1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

Boiler launch temp

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by HeatFarmer, Oct 23, 2012.

  1. HeatFarmer

    HeatFarmer Member

    Joined:
    Sep 22, 2011
    Messages:
    144
    Loc:
    Montville, Maine
    Based on info in this forum, when I installed my Eko 60 I set the boiler pump launch temp at 170ºF. Now that I've had 10 months of burning under my belt I am asking the question, "why?"

    What is so special about 170º, apart from the fact that it is the highest launch temp setting available on the EKO 60? I understand that you want the boiler to start pumping when the water is hot and return water won't condense inside the boiler.....but isn't that what the termovar mixing valve and a by-pass loop is for? Keeping water under 140º from returning into boiler?

    I am asking this question as I am trying to get my storage back up to temp after having to tear it down and refill with 50º water when it is 38º outside. I fired the boiler overnight and only had 70º water this AM....the EKO likes to kick on at 170º rise to 180º and cool back down to 150º thereby, shutting the pump off. It seems to cycle on-off-on-off like this in 20 minute intervals, while not rising the water in the storage much more than a few degrees each time.

    So....I've lowered the pump on temp to 150º to see if that increases my heating cycles so I can at least get the tank up to 120º in the next few hours so I can do dishes--we haven't had hot water for a couple of days now since the storage tank has been down..... If this lower temp works, I might leave it like this, as I would have heat in the house and shop soone...

    I understand--sort of--the the 170º temp helps keep the boiler & pump from dragging down storage temp on cool-down, but there must be a better way.

    Love to hear thoughts on this.......

    Helpful Sponsor Ads!





  2. maple1

    maple1 Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    3,666
    Loc:
    Nova Scotia
    Do you have a laddomat/loading unit? Or a danfoss type mixing valve? Or maybe something different. Mine has a laddomat type, and I'm not seeing the swings you are mentioning. It is controlled primarily via stack temps. Once on, the boiler return holds steady between 135 & 140, and the supply stays about 160 - but rises gradually once storage starts sending some heat back. Do you have a thermometer on your boiler return? Is it steady at 140 or so?

    EDIT: And do you have a ball valve installed on the bypass loop before the mixing valve?
  3. HeatFarmer

    HeatFarmer Member

    Joined:
    Sep 22, 2011
    Messages:
    144
    Loc:
    Montville, Maine

    I've got a Danfoss on the return with a ball valve on the loop. Once my Storage is up above 150, then I don't see swings at all. It's just when it's at or below 100º that there can be issues.

    Right now, with the boiler showing 160º+ I am only seeing 118º heading into the storage heat exchanger, with 95º returning from the loop. By keeping the pump on at 150º I am seeing a rapid rise in storage temp--about 2º every ten minutes or so. With temps like that I won't tamper with the mixing valve loop ball valve until I have a steady tank temp of 130º or so..... I wish I could automate some of this, but the boiler is 120ft from the storage tank in different parts of the building and wiring between the two is near impossible without running the controller lines to 250 feet or so...plus, I can't afford the system, if it exists, which would automate this all....
  4. heaterman

    heaterman Minister of Fire

    Joined:
    Oct 16, 2007
    Messages:
    2,989
    Loc:
    Falmouth, Michigan
    The magic number for boiler water temp in any non condensing type boiler, regardless of being fired with wood, oil, gas or coal, is 140*. Boiler water temps below that will almost certainly cause problems with condensation in the boiler itself and possibly the flue. No good.

    Use a pump aquastat or mixing valve to keep the temp above that number.
  5. maple1

    maple1 Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    3,666
    Loc:
    Nova Scotia
    I'm thinking that swings in boiler temps like you're seeing would have to be caused by water that is too cool coming back in your return - which is why I was asking if there was a thermometer on your boiler return line, to see if that is the case. Is it a long run between the boiler supply fitting, around the bypass loop thru the Danfoss & back to the boiler return fitting? If not I'd suspect the Danfoss isn't working quite right for some reason. But, neither may be the case if the circ starts as soon as the water at top of boiler gets up to launch point, with a cool boiler - because if the bottom of the boiler is cool, the stat will see that as soon as it pumps out the hot water at the top. So kind of alluding to your original question, a higher launch temp would serve to help alleviate that since there would be more hotter water in your boiler before it launches. I take it that you are limited to a 20° differential?
  6. flyingcow

    flyingcow Minister of Fire

    Joined:
    Jun 4, 2008
    Messages:
    2,270
    Loc:
    northern-half of maine
    I don't have the same boiler, but i do have termovar valves, but mine is the loading valve for mixing at boiler. Plus i have the termovar for feeding the house, where it splits by the tank. But I have the same thoughts as Maple1.


    FWIW- I have a 102,000btu unit. 1st time I fired it it was about -10f outside, 5mph breeze. House had been without heat for 3hours? during the final hookup, must have been down to 60f in the house. I had 820 gals in an unpressurized tank at about 55f. From when I threw the match it was 12 hours and the tank was at 180f on top170ish mid and 165bottom. plus heated the house up and kept it warm.
  7. JP11

    JP11 Minister of Fire

    Joined:
    May 15, 2011
    Messages:
    1,100
    Loc:
    Central Maine
    Everybody's setup is a little different.

    My vigas starts circulating the water at 104 boiler temp. The danfoss will only have the water going around in a loop AT the boiler till 140, then it starts letting a little of the return water in. I'll see my biggest deltas here... when it's only letting a little cold tank bottom temp in.

