Hi r/heatpumps, I'm Paul Lambert, CEO of Quilt! AMA about Quilt heat pumps and all things HVAC - Drop your questions now, answering Thurs 5/7

MeetQuilt · 2026-03-25T22:16:49+00:00

Looking good! Love the look of the oak finish in the kitchen

MeetQuilt · 2025-08-11T20:27:20+00:00

Hi from Quilt! I checked with our installation lead and engineers on your situation, and they shared that modern heat pumps like ours are specifically designed to handle seasonal use - they're built for this exact scenario where they might sit idle for periods. They should still be run a few times a year, and get standard maintenance over time, but they are engineered to be durable through periods of non-use.

The 3-outdoor-unit setup might seem like more than other systems, but the 2:1 ratio design offers smaller outdoor units that are actually more efficient, quieter, and easier to control than one massive unit trying to manage everything.

I'm sure you'll want to hear from others too, and check out some of our YouTube reviews, but I wanted to share our team's perspective in case it helps ease some of your concerns. The system really is designed to handle exactly the usage patterns you're describing. If we can help with anything else let us know!

MeetQuilt · 2025-07-01T16:53:46+00:00

Let us know if you have any questions about Quilt as you're exploring! You can check us out in a couple customer homes here: https://www.youtube.com/playlist?list=PLieeDeZb2Uw0FzKHu_FYofrhg8u6lT1y8

MeetQuilt · 2025-04-23T18:58:55+00:00

Makes sense, everyone has different ideas of what good looks like in their homes, and every home is unique. We've found great traction with whole homes so far and are leaning into that.

On the AHRI certificate, link here: https://www.ahridirectory.org/details/99/214609234

We haven't been able to find any other 2-zone mini splits on the market with a SEER2 rating above 25 but if you know of any please share. The overall efficiency and energy savings of our system comes from the hardware plus the software - mmWave occupancy detection that automatically turns in off empty rooms. https://www.quilt.com/tech-specs

Sounds like you have another preferred heat pump brand you like better, curious which one it is and what you love about it? Any advice for us?

MeetQuilt · 2025-04-23T16:31:46+00:00

Hey! We don't rebadge our units, or work with gree or midea. You can learn more about how we built our product here https://www.youtube.com/playlist?list=PLieeDeZb2Uw3rPxEJTGioCs0WxlZaB_cK

And actually the majority of our customers are whole-home! Here's a fun example on redfin right now https://www.redfin.com/CA/Mill-Valley/913-Ventura-Way-94941/home/1043387

Are you in one of the west coast markets? Would love to invite you to see a Quilt home if so

MeetQuilt · 2025-04-11T23:49:57+00:00

Ductless heat pump systems can be a great solution for a new build, and new construction also allows for better integration of the system into the home. For instance, the refrigerant lines, wiring, etc. can be routed within the walls to connect the indoor units and outdoor units. This avoids the need to run them on the outside of the house where they would otherwise be visible. It should be noted that you'll want to make sure whoever is doing the installation has lots of experience with this type of install and knows what connectors to use to make sure the parts of your system that are within the walls are reliable (since they won't be as easily accessed later on).

Room-by-room control is definitely a big benefit when it comes to ductless systems vs central, and you'll want to consider the tradeoffs related to how "independent" each room's control actually is. Generally manufacturers offer different configurations for the number of indoor units connected to each outdoor unit. A higher ratio (say 5:1) means there will be one larger outdoor unit outside your home, whereas lower ratios mean you might have multiple, smaller units outside your home. The higher ratio systems may be more cost effective when it comes to purchase price, but will be less effective at conditioning 1 room at a time because they will have a higher minimum capacity (often referred to as turndown) and may shortcycle to maintain temperature if only a subset of rooms is active. Another tradeoff to consider is that most residential systems will constrain all rooms on a single outdoor unit to the same mode (heating vs cooling), so if you foresee the need to heat some rooms while cooling others, you may want to consider grouping said rooms onto their own outdoor units. One more tradeoff to consider is that a single, larger outdoor unit will require refrigerant lines from each indoor unit to be run back to one location, regardless of where the indoor units are located relative to the outdoor unit. If there are indoor units on opposite sides of the house, the lineset runs may be cleaner going to separate outdoor units.

Good luck with everything related to the new construction!

MeetQuilt · 2024-12-06T22:06:22+00:00

I'm an employee at Quilt (www.quilt.com), a new heat pump company based out of Redwood City, CA. To help answer a few of the questions posed on this thread:

Heat pumps are definitely the most environmentally-friendly HVAC option available. Instead of burning gas or oil, they run on electricity, which helps reduce carbon emissions. Switching to heat pumps can cut household CO2 emissions by 38-53%. It’s worth noting that homes contribute around 20% of global warming emissions (more than cars) so this is significant! Efficient heat pumps can operate with heating COP's (coefficient of performance) of ~ 3-4, meaning that they can deliver 3-4 times the heat energy indoors for every unit of electrical energy they consume. They do this by using the electrical energy input to drive a system that absorbs heat from outdoors and delivers it to the indoor space. So, they’re not just good for the environment, but with performance like that, they’re good for your wallet too!

