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Homeowner with outdoor reset question

Eric_8
Eric_8 Member Posts: 66
I'm located on the New Hampshire seacoast and have a four year old house, 3500 sq ft. Standard or better insulation, weatherproofing, tightness, etc. 5 zones - 4 with fin tubed baseboard, 1 with a Beacon Morris horizontal heating unit (for the basement). All 5 zones use Taco 3 wire zone valves. One Taco cartridge circulator pump handles all circulation. There are programmable thermostats on two of the zones with 4 degree setbacks on each.

Heating equip consists of: Burnham model PV714 boiler with a Beckett model AFG burner. I have a Honeywell R4184 Protectorelay Oil Primary Control that is installed on the burner and a Honeywell L8148 Aquastat installed on the boiler which fires the boiler and turns on the circulator pump when a thermostat calls for heat. Also have a superstore tank for domestic hot water with a Honeywell thermostat.

I spent about $1750 on heating oil last year (very cold winter, I'm told - I'm new to New England) and look to spend about $2000 this year.

I am interested in outdoor reset controls but am unsure: a) how much of my current control equip I would have to scrap, b) how much oil/money I might expect to save, c) how much comfort I might gain. We are not uncomfortable now, though one zone can sometimes be a bit noisy when coming up to temp.

I have checked out Taco and Honeywell controls on line. Recommendations? I would like to do the work myself any pitfalls?

Thank you. This forum is really great and I appreciate any comments.

Comments

  • Jay_12
    Jay_12 Member Posts: 46
    tekmar

    Consider using a tekmar Boiler Control 260. It provides outdoor reset to the fin tube convector zones, logic for operating the DHW tank, and has outputs to zone the boiler and DHW pumps.

    A) The 260 is compatible with all equipment listed and would simply require changing a few wires.

    B) Independent studies have shown outdoor reset to save on average 12% on fuel.

    C) The rate of which heat is delivered to the room is more constant, resulting in improved comfort.

    Please check the tekmar website products section for more information: www.tekmarcontrols.com

    Jay www.tekmarcontrols.com 250-545-7749
  • steve_73
    steve_73 Member Posts: 1
    outdoor reset

    I am a homeowner who, seven years ago, installed an outdoor reset controller myself in my fin tube baseboard system. It is easy for someone with basic wiring knowledge and skills.

    I used an Erie Boiler Boss 2400 controller, http://www.invensysbuildings.com/pdfs/F-27015-1.pdf . This control offers outdoor reset with either a 15° or 30° differential, and indirect priority. As I recall, you keep the primary control and the indirect aquastat. The Boiler Boss 2400 has worked well for me. Installation and operation instructions are easy to understand.

    I think that you will need a mild winter and/or outdoor reset control to meet your spending goal. Last winter wasn't particularly harsh in southern New England, and fuel oil is about 40% more expensive this year.


  • I'm with Jay. These controllers can easily pay for themselves quickly, especially on larger systems.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Eric_8
    Eric_8 Member Posts: 66


    Thank you for the comments. The Tekmar 260 sounds like the ticket. A couple of questions: My DHW (superstore tank) runs on the same pump as the 5 zones of heat. It has a Taco 3 wire zone valve connected to the Honeywell aquastat. Jay you referred to pumps each for the boiler and DHW. Do I need to install a separate pump for my superstore tank to make the DHW priority override work on the Tekmar? I currently have two transformers (three zone valves per, total of 6 zone valves). Will I need another transformer?

    Thank you.
  • Jay_12
    Jay_12 Member Posts: 46


    Hello Tom,

    I would recommend you move the DHW aquastat wires from the Taco zone input to the 260 DHW demand input (DHW demand needs to be powered! and needs 2 VA). The connect the 260 DHW valve input to the Taco DHW zone input. This will keep the DHW priority without having to change any mechanical equipment.

    As for the transformers, you have to check the VA rating on transformers and then add up all the VA loads of all connected equipment.

