Best Of
Re: Unico potable water furnace, expansion tank pressure
That looks like you have 70 PSI water pressure on your system. DO NOT set the air pressure in the tank to 15 PSI. You may as well not connect the tank at all. If you want the tank to do the job it was intended to do, set that air pressure WITH THE TANK NOT CONNECTED TO THE SYSTEM to 65 -70 PSI air pressure.
If the tank is connected to the water pressure in the system, the water pressure in the system will compress whatever air is in that tank to 70 PSI. Don't measure the tank air pressure with water pressure on the other side of the tank.
Re: HVAC in New Construction in 2024
That table is full system COP including outdoor and indoor unit loads. A bad install can definitely hurt efficiency, but that is the case with any setup regardless of furnace/boiler/heat pump.
Anything duel fuel only makes sense if you already have the equipment. When you do the math on cost, the savings are in the order tens of dollars per year, so ROI of installing any extra equipment is never.
Kaos
Converting to a hot water heater
I had the annual Buderus furnace maintenance done recently. The hot water heating tank is integrated. I asked about checking the anode that self-deteriorates instead of the lining of the hot water tank. The tech showed me the price of draining the tank and checking/possibly replacing the anode. He also pointed out the system is 23 years old, and that age should be considered. He talked about a seperate water heater option. I declined checking the anode for now, even though it's about 5 years old.
The tech was describing a system I believe where the hot water is still produced by the furnace, but stored and partially heated in the stand alone electric heater. I'm thinking toward more of a completely seperate hot water heater. A co-worker with such a system turns his furnace off during warm weather. I like that option. Maybe the overall operating cost would be less with the somewhat integrated system using both the furnace and hot water heater? But I suppose the up front cost would be more with an integrated system.
I'm hoping nothing will have to be done for a while. The company i used just installed a new Roth double wall oil tank. It was only about $100 more than the standard Granby oil tank like what I had previously.
Re: Carlin Hot water heater keeps going on and off.
You find it on your combustion analyzer. Its DIY, until its not. Find an oil burner tech.
HVACNUT
Re: Carlin Hot water heater keeps going on and off.
Those numbers are found using the combustion analyzer that your Tech should have used on the most recent service. If your Tech does not have one of these Combustion Analyzer things along with a Smoke tester for oil heating work, then I would fire him and hire someone that knows how oil burners actually work.
There are several reasons for a primary control to go off by the safety lockout. …and did you know that you are only supposed to RESET ONLY ONCE. That is taught in every technical school when the students are learning about oil heat primary controls. I'm just saying that it sounds like your Tech does not subscribe to that well known rule of the trade. If the control locks out after you have reset it once, then the knowledgeable tech would take the burner apart and find the cause.
- Partially plugged oil filter
- Partially plugged fuel pump screen
- Partially plugged nozzle
- Dirty ignitors
- Ignitors out of adjustment
- Ignitor insulators cracked
- Ignition transformer or electronic ignition failing intermittently
- Incorrect combustion air adjustment
- Incorrect fuel pressure
- Partially plugged fuel line from the tank.
These are just the first 10 reasons that a technician with over 40 years experience might think of off the top of his head. There are many more reasons. Maybe these reasons will help to refresh your technician’s memory about what might be the reason for the flame failure lockout!
But don't be too harsh on your technician, everyone needs to start somewhere!
Mr. Ed
Re: AO Smith Gas Water Heater Warranty Replacement
water heater manufacturers are fairly eager to just process warranty lol. I do think the most pressing concern is getting a plumber in there that knows how to sweat copper!
GGross
Re: Steam Boiler sizing?
When the boiler's capacity is well matched to the dissipation (the radiators and piping) the pressure should not rise significantly, since the the radiators and piping are dissipating 100% of everything the boiler can output. And it does not take much pressure differential for steam to move. Once the radiator vents close the steam condensing inside the radiators makes a vacuum (or less pressure). So unless you overwhelm the radiator with steam the pressure should not rise significantly. The vents are only there to provide a means to expel the air from the system so the steam can get to the radiators.
In the case of an oversized boiler. The radiators can't keep up with (dissipate) the boiler's output so the result is the pressure rises. IMO running the boiler to maintain higher pressure than needed to fill the radiators is wasteful (other than maybe the coldest day of the year if the system as a whole is undersized for the heat-loss of the structure).