    No shocking of the jacket.. just coming up slowly, and letting water out to storage slowly.. till the return water is 140. Away it goes to 195.

    JP
  8. stee6043

    stee6043 Minister of Fire

    Joined:
    Aug 22, 2008
    Messages:
    2,291
    Loc:
    West Michigan
    I personally run the "first fire" for storage a bit differently than most other fires throughout the year.

    It takes quite a lot of time to bring cold storage up to useable temps, at least in my case. There is no way around the fact that a significant portion of your boiler output is being used to simply keep itself warm (Danfoss) when the storage water is in the 50's and 60's.

    I run my pump on low and make sure there are no loads on the system during the first "heat up". Until the water is starting to approach 100 or so I don't think running 150 pump-on is a bad thing. You really have to nurse the system along at this point.

    Once your water temps start pushing in the 100's you should be able to maintain at least 20 degree temp rise on the water. This should mean 160 if your Danfoss is always mainaining 140. As storage temps approach 140 at the bottom I typically begin increasing pump speed. Once boiler output is maintining 180+ (160 in) I am typically on high pump speed.

    Your mileage may vary. This system has worked well for me over the years...
  9. Bob Rohr

    Bob Rohr Minister of Fire

    Joined:
    Jan 9, 2008
    Messages:
    678
    Loc:
    SW Missouri

    If the boiler is cycling before the load is satisified, it sounds like maybe you are under pumping? What size pump are you using to flow thru the Themovar? Flow rate?

    I don't see any harm in lowering the temperature to 150, the themovar should still protect the boiler.

    hr
  10. DaveBP

    DaveBP Minister of Fire

    Joined:
    May 25, 2008
    Messages:
    1,051
    Loc:
    SW Maine
    Have you tried gradually turning down (more closed) that ball valve on the return protection loop? That might help let more storage water to the boiler. First fire with cold storage water is going to heat slowly and maybe even produce a little condensed water in the flue. Some on this forum have reported several full load fires to get the tank temperature up to fully heated.
  11. rkusek

    rkusek Minister of Fire

    Joined:
    Mar 19, 2008
    Messages:
    518
    Loc:
    Nebraska
    The gassification should be more optimal at 170+ than at 150 in my experience. HeatFarmer, what is the setting where you turn the boiler circ off (forgot what is called)? That should keep it from dropping down to 150. I think mine is 165 and 5. This year I will run it more like 170 and 5. I wouldn't worry about the circ cycling on and off, more important to keep the boiler hot, IMHO.
  12. rkusek

    rkusek Minister of Fire

    Joined:
    Mar 19, 2008
    Messages:
    518
    Loc:
    Nebraska
  13. Whittlesey

    Whittlesey New Member

    Joined:
    Nov 29, 2012
    Messages:
    7
    It sounds like you are not producing heat like your Eko should. It takes approximately 1 million BTU’s to heat your 1100 gallon storage from 50 to 170. If it takes longer than 5 hours, then either your boiler is not producing its rated 205,000 BTUH, or you are not moving that heat into the tank. The math is never wrong. If your pump is cycling because of low boiler temp (without seeing your setup) I would tend to believe you are not getting anywhere near the required heat output from your burn.
  14. stee6043

    stee6043 Minister of Fire

    Joined:
    Aug 22, 2008
    Messages:
    2,291
    Loc:
    West Michigan
    This would be accurate if you were able to ignore the fact that a significant portion of the output of your boiler during a cold thermal storage start-up is being used BY the boiler to maintain it's own temperature. If we wanted to exercise some really wild thermodynamics, fluid dynamics and heat transfer skills we could calculate how much of the boiler output is being used at the Danfoss valve to bring 50 degree water up to 140 before it's returned to the boiler.

    The math never lies indeed. My observations suggest that a cold start with 1000 gallons of storage will yield something less than 50% system efficiency, probably closer to 30-40% in my case. But this has nothing to do with the output of the boiler itself. System output is a function of how much heat is left after you maintain return temp anytime your return temp is below 140. Boiler output, all things being equal, is likely going to be fairly consistent once you've established a strong fire, have the refractories dried out and get the water jacket up to a decent temp. And last, advertised outputs/efficiency are worth just slightly more than the paper their printed on no matter which boiler we're talking about.
  15. goosegunner

    goosegunner Minister of Fire

    Joined:
    Oct 15, 2009
    Messages:
    1,232
    Loc:
    WI
    Bob,

    Could he be over pumping, or flowing too many gpm for the output of the boiler? Meaning bringing in too much cool return water to maintain a decent delta t therefore dropping the boiler temp below the setpoint of the circulator on.

    gg
  16. 700renegade

    700renegade Member

    Joined:
    Nov 20, 2008
    Messages:
    139
    Loc:
    NE Wisconsin
    No expert here, but my first thought is also overpumping. Sounds like boiler is running in idle 50% of time, thus the low delivered BTU's in a given timespan.
  17. Whittlesey

    Whittlesey New Member

    Joined:
    Nov 29, 2012
    Messages:
    7
  18. KenLockett

    KenLockett Member

    Joined:
    Dec 27, 2011
    Messages:
    188
    Loc:
    Eastern Upstate NY
    Is this Pete Whittlesey who was stationed at Griffiss AFB from 1984 - 1988?
  19. jebatty

    jebatty Minister of Fire

    Joined:
    Jan 1, 2008
    Messages:
    4,264
    Loc:
    Northern MN
    Heatfarmer has not responded since Oct ... is your problem solved?

Share This Page