How do I handle this HVAC edge case for another week?
November 3, 2023 2:25 PM Subscribe
I have a new heat pump outdoor unit showing up (hopefully) next Friday, but it's going to be warm and I want to be cool until then.
My heat pump control board broke last week. The AC guy came and rigged it so that it would stay in cool mode. Trouble is, it is *always* in cool mode, i.e. it can't be controlled by the thermostat anymore, it's just stuck on. I can toggle the breaker to turn it on and off, and I can hear/feel the refrigerant circulating indoors.
My other breaker is connected to the indoor unit/fan and Nest thermostat. Trouble there is, it only detects the *heat* signal. So I can only start the blower if I turn the thermostat to heat, the "turn fan on" option isn't available anymore. I have a 10 kWh electric heater (at least that's what's written on the breaker panel?) somewhere in the system, I can feel it when the blower turns on. I don't need it right now (or ever, it almost never freezes around here, and if it did this place would still be 20 degrees warmer, and anyway I have/will have a heat pump.)
So until next Friday when the unit is replaced, I would like to be able to manually switch on the AC condenser, start the indoor fan, and cool the house. *Without* running the heater. But the thermostat, indoor unit, and heater seem to be on the same breaker.
It's going to probably get above 80 F next week. Assuming the AC tech continues not to return my calls ... I wonder if I can put a box fan in front of the refrigerant line and it won't ice up and destroy everything. Or if I can somehow disable the electric heater and run the indoor unit's fan. Or if I should just sleep on the patio until next Friday.
My heat pump control board broke last week. The AC guy came and rigged it so that it would stay in cool mode. Trouble is, it is *always* in cool mode, i.e. it can't be controlled by the thermostat anymore, it's just stuck on. I can toggle the breaker to turn it on and off, and I can hear/feel the refrigerant circulating indoors.
My other breaker is connected to the indoor unit/fan and Nest thermostat. Trouble there is, it only detects the *heat* signal. So I can only start the blower if I turn the thermostat to heat, the "turn fan on" option isn't available anymore. I have a 10 kWh electric heater (at least that's what's written on the breaker panel?) somewhere in the system, I can feel it when the blower turns on. I don't need it right now (or ever, it almost never freezes around here, and if it did this place would still be 20 degrees warmer, and anyway I have/will have a heat pump.)
So until next Friday when the unit is replaced, I would like to be able to manually switch on the AC condenser, start the indoor fan, and cool the house. *Without* running the heater. But the thermostat, indoor unit, and heater seem to be on the same breaker.
It's going to probably get above 80 F next week. Assuming the AC tech continues not to return my calls ... I wonder if I can put a box fan in front of the refrigerant line and it won't ice up and destroy everything. Or if I can somehow disable the electric heater and run the indoor unit's fan. Or if I should just sleep on the patio until next Friday.
Without knowing your exact climate--particularly how cold it gets at night--I can't be certain if this would work for you. But I do know that when temps are between, say, 55 at night and 85 during the day (so, like, 12 C - 30 C), we generally don't have either the heat or AC on.
DURING THE DAY: Close all windows before the hottest part of the day, and close curtains on any window that gets direct sunlight. If you have working double hung windows, you can crack the upper half to let hot air escape--but that's pretty uncommon these days.
AT NIGHT, ONCE TEMPS HAVE COOLED A BIT: Open all your windows. Once the indoor temperature has gotten to where you want it, close most of the windows. (It's good to keep a few open for circulation; one open window in a 1000 sq ft house won't cool it down too much further--and it's better to be a degree or two below target temperature when you wake up rather than a degree or two above).
We lived in NYC for 10 years without AC, and while there was always an uncomfortable week when the highs got into the upper 90s, this generally got us through the rest of the summer fairly comfortably.
posted by thecaddy at 2:49 PM on November 3, 2023
DURING THE DAY: Close all windows before the hottest part of the day, and close curtains on any window that gets direct sunlight. If you have working double hung windows, you can crack the upper half to let hot air escape--but that's pretty uncommon these days.
AT NIGHT, ONCE TEMPS HAVE COOLED A BIT: Open all your windows. Once the indoor temperature has gotten to where you want it, close most of the windows. (It's good to keep a few open for circulation; one open window in a 1000 sq ft house won't cool it down too much further--and it's better to be a degree or two below target temperature when you wake up rather than a degree or two above).
