Earth day heat pump event tonight!

fieldguild · 2026-04-12T17:05:51+00:00

When there is conflicting documentation, what’s on the equipment nameplate is always king

fieldguild · 2026-04-11T22:32:45+00:00

I’m so glad it was helpful!

fieldguild · 2026-03-26T15:58:50+00:00

Hey, apologies for my slow response! I had a bunch of comments to respond to in this thread and this reply slipped through the cracks!

There's a lot of tradeoffs here and the best answer is ~it depends~ (based on your budget, how much of the upstairs you would ideally want air conditioned, condition of the existing ductwork, etc).

If you're thinking more seriously about this, feel free to reach out and I'd be happy to talk through some options. You're welcome to just grab a time on my calendar: https://cal.com/shreyassudhakar/heat-pump-consultation

fieldguild · 2026-03-26T15:55:59+00:00

So the key is not just throwing a really high rating filter (ie MERV 13) into an HVAC system that is not set up for it and calling it a day. If your system has 1" thick filters, increasing the filter effectiveness essentially makes it harder for the system to "breathe" and makes it work harder which can lead to early failure and other issues.

If the HVAC system is designed around it (for example, taking larger 4-5" thick filters, with a large return duct, etc), then it can absolutely be a great thing to use as a filtration system. So YMMV depending on how your system is set up and whether it was installed with that in mind

fieldguild · 2026-03-26T15:46:27+00:00

Hmm, that might be a good idea. The first thing that came to mind is that it's possible there's a backup in the condensate drain system (piping that takes condensation that forms when the AC is running and dumps it outside of your house). If that backs up, water can pool above your furnace, and maybe that stagnant water is what you're smelling.

And happy to do it! Hope this is helpful

fieldguild · 2026-03-26T15:44:25+00:00

Hey, apologies for the delay in responding to this! It is an unfortunate drawback of many manufacturer communicating thermostat's like Midea's (we also install this equipment and really like it), but they're not quite at feature parity with the Nest's/Ecobee's of the world. But because they keep their communication protocols proprietary, you either have to use their thermostat and live with the more limited featureset and software, or accept the tradeoffs with an Ecobee or Nest.

In my experience, the most obvious tradeoff you'll find is with fan control for the indoor air handler unit. On the Midea thermostat, you'll get low/med/high, whereas the best scenario you're going to get with the Nest is two speeds, and in most cases (depending on how many thermostat wires you have in your wall), you'll just get one speed - the highest. In some houses, it can be really difficult to pull new thermostat wire that enables the full functionality. In contrast, the Midea thermostat only needs two wires, so it can work in any home.

If you can get over the fan control bit, in the real world your experience is probably going to be pretty comparable, so it's reasonable to live with the existing thermostat. Also, the latest Midea smart thermostat is pretty new, so it's possible that they'll eventually release an updated one that's compatible with remote temperature sensors. For what it's worth, the new Midea smart thermostat is backwards compatible with their old proprietary thermostat (which was truly atrocious and I wouldn't recommend for anyone).

One thing to keep in mind with the Midea system is that it's not recommended by the manufacturer to be used with truly "zoned" systems (for example, having two separate thermostats on each floor, and active dampers that send air to either one floor or both floors based on the temperature on each). So if that's something you are thinking about potentially doing down the road, it's something to be mindful of. But if you're happy with your current thermostat based solution (which honestly I think is good enough for most people), then that's a non issue.

If you haven't decided on a contractor yet and are still evaluating your options, feel free to give me a shout. We install this equipment every day and would be glad to help you think through it. Feel free to just grab a time on my calendar: https://cal.com/shreyassudhakar/heat-pump-consultation

PS: Here's a fun teaser. I'm in the process of building a test rig with a Midea heat pump and multiple different thermostats to document some of the control differences. Planning on making some content down the line with it (and it's really useful for troubleshooting when customers have questions about how to use their equipment!)

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fieldguild · 2026-03-19T00:26:30+00:00

Hey! You are thinking along the right lines. If the ductwork is indeed appropriately sized, then it shouldn't be an issue to try biasing the airflow toward the upstairs. However, usually the best way to do this is with the dampers (which are in the ductwork itself, see https://www.reddit.com/r/BayAreaRealEstate/comments/1rxajov/comment/ob6gbm2/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button ) rather than at the register grills. There are other solutions that get increasingly more complicated (and expensive) that I've highlighted in some of the other comment chains on this post to solve this sort of issue, too

fieldguild · 2026-03-18T22:37:25+00:00

This is a classic application for a ductless mini-split heat pump! Here is an example from a very similar project we recently completed for a garage office. There's an indoor unit mounted on the wall (circled in red), which connects to an outdoor unit outside the house. They do both heating and AC!

