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HVAC:


This house, made in 1953, was originally coal heated, though with a modern blower-based air. It was later
replaced with home heating oil, then natural gas, and after I got it, with a 93% efficiency heat pump, giving
it central AC for the first time. (it had been window AC units before that)

The city had sent out an offer of a free "energy audit" with free goodies so I scheduled an appointment. After
the inspection, I got coupons for blowing in insulation into my walls (they were HOLLOW!) and also a coupon for
a big discount on a new more efficient furnace. Coupons expired in 90 days! Ug, I don't like being rushed, but
the savings were huge, so that's when I got the new (Coleman 93%) furnace.

03/17/2006: purchase date

xx/xx/xxxx: needed a replacement "exhaust unit" (external exchanger) fan. Once installed it spun backward.
They claim it was a defective motor, and were here well after dark replacing it with another motor, which
worked fine. (all under warranty)

xx/xx/xxxx: came home from work one summer evening, 92F in the house. HVAC was on, trying to cool down, but
vents were pumping out heat. Tech comes out and checks outside unit, "the furnace is calling for heat", so the
reversing valve outside was doing heating instead of cooling. Can't open the furnace to check the board since
it has a kill switch on the door panel that will kill power to the furnace when the panel is opened. Open it,
test, looks fine. Close the hatch. NOW it works fine. Gremlins! So now that kill switch is taped over in
case it does it again. (it never has)

01/14/2012: installed "whole house humidifier" accessory, taps water off the water heater. Simple turn dial
humistat control in the basement.

07/17/2012: was running humidifier in the summer since the house was a bit dry. AC wasn't working well, called
a tech and they educated me that you don't run a hot water humidifier while trying to run the AC. Doh!

12/17/2013: wake up Saturday morning to 54F. Furnace keeps turning on and off, never heating. Checked intake
and exhaust ports on side of house, clear. Called tech. Comes over, says airflow problem - no I checked that.
No it's the vacuum sensor not working. Common problem with colemans, his last call this morning was this exact
same problem on another coleman. Hope you have another spare in the truck? sure do, common issue. OK just
replace it. No he wants to show me the pricing sheet first. (uh oh) It's "normally $300 but since you're a
club member we'll discount parts, $200 for you." Uh no I am not an idiot, that's a bit if plastic, a spring
a membrane, and two strips of brass, there's no way that costs $200 let alone $300. Checked online. MSRP on
this exact vacuum sensor is $18. GET OUT. He gets this evil grin and tells me "your furnace won't work if I
don't fix it!" My furnace will be running before you can get down the street now get out. Hotwired it, got
the furnace running. Took sensor upstairs, open. Exercised the vacuum hard a few times. Restored switching.
Swapped it back in. Ordered a ($18) spare. Spare is still sitting on the furnace shelf 10 years later.
Scamming repairmen piss me off. Found out later that this group's techs work on commission and it's in their
financial best interest to scam customers.

02/28/2019: furnace won't turn on. find blown 2a fuse on board. replace, pops immediately. tech comes out,
wires in external unit rubbed through insulation, shorting. He figures I can probably fix this myself, and
just run on gas heat until then

06/10/2019: finally decide to just have the tech fix the exhaust short. he replaced wires, added split loom
tubong over them to protect wires.

xx/xx/xxxx: humidifier stopped working. Humistat isn't working anymore, won't close contacts. Just wired it
to be on all the time. Excessive humidity caused particle board in attic to sag, had to tear it out.

xx/xx/xxxx: Made my own basic humistat that ran for awhile. Eventually it quit working properly.

xx/xx/xxxx: bought a new humistat, same exact as original. Its a simple bimetallic spring type, no heuristics.
The valve now cycles rapidly during transitions, sometimes for 20 seconds or more. I imagine that's really hard
on the contacts AND on the value, maybe what killed the first one.

04/02/2023: external unit rattling loudly. regular maintenance check time, I tell them to send a tech to check
it out while doing regular work. They sent a salesman instead, who clearly had no idea how HVAC worked and
could only keep repeating to me "it's old, it needs to be replaced". Called a tech from another place. He comes
out, bad bearings in the motor. Not super cheap but $450 beats a new furnace.

12/21/2024: replaced humistat with one I constructed myself. It's got heuristics in it that should prevent the
valve from oscillating at a single set point. I currently have it set to turn on when humidity drops to 45%,
and turn off when the humidity gets up to 50%.


2024 humistat project

battery-operated talking thermostat

furnace emergency power project

Thermomiter and Hygrometer



last updated 12/22/2024 at 19:54:04 by make_www_index.command version 2024.07.09.A