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Boiler Question

Ken_40
Ken_40 Member Posts: 1,320
"Domestic priority" - may we assume you have an indirect domestic hot water maker, driven off a dedicated zone of the heating/boiler system?

If so, all's well - as is!

And no; all boilers are capable of going from ambient to limit all the time. There is no "thermal shock" per se, anymore than your coffee pot at ambient having 212F coffee/water drop into it every morning. Boilers are designed for that event, repeatedly.

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Comments

  • Roland_6
    Roland_6 Member Posts: 8
    Boiler question

    Hi All,
    First off I want to thank you gentlemen(and if so,ladies) for your terrific help. As I've said preveously, I have a new Burnham PVG-4 Boiler. I have re-printed the installation manual and read it through a few times. Some information I cannot seem to find. What determines the boiler low temperature setting? At this time the heat function on the thermostat is turned off and only the DHW priority is active. When DHW is called for, the burner runs till the supply temp reaches 156*. When DHW is satisfied, the supply temp slowly drops to less than 100* sometimes as low as 70* if no DHW is called for,for an extended period of time. Does this not put a thermal strain on the boiler elements? Not to mention condensation?Also, when the heating season does start ( hard to imagin as the outdoor temp has been in the mid 80's for days in the New York City Suburbs no less). What will keep the boiler supply temp above the condensation point of approximately 135*? And how will my plan of installing and Out Door Reset affect the boiler operation
    Thanks again,Roland
  • Aidan (UK)
    Aidan (UK) Member Posts: 290
    There is no low limit

    on this boiler. A low limit is typically found on boilers that have a tankless coil. It's used to maintain a minimum temperature in the boiler so when there is a demand for hot water, it will heat the flow of water through the coil.

    As far as the temperatures your citing, there is thermostatic switch (aquastat) on your indirect that senses the water temperature in the tank. When the tank water temp drops below a certain value, it tells your boiler to turn on and send hot water into the indirect to reheat the water in the tank. Once this switch is satisfied, it turns off your boiler.

    Based on the temperature readings you are giving, I assume your reading the tridicator gauge (temp gauge on the boiler). Your indirect is very well insulated. Depending on conditions, it will usually lose approx 1/2 - 1F per hour. If there is no call for hot water, the indirect tank may turn the boiler on 2-3 times a day for a few minutes.

    The boiler and connected piping is not insulated like the indirect, and it can lose temperature much more quickly. That's why you saw temps as low as 70 but the indirect, being well insulated, still had sufficient hot water stored inside and did not turn on the boiler.

    It really doesn't strain your boiler. Just because your boiler is sitting at 70 or 90 degrees is not a concern with respect to flue gas condensation unless it was on.

    Flue gas condensation occurs when the flue gas come in contact with the cool surfaces in your chimney and vent piping. Two of the byproducts of combustion, sulfur dioxide and water can mix together forming an acidic condensate which will attack all the surfaces it comes in contact with including the boiler itself.

    The more efficient the heating appliance, the lower the flue gas temperatures. The lower the flue temperature, the higher the potential for condensation to occur. This is why your boiler vents with stainless steel. Having the boiler sit there, not operating with a temperature under 135F does not cause this to occur.

    When your boiler fires up, the return temperature will be a function of several conditions - the high limit, gpm, system efficiencies, heating load, heating cycles, stack temperature, etc. The condition you are trying to avoid is called sustained flue gas condensation - a situation where the flue gas temps are so low, condensing occurs on a continual basis.

    Think of the tail pipe of a car. Ever notice in the cold weather, when the car has been running for a minute or two - the liquid dripping out of the tail pipe - thats condensation. But once the car is running for a while and the engine and exhaust pipes warm up, this goes away. Same thing for your boiler provided the flue gas temperature stays above the dew point of the exhaust gasses.

    If your using an indoor outdoor reset with this boiler, the curve will have to be set such that sustained flue gas condensation doesn't occur. If you had a condensing boiler, designed for condensation, you might be able to have the low point of your reset curve at around 90F if you have radiant heat. You need to look at your radiation loads to know how to set your reset curve. Your contractor should be able to help you with this.