    Please call if you have any questions.

    Jay www.tekmarcontrols.com 250-545-7749

  • psd_2
    psd_2 Member Posts: 3
    Study before making a decision

    Tom,

    I also live in NH and have a new unit with outdoor reset control. There are some things to consider before you make your final decision.

    Outdoor reset can get tricky when also using T-stat setbacks. Depending on your heating curves, they may be sufficient to maintain temperature, but may produce long recovery times when transitioning between night/day temperatures. You may be able to overcome this by letting the control perform the transition rather than the T-stat.

    If you let the control perform the transitions and keep the T-stats fixed, then you most likely would be running in constant circulation when on the night time heating curve. The boiler can not satisfy the T-stats on the reduced heating curve. I personally don't prefer constant circulation as there is a constant circulator hum that can be heard through the fin tube baseboard. Others are strong advocates of constant circulation, particularly due to the comfort factor (smoother heat). Some are also advocates of fixed temperature (no setbacks at all boiler/T-stat). If you can afford it and think the environmnet can afford it, then it would provide the maximum comfort.

    There will obviously be $$ saving due to reduced standby losses. The amount of the savings will depend on how you run the system. If you have family at home all the time and can't take advantage of setbacks, or don't bother with setbacks, then the savings can be significant. On the otherhand, if you're away more than at home, and can use setbacks for reasonable durations, but need/want quick recovery, then there are other tradeoffs and/or less gain.

    I am trying to balance outdoor reset with use of moderate setbacks but require reasonable recovery times ... because schedules are not very predictable. It's proving to be challenge. Use of a controller capable of a room sensor can help. In this case the room sensor works with the controller to close the feedback loop and can provide the best of both worlds. It's best used when there is clearly one dominant zone as all the others go along for the ride.

    Other considerations -

    Outdoor reset can lead to more issues with condensation in chimney and/or breaching/boiler due to the lower boiler operating temperatures. This is particularly true in the milder months. Many of the new boilers are designed for this, but some don't take too kindly to it, and quickly scale or soot up. Condensation in chimneys can be a real issue and can quickly lead to breakdown. Use of a properly sized SS chimney liner helps maintain heat and proper draft and prevents masonary corrosion. Maintaining proper draft to prevent exhaust oders can also be an issue. Using a cool/cold outside chimney (even with a liner) when firing an efficient boiler at lower temperatures can produce oders until a good draft is established. This can be compounded when/if flue gases condense in/near the breaching.
  • Eric_8
    Eric_8 Member Posts: 66


    Jay, Thank you. Very helpful and I may just give you a call.

    Steve, Thanks, also. With regard to thermostat setback. I can do without if savings are greater with outdoor reset. I'm using setback primarily to save money. If I can save more with outdoor reset and get a little more constant comfort, so much the bettr. The only qualifier to that is the upstairs zone, which we like to keep 4-5 degrees cooler in the evening for comfort and better sleeping.

    Someone is usually home a lot. I work out of the home and my wife stays home with our two young children. If I understand you correctly, that means we are likely to save with outdoor reset.

    Thanks, again.
  • psd_2
    psd_2 Member Posts: 3


    Outdoor reset would be appropriate for your "mostly" at home life style and should provide comfort as well as savings. Just don't overlook the other considerations. These are real issues and could lead a bigger investment and longer payback period.
  • Bill Nye_2
    Bill Nye_2 Member Posts: 538
    Optimum Start

    PSD, The Tekmar control when used with the tekmar RTU's can give you optimum start. It will allow a quicker recovery . Reduced water temperature, what are we talking 30-40°?, should have very little effect on the flue gas temp. Unless you have a modulating boiler the flame is the same. It don't know for nothing, it's just on or off.

