Modcon with IHW Tweaking

Discussion in 'Boiler Forum' started by chris24, Jan 10, 2011.

  1. David1

    David1 New Member

    Messages:
    11
    Location:
    01453
    Alpine questions

    Dana,

    Your posts are informative and helpful thanks. I find myself in the same position. My Alpine 150 might be too big but I'm not sure. I am 20 minutes north on 190 so you know the climate. If it is oversized I am thinking it is not by much, maybe I should have 105 ??? The house is 2700 ', half of it 100+years old and the other half 7 years. I have in total 125 ' of fin tube emitters broken into two zones one at 65' and the other at 60'. The plumber installed p/s piping as directed by the installation manual. I believe the plumber did a heat loss calc, he mentioned that he thought I would be using the 105 but the "Load" was right on the edge and he was afraid of 0 degree days.The boiler appears to be short cycling and I question the need of a buffer tank. A side note here, the boiler has been recording Hard Lockout # 25. I have been in touch w/ Burnham, they have some type of fix using a bleed resistor and a wiring modification. Your thoughts ???
  2. tk03

    tk03 New Member

    Messages:
    56
    Location:
    Harrisburg, pa
    David1
    I don't believe he did a heat loss. Did he measure all the door, windows and house size. If all the radiation in your home is no more than 125 ft that is about 75k worth of radiation. Any boiler size larger that that is a waste of boiler. The radiation will not put out more that it is rated for no matter how large the boiler is. Usually the boiler is smaller than the amount of radiation.
    Turn down the heating fan speed down to about 3000 rpm's.
    Is it making DHW?
  3. David1

    David1 New Member

    Messages:
    11
    Location:
    01453
    TK,

    the plan is to install a SuperStor Indirect. The take offs w/ ball valves were installed on the headers.I think he said that the indirect load would be larger than the fin tube. We have a 3 bedroom house 4 people, two teenage age girls ! We do not have the tank yet. At this point I have 50 gallon gas fired hot water tank, 3 years old into a 6 year warranty.

    As far as the heat loss, I was not here when he stopped by my wife was. He did mentioned to me later that he was surprised to find that I had 25 windows. I'm hoping he did some type of calc ! On the fan speed, are you talking about dropping the factory setting from 5000 down to 3000?
  4. tk03

    tk03 New Member

    Messages:
    56
    Location:
    Harrisburg, pa
    Yes down to about 3000 rpm's for the heating fan. If you have a 50 gallon gas fired tank a 35 gallon IWH would give you more hot water. Pipe it in 1" for the best recovery even though the tank has 3/4" tappings for the boiler piping on the tank. Take a look at stone lined tanks as they require a smaller boiler for the same output. That would allow you to tuen the fan speed down for hot water also.
  5. mage182

    mage182 Member

    Messages:
    64
    Location:
    NY
    I ran the boiler for about 6 hours on Satuday (~38*F). The outdoor reset had the unit working on 130* water and when I shut it off the house was at about 62*. Almost the entire time it was on the Max Efficiency level showed.

    I didn't check to see if the unit was cycling a lot. I was doing other things. But if the return is coming back cold enough to condense then that should be good right?

    I found a friend of the family who does HVAC and says he has experience with modcons. He's going to come over this week and look at everything and see if he can tweak it to work the best once the house is warm and it's just maintaining temp.

    Here is another question. What is the technical difference between the 80, 105, and 150 models? Gas jets? something to do with the burner element? Would it be possible to pay a technician to swap out those components to lower the model output? I wonder how much the parts would cost?
  6. tk03

    tk03 New Member

    Messages:
    56
    Location:
    Harrisburg, pa
    The difference is burner size and fan speed.
    You can lower your input and get a smaller unit.
    When the unit is running press the status button and than there are little arrows on the right and left side mid screen. Press the right arrow until you see black lines. The top two are supply and return temps. Deduct the return from the supply and that is your system delta T. What is the result?
  7. mage182

    mage182 Member

    Messages:
    64
    Location:
    NY
    Using the numbers from above on Saturday. When I was running the unit the water going out was 130 and coming back in was between 117 and 121. So the delta-t is 9-13. Keep in mind this is during the process of heating the house from the boiler being off for weeks, so we started with a house that was approximately 40*.
  8. Dana

    Dana In the trades

    Messages:
    2,840
    Location:
    01609
    mage182: The return water is going to be colder when the house is cold. The more relevent numbers will be be gotten when the house as at or near the conditioned space temp you're planning to run it. But yes, return temps below 120F are good, but short-cyling will still rob the system of efficiency.

    I doubt you'll be able to swap burners to "convert" to a smaller unit.

    It's hard to estimate the heat load of antique homes with uninsulated air-leaky second floors, but jadnashua is correct- it's still going to be oversized for even a fairly leaky house that size in an L.I. climate (maybe even oversized but ridiculously so for an uninsulated house in the Adirondacks.) And blowing in some cellulose and doing even moderate amounts of air-sealing would usually be a cost-effective comfort & efficiency improvement cutting the heat load (and bills) by a few 10s of percent.

