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Call a pro. AC systems are not DIY. The things you're looking for exist (and are often mandatory) in the commercial/ non-residential market, but they are not I

Call a pro. AC systems are not DIY. The things you're looking for exist (and are often mandatory) in the commercial/ non-residential market, but they are not IoT, and they aren't cheap. For instance, most commercial spaces have a MAX value on percentage of recycled air; a minimum amount of air fed into the return must be fresh air drawn from outside. >should be able to cheaply add networked sensors, fans, filters, and vents Sensors can be ok... But your homes's AC design, even if based on simple building code lookups, is based on some fairy complex engineering which rely on certain assumptions. If those assumptions aren't met, the design usually must be approved by a licensed engineer. This is why you don't see more independently controlled vents on the market. No professional is going to install products that don't meet code, unless an engineer has stamped the plans. (Which includes operational logic.) Ignoring regulations, you shouldn't just add controlled vents to a system (or manually close existing vents) without compensating for that elsewhere. You likely need a variable speed blower, controlled/compensated return air flow, and system logic to control it all. Will the house blow up if you install them yourself? Probably not. But it could result in a system operating much less efficiently, increase the number of system cycles (reducing system lifetime), cause duct ruptures/leaks due to increased back pressure, and most likely, cause condensation in places other than the condenser, possibly causing mold to grow and/or rot. Which leaves 2 options: installing a commercial system with the integrated vent control you're looking for, or adding sensors for input for when the system should run, without modification. Biggest simple change you can make for immediate impact? Change your filters every month, even if it means using 12 $3 fiberglass filters instead of 1 $36 hepa filter. For instance, I run a list of room temps through a simple max function to ensure my AC and/or blower runs until the hottest room falls below the set temperature. If this results in wildly unbalanced temps throughout the house, you have a bigger issue, and likely need your system resized/adjusted by a professional. Related, and because most people don't realize it, your AC is an engine. You want it properly sized and to run constant, when needed. Think of your car: is it more efficient to make a trip by many intermittent 100mph sprints, or driving 55mph without stopping. Multi stage compressors now act like car transmissions to dynamically "size" the system as needed, but run constantly with minimal stopping.

jacquesm 6y ago
This is all spot on. The engineering that goes into HVAC systems is under appreciated. When messed up the system that is supposed to give you fresh air can easily become a source of pathogens. You also want filters on ingress and egress (to ensure critters don't have a path into your house), and you want to have a nice fat overdimensioned heat exchanger between the two airstreams to ensure that you're not heating the world instead of your house. +1 on the rapid change of filters, much better to change a filter frequently even if it is a bit lower performance than to let one sit for too long, but keep an eye on your electricity cost, that is the factor that should decide the quality filter that you purchase and frequently you replace it. Ground rule: the better the filter, the more it will absorb, the better the chances that something you really don't want lodges there and starts spreading if the filter gets overloaded. Fiberglass filters are a good compromise between energy efficiency and cost, they have excellent working surface compared to their physical size and tend to have a relatively long working life before they 'join the other side' and become a source of contaminants rather than a filter of contaminants.
cbhl 6y ago
> For instance, most commercial spaces have a MAX value on percentage of recycled air; a minimum amount of air fed into the return must be fresh air drawn from outside. I live in a highrise in SF and this bit me during the wildfires this year. The air conditioning would pull in smoke from outside. I ended up turning it off altogether on the worst AQI days, and buying lots of replacement filters for both the furnace and some off-the-shelf air purifiers.
clusterhacks 6y ago
I am in the mid-eastern United States and my experience with professional HVAC technicians has been very poor across several providers. Most techs I get from companies have been very poorly informed and almost hopeless at "debugging" any performance or functional problem. The operating model seems to simply be to replace parts in a pre-determined "likelihood of failure" model. I don't blame the techs - I liked most of them but after casual conversation it seems clear that most of them don't get much training. I guess my main complaint is that while I definitely want to "call a pro" my experience finding a good professional in HVAC (and plumbing for that matter) has not been particularly successful. And don't get me started on part pricing - I am very happy to pay for knowledge (with high hourly technician costs) but more than once I have had easily purchasable OEM parts massively marked up by HVAC companies in what seems just like price gouging.

jacquesm 6y ago

This is all spot on. The engineering that goes into HVAC systems is under appreciated. When messed up the system that is supposed to give you fresh air can easily become a source of pathogens. You also want filters on ingress and egress (to ensure critters don't have a path into your house), and you want to have a nice fat overdimensioned heat exchanger between the two airstreams to ensure that you're not heating the world instead of your house. +1 on the rapid change of filters, much better to change a filter frequently even if it is a bit lower performance than to let one sit for too long, but keep an eye on your electricity cost, that is the factor that should decide the quality filter that you purchase and frequently you replace it. Ground rule: the better the filter, the more it will absorb, the better the chances that something you really don't want lodges there and starts spreading if the filter gets overloaded. Fiberglass filters are a good compromise between energy efficiency and cost, they have excellent working surface compared to their physical size and tend to have a relatively long working life before they 'join the other side' and become a source of contaminants rather than a filter of contaminants.

cbhl 6y ago

> For instance, most commercial spaces have a MAX value on percentage of recycled air; a minimum amount of air fed into the return must be fresh air drawn from outside. I live in a highrise in SF and this bit me during the wildfires this year. The air conditioning would pull in smoke from outside. I ended up turning it off altogether on the worst AQI days, and buying lots of replacement filters for both the furnace and some off-the-shelf air purifiers.

clusterhacks 6y ago

I am in the mid-eastern United States and my experience with professional HVAC technicians has been very poor across several providers. Most techs I get from companies have been very poorly informed and almost hopeless at "debugging" any performance or functional problem. The operating model seems to simply be to replace parts in a pre-determined "likelihood of failure" model. I don't blame the techs - I liked most of them but after casual conversation it seems clear that most of them don't get much training. I guess my main complaint is that while I definitely want to "call a pro" my experience finding a good professional in HVAC (and plumbing for that matter) has not been particularly successful. And don't get me started on part pricing - I am very happy to pay for knowledge (with high hourly technician costs) but more than once I have had easily purchasable OEM parts massively marked up by HVAC companies in what seems just like price gouging.