    I know what are you saying about your reset and recovery, same as the other thread, BUT it doesn't have to be so hard. I know you want your bedroom cooler. I do too, I have mine on a zone with a zone valve and a t-stat just for the bedroom. Do you need the room to recover in the day time? I'm never home so I leave the night setting of 4-5° cooler than the rest of the house all the time. Set it and forget it. {Ronco}

    You're already saving a ton of bucks with the reset because you are matching the supply to the load. You are replacing the heat at the same rate at which is being lost to outdoors. I'm trying to tell you to lose the damn t-stats. Most controls will reset the water temp for the night or unoccuppied mode. You reset the water another 10 degrees or so [you decide] and it will let the house be cooler, yes, no ??


    Let me think about it , maybe I can try to paint a clearer picture.
  • psd_3
    psd_3 Member Posts: 86


    There's a lot more to it than ON or OFF.

    Flue gas temperature IS an ISSUE. There are many threads that discuss the cons of cold start and PIN type boilers just for this reason (significant scaling). I agree with you that on cold days it is not an issue as the boiler never cools now by more than 30° or so and the boiler is sitting above the critical flue gas temperature. However, on mild days you're looking at repeatedly firing into a boiler core that may be 90-110 degrees F. The flue gases are further cooled by the efficient heat exchanger. Here condensation and scaling/sooting would be a real issue if the equipment isn't designed for it (even with pump logic to prevent the circulators from running during these mild starts).

    Also, this moisture with a high sulfur content produces sufuric acid which eats at masonary chimneys. A whole industry of liner manufacturers with fancy alloys 316-Ti, AL 29-4C has grown out of this quest for greater efficiency. Their purpose is to handle condensation and maintain draft in the adverse environments created by low-temp firing with increased heat extraction.

    The heating industry is also very concerned about managing adequete draft under these considitions. Poor draft = poor combustion = poor efficiency = increased scaling, sooting, and increased emissions.

    The never ending quest for more energy out of every drop comes with a whole host of interesting complexities and issues. My point is that it's not a plug-and-play deal, and Tom should investigate some of the side-effects and trade-offs before leaping in.
  • Bill Nye_2
    Bill Nye_2 Member Posts: 538
    Yeah but

    were talking about houses here, not commercial buildings. Your heat loops have a finite amount of water content, 10 or 15 gallons at the most. Unless you have 2" iron pipe and Huge cast iron rads. The boiler/burner is going to get up past the condensation point pretty quickly.

    A better way might be a 3 or 4 way valve or injection. You could run your boiler a little hotter and still maintain a lower system temp.

    What I like about constant circ is the flywheel or inertia effect. Once you pay to heat up the pipe and fittings and heat emmitters and objects in the house I just feel it makes more sense to keep it warm than let it cool off only to have to heat it again next cycle.

    I have a Viessmann Vitola so low return temps have no affect. When you are in a temperature zone where you need low output at the heat emmitters there is not much demand on the boiler. The Vitola has a little more water content than some boilers so it runs longer when it runs and is off for a very long time when the pump is circulating the heat.

    The trick is , dialing in your curve and tweaking it to it is just right. Even then....... tonight I admit I turned my parallel shift up about 5°. It is 3° F outside and my living room felt cool. When the temperature outside comes back to normal I will set it back.

    But I still say the oil burner burns oil at X °F, the thermal efficiency of the boiler stays fairly constant [until it soots up] If we vary the water supply temperature 20 or 30° it should not have a great influence on the flue gas temperature. The thing is you need a long enough burn cycle to get above dew point. As with the low limit control, 120° is not such a crime because the boiler will get above that rather quickly.
  • soot_seeker_2
    soot_seeker_2 Member Posts: 228
    tekmar 256 - external components recommendation

    hi,

    i have a separate (oil) hw heater with it's own gun so i'm planning on putting in a tekmar 256 for the boiler. this control requires an external dry closure via an aux relay from the line voltage 'call for heat' and a 24v supply for the T-256 itself. are these 2 components convienently available together in a control box of some sort or do you typically purchase them separately & mount the relay & xfmr in a separate box? i'm curious as to what you recommend parts-wise for this or what you typically use.

    thanx,
    ss
  • psd_3
    psd_3 Member Posts: 86


    Bill,

    You have an appropriate system, which is specifically designed for this type of operation. Is your chimney lined with AL 29-4C or at a minimum 316-Ti? If not, you should periodically check for signs of condensation damage.