109A_5
Re: Steam Boiler sizing?
If the new boiler size is basically the same as the old one, I would expect the overall system performance to be about the same as it was.
If I was in this situation, stuck with an oversized boiler that cycles on pressure, I'd add a delay timer to the control circuit. So once the boiler trips off on pressure it can't restart until a delay (in minutes) has expired. Skipping most of the useless cycling.
The way I see it, if you are cycling on pressure the radiators are pretty much full and not getting much hotter. And for comforts sake you may not need them to be hotter longer per thermostat cycle. I do not see a point in cycling the boiler on and off rapidly to maintain the steam pressure roller coaster of a pressuretrol or vaporstat hysteresis (pressure differential).
109A_5
Re: HVAC in New Construction in 2024
There have been many discussions on heat pumps and furnaces/boilers, so I thought I would put out some of the points that seem to keep recurring.
Heat Pumps in Cold Climates: Why Hybrid Systems Make More Sense: Heat pumps are a remarkable technology, but in cold climates with high electricity rates, they can be expensive to install, replace, and run. Fortunately, hybrid systems with a boiler or furnace offer a smarter, more flexible solution.
Bosch recommends mini splits with boilers, not just heat pumps alone. In a training session two weeks ago, they also stated that heat pumps in New England are not a good application because the electric rates are so high.
NREL study shows a seasonal COP of 2.1 (210% annual efficiency) - that's almost $6/gal oil equivalent. Since the COP drops further with lower temperatures, electric bills increase rapidly. This May 2023 NREL Field Validation of Air-Source Heat Pumps for Cold Climates study shows the wide disparity between manufacturers ratings and field performance, with an average seasonal efficiency (COP) of 2.1. On a unit of energy basis, $0.30/kWh is the equivalent of $12.18 per gallon of oil and $8.79 per therm of natural gas. New York residential electric rates increased 50% from 2020 to 2024, and 4% in the prior 7 years…Northeast states are leading that trend and forecast to increase further.
Studies show 60% to 80% of people turn off their heat pump below 35°F, often due to high electric bills and the air the blow is colder than furnaces (multiple studies p 18-19). That’s often the right choice economically and environmentally because furnaces and boilers will cost less to operate and they use less source energy compared to electricity generated with natural gas (EPA Clean Air Markets Program Data CAMPD 40% power plant efficiency in New England less 8% transmission and distribution losses); and they have lower carbon intensity (GREET 2022 1.06% natural gas fugitive emissions means natural gas 20 year lifecycle has a 36% higher carbon intensity than fuel oil). Even more so when temperatures drop below freezing.
Imagine a power plant as a hungry pizza eater. You feed it 8 slices of natural gas, but it gobbles up 5 slices just to generate and deliver electricity to your home. That leaves only 3 slices of usable energy. A 210% efficient heat pump can stretch those 3 slices into 6 slices of heat. But if you use a boiler that's 87% efficient, it skips the power plant altogether and turns 7 out of 8 slices directly into heat, more warmth, less waste.
Furnaces and boilers deliver warmer, more comfortable heat (cold climate technical data p A230). For comparison, the air leaving mini split heat pump heat at 91°F can feel like cold air blowing at 73°F just a few feet away. A better air sealed and weatherized house with high efficiency windows and doors can improve winter heat pump comfort.
Electrification will require that the residential grid grow 4X. Cold climate heat pumps consume close to 2X as much electricity as a typical home, and EVs use the equivalent of another home's worth of electricity. In the near term, that means if just 10% of cold climate homes fully "electrify", the residential grid will need to provide almost 30% more electricity (and that does not include overall grid load impacts from AI impacts). And the cost of utility scale battery back up is astronomical, they last about 10 years and cost about $300 to $500 per kWh of storage - that's just $0.30 of electricity.
Heat pumps aren’t just expensive to run, they’re expensive to install and replace. In Rhode Island, representatives indicated that converting low-income homes to heat pumps cost the state $20,000–$25,000 per home this year. Over time, that’s $75,000+, compared to a single boiler that lasts decades.
Hybrid systems make sense, especially in a volatile energy future. It’s not all-or-nothing as hybrid systems let you choose the best tool for the job, season by season. Choosing to heat with a heat pump or a boiler/furnace could be for personal comfort, operating cost, emissions, source energy consumption, and more.
Roger
Roger