Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Efficiency: Combi Core Vs. Boiler and DHW storage tank?

I'm building a small house in Seattle.   The hydronic heating shop looked at the plans and sized the system, and says I can either use a combi core or boiler and dhw storage tank.   He's pushing the boiler/dhw tank.    Which system will use less energy?   To me, it seems the combi core would be more efficient, as the domestic hot water doesn't have to travel a few feet and sit in its own little tank, cooling down all the while.   I know for sure which one will cost more:  the boiler.   And another thing, how come in Seattle I have to add an external low water shut off switch when there's already one installed in the boiler?  

On my way out the door I saw a wall-hung combination boiler and on demand hot water heater.   Seemed pretty great to me.   Anyone know about these things?   I'm guessing you don't put them in mansions in Miinnesota, but for a small Seattle house?  

OK, enough questions for now.  

James Barnett


  • Selection

    The boiler is more expensive until you figure the replacement cost of the CombiCor boiler.  All the ones I (and many others) installed fail at the heat exchanger within the first few years. I'll be in San Francisco next week to replace one with a regular water heater and an external heat exchanger (Taco X-Pump Block).

    I've had very good luck with the Triangle Tube Excellence combi boiler:


    And talk to Paul Pollets; he's in the Seattle area and know his stuff.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
This discussion has been closed.