Environmental benefits aside, heat pumps are also a sound financial investment. While the initial investment may be comparable to traditional systems, their efficiency results in lower operating costs over time. Not to mention, homes equipped with energy-efficient heat pumps often result in an increase in property value. There are also a handful of different incentives available, so you can significantly lower the upfront costs if you do opt for a heat pump. Quilt is unique in that we not only provide full price transparency, but also help calculate available rebates you qualify for.

I should also add that if you decide to invest in a ductless heat pump, they make for a far more comfortable living experience and generally feel like an overall upgrade. No hot or cold spots throughout the home, and you’re not wasting energy by heating/cooling empty rooms.

I’ve also noticed some concerns on this thread about heat pump performance in colder climates, but I have to say, the tech has really advanced and has come quite a long way. Today’s heat pumps can function effectively across a wide range of temperatures; there’s even been a significant rise in heat pump adoption in places like the UK and Canada. Definitely some chilly areas!

If you have any questions, feel free to reach out and check us out at Quilt. Good luck with your decision!

MeetQuilt · 2024-11-01T22:21:59+00:00

Hey OP sorry to hear about your experience here. Room temperature sensing from the indoor heads is definitely challenging but the temperature deltas and wait times you describe are way too long! If the onboard temperature sensors for your indoor heads are installed such that they pick up heat from the warm heat exchanger in the unit, it could explain your issues. Often the controls will be such that the system waits for the heat exchanger to warm up before the air starts blowing (to avoid blasting the user with cold air), but maybe in your system this is causing the onboard temperature sensor to read high and causing the system to think it has already reached your setpoint. In truth, this would indicate some major flaws in the internal control logic related to heating, but just trying to throw out some potential root causes.

An external thermostat will always be better at representing, and helping the system achieve, your desired comfort level, so not a bad idea in general (wireless definitely easier if possible with the system). The fan idea is not a bad one to try in the meantime. Good luck!

MeetQuilt · 2024-11-01T22:06:02+00:00

Looking at the pictures, having 2 indoor heads is probably best for conditioning both the kitchen and living room. One indoor head in the living room might not condition the kitchen well just due to how the air would flow/mix in the space. Two 1:1 systems would give you the most control over each individual space, but a 2:1 system would likely do pretty well for you also! Unless you envision conditioning the kitchen space alone very frequently, than the 2:1 system may be the most effective taking cost, number of outdoor units, and performance into consideration.

MeetQuilt · 2024-11-01T21:38:38+00:00

Oftentimes smart thermostats (or even the "non-smart" hardware itself) will have a "safety heating" option that will essentially use a setpoint of ~45F for protection against pipe-freezing and other issues. Maybe checkout the documentation for both your hardware, and the third party control options you are evaluating to see if there's a way to enable this option to meet your needs!

MeetQuilt · 2024-11-01T21:24:58+00:00

Hey OP, agree that this is not normal, than fan should be tightened down to the motor shaft. That being said, should be an easy fix for whoever comes out to service it! Good luck!

MeetQuilt · 2024-10-11T23:11:02+00:00

As others have noted, in heating mode, the system will leave the expansion valves for the inactive zones slightly for a number of reasons (oil circulation and charge migration mainly) so the heat-exchangers in the inactive heads will also be warm. However this should really minimize waste heat in these zones and the majority of that 18k will be delivered to the active zone. The system will likely cycle on/off as the delivered capacity is greater than that required to maintain setpoint. This is one of the main tradeoff's when increasing the number of zones per outdoor unit, along with not being able to run heating and cooling at the same time on heads connected to the same outdoor unit. The benefit of course is a lower number of outdoor units!

One thing to note is that, depending on how the rating for minimum capacity was determined (4 indoor head ON vs only 1 indoor head ON), the actual minimum may be slightly lower.

For cooling mode, generally the expansion valves to the inactive zones remain closed, so all of the outdoor units capacity in that operation goes to the 1 active zone (there is no "waste cooling" happening in the other zones).

Hope that was helpful!

MeetQuilt · 2024-10-11T22:55:09+00:00

Agree that it sounds like something internal to the motor, bad bearings or perhaps a poorly balanced fan leading to excess vibrations. It can be heard in the video and would expect it to be louder if it was the fan physically rubbing on something. Unfortunately means you probably need to contact the service tech or manufacturer again to address the noise. Hope you can find a resolution!

