Heat Pumps

Original article in The Telegraph

The energy secretary being interviewed is in favor of heat pumps.

The only 'worse' that he seems to be led by the interviewer into 'admitting' is that they have a lower discharge temperature than people are used to from gas boilers, which we all sort of know. Even my current 97.5% gas furnace has a much lower discharge temperature than the < 80% furnace it replaced, so it heats the house more gradually and steadily most of the time, needs a higher airflow at top output, and doesn't put out that super-warm air that was sometimes so nice to stand in after coming in from sledding.

It's a tie-in to this earlier Telegraph article, "Home radiators will have to be 10 degrees cooler for Britain to reach climate targets".

Again, they mean the discharge temperature: the radiator itself may operate at 50 ℃, rather than 60 ℃ as it might now operate on a gas boiler system. Can't quite tell if the headline is trying to confuse readers into thinking they'll have to keep their homes 10 degrees cooler.

The article may have a worthwhile point that if the home is older, poorly insulated, and the existing radiators were sized to heat it adequately assuming 60 ℃ water, some of that may have to change in order to heat adequately with 50 ℃ water.

 

Gas Boiler? Weren't those abandoned for home use many decades ago? Why in the world would anyone want pipes & radiators still?

Forced air is by far a preferred choice for new home construction.

 

I don't know, I thought hard about hydronic last time I was thinking about this place.

Nice tidy coils tucked away in floors and walls, no big ducts, easy to zone, easy to integrate with water heating ....

 

Soon as I saw this post my BS detector went off and so I go to the Googlies and type in:

"Are heat pumps more efficient than boilers?"

The answer: "Well-maintained modern heating boilers can easily provide up to 98.5 percent AFUE (energy efficiency). But the heat pump blows away even this near-perfect rating. Because heat pumps recycle heat energy from the air, water or ground, a modern heat pump can achieve up to 400 percent efficiency." https://shiptons.ca/shiptons-blog/heat-pump-vs-heating-boiler-which-one-should-you-choose

 

we have hydronic, but i don't like it. very complicated systems with switches, pumps, valves, storage tanks and miles of piping.
i much prefer the quick warmup of warm air, and the ability to turn it down for cool sleeping and back up in the morning.
radiant needs to stay a near constant, as the warm up and cool down are very slow processes.

the only downside to warm air is zoning and lack of humidity, and the humidifiers need constant attention.
but you get a twofer with a/c.

no idea which is more efficient, or the value of heat pumps across the board. they might work well in an english climate

 

Well, that's the trick of the piece. Nobody in it said the heat pumps were less efficient. The question posed in the interview was about them having a lower discharge temperature—to which the energy secretary replied they aren't much worse, which the article writer (The Telegraph's "Sunday political writer") transformed into the energy secretary "admitting" that heat pumps are "worse".

 

That looks like a scare story written by someone who doesn't understand the difference between 'heat' and 'temperature'.

"While gas heating can pump 60C water into radiators, the Government's Climate Change Committee assumes heat pumps will operate at 50C."

I wonder if they'd freak out that I've never set mine to heat up even to 25C. Though I am using a ductless minisplit (and its air discharge temp does exceed the setpoint), not a water heater to drive radiators. If just 50C is a problem for some radiator users, maybe they'll need to replace their old radiators with larger units, or do some building envelope improvements to tightened up their homes. A worthwhile move even without changing the heating system.

That is a dead link from here, but this one works: Heat Pump Vs Heating Boiler: Which One Should You Choose? | Shipton's Blog | Shipton's Heating and Cooling

We should clarify that those efficiency numbers don't have the same source basis. The heat pump 400% claim is from the electric wall socket, not from the natural gas pipe, so the gas first needs to be converted to electricity, still a fairly lossy process. Today's best 'converters' are CCGT power plants at a bit over 60% efficient, bringing the heat pump overall efficiency down to 'just' 250% when sourced from natural gas. Less eye-popping, but still a very considerable improvement.

FWIW, a heat pump wall plug efficiency of 400% implies either mild outdoor air temperatures, or an HSPF (heating season performance facto) of 13.6, which is still bleeding edge with a somewhat sparse product selection for ductless minisplits, or exceedingly sparse for central units. My older minisplit has an HSPF rating of 10, while ratings of 12 have since become very common.

Heat pumps also do their very best when used "very slow".

"Very slow" natural temperature changes, from heat leaking out or in through the building envelope, are a prerequisite to home energy efficiency. If your interior temperature changes quickly when the HVAC system is turned off, then the house is not energy efficient and could use some improvements or upgrades.

