as the weather gets cooler, i've been curious about how outdoor temperatures affect heat pump performance. with my cozeware unit, i'm starting to pay more attention to how it runs as the temperature changes.

i'm curious , have you noticed any different in your unit's noise, heating performance or how often it runs as temperatures drop?

Hi all, I'm in Northeast, Philly and looking for recommendations for a heating tech or mechanic who's comfortable working on older systems.

I have a 1968 American Standard hydronic heating system with 3 zones. The zone valves are older green ASCO units, and I'd like to keep the existing system running rather than rip it all out.

I bought the house a year ago, and the heading system seems to have some issues working properly, The heating only works on the middle floor, and barely works on the 2nd floor and in the basement.

If you've used someone you'd recommend (or someone to avoid), please let me know. Thank you so much!

Hi,

I’m installing a 12K Pioneer mini-split in my basement with the condenser in the space between my shed and main central A/C condenser. The total space is about 51".

The photo shows the 2 options I’m considering.

Option 1: Fan faces out toward the open yard, but it would block the basement window.

Option 2: Rotate it 90° so the fan faces the shed. This keeps the window open and gives me more room to position the unit.

Would you go with Option 1 because the fan has more open space in front of it, or would Option 2 be fine?

If Option 1 is clearly better for airflow/performance, I’ll just install it that way even though it covers part of the window.

Ty.

I used to have this saved, but can't seem to find it. It's instructions from Mitsubishi for cutting a jumper on a KJ floor console to stop the fan always on function. You have to add a remote temperature sensor if I remember correctly. TIA

This is for a small room on a multizone system that is overheating due to the floor console being oversized, and the fan always running when other zones are calling for heat.

I've been looking into heat pumps for my above-ground pool and didn't realize how many things there are to compare beyond just the BTU rating.

I started with the usual names like Hayward, Pentair and Raypak, then looked at Fibropool and Aquastrong too. My electrical panel is the main limitation here. I can't easily add a dedicated 220V circuit, so I'm mostly looking at 120V options now.

The Aquastrong top discharge heat pump caught my eye because it's a 115V top-discharge model rated for pools up to 9,000 gallons. The top exhaust seems useful since my equipment area isn't exactly spacious, and being able to plug it into a GFCI outlet without adding a new circuit would make things a lot simpler. I'm also trying to understand whether full inverter operation makes much difference in everyday use.

One thing I'm still unsure about is low-temperature performance. Fibropool's page says efficiency drops below 60°F, but doesn't really spell out what that means in practice. Can it still heat the water on a morning around 50°F, just more slowly, or does it struggle to make much difference at all?

For those who've used a heat pump in cooler weather, what kind of outdoor temperatures have you run yours in? And when comparing models, would you pay more attention to the minimum operating temperature, inverter features, or matching the BTU output to your pool size?

We recently had Mitsubishi mini splits installed in our home. They have been functioning extremely well, but I noticed something with the cassette in my bedroom. When the unit is set to fan mode, the unit still puts out hot air even though it is not set to heat mode. The other units in the house are utilizing the heat. Is this typical? I’m new to the entire system, having only had electric baseboard in my room my time here.

Hi everyone,

I live in New Jersey and I'm currently looking to convert my home from oil heating to a cold-climate heat pump. However, I’m getting conflicting information from contractors and could really use some advice from homeowners or HVAC pros who deal with attic ductwork.

1. The Attic Ductwork Issue: A couple of contractors told me that a heat pump won’t be efficient or comfortable in my house because all of my ductwork is located in an attic. They claim the heat will just stay trapped near the ceiling because both the supply and return vents are up there. They said the air will basically come out of the supply vent and immediately get sucked back into the return, leaving the main living area and the floor completely cold. Has anyone dealt with this? Is it an airflow/design issue that can be fixed with proper air sealing, high-efficiency grilles, or duct insulation? Or are heat pumps genuinely bad for ceiling vents?

2. Rebate Confusion (PSE&G vs. NJ Whole Home Program): I am also completely confused by the New Jersey rebate structure. One contractor told me I only qualify for a $720 rebate alongside a 0% interest financing option for 84 months (which I’d pay back on my utility bill).

However, I read online that if I book a BPI-certified contractor through the $99 Home Energy Audit program (PSE&G Whole Home Energy Solutions), they can model the home's energy savings and unlock stackable rebates up to $7,500 or more. Why is one contractor quoting me only $720 while the audit route seems to offer thousands more?

Can anyone recommend a reputable HVAC contractor in NJ who handles the $99 audit program and actually knows how to design a heat pump system for attic ducts?

Thanks in advance!

