Finally Installed GE Hybrid Heat Pump Need Advice

rberq wrote: What I am trying to figure out is, what percentage of my oil bill is going purely to the boiler standby losses.

http://www.nora-oilheat.org/site20/uplo ... cyTest.pdf

Check out page 7.

markviii wrote:Check out page 7.

Wow! Thank you, Rob, that is exactly what I was looking for. If I am interpreting it correctly, my whole-house boiler with indirect Superstore tank for DHW is TERRIBLE when providing only DHW in the summer. It looks like it is only 38% efficient in terms of hot water delivered vs. oil burned. In the Winter, some of the standby loss could be captured to heat the house, though right now that is not happening except by accident. So at least for Spring/Summer/Fall, an electric heater would be an improvement. Not cheap, but an improvement.

Glad you found it informative. The real efficiency number depends on a lot of things. Combustion efficiency, thermal efficiency, how well your boiler and piping is insulated, plus the aquastat settings. As a comparison, my wife and I take 7-10 minute showers, do most laundry on warm, and the boiler burns an average of 1 gallon per day to make hot water with a 30 gal. indirect.

#1 & #2 comparisons on that link made no sense to me. #1 was cast iron boiler, tankless. #2 was cast iron boiler, indirect. In that chart, #2 is less efficient & wastes more oil than #1. This is 100% opposite of what I found after installing an Amtrol indirect boiler. It's 42 gallons - which is at a minimum 4 times the capacity of the tankless setup. We have hotter water for longer, & with a better recovery rate, & I saw no increase in oil usage. If anything it used less. Hard to tell after installing those coils in the stove - they've paid for themselves even after getting screwed by Hilkoil on the warranty.

As far as standby losses .... when I manually run the circulator on the indirect to remove excess heat, the water gets up over 150° - if I don't run the hot water, it might lose 5° in 12 hours. I find that amazing. The boiler alone will lose 5° in less than an hour.

Smitty, tests #1 and 2 did not use the same boiler. Note that the second one was not as efficient even in steady-state operation.

The least expensive route would be to buy a coil and instal it in your stove. I run my stove about 7 months out of the year so if you do the same you'll have low cost hw for those months and then you can just run your current setup the rest of the time. If oil prices get too crazy then you can look into alternatives like a heat pump for those remainig months.

rberq wrote:

traderfjp wrote:You are keeping a boiler at 160/180 to heat water to about 125.

No, my boiler is cold-start, so if there is no call for heat from the Superstore tank the boiler itself can go stone cold. But in a sense you are correct, because during daylight hours there is often enough hot water use that the boiler never cools down completely. Therefore I have more or less continuous standby losses from the boiler and piping, except at night. What I am trying to figure out is, what percentage of my oil bill is going purely to the boiler standby losses.

SMITTY wrote:#1 & #2 comparisons on that link made no sense to me. #1 was cast iron boiler, tankless. #2 was cast iron boiler, indirect. In that chart, #2 is less efficient & wastes more oil than #1.

Makes sense to me, IF the boilers had been the same in both #1 and #2. With indirect, there are standby losses from the boiler AND the storage tank AND the piping in between. With tankless standby loss would be only from the boiler.

In your situation, where you swapped out the boiler AND went from tankless to indirect AND put coils in the coal stove, it may be hard to tell which change(s) contributed how much to your savings.

The water usage pattern is also a factor. With frequent use, the indirect system will call on the boiler more frequently so it will never cool down all the way, therefore will have constant standby losses. In my personal circumstances this does appear to be true. Additionally, because my boiler can heat the whole house it is way over-size for heating just DHW, so there is all the more boiler and water mass suffering standby losses. And the long run of pipe between my boiler and the storage tank is lots more surface area producing standby loss.

Your system is optimized to work when the boiler is making heat for the whole house. It's very ineefecient when you are only making hot water. I could never understand why anyone would choose a boiler and indirect storage tank over a dedicated oil fired hot water heater. 99% of plumbers suggest the indirect system. I like the ability to turn off my boiler in the summer and just fire the hot water heater.

rberq wrote:

SMITTY wrote:#1 & #2 comparisons on that link made no sense to me. #1 was cast iron boiler, tankless. #2 was cast iron boiler, indirect. In that chart, #2 is less efficient & wastes more oil than #1.