We lived in NYC for 10 years without AC, and while there was always an uncomfortable week when the highs got into the upper 90s, this generally got us through the rest of the summer fairly comfortably.
posted by thecaddy at 2:49 PM on November 3, 2023
I'm not an HVAC professional, and I consider myself just knowledgeable enough to be dangerous. With that disclaimer out of the way, thermostat wiring should be fairly standardized, so an easy way out would be to disconnect your Nest thermostat and wire in a cheap "dumb" thermostat that has a fan switch on it. If you do this, take photos of the placement of the wires before disconnecting your Nest thermostat as you'll need to refer to that to correctly place the wires in the other thermostat, and to put the Nest thermostat back into place when you're done.
Be sure the breaker to all your HVAC equipment is off before doing this replacement.
posted by Aleyn at 3:02 PM on November 3, 2023 [1 favorite]
Be sure the breaker to all your HVAC equipment is off before doing this replacement.
posted by Aleyn at 3:02 PM on November 3, 2023 [1 favorite]
Your 10kW backup heating coil is quite likely to be on a different breaker (a pair of them, in fact). Are you sure you aren't able to disable it separately?
That said, your heat pump indoor unit should be running the fan in cool mode, so it sounds like your guy rigged it in a way that doesn't really work. If you really want to mess with this, you could simply take the Nest off and connect the green wire (the fan wire) to the red wire (power). This will cause the fan to run continuously (so you can turn it off at the breaker).
I would not recommend running your heat pump without power to the fan, that's just asking for trouble. A box fan is not going to move enough air.
posted by ssg at 4:57 PM on November 3, 2023 [3 favorites]
That said, your heat pump indoor unit should be running the fan in cool mode, so it sounds like your guy rigged it in a way that doesn't really work. If you really want to mess with this, you could simply take the Nest off and connect the green wire (the fan wire) to the red wire (power). This will cause the fan to run continuously (so you can turn it off at the breaker).
I would not recommend running your heat pump without power to the fan, that's just asking for trouble. A box fan is not going to move enough air.
posted by ssg at 4:57 PM on November 3, 2023 [3 favorites]
I AM an HVAC professional, and honestly I’d recommend just leaving it off until the new unit is installed. Jiggering units to run when they shouldn’t, band-aids and temporary fixes, AC guys who stop returning calls, and then homeowner workarounds on the workarounds are how systems end up going from one component being replaced to this conversation: “Well, I can try to undo everything that’s been done here, and reverse engineer whatever fix was done, but honestly that’s all billable time and there’s no guarantee I can unfuck this.”
Like this is the perfect recipe for things to go WAY badly. Please just get a window unit.
posted by HVACDC_Bag at 5:53 AM on November 4, 2023 [2 favorites]
Like this is the perfect recipe for things to go WAY badly. Please just get a window unit.
posted by HVACDC_Bag at 5:53 AM on November 4, 2023 [2 favorites]
Response by poster: The dénouement: I got the new heat pump installed on schedule, but it still wasn't working properly. Turns out the Nest *base* had shorted out and was circulating random signals everywhere. I had no idea that the base had a microcontroller, I thought it was just passive wire terminals. So I dunno, what's the chance that my defrost board and the Nest croaked at the same time?
Que sera sera. I needed a new heat pump anyway, the salt turns things to mush around here.
posted by credulous at 9:53 AM on November 22, 2023
Que sera sera. I needed a new heat pump anyway, the salt turns things to mush around here.
posted by credulous at 9:53 AM on November 22, 2023
You are not logged in, either login or create an account to post comments
But when the highs are between 80 and 90 (and if it gets cooler at night) I don't generally use any AC. My technique is to put my biggest window fan in an upstairs window and open the downstairs windows. The fan points OUT and I run it late and in the early morning to exchange all the house's warm air with cool outside air. Then in the morning when it starts warming I close all the windows and cover them on the sun side. If you keep it dark indoors, don't let any sun shine in, and don't run your oven, it'll be just fine. If it's a little uncomfortable in the hottest part of the day, a ceiling fan or a box fan in the room with you can make all the difference.
posted by fritley at 2:48 PM on November 3, 2023