Then when the HVAC is turned on, a slow change rate is ideal for modern heat pumps, as their best efficiency is at lower power rates with smaller temperature differences across the heat exchangers. And low fan speeds that don't waste a lot of power to move air rapidly.

This is one advantage of zoned systems, so the sleeping area can be kept at lower temperature than active living areas full time. No thermostat setbacks at night or warm-ups in the morning. No reduced-efficiency surges in heat or cooling needs, thus also providing a smoother gentler load to the electric power grid.

Thermostat setbacks do pay back for inefficient homes. But for climate change issues, there is much more to be gained by improving the building envelope to the point where thermostat setbacks become counterproductive.

 

Unless you live in Texas then you just get duct free with an insert in the wall of each room and a flooded house and an $800 “heating” bill if actual weather happens

 

Many of the homes in my region use oil. Had a coworker that even used coal at his home.

Going to a condensing gas boiler and ducted hot water tank was a major improvement over the half century old oil boiler, with summer hook up for hot water, they replaced.

The lines for my radiators aren't tucked into the walls, and water leaks will be worse than air leaks. With cats keeping them clean isn't an easy task. Changing filters will likely be easier.

There is pluses, but I'd rather get away from gas, and get air conditioning too.

 

Past the clickbait, like moving to a BEV, heat pumps get greener as grids become cleaner every year.

Many grids, like here in PG&E land are substantially greener than a 100% NG grid source scenario - rapidly growing solar PV and batteries, onshore wind, some hydro, winding down nuclear, ~no coal, and offshore wind to come on board in a few years….

 

My house has a coal chute. I found oil-burner nozzles discarded in the crawl space. It had a natural draft gas furnace when I bought it. I changed that for a condensing one a decade ago (after looking at geothermal, but there would have been complications).

It's sort of a living history of home heating technologies. No fireplace though.

 

You had me at "storage tanks and miles of piping." Think of how many crumbled cookies could fit into a system like that? Could be a game changer for the cookie crumbling biz?

 

Each one of them or ideal or different regions of the country in different housing construction methods and materials.

Texas and northern Dakota are too good extreme examples along with Florida

But ducting could be an issue in an area where houses were billed out of brick with no space and walls or ceilings are floors on flat slab been having large 10 inch ducting or bigger for your main trunk and nowhere to put the smaller branches that is a regional concern and you may be forced into another heating method that is more economical and efficient

Whether they’re heat pumps or fossil fuels to make them more energy efficient they have to lower the outlet temperature if you have noticed the slow loss of discharge temperature over the last 50 years

then you have the other extreme of mild climate like where I live in San Francisco we’re freezing cold when it hits 40° outside Fahrenheit and when it’s 78° with nearly little humidity we call that hot and 85 or 90°F is unlivable for us. Which we used to barely ever have such days in our past history in San Francisco.

but whether it’s a boiler or coal fired or oil or a heat pump none of them are efficient went in properly installed and unfortunately whatever they’re rated at four efficiency 90% of them never achieve that just because of the installation by the technician and the contractor.

take track houses for example if they’re ducted they have the smallest undersize ducting very poorly routed flex duct with bends in kinks and usually very leaky because it was the lowest cost to bid that one in the project for installation.

So in the ducted scenario there’s usually a lot of high static resistance lotta friction loss undersize duct so that house in Texas that really truly needs a 5 ton system even if he bought the most energy efficient 19 SEER Unit with flex duct under side vents with high restriction friction loss and probably even the blower motor is set on the wrong motor speed tap you’re lucky if you get 15 SEER.

In the exact same thing goes for a fossil fuel furnace does not matter if it’s 98% efficiency if it is not ducted properly which they usually never are so if he comes a 80 SEER unit.

this is more of reality.


Then what part of the country you live in and the labor rate can drive the cost of your system to install so incredibly high in 30 years you would never recover your return on investment which is supposedly savings that has.

unless you’re lucky or unlucky enough to live in one of the extreme climates where you could get that return on investment back sooner with a extremely energy-efficient unit that was installed properly.

Labor rate here in San Francisco if you wanted to install hydronic‘s in the existing house you might as well build a new house somewhere just getting the permits and inspection fees will eat up any savings that the unit could’ve gained you in this ridiculous communist city of San Francisco.

Hydronic‘s when done correctly is really nice I have one person that we stay at their house on weekends as a getaway towards Muir Beach on a hillside facing the ocean it’s comfortable to walk around barefooted because the floor is always warm in the house is always evenly distributed with heat.