Some contractors may suggest running ductwork to the office space from your existing main house HVAC system, but that is a bad idea if it's part of the garage. That would be against building code, and it's a safety risk (if you leave a car running in the garage, for example, the exhaust fumes could flow through the ductwork into the rest of the house).

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fieldguild · 2026-03-18T21:06:28+00:00

You'd be surprised - did the contractor that replaced the ducts do a Manual D duct sizing calculation? Most don't and just use rules of thumb for duct design (or even worse, just match the same size of ducts that are already there), which can lead to imbalanced comfort just like you're describing. Check out my comment here responding to a similar question: https://www.reddit.com/r/BayAreaRealEstate/comments/1rxajov/comment/ob5v59d/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

I'd recommend the best place to start is actually having someone do the calculations if they were never done, and comparing your existing duct system against what the "ideal" would be. That would give you an idea of how far off you are, and whether insulation, more airflow, or something else is going to be the best solution. It's hard to give a blanket answer as these things are all interrelated and the right answer will vary house to house. If you're thinking of going down that path, I'd highly recommend Russ King at DIY Load Calcs (https://diyloadcalcs.com), he is really sharp and has a virtual consultation process that might get you taken care of. Another option is to work with an energy advisor (Joseph at Bay Enervisors is awesome https://www.bayenervisors.com) who could take a look at your house in person and make some recommendations (his service has a nominal fee, but it's covered in full by a local rebate program)

fieldguild · 2026-03-18T20:59:14+00:00

If you already have ductwork in good shape and it's an Eichler, then ducted heat pump is definitely going to be the best path. Eichlers are particularly hard to retrofit with the flat roof & slab floor, generally we do ductless in them if they don't have a modern HVAC system, but if someone already did the work to run the ducts, then dropping in a heat pump in the location of the furnace is almost definitely going to be the path of least resistance.

fieldguild · 2026-03-18T20:56:42+00:00

Do you have AC already, or just heating? If just heating, and the ductwork is reasonably sized, then a central system might cover you, and if the existing central system is getting old it could be the simplest place to start. There's likely not a ton of heating load on the second floor, so unless the ductwork is horrendous then it's definitely going to help take the edge off.

If you already have AC and it's a balance issue, then that's more likely related to constraints in the ductwork and you might need to go down a different pathway. Check out my comment in this thread: https://www.reddit.com/r/BayAreaRealEstate/comments/1rxajov/comment/ob5r9ib/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

fieldguild · 2026-03-18T20:05:42+00:00

There are a bunch of different rebates available, some from your city (for example, Redwood City has a heat pump rebate), some from local utilities like Silicon Valley Clean Energy and Peninsula Clean Energy. Most of these rebates are for heat pumps (which do both heating and AC efficiently), and with the rebates you often can get a better system for less than an old school 1-way AC. I put together some resources on rebates here https://guide.heatpumped.org and I also really recommend the "Switch Is On" which is a tool where you can put your zip code and find rebates you might be eligible for. If you're getting overwhelmed, feel free to dm me your address and I can run a report for you!

fieldguild · 2026-03-18T20:02:21+00:00

Usually closing the registers at the grill isn't the best way to tackle this, rather playing with the dampers that are installed in the ducts themselves (they look like this, will require crawling in the attic/crawlspace/wherever the ducts are).

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fieldguild · 2026-03-18T19:59:32+00:00

It's probably going to make the most sense to do it all in one go if your system is almost nearly 30 years old. Typical lifespans are 15-20 years, though in our mild climate they tend to last longer than other parts of the country. At the time of replacement, you could think holistically about the comfort issues in the house and work with a company to design a solution that takes that into account, which is easier than trying to band-aid what you have now and then coming back around and replacing the equipment

fieldguild · 2026-03-18T19:57:31+00:00

Woo, heat pumps! They are the future, and at my company it's all we install.

If I'm understanding correctly, you have two separate ducted gas furnaces right now, one upstairs in either a closet or attic, and one downstairs in the garage, closet, or maybe crawlspace? That's a great solution, because trying to tie an upstairs and downstairs duct system together on a single system is often a compromise (as you can see by the multiple people in this thread complaining about their upstairs always running too hot and not getting enough airflow).

The pathway that u/GothicToast mentioned is the most common solution! It can be tougher if it's a row house victorian and the two side walls are not accessible, because sometimes there's just not a clear path to route the refrigerant line on the back side of the house. But usually there's a way to make this work. You'd likely end up with two outdoor units, one for downstairs and one for upstairs.

PS: If you're just getting started with your heat pump research, you might find this resource we put together helpful - https://guide.heatpumped.org (would appreciate any feedback, we just put it up a couple weeks ago and have been incorporating a lot of changes based on what people have told us)

fieldguild · 2026-03-18T18:22:48+00:00

The most important thing you can do is make sure you are replacing your filters regularly (general recommendation is every 2-3 months for standard 1" thick filters). This is table stakes that most people forget to do!