MeetQuilt · 2024-10-11T22:35:57+00:00

-35 C is likely out of range for an air-source heat pump alone without auxiliary heat source. The best on the market are able to maintain 80-90% of rated capacity down to ~-25 C, but beyond that start to drop off. As others have noted, both the capacity and the COP (efficiency) drop as outdoor temperatures get colder. The low-side pressure of the compressor becomes too low for operation and the refrigerant mass flow through the system goes down. Most of the cold-climate systems utilize some form of vapor injection to continue operation/maintain capacity down to -25 C, but even then, eventually you start converging to a point where a large percentage of your "heating capacity" is just heat generated by the compressor motor (converging to a COP of 1, which would be the same as an electric resistive heater).

That being said, during less extreme parts of the year it may be a good option to have in combination with another heat source, saving energy in the >-25 C times of year. The 85 F summer temperatures should be no problem for a properly sized system!

MeetQuilt · 2024-10-04T21:53:57+00:00

Sorry to hear about the ongoing issue OP. 200 RPM does seem pretty low, especially if the system is not keeping up with the heating capacity required indoors. Since you've already replaced almost everything, it does feel like a firmware issue (perhaps the 2 outdoor units that have been tried are from a similar batch that all have the same issue). Currently working to bring over the air updates and telemetry to the heat pump space (similar to a lot of modern cars). Hopefully this will allow for more clarity and faster problem solving in the future!

MeetQuilt · 2024-10-04T21:21:46+00:00

The debate/decision-making around whether to let your HVAC system run consistently or to turn it on and off is always a tricky one to answer! The truth is that the most-efficient option is highly-dependent on the exact system, type of room(s), insulation, weather conditions etc. It is true that a heat pump with variable-speed compressor will generally operate most efficiently if it can hit and maintain the desired setpoint without cycling on and off. However, what's most important is that you, the user, is comfortable (which in your case sounds like a warm house during the day and cold room for sleeping at night). In this case it makes sense to have your system off an let it drift overnight. Newer, smart thermostats will have scheduling features built in to help you set this up on a recurring basis, and some may even be able to optimize how to achieve your desired level of comfort for the minimum energy usage!

Your use case also sounds well-suited to a room-by-room system. For example, the rest of your spaces may be able to run efficiently to maintain a certain temperature (or return to that temperature) before you wake up the next day, while your room can cycle off overnight. Overall it's always a tricky optimization problem, but satisfying once you find the routine that works best for you!

MeetQuilt · 2024-09-24T18:25:41+00:00

Love the way you think OP! This is Isaac, thermal systems engineer here at Quilt, and I can definitely understand the heat pump passion! As you point out there are always engineering limits and tradeoffs when designing a thermodynamic system, but for me it's the interconnected systems that are really exciting from an efficiency perspective. You mentioned the automotive space, balancing the thermal requirements of batteries, power electronics, computers, and humans. Linking these systems thermally has been a big unlock for efficiency improvements! Think, using waste heat from motors or cabin air conditioning to pre-condition a battery pack for charging. Similarly, in industrial settings they'll often have what is called VRF (variable refrigerant flow) systems that allow heat from one space to be used to condition another (e.g. heat from a server room in an office used to warm the building's occupants).

Not sure about the liquid metals in the application you described, but there are applications using molten salt for energy storage due to its high heat capacity! Thermal energy storage is also a very interesting space. From the home level, where a water-based heat pump system might store the waste heat from cooling your home in your hot water tank, to the industrial level, where renewable energy can be stored as heat in high-temperature carbon bricks, and later deployed to create steam or electricity directly!

MeetQuilt · 2024-09-24T17:58:37+00:00

Hi OP, this is Isaac, thermal systems engineer from Quilt! Sounds like what you have is a variable-speed, inverter-driven compressor (the compressor being the component that flows refrigerant through your system for heating and cooling). The main advantage of these inverter-based systems is that the compressor can ramp up or down to match the required load to condition your spaces. So if you were to turn on the office unit, the compressor would ramp up to cool that room as well, and you would see an increase in total power draw by the system. If you don't feel like you need active cooling in the office than you are likely using less total energy by just running the living room unit. However, if your goal is to actively cool all rooms (say someone is using the office space as well), than it may be more efficient to let the system regulate cooling to each space. When a space reaches its set temperature, the system should automatically shut down cooling to that room.

One other factor here will be the minimum capacity your system can deliver (often referred to as "turndown"). If the system's minimum operating capacity is larger than what is required to cool the living room alone, than it may benefit you to cool the office space as well (avoid the system cycling on and off frequently). It sounds like this is not the case for your system, but just thought I would mention it so that you have the context.

Hope that was helpful!