Except when the sun is overly strong they have far too many windows and no air-conditioning but with the Seabreeze and open the bottom floor windows on the first floor and the top floor on the fourth floor the fresh air takes care of that in that particular circumstance.

Electricity here in San Francisco in California usually when you use a lot you’re paying $.34-$.36 a kilowatt hour

Compared to where my aunt lives in Washington state the last I heard she was paying nine cents a kilowatt hour running electric is economical where electricity is cheap.

and gas is three times higher the price.

so you always got to take an account the region of the Country that you reside.

My family in Pennsylvania grew up on coal and oil furnaces.

Unfortunately even the 98% natural Gass furnace is often oversized and it’s running on its first stage too often in this mode they are not 98% they are more like 80% and when they’re way too oversized and it hits that second stage where it is 98% it heats up the house so fast it rapidly turns off again making it less efficient

Contractors always like to oversize furnaces and heat pumps. Doing their load calculations for that one percent of the year for those 3 to 8 days that are the highest expected temperature

that is when your gas fired furnace or your electric heat pump will work it’s most efficient because they will not be cycling off and on

If you were in a humid climate area of Texas Louisiana Carolina Florida any place like that.
You’d be better off with a slightly undersized heat pump that was struggling to stay up with the temperature and allow your indoor temperature to get a little bit higher. Even though you cannot keep up with the heat outside that evaporator coil would never turn off because it’s slightly undersized so the coil would be running cold or constantly removing more moisture lowering the humidity inside the house making it much more comfortable with a lower humidity have a slightly elevated indoor temperature.

On the other hand Contractor throws at 5 ton heat pump that turns on for 15 minutes call the house and then turns off so just as it starts running efficient after that 15 minute run time it turns off and then all that water in the thins in the pan on the coil start evaporating back out into the air as soon as the heat pump turns back on before it gets cold the hot air of the house pushes through that wet coil evaporator in that water right off out of the coil and push that humidity right back into the house.
And then again at 5 ton unit just when it’s starting to run a cold coil and get efficient it cool the house down in a chair to back off and starts the inefficient cycle all over again repeatedly.

this is how the majority of the houses are set up in the United States.

that house would be better with a 3 ton air conditioning unit that is more suited for the 278 days a year that are mild temperature and sometimes even a 2 1/2 ton unit would do better.
Then using a 5 ton unit that was only good and energy efficient for eight days of the year.

here in San Francisco mild climate 9000 BTU to 12,000 BTU unit is all you need and you can run it off solar off your roof The majority of the daytime hours because it’s only drawing 300 W to 900 W depending on the heat load or cooling load.

as I’m talking standing in front of my 12,000 BTU wall mount unit that easily over heats 1200 square-foot office space if I accidentally left on high fall asleep and wake up in a sweat.

it needs to be downsize to 9000 BTUs but I got the 12,000 BTUs for free by a customers ordering mistake and when I got this office space I threw it in here been running every day 24 seven since 2014.
And I still have never done a service or even check the refrigerant charge on this thing.

I’m always fixing everybody else’s heat pumps and servicing them other than running a vacuum cleaner with a brush and cleaning the filter.

Heat pumps last a good 30 years (“ when properly sized properly installed and properly maintained and in lightning strike areas of the country 100% must have surge protector or you will lose circuit boards“)

Back in 2008 I install a Fujitsu on my mom’s house house built in 1940 had no insulation had four 9000 BTU wall mounts installed around the house I’m about to remove that unit.

I insulated the walls insulated the ceiling and the roof painted the roof white so it doesn’t get hot in the summertime.

Going to install an 18,000 BTU unit for the whole entire house through central ducting system that was original gravity fed furnace that was removed. The 18,000 BTU furnace is even a little big just want it for the airflow because a true real HEPA filter ration system is going to be added in the filter system is going to be massively big to compensate for the pressure drop.

A second small 9000 BTU heat pump it’s going to be installed and placed in a central hallway location to flood heat or cooling into open doors down a hallway that will probably run 300 days of the year without ever needing the 18,000 BTU vertical installed heat pump in the garage that will only be used for filtering the house air in moving it around keeping the house humidity and temperature stable throughout the house with the fan only mode heat pump turned off.
LG unit ran off of solar panels the batteries I got for free to run throughout the night.