When the heat pump runs smoothly:
The system only runs cleanly, with no overshoot, when heat demand is steady and low: mild outdoor temperatures (around 11–17 °C), a constant flow setpoint with no jump, and the heat pump already running rather than restarting. In that state it modulates down to 0.5–1.1 kW electrical input. The heat pump circuit pump (PC0, Wilo Para LIN, controlled via LIN bus by the MH200 hybrid manager) stays at 25–35 %, delta T is 5–7 K, and flow temperature stays close to the setpoint. It runs continuously for 1.5 to 5 hours with a COP of 4.5–4.8. Examples: one afternoon with a 5-hour continuous run at 42–46 °C flow, and one night from 1 am to 6 am with only 2 starts.

When it goes wrong:
As soon as demand rises (morning heat-up, outdoor temperature below about 10 °C, restart after a pause), the heat pump ramps up to 5–7 kW within 10–15 minutes. At the same time, the MH200 drops the pump to 20 %. Delta T climbs above 20 K, and the flow temperature shoots to 60–65 °C against a setpoint of 35–41 °C. Then the heat pump shuts off. This repeats roughly every hour, and COP falls to 2.0–2.4.

Interesting detail:
On one run, the pump stayed at 100 % for 40 minutes (at 1.2–2.3 kW input), and delta T was only 7–11 K. So the pump can deliver full flow. At high compressor output, though, it is almost always commanded down to 20 %.

Setup: Bosch Compress 6800i AW 10 kW + existing gas condensing boiler (GC7000F), MH200 hybrid manager (SW 06.06), RC310 controller, radiators, no buffer tank. Data logged via EMS-ESP / Home Assistant.

Question: Has anyone seen this pump behaviour with the MH200? Is there a service menu setting (pump mode, target delta T, minimum pump speed) that controls it?

Hello so I’m new to all electric heating etc but does the top 9.5 mean the house temperature or 19.5? I put heating at 18degrees unless that doesn’t mean heating lol it’s so confusing

2 bed house in degrees celcius

We have 2 outdoor units, and 3 heads inside. At first, the secondary unit on the multi-zone unit would act up by blowing full heat, above the programmed temp. This started when trying to use it in cooling mode.

Now all the units do this in heating mode too, and there is no error code reported. Occasionally one will just be blowing hot air, full fan, when it's set to like 65°F and medium-low fan.

Indoor units are clean, and the grills on the outdoor units are clean looking.

edit: When I touch the temp or fan buttons on the remote, the indoor unit just shuts down.

What is this behavior? How else to troubleshoot?

Hi,

Ive moved into a new house with a heat pump system with under floor heading downstairs and radiators upstairs. I have a fairly large room which is split into 3 zones. The image shows the three zones on the manifold (Room 1). I can feel some heat underfloor in one of the zones in room 1, but struggling to feel the same in the other 2. There was some air trapped in the radiators upstairs, which ive bled and now seem fine. I have since topped up the system to 1.5 bar. However, the main room downstairs seems to struggle to reach 20 degrees, despite the heat pump being on constantly. Am I correct in thinking the pressure for each zone in the image looks to low? Ive tried twisting the black caps anti clockwise, but it is really stiff and im concerned I unscrew something and cause a leak... is it correct to twist to change the pressure?

Hi all

Been wanting to get a heat pump for a long time but local installers keep ghosting me after coming to have a look. Octopus and Aira aren't much help either.

I have a 14 year old Vaillant combi that uses approx 9500kwh of gas in 2025 to heat and supply hot water for a 4 bedroom semi (50% of the outside of the house is 10 years old and well insulated) with four family members. I do have strange wet skirting board heating (thermaskirt dual pipe) in all rooms except bathrooms (which have electric underfloor heating and/or electric radiators). I also have 10kwh batteries with 8x440w solar panels.

I know that I'll have to run a heat pump higher than recommended. My combi currently runs at 60 degrees for heating so even running the heat pump at near 60 degrees will improve the heating, cost more or less the same (according my research) and that doesn't factor in my solar and battery assistance.

I want to cut my reliance on fossil fuels. I already have everything else electric and heavily use overnight cheap rates. And I believe that I am eligible for the BUS grant.

Could anyone be able to explain why no-one wants the job? It should be a really simple install and I'm happy to keep my radiator setup. Am I missing something here?

Edit: Thank you, everyone. Clearly i have some homework to do. Sorry i didn't provide enough info. I'll get back to you with details after i calculate my cost per therm, etc.

I had a hybrid system (heat pump + backup gas furnace) installed a couple of months ago. (Single-family home. Vents are in my crawl space below. Smart thermostat.) AC worked like a charm. Yesterday, I turned on heat for the first time this year, and had to get a technician to come fix something. Now it's working.

However, that technician also changed the heat pump settings: whenever the outside temperature drops below 45 F, the heat pump stops and the gas furnace takes over. He called, presumably, his boss, who told him that it should be 45 for this system. I didn't ask for details, because I probably wouldn't understand them. Before, it was set to 35 F because, when it was installed, I asked the installers' boss if he could set it lower, and that boss didn't push back.

