High Efficiency Water Heater vs Boiler with Indirect

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BigfootC

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I heat my home, and get domestic hot water, with a propane fired Munchkin 80M boiler with a 45 gallon Superstor indirect tank. I have radiant floors which draw the heated water out of the Superstor via an injection pump with an outdoor sensor to control flow. The Munchkin only heats the water in the Superstor. System has worked well over the years. Unfortunately, the boiler has failed and is out of warranty so I am considering 2 different options: (1) replace the boiler and reusing the Superstor or (2) replace the Superstor and boiler with a high efficiency condensing water heater (Polaris). Which setup would you choose? I am especially interested in reliability and lifespan expectations as well as cost to operate.
 

Dana

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Getting to the right solution usually requires an analysis of the actual heat load. An 80K boiler would be pretty oversized for most homes, and with the SuperStor you might be able to down-size the boiler. How old is the SuperStor?

An HTP Phoenix Light Duty water heater might be a cheaper/better alternative to the Polaris, since unlike the Polaris it's specifically designed with combi space heating in mind, and can modulate down to 25,000 BTU/hr, making short-cycling less likely. I'm not sure if they have a propane version out there yet, but it's worth asking.
 

BigfootC

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The Superstor is about 14 years old. I did an analysis of actual heat load based on my annual propane usage and got 47,792 BTU is needed. I am heating about 4800 sq feet.

I will have a look at the HTP Phoenix Lite.
 

Jadnashua

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I think the SuperStor has a lifetime warranty, so if it isn't leaking, you could reuse it. If it is, you can probably get a new one but installation costs are not included in the warranty.

Do you have a separate WH for the home? It's generally not a good thing to use potable water as part of the heating loop unless you have a heat exchanger in there somewhere and keep the actual heating loop isolated.
 

BigfootC

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Yes, the Superstor does have a Limited Lifetime Warranty and it is not leaking. If I go for replacing the boiler I would reuse it. I use it for both DHW and heating the radiant floor water. There is a heat exchanger separating the floor water from the potable water .

Because the high efficiency condensing water heaters combine the tank and the heater they have a smaller footprint and in the case of Polaris fewer parts (no primary circulation pump). Has anyone had experience with Polaris water tanks? What is their expected lifespan. Are they more reliable than condensing boilers? Any negative experiences?
 

Dana

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The Polaris operates within a narrow temperature band from it's setpoint, and can short cycle in space heating applications. There are some well established hacks that involve pulling the control board and swapping electronic components to give it a higher differential range, violating the warranty. There isn't any thing particularly attractive about it from a space heating appliance point of view, other than it's condensing efficiency and stainless construction. A purpose made tank type combi heater or a Phoenix Light Duty set up in combi-mode would be an easier DIY.

Given that you already have a well functioning system that meets your needs, you'll probably be better off with another propane fired stainless heat exchanger mod con like the W-M ECO-70 or similar, which has a comparable high-fire output to the Munchlin 80M and somewhat wider modulating range. There's no point in re-defining the whole world here.
 

James Flores

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Replacing your old boiler with a new efficient one can save you hundreds of dollars. When planning to replacing your boiler, it is important you make the right decision. We were also having some boiler related issue and thought if we would have to replace it but when got it checked by the heating repair service Morristown NJ, it was not the time to replace it.
 

Jadnashua

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FWIW, some boilers are quite efficient, some can approach 98% during heating modes, and don't take much of a hit while heating an indirect. Older boilers that can't be cold started, that need to run hot all through the summer may be better for economy with some other way to heat the water for bathing. Even in the winter, my boiler might cool off to nearly room temperature in between calls for heating, whether that is space heating or water tank, so it does not have huge standby losses.
 
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