Here in San Francisco gas is cheaper you would never want to change over to a heat pump just because of the price of electricity.
But I install my own solar and my own electrical and battery banks so I don’t have to pay for that in this case the return on investment is much sooner than a customer that would have to pay the labor and pay full price for the system.

so it all comes down to what part of the country you live in and what price and what type of energy per therm or per kilowatt hour you pay for

and then the installer is the only one who could make it not perform efficient but the customer will never know it because they do not have the instruments or know how to actually test the system is achieving its rated efficiency.

But to prove that to the customer you can insist for a few hundred dollars more that your contractor install since he predict so you can monitor the efficiency of the operation of your system and actually see problems start developing before there’s actual failure

Sensi Predict HVAC Monitoring Kit by Emerson

here is the link above and then the link below if you want to monitor your actual air quality to see and predict into proof that you MERVE 16 filters 20”X30”X5” are actually filtering properly in are size correctly to clean the air.

HAVEN IAQ Central Air Monitor

insist that your contractor have somebody measure your newly installed system with measureQuick and give you a print out and reading to actually prove that it is working up to their efficiency standards that you paid all that extra money for

measureQuick &#8211; Connect. Perform. Prosper.

Don’t trust contractors and don’t trust contractors who send out salesman to make their hard sales and then they install using the cheapest labor they can take advantage of to pop your system in and believe me they are not thinking of your highest efficiency they’re thinking of their highest profit margin

 

Outside of the big cities in Texas we only have electricity unless you want the expense of a large propane tank. Propane's cost per btu is equivalent to straight electric strip heat. Heat pumps are at least half the operating costs.

So heat pumps with electric strips for backup is the norm. Two stage units allow for 20% oversizing which becomes important when your large house only needs 48,000 btus of cooling but could use more than the 60,000 btus of heating in a week long ice storm. So a five ton two stage heat pump with 15kw of electric heat (about 50k of additional btus) can pump out around 100,000 btus of heat when needed but can stage to heat pump high at 60,000 btus or reduce to heat pump low at 40,000 btus where it will run 95% of the time.

The downside of heat pumps in the winter is they are difficult to backup with a generator.

What many of us do is concentrate on building insulation and air sealing. Some of the better new construction housing employs zip sheathing and encapsulated attics enabling a 2800 sqft house to run on a 30k btu heat pump staging to 20,000 btus.

However the biggest climate challenge is in our cars that have to reduce 130f to 75 in a few minutes. Toyota does a good job with their inverter driven variable capacity compressors. Add some low-e tint, a garage and the car is decent in those 95-100f months.

A week long Central Texas storm last February

 

Inverter unit here. My prior replies about higher efficiency at lower power, were based on inverter / variable speed equipment, not 1- or 2-stage. Minimum heating rates are a small fraction of rated output, with fan and compressor noise levels also sharply reduced. No jolting start-ups.

I have half as much house here, built in a then-unincorporated area in the 1980s, on a building permit squeezed in just before the county's outdated energy code was updated. All incorporated areas had updated previously.

Some air sealing inprovements happened ~15 years ago, then more sealing plus floor and attic insulation improvements happened between 10 and 5 years ago. No changes to the walls or windows yet, as the investment substantially exceeds the expected return.

A dozen years ago we installed a minisplit single zone heat pump, 1.25 ton (15,000 btu cooling, 18,000 heating), covering most but not all of the house. The original electric blowers remain in place, and are still used at the far end of the house. But enough heat from the main zone heat pump 'leaks' down the hallway that those far end blowers are just supplemental now, used much less than before the heat pump was installed.

I'm thinking of adding a second unit of the smallest available size (9000 btu/hr) at that far end for better efficiency and comfort during the coldest parts of winter, and as a (sort of) backup. And to add summer cooling there, where we sleep, now that hotter summers are showing up. Our very first 100F day occurred shortly after heat pump installation, but more have appeared since, pushing the house record up to 107F during the PNW 'heat dome' event early this summer.

If this house were built to current area standards, I have no question that a smaller unit would be sufficient in our coldest conditions, but we'd still want multi-zone.

 

Usually people like that have undersized and leaking ducts combined with clogged evaporators and leaking refrigeration systems that get charged up in late spring. The unit may be oversized for cooling and gets by with a fresh charge in the summer.

Half the time the thermostat is not adaptive with outdoor temperature in order to properly stage auxillary heat strips. Add in hvac techs that either gas and go or sell a new system and heat pumps gain a bad reputation when their original installers and current techs are the problem. Of all tradesmen, residential hvac techs are often the least skilled in modern techniques. Even conventional two stage heat pumps have on demand defrost and "hot discharge temp" features to satisfy comfort complaints with equipment that can be repaired using local stock.