    On cool/mild days, my Buderus with a 5" lined chimney, will produce a plume of water vapor at the cap for 2-3 minutes. It starts to dry out when the stack temp approaches 300F. Stack temp tops out at ~340F. Many of my heating cycles will only last for a few minutes, the time between Hi/Lo differentials. Reaching the dew point 25-30' up the chimney doesn't always happen. It is most noticable when my boiler is operating at low temp.

    I know folks with similar systems who are now either lining their chimneys, or are rebuilding them due to condensation damage. Buderus and Viessmann recommend chimney sizes that match breech size, and many of these are 5" now.
  • Jay_14
    Jay_14 Member Posts: 39
    256 or 260

    Hello,

    The 256 is the basic outdoor reset control from tekmar. The 260 is the next level up. Basically the 256 requires a dry contact to provide a boiler demand signal whereas the 260 requires a 24 Vac or 120 Vac signal. The 260 has additional features such as DHW pump / valve logic and an indoor sensor input.

    Jay www.tekmarcontrols.com 250-545-7749
  • soot_seeker_2
    soot_seeker_2 Member Posts: 228
    Jay - can you help answer this?

    Jay - can you help answer my previous question about the 256?

    are the 2 components (24v xfmr & 120v relay) convienently available together in a control box of some sort (any namufacturer) or do i typically purchase them separately & mount the relay & xfmr in a separate box? i'm curious as to what you recommend parts-wise for this or what you typically use. white-rogers, etc? any recommended parts?

    thanx,

    ss

  • Jay_12
    Jay_12 Member Posts: 46
    components

    tekmar carries a 24 Vac coil relay part number is 003. There is also a 120 Vac coil relay part number is 004. tekmar does not sell enclosures or transformers.

    I generally recommend using the 260 over the 256 simply because all the wiring is done for you in the 260. The 260 has a built-in contact for the system pump. The 260 is powered using 120 Vac so it doesn't necessarily require a 24 Vac transformer.

    I think this answers your questions. If not, please give us a call at tekmar customer service: 250-545-7749. We are open 7:30 to 4 Pacific Time.

    Jay
  • Ron Schroeder_2
    Ron Schroeder_2 Member Posts: 176


    Hi Tom,

    I personally prefer the DHW indirect on it's own pump for flow reasons. To get the maximum recovery from an indirect, they usually need more flow than what a "007" will pump thru a zone valve. On my own system, my indirect is plumbed with 1" pipe as directly as possable and has it's own Grundfos UP15-42 pump that is about the same flow as a 007. All the heating zones are on a seperate pump with a flow that is less than a Grundfos UPS15-58 on it's lowest speed.

    I am not saying that you need to re-pipe your indirect, but I would like you to be aware that there is more capacity if you need it.

    Ron
  • Eric_8
    Eric_8 Member Posts: 66
    Chimney lining

    OK, a little slower for us homeowner newbies. My chimney is 4 years old, clay lined. PSD, are you saying this may not be satisfactory and I should look at a 316Ti (which I assume is some kind of stainless liner?)? Sounds expensive. I'm trying to save money, but I don't really feel like burning my house down or ruining my boiler. Is this really a serious concern?
    Thanks.
  • psd_3
    psd_3 Member Posts: 86


    Tom,

    There are a number of considerations here -

    It's not likely that you'll burn your house down anytime soon. However, over time any condensation that forms inside the chimney, as a result of reduced stack temp and/or shorter burn cycles, will eat away at the masonary. This could cause damage that would ultimately degrade the integrity of the flue and chimney.