Makes sense to me, IF the boilers had been the same in both #1 and #2. With indirect, there are standby losses from the boiler AND the storage tank AND the piping in between. With tankless standby loss would be only from the boiler.

In your situation, where you swapped out the boiler AND went from tankless to indirect AND put coils in the coal stove, it may be hard to tell which change(s) contributed how much to your savings.

The water usage pattern is also a factor. With frequent use, the indirect system will call on the boiler more frequently so it will never cool down all the way, therefore will have constant standby losses. In my personal circumstances this does appear to be true. Additionally, because my boiler can heat the whole house it is way over-size for heating just DHW, so there is all the more boiler and water mass suffering standby losses. And the long run of pipe between my boiler and the storage tank is lots more surface area producing standby loss.

markviii wrote:Smitty, tests #1 and 2 did not use the same boiler. Note that the second one was not as efficient even in steady-state operation.

Ahh ... now it makes sense!


I installed the indirect 3 years before the coils, so the change after installation was obvious pretty quick. The indirect seemed to keep the boiler from firing intermittently during the day in the summer. Every time you washed your hands before, it would send ice cold well water through the boiler & cool it down - so it seemed like it was constantly firing just to maintain temperature. Now I only notice it firing when there's a big draw of DHW, or if the low limit is reached. Boiler cools off quick down there in the summer. Never gets above about 62° all summer long.

The coils made a HUGE difference in oil consumption. I used to barely make it 8 months before needing a fillup. Now I'm on the same oil from 11 months ago & still have over a 1/4 tank left! I can probably drag it out until next fall, hopefully.

traderfjp wrote:I could never understand why anyone would choose a boiler and indirect storage tank over a dedicated oil fired hot water heater. 99% of plumbers suggest the indirect system.

More $$$ for the plumber? More $$$ for my oil company which sold and installed the system, and more continuing $$$ for the excess oil burned? Ignorance on the part of the plumbers? Or just enthusiasm -- after all, if what you do is solder pipes, then the more pipes the better!

rberq wrote:

traderfjp wrote:I could never understand why anyone would choose a boiler and indirect storage tank over a dedicated oil fired hot water heater. 99% of plumbers suggest the indirect system.

More $$$ for the plumber? More $$$ for my oil company which sold and installed the system, and more continuing $$$ for the excess oil burned? Ignorance on the part of the plumbers? Or just enthusiasm -- after all, if what you do is solder pipes, then the more pipes the better!

If installing a new system, an oil boiler installed with an indirect water heater would be cheaper to install than an oil boiler and a separate oil fired water heater when taking into account all aspects of piping, controls, venting, etc. Also, there is only one oil burner to maintain, not two.

OK, measurement begins today. I installed a meter at the inlet to my Superstore tank, so I can measure how much domestic hot water I use per month. I know from several years of records that I average 22 gallons of oil per month to make hot water. Also I just filled the oil tank a week ago, so beginning metering of water and beginning drawdown of the oil tank coincide. So in a few months I should have pretty accurate figures as to how many gallons of hot water a gallon of oil will make. Then it will be very easy to calculate the savings (or not) of switching to an electric water heater.

I maintained two burner heads for over 20 years. Each head was given a new nozzle and filter once a year and each appliance was cleaned. This amounted to about 1.5 hours a year for maintenance. This is a small price to pay for all the advantages of having a dedicated oil fired hot water heater.

Anyway, I just received my first electric bill with the new hybrid electric heater. My usage was 100kw over last year. This was for two months of usage. I'm very happy with the bill and how the heater performs. The best part is that I used 0 oil this summer for hot water.

traderfjp wrote:I just received my first electric bill with the new hybrid electric heater. My usage was 100kw over last year.

I don't know how high your electric rates are. Ours are about 16 cents per kwh. So you made hot water for only $16 for the month. I'd be happy with that too.

We pay 19c a kw. Not the highest in the country by higher than the mean. There are many variables for a summer electric bill. Honestly I feel like I've used much more electricity this year over last year but..... We sided the house this summer but ran the AC much more. I also have an electric chlorinator which is new and pulls a few watts and a pool pump that I leave on all the time. For the first month of the year I ran the old power hungry pump but then changed over to a new more energy efficient pump. I will know better with a winter bill. But overall I’m very happy since I didn’t see a big surge in power consumption.