    Hope this answered your questions

    Good luck

    Glenn
  • Roland

    As others have already stated, when a call for heat is encountered from either a zone of heat or the Indirect Water Heater, the boiler will turn on and fire up to the boiler's desired high limit setting. If the gauge reading you are seeing is the hottest the boiler is getting on the supply outlet, then either your boiler aquastat is set too low or the temperature gauge is a bit off. The boiler high limit should be and is most often set for 180°F to 190°F. You can check the setting by looking inside the boiler vestibule. You will see a control on the control panel with a silver wheel type dial with numbers. The setting opposite the pointer at the top should be set at 180°F to 190°F. The wheel will have a small semicircular bumpout on its rim at the 190°F setting.

    While the burner is operating, you should expect to see it shut off when it reaches its high limit. The control has a fixed 15°F differential meaning it will stay off and cool down 15°F to approximately 165°F if it were set for 180°F. At this point you will hear it fire back up but the fan-proving and ignition sequence of this boiler takes about 45 seconds. During that time you could expect to see it drop down to 155°F or so and then swing back on up again. My advice would be to get your installer to check those settings and correct them. Operating the boiler at constant temperatures below 150°F can breed excessive flue gas condensation which may prove to be detrimental to the life of the boiler in the long run. When there is no call for heat the boiler simply does not run. This is referred to as "Cold Start". Depending on how long your "Off Cycle" is, you could expect to see it cool down to ambient room temperature if it stays off long enough. Hope this helps.

    Glenn Stanton

    Manager of Technical Development

    Burnham Hydronics

    U.S. Boiler Co., Inc.
  • Roland_4
    Roland_4 Member Posts: 84
    Burnham PVG-4 Boiler Question

    Thank you to all who have responded to my questions. I greatly appreciate the in-depth answers. I have stated in a previous post that my new boiler came installed with a Argo ARM-2 switching relay with prioity. My aim is to have installed the companion DPM2 outdoor reset control.What will keep the ODR control from allowing the boiler to operate below the condensing temperature assuming it's function is to adjust the water temperature based on outdoor temperature. In other words, what sets the minimum temperature using the ODR control. I have limited knowledge of heating systems and prefer to leave this work to experianced (and licensed/insured)professionals. I would like to educate myself as much as possible as to the finer points of the systems operation. Roland.........
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    Essay Tekmar

    The concepts outlined in this attachment apply to ODR. Even though you have the Argo version, this may help you understand the functionality better.

    I've also given you a chart with different ratios so you can see the effect of your settings with the ARGO control.
  • Roland

    My advice would be to not use the Argo Reset Control due to the fact that it has no provision for Minimum Boiler Supply temperature settings. The Tekmar based controls such as the 260 tekmar and Taco PC700 do have Minimum Boiler Supply settings and therefore will provide protection for the boiler regarding possible flue gas condensation. Operating below 140°F for prolonged periods of time with this boiler will breed flue gas condensation. The PC700 Taco control will require that you also change to their EXP Zoning Control since it plugs directly into a jack on that control. The 260 Tekmar can be adapted to your present control using conventional wiring. Hope this helps.


    Glenn Stanton

    Manager of Technical Development

    Burnham Hydronics

    U.S. Boiler Co., Inc.
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    Correct

    Missed that, he could play with the curves but, I agree, he probably is better off with the Tekmar control - but he could use a 256 instead of a 260 a lot less money functionality as the Taco control.

    If you have an EXP Taco relay, agree use the PC700 simple plug in.. If you don't, look at the Tekmar 256. Spec attached. Note there is no DHW priority with the 256.
  • Hey Glenn

    One of us is going to have to change their name on this site before someone thinks they are reading my posts when they are yours or vice versa! The names are too close in spelling. Whadya think?

    Glenn Stanton

    Manager of Technical Development

    Burnham Hydronics

    U.S. Boiler Co., Inc.
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    middle initials ??

    Good catch on that min boiler temp. Surprised I never realized that that one before.

    Middle Initials maybe?? Actually, your signature line is more impressive you win. What do want to do?
  • That worked!

