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Kick Heater not compatible with high-efficiency boiler?

sskraly Member Posts: 1
We are replacing a 25-year old cast-iron boiler + standard 50 gallon direct-fired hot water tank (rated 40 gal/hr recovery). Goal is more hot water (3 girls who like to take long showers, and we seem to run low on hot water after the first shower), quick recovery, and trouble-free heat. Got a quote for a Weil-Mclain GV90+4 + WM Indirect 40 gallon (might go to a ~55 gallon to get more hot water). Second quote was a Viessman B2HA-35 + Vitocell 53 or 79 gallon Indirect. Viessman is about 50% more expensive, but is more efficient (95% vs 90%?). However, we have a kick heater in the kitchen and the Viessman guy said that this might be a problem with the high-efficiency boiler, i.e. the system would have to run much hotter to turn on the kick heater, so this negates the benefit of the high-efficiency boiler. He said we should go back to baseboard but that's not an option.

Does this make sense? I think that the kick heater needs ~120 degree water to turn on. From a similar model: "For consistent response of the reverse acting thermostat, and effective outlet air temperature,
the average water temperature should not be below 120° F (49° C). Blower motor shuts off at
105° F (41° C) and will not operate until water temperature reaches 120° F (49° C)."

Will we have problems with the kick heater?

Any opinions on whether the Viessman is worth the much higher cost? Seems like it would take 10+ years to make up the extra cost.

Reliability: Viessman has a reputation as a higher-quality unit, but many people are telling me that ANY high-efficiency unit will be LESS reliable than a more conventional cast-iron design like the Weil-McLain.

Thanks in advance for any advice!


  • Aaron_in_Maine
    Aaron_in_Maine Member Posts: 315
    If you have baseboard heating the kick heater should not have a problem. Even with outdoor reset on the boiler the temp when it's cold outside should be enough to kick on the heater. The shoulder seasons are when it might not kick on.
    Aaron Hamilton Heating
    ahheating@ yahoo.com
  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited December 2015
    Need to change the aquastat in the kick heater. Most companies make low temp aquastats for them precisely for this reason. If its a Beacon Morris K42 or K84 Part # is KR02024-002 Kick will cut in at 110 degree water.

    Here's the deal with Vitodens.. The 200 sports Lamada Pro Combustion. Boiler will always operate at it's peak combustion performance which means less wear/tear. Also have a limited lifetime warranty on the heat exchanger. Warranty is pretty much the same as any cast iron boiler.

    While everyone is always caught up in using the AFUE difference in calculating savings it's really smoke and mirrors. Have to remember that Vitodens is modulating btu/hr output based on what's going on outside. That cast iron boiler is firing a fixed btu/hr rate each time it's fired. Nobody ever takes that into consideration.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
    Robert O'BrienIronmanHatterasguy
  • Ironman
    Ironman Member Posts: 7,373
    Go with the Viessman, you'll be glad you did in the long run.
    Another option with the toe kick if its zoned by itself: this creates a micro zone which can short cycle any mod/con boiler. If that's the case and you don't want to combine it with a larger zone, then you can have your installer do this: create a parallel loop off of the HYDRONIC loop of the indirect with its own circ that's activated by the thermostat for the toe kick. This way the micro zone has the capacity of the indirect for a buffer to prevent short cycling the boiler.
    We've done this regularly and it works great. I can post a diagram if you need it.
    If the toe kick is tied in with a larger zone already and you wanna leave it that way, then follow Chris' advice to the letter.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Gilmorrie
    Gilmorrie Member Posts: 185
    As mentioned by Chris, Beacon-Morris (and probably other manufacturers) offers a lower-temp thermostat for their kickers. I needed one for a heater installed at the end of a monoflo zone, and they sent me one at no charge.

    I have two Beacon-Morris units, and have been pleased with their performance. If installed under a cabinet, you need to cut a hatch in the bottom of the cabinet in order to provide access to the heater for maintenance and to clean the coils.
  • bob eck
    bob eck Member Posts: 930
    To get you best bang for your dollar get a complete heat loss on the home to put the right size boiler in. To get the highest efficiency out of your condensing boiler you need to have enough baseboard or cast iron radiators to run the boiler at low BTU input with low water supply temps. If you need to run high water temp 170deg - 180deg Supply water temp to heat the house because there is not enough baseboard to support a low water temp condensing boiler then I would go with a cast iron gas boiler. You could add baseboard to you system so you can run a low water temp condensing gas boiler. As other people told you check with the kick space heater manufactuer to see if they have a low temp sensor. There are all kinds of gas boilers on the market that is why you need to hire a competent Heating contractor and they can give you options on what boiler is best for your type of system.