    There are a number of factors involved that lead to this being a real concern, or not -

    Is it a cold chimney (typically outside chimneys are)?

    What is the size of the flue and height of the chimney and dimensions of the breeching?

    What is the BTU load and steady-state efficiency of the heating appliance?

    You can see what some of this mean in NFPA31, or excerpts found in this liner sales literature:

    http://www.protechinfo.com/pdf/1153.pdf

    Ultimately, it all boils down to proper drafting and sufficient temperature inside the chimney to prevent sustained formation of condensation. The older PIN type boilers never had such a problem because they'd run stack temps of 500+ F degrees. Efficient modern boilers running with lower core temps produce stack temps closer to 300F. Here condensation can be a real concern. If you have doubts about your specific situation and/or want some professional advice, I'd recommend that you talk to some chimney contractors in your area.

    The Burnham V7 is a PIN type boiler, but I'm not sure what its efficiency rating is ... probably mid 80's. You may be ok here if you're not down firing it and keep your stack temp reasonable. The folks at Burnham could probably give you some guidance as well.

    Also, check out some of the other threads dealing with "condensation", "PIN boilers", and "liners" on this forum.
  • Tom_58
    Tom_58 Member Posts: 4
    Outdoor reset with Burnham v7

    I'm dredging up this old thread because, I started it almost a year ago and have one additional question. I am about to buy the tekmar 260 control to take advantage of the outdoor reset features but wanted to make sure I wasn't trading some efficiency gain for a bigger potential problem with thermal shock (low temp return) in my Burnham V7 series which, I am learning, may have been a little prone to leaking. Not slamming the Burnham at all. I've had nothing but good service out of it for almost 5 years, just don't want to make a mistake now.

    I'm capable of doing the wiring on the 260 myself, but if I need to include 2 or 3 way mixing valves, etc. then any fuel cost savings gets eaten up pretty fast with additional plumbing/boiler work which I don't feel comfortable doing myself.

    Any thoughts? Thank you.
  • Ron Schroeder
    Ron Schroeder Member Posts: 998


    Hi Tom,

    Thermal shock is not cold water return, rather it is the DIFFERENCE between the current boiler temperature and the return water temperature. Proper boiler piping and boiler min settings on the 260 will prevent thermal shock and condensation.

    Ron
  • Joe Brix
    Joe Brix Member Posts: 626
    The 260

    has a min boiler temp for the reset which you could keep at 140°. You'll probably wire up to the current aquastat which could still maintain minimum boiler temps. If you're not using an indirect or plan on getting one in the future, you may not want to bother with the 260 and get the 256.
  • Tom_58
    Tom_58 Member Posts: 4


    Ron,
    Thanks for the reply and the clarification. Then, if I understand you, assuming everything is plumbed, wired and adjusted properly, I should be fine using the tekmar 260 with what I have?

    Thanks
  • Tom_58
    Tom_58 Member Posts: 4


    Joe,
    Thanks. I do have indirect DHW (40 gallon Superstore tank with a honeywell aquastat), so I'm looking to the 260 to make it all work.
  • Ron Schroeder
    Ron Schroeder Member Posts: 998


    Hi Tom,

    Should be fine. What is your fuel type? Different fuels have different minimum safe boiler temperatures.

    Ron
  • Tom_58
    Tom_58 Member Posts: 4


    Ron,
    I use #2 heating oil.
    What would a good, safe min. boiler temp be for my set up?

    Thanks,
  • Ron Schroeder
    Ron Schroeder Member Posts: 998


    Hi Tom,

    Oil combustion products condense at a lower temperature than gas, around 115 degrees so you should have the true boiler minimum above 120. If I remember corectly, the 260 allows the boiler to go 1/2 of the differential below the "boil min" setting so don't forget to add 1/2 of the differential to 120 to get the setting for "boil min"

    Ron
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