    I try to avoid using my middle initial in articles and postings due to the fact that my initials are "GAS". Had a difficult time years ago when a large oil company I was calling on started buying from me and the invoices arrived at their main office with my initials "GAS" on them. To satisfy their wishes I had the company I worked for back then change my initials in the computer system to "MUD" instead. Lest I will never be accused of favoritism toward either fuel and to a few choice people in this world I will remain simply "Mr. MUD"!

    Glenn Stanton

    Manager of Technical Development

    Burnham Hydronics

    U.S. Boiler Co., Inc.
  • Roland_4
    Roland_4 Member Posts: 84
    Boiler Question

    Thank you all for your valued input. At the very least I'm convinced I'd never want to change careers and become a heating contractor. I had no idea of the minutia you guys have to deal with. I called ARGO Controls and the tech confirmed that under cirtain conditions, my boiler could indeed operate below condensing temperature rather frequently. It seems this would most likely happen when outdoor temps are above 55* acording to their formula. Makes this device look less usefull. I did notice that the Tekmar 260 needs a high limit DHW aquastat. How do I know if my Super-Stor tank has one? Is this something my heating contractor would have to add? Roland........
  • Indirect High Limit

    Your SuperStor indeed has a high limit aquastat of some sort....depending on the model and age it could be a Honeywell L4080 aquastat or some other model.

    Glenn Stanton

    Manager of Technical Development

    Burnham Hydronics

    U.S. Boiler Co., Inc.
  • Roland_4
    Roland_4 Member Posts: 84
    Boiler question

    Thanks Glenn. I don't know which aquastat is on my Super-Stor. I'll check when I get home. All I remember seeing is a two wire cable from the S/S to the Argo relay box.
    Roland.........
  • Roland_4
    Roland_4 Member Posts: 84
    Boiler Question

    The DHW aquastat is a Honeywell L4080B. How can this unit interface with the Tekmar 260 as it requires both a high limit and water temperature input? Thanks,Roland
  • Roland_4
    Roland_4 Member Posts: 84
    Boiler Question

    FYI. Aquastat on boiler is set to 195*.
  • Interfacing

    The Tekmar 260 operates by receiving a voltage signal from your Argo Zone Relay switched through Terminals A & R to the Heat Demand Terminals on the 260. This voltage is usually 24v AC. The same goes for the Indirect except that the voltage signal is switched through the L4080B on the indirect to the DHW Demand Terminals on the 260. Instead of using the Priority Zone on the Argo relay to control the Indirect Circulator, it will be connected to the 260 DHW Pump terminals instead. Priority mode will now be handled out of the 260 which will energize or deenergize terminal W of the Argo relay to take the heating zones in and out of DHW priority mode. Sounds complicated but in reality it is very simple.

    Glenn Stanton

    Manager of Technical Development

    Burnham Hydronics

    U.S. Boiler Co., Inc.
  • Roland_4
    Roland_4 Member Posts: 84
    Boiler Question

    Glenn, thank you for being so generous with your time. A rare trait. The heating contractor who installed my equipment is a super nice guy. He did not B.S. me into anything I would not need. However, he's a bit shy when it comes to add-on electronic boiler controls. I could not convince him to install the Tekmar 260. He's old school, and I can appreciate that. Less stuff means less to go wrong. Do you have a lead on a heating contractor in the Nassau County area of Long Island, N.Y. who could install the Tekmar unit? My zip-code is 11510 if that helps. I interviewed many heating guys before this burner install and none of them were comfortable with anything electronic based. Last question, do you know where I can find any information concerning actual fuel savings using a Tekmar control device? I fully understand that there are a lot of variables which determine any cost savings, but, a few testamonials would be appreciated. Thanks again, Roland
  • Roland

    Just enter your Zip Code in the "Find a Professional" section of this site. You will find it under the
    Resources tab. As far as estimated fuel savings, you can find essays on that topic at tekmar's site at www.tekmarcontrols.com .

    Glenn Stanton

    Manager of Technical Development

    Burnham Hydronics

    U.S. Boiler Co., Inc.
This discussion has been closed.