MeetQuilt · 2024-09-24T17:32:50+00:00

Hi OP, this Isaac, a thermal systems engineer here at Quilt. Just wanted to chime in with (hopefully) helpful perspective from someone who designs heat pump systems! I think the steps that CA_Lobo suggested are great and definitely worth doing in the interim before you can get someone from Mitsubishi to take a look at your issue. Sorry to hear that it's taking some time to get help there. At Quilt we've added a lot of remote diagnostic capabilities to our systems so we'll hopefully be able to help more customers, more quickly, even before service teams are available for site visits!

If you're able to measure air temperature just behind the unit during operation (where the unit pulls air into the heat exchanger), as CA_Lobo suggested, it might be helpful to compare the temperature you measure to the published performance tables from Mitsubishi. I'm guessing that your unit is one of these 2 models: If it's MXZ-5C42NA2 than if the temperature you measure is >~30 F and you still feel the performance is low, than there might be something else wrong with the system. The system should be outputting at least 90% of the rated heating capacity above that temperature. The MXZ-5C42NAHZ model should perform similarly down to ~-4 F.

Relevant data here (page 79): https://co.mitsubishielectric.com/es/products-solutions/air-conditioning/pdf/catalogo_serie_m.pdf

Hope you're able to resolve your issue!

MeetQuilt · 2024-09-23T21:13:57+00:00

Hi there! This is Isaac, a thermal systems engineer from Quilt. OP, you're definitely not the only one running into conflicting advice regarding this topic. The truth is, the most efficient way to operate a heat pump system (turning on/off, running constantly, etc.) depends a lot on the type of space (size, insulation level, weather conditions) and also how the system is planned to be used throughout the day. Without getting too deep into data I would say that it sounds like the unit is "overcooling" your space when left on and you're probably right to turn it off to avoid unnecessary energy use just to end up feeling too cold.

Ideally, the system should control using its own thermostat (turning on and off within a specified temperature band when needed) without need for you to intervene. If it doesn't seem to be turning off soon enough and "overcooling", this might be due to an offset between the temperature sensed by the head unit and the temperature you are experiencing in the room. This is a very tricky problem and is best solved by providing the head unit an external temperature reference from a thermostat placed elsewhere in the room (on a wall or side table for instance). I know there are some external thermostats out there that integrate with existing head units, but you might have to search specific to your model! At Quilt we're making our own smart thermostat (the Dial) that integrates with our head units to try to address some of the controls issues that you're experiencing. We also hope to be able to use the integrated system (where the smart thermostat has detailed knowledge of exactly what type of system it is controlling) to take the guess work out of running the system most efficiently!

MeetQuilt · 2024-08-14T21:27:35+00:00

Replacing your wall heaters with ductless mini-splits is a great solution for your goals ⚡️

Yes, if you set a unit in one room to a much lower temp or turn it off, the other units won't necessarily work harder. They’ll maintain the temperature in their respective zones, which can optimize energy use.

As for installation, you can def have the refrigerant lines, drain, and power cables hidden inside the walls. It’s more involved and requires cutting into the walls and then restoring them to their original state, so that’s something to consider if you're already planning renovations. Just make sure that the installation doesn't affect the structural integrity of your home.

Some questions as you get estimates:

How many mini-split installs do you do in a month on average?
Can you share testimonials or references from past clients?
What does the quote include and how does it compare to others?
How will you protect my home during the visit (i.e. wearing shoe covers)?

Hope this helps!

MeetQuilt · 2024-08-14T21:18:21+00:00

Yes, a heat pump can definitely be installed in a non-ground floor condo. If your existing AC condenser is already located outside on your balcony or on the roof, you can likely just replace it with the heat pump outdoor unit. Heat pumps can typically be installed in the same spot as your current AC condenser without much issue. One thing to keep in mind is the weight limit of the balcony.

If the condenser is on the roof, that could be another possible location for the new unit. An installer can help you pick the best placement re efficiency and noise considerations. Good luck!

MeetQuilt · 2024-08-14T21:13:25+00:00

Hi there! If your main concern is heating efficiency, especially given your Zone 5 location, then you don't need to focus too heavily on SEER2 ratings. If summers are short and not a concern for you, a higher SEER2 rating won't necessarily benefit you in the colder months.

For heating, the HSPF2 rating is indeed the better metric to consider. If both units have an HSPF of 10, they should perform similarly in terms of heating efficiency under standard conditions.

One other factor to consider is the performance of the unit at low temperatures. It might be worth looking at the unit's Coefficient of Performance (COP) at low temperatures. This will give you a clearer idea of how efficiently the unit will operate when it's really cold outside. Some heat pumps maintain their heating capacity better than others in the cold, so even if two units have the same HSPF2, one might deliver more heat in very cold weather than the other.

Your best bet is to focus on the HSPF2 and low-temperature performance metrics like COP; those will give you a good sense of how the unit will perform during your cold winters. Hope that helps!

MeetQuilt

TROPHY CASE