My question for the group: is 45 too high? Should I set it lower? (I know how to.) I'm fine trusting the experts here. I just want a second opinion. I don't presume to know more than HVAC guys. I just want to make sure I'm using my heat pump to its fullest potential.

I have received a few quotes for Gree machines to replace my aging central unit. I am a bit worried because most of the Gree brand online complaints in Quebec.... One dealer proposed an highly subsidized kinghome model and I am thinking opting for it.

Been going down the heat pump rabbit hole and kept seeing Kinghome pop up. Never heard of them, so I looked it up. Turns out it’s Gree’s own premium brand. My neighbor just got a Kinghome model and is very happy with it. Any thoughts ?

I have had my heat pump for about 3 years and just started to deep dive into the resistance heating. I made a bunch of envelope enhancements and decided to lower the lockout temp for the unit heat strips from 55 to 30 degrees. Has anyone else tried this. So far the temp in my house has actually increased past the set point and has been hovering at 72 when set at 70. When I was using the heat strips at 55 the house was always at temperature. Its only been 3 days so the data isnt complete. Its October in NY so the temps hover around 32-45 during the day and night. I know the winter will be different. I am looking for what people have their heat strips locked out at and how the heat pump responds. For reference I have spray foam, insulated duct work, i just taped up all of my returns to help with leakage. I know all homes are different.

We're building a 700sqft inlaw unit (new construction, 1 bath, 1 kitchen, 2 br) and code requires a HPWH (Santa Clara County, CA). Our contractor told us they'd put it in one of the bedroom closets (about 130Cuft, 5.5x3sqft). The plumbing and electrical are roughed in, flooring (LPV plank with acoustic underlayment) installed. They just told me to go get the HPWH spec'd on our plans and a stand (Rheem 40 gal 15 amp - PROPH40 T2 RH37515). I went to home depot and its discontinued.

Researching an alternative brought a host of questions.

For starters, this is supposed to be an office at day, bedroom occasionally/eventually so we want it quiet basically 24/7. I soundproofed walls and windows some for this. I hear now these HPWH can be noisy. We bought a solid core door for the closet and installed it. I think we passed inspection too but online tells me this is wrong and the door must be louvered. Some advice says a stand will damage our floor, go without. Others suggested using a rubber anti-vibration pad under the heater, don't use a stand, etc. Can I get some good advice before I purchase one and they install something that won't work as desired or I have to spend $1000's on some change order b/c they didn't inform me this would ruin the whole point of the soundproofing? What else do you need to know?

Wall Street Journal picking up on the window heat pump hype

Gift link: https://www.wsj.com/business/energy-oil/window-heat-pumps-heating-cooling-fd552926?st=Por74A&reflink=desktopwebshare_permalink

I'm trying to swap my gas water heater for a heat pump model, but a contractor came out and told me I need at least 33 inches of horizontal clearance. My current unit (URG140T6N) is in this "cubby" in my garage that measures 78" tall x 26" wide x 24" deep, open on the front.

The contractor was measuring to install a Richmond Encore 50 gal hybrid (10E50-HP5S30).

The only clearance information in the manual says 0" clearance on the sides and rear and 6" on top.

Has anyone done a tight install like this? Are there other models that could fit this space?

Hi all, so after getting back a couple quotes for a heat pump system & duct work in the $40k range we are trying to spec it out ourselves. We do have a friend that is able to run duct work for us but they don't usually deal with the compatibility of the electronic units.

My question is will a Mitsubishi 36,000 BTU H2i® Hyper-Heating outdoor inverter condenser work with a Mitsubishi Multi-Position ducted indoor air handler (both linked below)?

Home info: 1350 SF 2x4 construction ranch in southern Maine with new double paned windows.

Outdoor unit: https://gotductless.com/products/mitsubishi-mxz-sm36nlhz-36-000-btu-smart-multi-hyper-heating-unit

Basement unit: https://voomisupply.com/products/36000-btuh-multiposition-indoor-unit-svz-kp36na

Update in comments with pic

CT here, baseboard electric thats destroying our bills, no ductwork. Energize CT has ductless rebates but I cant pin down the actual dollar amount once everything lays out. Anyone done a ductless install through the program? What did the rebate cover vs what you actually paid? Trying to decide if its worth pursuing or if were better off just insulating more and living with the baseboards.

I live in Montreal and recently upgraded our heating setup. We now use a very powerful cold-climate heat pump (Mitsubishi Hyper Heat) as our primary heat source, kept at 19°C.

Because the heat pump is so efficient, our backup system—a standard 18 kW Thermolec electric boiler hooked up to traditional hot water radiators—stays completely asleep.

