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Out dor reset system design

Lee_3 Member Posts: 17
what are my mod con choices for a 1500 sq foot 35 - 40 year old house, in southern NH. I supect that Vitodens is out of my price range. I would need something that could modulate well below the 50,000 max I would need on design day.

Given the old bang bang over sized sytem. My objective is to save money and increase comfort. It is starting to sound like I may want to consider a basic CI unit with Out door reset and either an indirect or on demand HW heater. I susupect this would save more than the mod con and current HW heater.

You guys are a great help.


  • Lee_3
    Lee_3 Member Posts: 17
    Outdoor reset system design

    What components are in a well designed basic outdoor reset system for two zones of fin tube on 2 floors of 750 sq feet each?
    Lets say my pro uses one of the new Burnham SCR gas boilers as the basis, what other components and controllers are needed? Some of you have mentioned the Teckmar 260 as the reset controller will a mixing control also be required or is that integrated into the 260?

  • ALH_4
    ALH_4 Member Posts: 1,790
    Tekmar 260

    The tekmar 260 resets the boiler directly. There are piping and wiring diagrams in the tekmar 260 data manual. There is no need for mixing because any cast iron boiler can be reset within the range that hot water baseboard functions. It also provides DHW priority. You can, but do not have to, use one indoor temperature sensor and an occupied/unoccupied switch to set the boiler temperature back when you are not home.

  • Brad White_113
    Brad White_113 Member Posts: 4

    You can save even more fuel by using a 4-way mixing valve or primary/secondary injection and dividing/separating the boiler and radiation circuits. This way you can reset the boiler within it's limits to protect it but also go deeper on reset on the radiation side.

    If you just reset the boiler temperature, you may find that the boiler is over-sized as so many are. The minimum temperature to protect the boiler may well be close to the temperature you need to heat your house on a design day. You cannot set your temperature lower so your savings range is reduced.

    I suggest you perform a heat loss calculation and radiation inventory to find out what temperature supply water you will need. From there you can make a more informed decision. Personally, I think it is worth it to use deeper resets.
  • Lee_3
    Lee_3 Member Posts: 17
    I have measured the length of fin tube per room...

    I have measured the length of fin tube per room, took off the covers and measure actula fin length. I will convey this to the pros comming in to estimate the job. I was under the impresion that going the mixing route would allow lower temps and more savings even . My question is what controls this device? Is the Techmar 260 enough or do I use another type of controller/ model.
  • ALH_4
    ALH_4 Member Posts: 1,790
    Mixing Valves

    A Tekmar 260 resets the boiler only. With the cost of a control, valve and actuator for a mixing valve setup it may be more economical to go with a modulating condensing boiler. The hot ticket for a mixing valve setup is the Dekamatik-HK1 universal from Viessmann. However just the components for the mixing valve setup are going to cost 2/3 of what a decent condensing boiler would. What I found when quoting systems was that either it ended up being a simple cast iron high temp system or a modulating condensing boiler. The mixing valve setups brought the prices very close together. There is generally more labor associated with a mixing valve system than with a condensing boiler.

  • Weezbo
    Weezbo Member Posts: 6,232
    Taco makes a handy 4-X mixing valve,

    called an iI series R i have only used the 1" however they have one larger at the 1 1/4" size and one smaller at the 3/4" size.

    to day i went in to see about ordering a few more 1" and a couple 1 1/4". it hs its own controler with out door reset might look at it at least, on TACO's web site.

  • Joe Mattiello
    Joe Mattiello Member Posts: 703

    I provided a link to the Taco radiant guide for reference. This will give you some great ideas, and Enlighten you of all the products available for radiant system using outdoor reset.

    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
  • Dennis
    Dennis Member Posts: 101
    The length of fin tube is not a good guide sizing a boiler,

    most installers put convector in every inch of cover. This way the corner bedroom that measures 8x10 has 18 feed of convector, the bathroom, and kitchen have almost none. The living room is usually good for 25 feet. The house has 250 feet of convector, and an actual 40,000 btu of loss.
    What you really need to do is match the convector to the heat loss for each room, and size the heater to the actual load. If you home was piped in this manner you would not need any zone controls.

    Looking at the future of energy costs, I would go for a modulating, condensing boiler, most come with temperature reset included. A cast iron boiler, and a Tekmar controller is about the same price as a Munchkin boiler look at the T-50 wall mount, you would have to install their reset controls, which are cheap in comparison. If you go Munchkin have a "Vision" (factory) certified installer put it in, as he can install the controls which a non certified installer cannot buy.

    I resently installed two Munchkin 80K boilers in two 3500 square foot twin homes (each share one party wall)each house has an indirect 45 gallon, and two hot water coils in the cooling duct systems.
    One house has a zone of convector in the basement, and a 8 gpm shower spa (developers house). His house has a mixing valve on the 45 gallon tank with storage temperature set at 175 degrees.
    All the competition said it wouldn't work as did the gas utility.
    Well they were all wrong, another amazed customer.

    The competition wanted to install 3 condensing gas furnaces totaling 200,000 btus, and a commercial 75 gallon water tank in the developers house. There is more than one way to beat the competition, and that is good.
    Just do it, right.
  • ALH_4
    ALH_4 Member Posts: 1,790

    In my opinion......If it comes down to the choice between the indirect and a condensing boiler, I would lean toward the cast iron boiler with a tekmar 260 and an indirect. It doesn't hurt to get a quote both ways. Some of the new condensing boilers are priced pretty competitively. Whatever you do, definitely get the indirect water heater.

  • Rollie Peck
    Rollie Peck Member Posts: 47
    Outdoor reset

  • Rollie Peck
    Rollie Peck Member Posts: 47
    Outdoor reset

    Hi Lee:

    I recently replaced my 40 year old cast iron boiler
    with a new Viessman boiler, Viessman 4-way valve and
    controller, primary/secondary pumps and a buffer tank.
    By far the most valueable part of the project was a
    knowledgeable contractor!!!!
    He let me do the piping and wiring, but he decided on
    the parts to use, how to use them, inspected everything
    before start up and tested for proper combustion and
    operation after startup.
    If you want to do something similar, find a contractor
    that is knowledgeable and willing to work with you to get
    a safe, economical and trouble-free heating system.
    Be willing to pay for his time, knowledge and effort,
    and a fair profit on the parts. Treat him like you would
    want to be treated.

    Rollie Peck

  • Jed_2
    Jed_2 Member Posts: 781
    What good

    is a Mod/Con connected to fin tube baseboard? How often is that boiler going maximise it's efficiency, given an existing total length of fin tube? In a northern climate, that boiler's not gonna want to condense to meet the heat load. How does a Mod/Con match a fin tube system?

  • ALH_4
    ALH_4 Member Posts: 1,790
    The con might or might not

    but the mod part will do something. Plus they are sealed combustion. With the price of the components and labor to do much with a cast iron boiler, some of the modulating condensing boilers arent far off. Take a sealed combustion cast iron boiler and add a tekmar 363 and you could almost have a 24/32 Vitodens 200.

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