Got any kids? For the price difference I’d go up to a 50 but if it’s just one or two if you, I guess 40 gal works.
Worth upgrading 13 year old boiler to mod/con with heat pump?
- Thread starter mattd
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Got any kids? For the price difference I’d go up to a 50 but if it’s just one or two if you, I guess 40 gal works.
2 kids. We have never run out of hot water with the 40 gal we’ve had.
Therms, and kwhr are interchangeable. There are 29.3 kwhr in one therm, so the cost of electricity at your place is $8.5/ therm at a COP of 1, but is $3.40 at a COP of 2.5, and $2.83 at a COP of 3.0. I’m not sure what the efficiency of your boiler is but I can guess it’s 90%, so it’s cost is $2/.9 = $2.22 per therm. The break even COP is at $8.5/$2.22 = 3.8 which might occur at a temp of say 50 F.
You can see it’s hard to beat natural gas because of the difference in cost per therm. Having said that I hope you run the heat pump when it’s below 32 F to see how it does. Also, you might make sure the electrical and natural gas costs do not include the fixed costs when comparing the two.
There some other costs to consider like the cost of the circulation pumps on the boiler so you can jack up the boiler cost a bit and you can mix in some “free” power if the utility is giving you a good deal on how it credits you for power.
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Circulator pump is 85 watts and blower on the burner is low also. I do plan on running the heat pump below freezing. I want to see what it’s capable of. Worst case I I pay a little more for electricity during this test and save money on gas. As I stated, I did the math before about the boiler run cost (gas only) and it was around $0.085 per kWh reguardless of temp.. At 47 degrees the heat pump is around $0.06. At 5 degrees heat pump is $0.145 per kWh.
Boiler efficiency is 82%.
Customer charge (connection fees) is 14$ for gas and 6$ for electric. They are not included in the cost of operation.
Any condensing boiler gets there efficiency from the condensing that only takes places 140° or less return temp. The cooler the better. Above 140° drops to 87%. System would need piping changes primary/ secondary loops minimum.
Heat pumps all loose capacity the colder it is even hyper heat units. Manufacturers have all that info.
Heat pumps all loose capacity the colder it is even hyper heat units. Manufacturers have all that info.
I understand all of that. This hyper heat unit is rated at 42000 btus at 5*F. The entire boiler set up would be changing including primary/secondary loops and direct vent piping.
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Do you use radiant heat in floor where boiler temps can be lower (where efficiency rated high) or higher temp baseboards where you typically cannot approach the best efficiency of a boiler?
Baseboard.
Leave existing in place and maintain well , you’ll never likely recoup the savings in fuel vs removing a working boiler. Put your money into better insulation, windows etc.
I'm not in super cold climate but from what I understand this is the biggest concern of going heat pump and yank out your boiler + baseboard, others already mentioned above:
1) baseboard hydronic is a bit more comfortable and it has less of a "dryness" concern than blowing air constantly through the heat pump. I am not sure if this is correct but I never like dry hot air in the winter circulating around me.
2) the biggest concern assuming all equipment works perfectly is the uncertainty of electric rate in the winter. It is still likely depending on the gas price (that's what powerplant burn) but it is way less volatile than electric.
3) durability of an older 82% boiler is likely better and likely cheaper and faster to replace if it breaks down.
4) emergency power needed to run the boiler + circulation pump is likely way lower than a heatpump as others mentioned, it is not a big deal in San Francisco but in your climate it is critical.
5) return on investment is lower and interest rate is going to stay high for a while, so factoring in the chances of putting money down and never get all of it back, stay put and use more gas instead of investing hoping the return is good.
1) baseboard hydronic is a bit more comfortable and it has less of a "dryness" concern than blowing air constantly through the heat pump. I am not sure if this is correct but I never like dry hot air in the winter circulating around me.
2) the biggest concern assuming all equipment works perfectly is the uncertainty of electric rate in the winter. It is still likely depending on the gas price (that's what powerplant burn) but it is way less volatile than electric.
3) durability of an older 82% boiler is likely better and likely cheaper and faster to replace if it breaks down.
4) emergency power needed to run the boiler + circulation pump is likely way lower than a heatpump as others mentioned, it is not a big deal in San Francisco but in your climate it is critical.
5) return on investment is lower and interest rate is going to stay high for a while, so factoring in the chances of putting money down and never get all of it back, stay put and use more gas instead of investing hoping the return is good.
I would always keep a boiler for back up
Heat. I wouldn’t remove it just because. I was looking into cost in investing in direct vent boiler for improved efficiency but determined the fuel savings cost vs cost of investment is not worth it. I paid for my heat pump in cash nothing is financed. And yes, a boiler will be much lower electricity demand vs a heat pump especially at cold temperatures.
This is exactly what I decided. My house is as insulated as it can be per the energy audit. I did some extra air sealing myself (tongue and groove board cathedral ceiling) on top of what the energy company did years back. All my exterior windows have been replaced except one picture window that I plan on in the spring. Others are 20 year old vinyl windows that I have been slowly upgrading to low E wood windows by Andersen. I’ve done 5 so far.
Finally got the water heater changed out and fixed a bunch of gaffed piping repairs that were made years ago in a pinch with shark bite fittings, as well as some shut offs for outside water supply that were original and leaking from the 50s. Added an expansion tank to the system also. I redid the piping for the make up water feed for the boiler too, it had so many 90* bends and unnecessary drops and rises, and was full of green and white corrosion. I need to get one more shut off, ran out of valves I bought didn’t account for one that needed replacing. Also have to clean up the piping to make it look nice (ran out of time) but it’s functional. Soldered all the joints and put in about 30 feet of copper pipe. Also had to redo the gas pipe drop as this water heater the gas valve as higher up than the old one. Couldn’t believe the price of type L copper now a days. Hot water heater works great . Heats the water faster than the old one and makes it hotter at a lower setting. Another bonus is I have much more hot water pressure, it must have been corroded internally restricting flow. In it for a little more than I expected but am happy with its performance thus far. I really have no complaints about the 11 year old whirlpool. Only repair in 11 years was a thermopile about a year ago.
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The backup heat strips are field-installed and sold separately from the air handler. The installer can choose from several different wattages as needed.
Mine is ductless. There are no heat strips.
JHZR2
Staff member
They typically have an outdoor reset that allows the working fluid temperature to fluctuate according to the ambient. This allows a higher efficiency to be gained when conditions allow, but drives the temperature up when it’s really cold out…
The backup can be heatstrips, or a natural gas furnace, or a propane furnace. Around here it’s common to have an integral heat pump heat exchanger with a natural gas backup.
My in laws 11 year old boiler a Buderus gas condensing has had three replacements of that sensor and once on control unit. Finally Bosch new owner of Buderus stopped making controller part and they have no heat situation but hot water so they finding a tech who can remove this optional part.
It saves for sure in energy however the tech calls and parts involved savings gets eaten fast with high efficiency boilers.
