (hot/common) and also 24v on the control water from the LWCO to the auto filler. When the LWCO calls for water, the voltage drops to zero.
After I messed with this a while it was getting late so I decided to just sit directly in front of my open boiler and document my jerry-rigged wiring (remember, just a generic 24v transformer, not the proper Weil-McClain part) and I smell something and see smoke coming form the transformer! I cut power immediately but knew by the smell this one died too. So I'm up at 6am to Home Depot to get another generic transformer and wired it up, this time leaving off the "Y" wire from the OEM transformer schema, which powers the LWCO and Auto filler (power goes from Boiler > LWCO > Auto filler). So far it is running fine with thermostat control and getting my house warmed up (24 degrees here this morning).
My question is - what do I do next? My plan is to get an OEM transformer and new LWCO and probe combo from supplyhouse.com and replace everything. I want to first install the OEM transformer and see if I'm getting the same voltage patterns to the LWCO but honestly I'm scared of smoking the $100+ OEM transformer again. Its hard because I'm not an HVAC technician and I don't have anything to compare the voltages to. If its just a wiring issue on my rigged setup then I'm OK with that and I can return the LWCO (I already bought a replacement probe once I solve this other issues).
tl/dr - Smoked two transformers while swapping out auto filler. Want to make sure I don't smoke the new OEM transformer and get everything running again.
14:18 UTC
HVAC Duct Help
We recently remodeled our kitchen and I need to move the HVAC duct. All of our duct work comes from the basement through 2x4 walls. When they built the house they notched all of the floor joists to access the walls and squeezed the duct work through little slits (probably why we have terrible air flow). I can't find the type of stack boot they used previously. It was alot longer than what they sell at Home Depot now. Any suggestions on how to make this work? I can't get the hole large enough to run a stack boot through it.
14:08 UTC
How to fix furance;s secondary or emergency condensate line that is capped
14:03 UTC
I want a smart thermostat. Question about wires
I'm looking to get a Nest thermostat gen 4, I used the compatibility checker and it checks out
My house has central air, I have a propane furnace inside and an outdoor air conditioner
What could be up with the 2 wires in W, also what's the deal with R & Rc, I can't figure out their uses/compatibility
I'm not touching anything until I learn more
13:53 UTC
What temp should I set my boiler to for my water radiators?
I have a Navien Combi Boiler and I’m wondering what the setting should be for the radiators.
13:51 UTC
Residential PTAC
Teenage son wants to move his bedroom to the half story attic space.
It's finished with a closet, but it's an oven in the summer, and cool in winter.
More insulation is a non-starter. I'm not pulling the drywall on the sloped ceiling to check that, and the central air is basically sized to the rest of the house.
I'd like to put a PTAC ac/heat pump in the cripple wall on one side. This space is vented to the outside through roof vents because this is also the space the attic fan pushes into.
Am I asking for a mold problem if the PTAC uses this space for heat rejection?
13:32 UTC
Hello. I have a runtru heat pump cycling a lot. Normal?
13:24 UTC
Siemens thermostat with gas filled bellows (membrane) - reliable?
I am thinking about buying this simple Siemens RAA30.16/GR thermostat on the used market (for peanuts).
It would be a backup unit (if the main electronic thermostat goes bad). It would be used for a hot water radiator system.
This is a thermostat that uses a gas filled bellows/membrane. Does it reliably measure temperature? What is the longevity of such mechanism? Can it work for a number of years without degradation nor failure? I only have experience with electronic thermostats (the quality ones can last 20+ years).
12:46 UTC
Fujitsu compatibility
Hey guys
I recently picked up a new-old stock AGYF09LAC for dirt cheap which according to specs would be matched with AOYV09LA.
However, I can also see that AOYA/AOY 18/24/30 LM 2/3 multi-split outdoor units would also work based on the Fujitsu 2010/2012 product catalog. The indoor unit seems to be F series, most outdoor units available around on Facebook Market and eBay are newer G series.
Someone nearby is selling a combo of AOY18LMAK2 along with 2x AUY12LBAB - pretty sure the outdoor unit from this set would work - right? I'm thinking of getting that and reselling the indoor units whilst I look for an extra floor standing unit. However, I'd prefer to get a newer G series outdoor unit if I could combine it with one of the G series indoor unit.
Seems the first letter after the digits is refrigerant type - L R410a and K is R32
Second letter: A single-split, M multi-split?
Is there some kind of rule/tool I can use to determine compatibility?
This is kind of helpful https://support.johnstonehvac.biz/hc/en-us/articles/360061315493-Fujitsu-Mini-Split-Nomenclature as it shows a that 3 letter models are previous generation and 4 letter models are next generation. However, this does not explain why AGYF would work with AOY units.
Thanks
12:06 UTC
New thermostat isn't calling firing the boiler. What did I do wrong?
12:05 UTC
Electric radiant heat
I am an hvac tech by trade, do general contracting now. Got a call about fixing a ceiling and radiant heat wire that was cut by previous plumbers. Cut an approx 12” x 12” square in ceiling, through electric heat wire.
How can I make repairs? Can’t see wire in plasterboard. Is this entire zone deemed worthless now? Can it be fixed? Tia!
11:31 UTC
Need help with diagnosis
Hi guys, was hoping to hear what are some of the possible issues with my A/C.
After turning on the A/C for a while, it will start to have this hissing(?) sound (got to turn up the volume to hear it). And the air that blows out is not very cold anymore. It happens quite randomly but its affecting my sleep because it occurs in the middle of the night. And I wake up to a room that's not cold.
I have tried getting my service ppl to fix it, but every time they come, they turn on the A/C for 15mins to 30mins and say it's cold, and nothing is wrong.
What could potentially be wrong with my A/C? Should I get another company to look at it?
11:07 UTC
Window unit acting weird, freezing up on “cool” mode and blowing cold on “fan” mode.
Hey y’all, I’ve had this window unit about 2 years and it started acting funky about a month ago. It froze up on “cool” mode one day,and after turning the power off it continued making a humming sound constantly. I decided to unplug it to let it defrost for a few days.
Fast forward, it’s defrosted. Once I plug it in it is still humming even when powered off (plugged in) and putting it in fan mode has it blowing obnoxiously cold air. I went outside to see if something odd was going on in the back of the unit and it has a strong exhaust smell coming out of it.
Any ideas what is going on? Can’t seem to find a similar situation googling the problem.
10:43 UTC
Friedrich mr12c1j
Hey y'all so my mini split stopped working ... It blinks the power led 7 times and the timer led 6 times. Does anyone know what this means? I downloaded all the manuals and nothing mentions what error code this is or what these blinking lights even mean for that matter. I appreciate any help just wanna be cool 😆
08:37 UTC
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