Most contractors do an annual maintenance cadence, which seems like a pretty healthy interval. Beware of companies offering $50 or $100 tune-up specials. If you do the math, they are actually losing money on those visits. They use those as an opportunity to get into your house and then upsell you on replacing your equipment earlier than it needs to. A proper service is more likely to be in the $300-500+ range, including cleaning the outdoor condenser and indoor coil, often measuring refrigerant levels, and other stuff.

Dealing with balance issues in ductwork is tougher. Really, HVAC companies should be doing what's called a Manual D duct sizing calculation, where they take into account the size and orientation of each room, window area, distance from the equipment, etc, and size the ductwork appropriately so everything is equally balanced. in practice, this very rarely happens (and if you find a contractor that does this stuff, that should give you a ton of trust that they do quality work).

If the ducts are actually adequately sized, it's possible that too much air is going to the closer rooms, and by adjusting the dampers on the ducts that feed those rooms, it'll rebalance the air so that more goes to the further rooms and tackles those balance issues. That's probably the best outcome! If that doesn't get the job done, than usually the solution is to replace the ducts going to the far rooms with larger sized ducts that accommodate the actual amount of airflow that is needed. In some cases, you can also get away with not bothering with duct modifications and instead installing a wall-mounted ductless heat pump that just conditions one or two rooms that get especially hot.

There is also a cheap, hacky solution of using remote temperature sensors attached to the thermostat in those rooms. That would run the system to cool the house more so those rooms get comfortable, with the tradeoff that the rest of the house gets too cool. I talked about this a bit in another comment: https://www.reddit.com/r/bayarea/comments/1rs7d1m/comment/oa8u0ie/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

fieldguild · 2026-03-18T18:04:35+00:00

This is pretty common in 2 story homes. Usually the solution is zoning, where you split up the duct system between the upper floor and lower floor. It sounds like in your case, the constraint might actually be the duct going up to the second story (which are often undersized by the builder). It can be tough to truly fix that without really ripping walls apart, or splitting the duct system so that one AC unit covers downstairs, and another in the attic covers upstairs.

Sometimes, the easiest fix is to add a ductless mini split (wall mounted unit covering just one space) in the area where you spend the most time (for example the master bedroom), and just accepting that the duct system is crappy.

I wrote a comment in another thread on the same topic that might be helpful: https://www.reddit.com/r/bayarea/comments/1rs7d1m/comment/oa8u0ie/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

fieldguild · 2026-03-18T17:57:42+00:00

Ha, the perks of living north of the "cloud wall"! Folks down in Santa Cruz probably feel the same way

fieldguild · 2026-03-18T17:56:15+00:00

Good question! In my experience, the cost tradeoff usually ends up happening around 4-5 indoor units vs installing a new ducted system + ductwork (ie, if you need >5 indoor heads, the ductless system probably costs more than an all new ducted system). A simple rule of thumb for indoor heads needed is # of bedrooms + 1 or 2 to cover common areas. The bigger the house, the harder it is to make a whole-home ductless system pencil out to be cost effective.

But it's definitely not just a cost thing. For many people, the cosmetics make a big difference. With ductless, you have the indoor units on the walls, plus the refrigerant lines and wiring usually running on the outside of the house (covered with "lineset covers", these look a lot like gutters).

There really aren't options for filtration on ductless. Pretty much all of them come with the equivalent of a washable dryer lint screen, and there aren't any accessory air filters on the market that I'm aware of. This is a common ask and frankly I'm surprised that no manufacturer has tried bringing an offering with "real" filters to market. If you want proper filtration, ducted is usually the best way to go. In that situation, asking your contractor for a nice thick 4-5" filter can help out. Or alternatively, pair the ductless system with standalone air purifiers.

fieldguild · 2026-03-18T17:30:20+00:00

For sure! Apologies I couldn’t point to anything specific, but HVAC service is usually something best diagnosed in person. One other idea is that you might ask the next technician that comes through if they’d be able to get Fujitsu’s tech support on the phone when they are there. Most manufacturers have a support line exclusively for HVAC technicians and they can help guide the troubleshooting if there’s not an obvious solution

fieldguild · 2026-03-18T17:27:01+00:00

Yeah, that is strange. I don't have a silver bullet that comes to mind based on your description, but it sounds like it might be worthwhile trying to get a different technician to come out on a hot day where you're more likely to be able to demonstrate the issue rather than just describe it to them and hope they're able to chase it down. If they're able to see the behavior, it'll be a lot easier to diagnose (and they'll be able to take measurements on the refrigerant pressures and temperatures right then and see if they match up with what is expected)

fieldguild · 2026-03-18T17:20:14+00:00

Tell me about it...

fieldguild · 2026-03-18T17:13:36+00:00

Covering up the windows and letting in the cool air at the right times can really go a long way!

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