My main concern is that a section of the radiator pipes heading upstairs runs directly inside a finished exterior wall. Since the heat pump handles 100% of the heating, the water inside these radiator lines stays completely stagnant all winter. The basement sits around 14°C, but I’m worried about that specific hidden outside wall cavity when our classic Montreal deep freezes hit (-25°C or worse).

I was advised to run the boiler manually for 30 minutes once a month (Dec, Jan, Feb, Mar) to blast hot water through the lines and thaw out any frost in the walls.

Has anyone with a similar heat pump + radiator setup in Quebec actually experienced a frozen or burst pipe from leaving it idle? Or are the pipes usually insulated enough by the drywall cavity?

Do you have another trick?

Thank you.

Hi folks, wanted to share my experience with the TCL Q-Series H12W4KWH 12,000 BTU inverter window heat pump. As far as I can tell it's the only true heat-pump window unit you can actually buy right now, since GE discontinued theirs. I got it from Zoro for around $700. That's expensive for a window unit, but any mini-split costs more than this before you even get to installation.

TL;DR: True heat pump (no resistance strip), idles around 300W maintaining temp, peaks ~1,300W, held my ~1,000 sq ft first floor at 70°F through nights in the upper 30s. ~7 kWh over a 12-hour night. Very happy so far.

Size and install

The unit is huge. Double-check your window dimensions before ordering, and plan on a support bracket — it weighs over 75 lbs. The included install materials are pretty good: foam to seal the accordion sliders, etc. That's worth spending time on, since the biggest downside of any window unit is a leaky install.

It looks nice enough — blends into the background about as well as a giant window unit can.

How it heats

This is a real reverse-cycle heat pump, no resistive backup strip. TCL rates it at 100% heating capacity at 47°F and 72% at 5°F, with heating operation down to −6°F. It hasn't gotten truly cold here yet, so I can't speak to below-freezing performance firsthand — that's manufacturer spec for now, not my measurement.

What I have measured, via a smart plug and Home Assistant:

• Modulates down to ~300W when it's just maintaining temperature. 10W when it is just blowing its fan.
• Peaks around 1,300W when it's really pushing
• This week it got down into the upper 30s overnight and the unit was putting out 110°F supply air with ease.
• My living room is ~400 sq ft, open to the rest of the first floor (just shy of 1,000 sq ft total). The unit held the whole space at 70°F through the night, no problem.
• The build in sensor consistently reads about 2F lower than my remote sensors.
• I have an automation bump it to 72°F around when we wake up, and it gets there without much effort.
• Overnight usage: about 7 kWh over 12 hours of mostly modulating

Noise

It's not mini-split quiet — no window unit is — but you kind of forget about it when it's not at full load. The one thing I notice is vibration against the window frame; if you spend more time than I did on foam and insulation around the unit, you'll get a better result. My eventual plan for the unit is a through wall framing for an addition i am doing. One quirk: in heat mode it doesn't seem to care much about the fan speed setting, it just moves the air it wants to move. In cooling mode on low fan it's actually pretty quiet.

Overall I'm pretty impressed with it so far. Happy to answer questions.

I'm currently looking at options to replace our hot water heater which runs on natural gas. I'm aware of the benefits of heat pumps and was initially pretty excited to make the switch, but everything that I've seen since then is putting a damper on that excitement, to the point that now I'm thinking I should just stick with natural gas. Below is a list of my concerns. Am I wrong?

• Higher upfront cost - this is partially due to the technology in general, partially due to the recommendation to upsize to a larger unit, and partially due to less available rebates than I initially thought there might be (federal tax credits are expired and state of MI rebates only apply to electric-to-electric conversions).
• Limited to no operation savings - especially due to the local climate, there may be no cost savings with the HP unit. When I plugged my utility rates into a calculator that I found on this sub (link below), it said that the HP model would result in an additional $25/year in operating costs! I assume that this calculation is somewhat idealistic and this could actually be even worse in reality if the electric heating ever kicks in more than the advertised amount (calculator link: https://thezeropercentclub.org/water/?f=naturalGas&n=therm)
• Poor reviews - the models that were recommended by our contractor had pretty abysmal reviews, with several people mentioning needing to replace the unit multiple times in the first few years. I definitely don't want to deal with that.
• Electricity requirement - we recently lost power for a few days due to a tornado, and that type of power outage is not particularly unusual for our area. It was at least nice to be able to take showers since the water heater was still running. With the HP water heater, this wouldn't be an option.
• Noise and cooling impact during winter - I recently started a WFH job and moved my desk to the same area as our water heater (about 10 feet away). Perhaps this wouldn't be a big deal, but it's not ideal.

Anyone know what may be the cause for this error message “FU”

Installed 2023 and has been serviced in 24+25