Hybrid v. Indirect v. Buffer Tank

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joehello

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I have a Burnham Boiler (oil fired, Model # 4WFH) about 10 to 15 years old. The hot water is heated by a tankless coil. The hot water isn't very hot because the mixing valve has stopped working because of mineral deposits. Before the mixing valve seized up there were issues with having enough hot water for a bath, etc.

It costs $350 to fix the mixing valve so I've decided to upgrade. I'm trying to decide between a new hybrid heat pump electric water heater (ie. http://www.geappliances.com/heat-pump-hot-water-heater/), an indirect water heater (http://www.radiantheatproducts.com/store/cart.php?m=product_detail&p=389) or a buffer tank (see in brochure....http://www.htproducts.com/literature/lp-81.pdf).

What's my best option? Which will be cheapest to buy, install and operate? Which option is most efficient and cheapest to run? Do I even need an indirect water heater or will the buffer tank be enough? Who makes good indirect hot water heaters and/or buffer tanks? how much should the installation charges be?

How much it will it cost per year to run the indirect water heater or buffer tank?

Thank you
 

Jadnashua

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An indirect during your heating season would probably be the most economical, but with an oil fired boiler, you'd have to worry about cold starts for the rest of the year. I'd guess, you really don't want to keep the boiler running 24/7/365. What might work out is to buy an electric WH that has a solar heating connection, and use that to the boiler. Turn the electric off during the winter, and only use the boiler as the heating source. Come summer, shut down the oil fired boiler and switch on the electric elements.

See what others think.
 

Dana

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The annual operational cost of a heat pump water heater in heat pump mode will be slightly more than, but comparable to an oil boiler + indirect, at 25 cents/kwh and $2/gallon heating oil. At an EF of 2.2 you get about 7500 BTU per kwh into the water, which is about $33/MMBTU. An indirect will deliver maybe 60% efficiency in winter, 40% in summer (if you're lucky). At 60% , with 138,000 BTU/gallon you're looking at 82,800 BTU/gallon, or about 12 gallons/MMBTU, which at $2/gallon costs you $24. But at 40% efficiency that's $36/MMBTU, more expensive than the heat pump water heater.

If you never expect heating oil prices to go above $2/gallon, that might be the economic choice. But you'd have to be drinkin' the frack-water to believe $2 heating oil will be the average over the lifecycle of the indirect. I expect you'll see $4/gallon oil within 5 years, but I'd be surprised to see 50 cent electricity. (At 50 cents/kwh that power would be more than 3x as expensive as rooftop solar power at 2015 pricing, even without solar subsidies!)

The new GE GeoSpring is much improved over the early versions (which you may find 10,000 negative reviews about online), now that it is several revisions into the design, and production has moved to Kentucky rather than the disparate Asian facilities. It's a bit loud- don't install it under your bedroom if you're sensitive, but it's not as noisy as a window air conditioner. Installation cost wise it's no worse than an indirect- probably cheaper. (Depends on how much DIY you're into.)

The recovery time in heat-pump-only mode is pretty slow. If you're looking to run 3-4 six to eight minute showers back-to-back it could be an issue, but there may be other solutions depending on your family's bathing habits. (A $600 drainwater heat exchanger would double the showering performance at no additional power use, but wouldn't fix tub-filling issues.)

A buffer tank does absolutely nothing for domestic hot water performance, but can be useful for quelling a system that is short-cycling the boiler on zone calls.

When not using the embedded coil in the boiler you are now free to run the boiler over a wider temperature range, with a lower low-temp, which has the potential to reduce the oil use well beyond the amount was needed just for hot water. A heat-purging retrofit boiler control can make that nearly automatic, and limit the short-cycling potential as well.
 
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