    David1: The guy almost certainly didn't do a heat load calc. If he did, he should be able to print out the room-by-room calclulation along with the parameters used, etc. (I'll bet he did one of those "lessee, it's mostly antique, figure 35BTUs a foot, times 2700 come out to 95K, not much margin for the 105, so mebbe we should bump it" kind of calculations. If history is any guide, the 150 would also be considerably oversized for almost any 2700' home in Leominster MA too (even half-antique.)

    My 0F heat load (measured) in Worcester is about 30K, and that is in a circa 1923 2x4 stick-built bunglow with known gaps in the insulation, mostly cathedralized ceiling in 6' rafters (not much insulation there, even where insulated), antique double-hungs w/circa 1988 exterior storms for 80% of the glazed area, etc.. It's a bit over 2000' of fully conditioned space and a bit over 1500' of semi-conditioned basement (where it never drops below 65F down there after insulating the basement walls and sealing/insulating the foundation sill & rim joist) so it's pretty much "as good as" conditioned space from a heat loss point of view.

    With all zones calling for heat the system is putting out ~42K (measured by delta-T x flow on the boiler loop) due to the hydro-air coil running the main zone when the radiant floors aren't keeping up, but it had no problem keeping up at -8F outdoor temps earlier this season. I literally CAN'T get more than 42K out of the heating system at the water temps & emitters I'm running (!), and that's less than half the full-fire output of the -105. (It modulates higher than that- up to ~60K out under heavy DHW load, but that's a whole other aspect of how I configured the system.) Your conditioned space may be somewhat bigger (maybe not, depending on how big your basement is and how the space is configured, but unless your windows are all leaky single-panes-no-storms your heat load would be well within the bounds of an Alpine-105, and most-likely within the bounds of the -80. (Single-panes with storms have U-value of ~0.5, so figuring 15 square feet per window the glazing factor adds less than 15K to the total at 0F with a 70F interior. Even if contractor-grade double-pane you're looking at less than 10K, lower still if better-quality.)

    Your smallest zone is 60' of fin tube, which would deliver only ~15K at minimal condensing temps- about half of your mid-mod output. Your bigger zone is only ~10% bigger so the 150 WILL short-cycle on zone calls if you try to run it at condensing temps. You'll probably have to run it at ~150F or so out, and tweak the flow back to get it to run min-mod with continuous burns between calls from the thermostats, and you'd be running ~87% efficiency. With a buffer tank in series with the boiler so that it particpates in every heating system zone call to stretch out the burns to 10min+ you could run it at low temp and hit the low-mid-90s without cycling the boiler into an early demise.

    In general, unless you've taken HUGE measures for reducing the heat load by weatherizing, when in doubt, go lower, not bigger on the boiler sizing. Since this was a replacement boiler, you probably could have done a pretty good whole-house heat load based on last year's gas usage and the approximate efficiency of the old boiler.

    With 2 teenage girls taking endless showers you might get better mileage & efficiency out of installing drainwater heat recovery than by installing a SuperStor. Either would give you the capacity you seek:

    [​IMG]

    (EFI in Westboro reps the PowerPipe version, and will sell direct out of their WI warehouse.) If you have 5' of vertical 4" drain downstream of the shower it can pay off- more than doubling the first-hour rating of a 50 gallon tank by returning half the heat to the incoming water stream. If you later installed a SuperStor when the standalone craps out the efficieny boost would still be there if you feed the SuperStor via the heat exchanger. Bigger is always better on these (longer, bigger diameter), since the installation labor stays the same whether it's a 30% unit or a 60% unit. Payback is shorter for the bigger units if you're running the shower more than 30 minutes/day.
  9. tk03

    tk03 New Member

    Messages:
    56
    Location:
    Harrisburg, pa
    Again I would reduce the input by turning down the fan speed. That will limit the input even when it needs to ramp up all the way. You can also change the rate of modulation. the boiler has a scale of 1 - 5. It is shipped at 3. Five is the faster modulation rate.
  10. David1

    David1 New Member

    Messages:
    11
    Location:
    01453
    Adding a buffer tank


    I have lowered the fan speed and have seen a marked improvement. My next thoughts are w/ a buffer tank. The loop is piped w/ P/S and the tees are spaced per the installation manual. From what I have seen, it looks like a buffer tank would be installed "inside" that closely spaced tee, in effect replacing it. The supply from the boiler hits the tank directly while the loop supply comes off the other tank outlet. The return from the loop again hits the tank and the return line from the tank (w/ the boiler pump) comes from the tank to the return of the boiler. At least, I think so. Does anyone know where I can find a piping diagram specific to the Burnham Alpine ? I want to make sure I maintain the benefits of the P/S piping. I do not want to void any warranties. Thanks again for all your help !
  11. tk03

    tk03 New Member

    Messages:
    56
    Location:
    Harrisburg, pa
    Normally the tank takes the place of your closely spaced tees. The system pumps in and out of the tank as does the boiler. I have seen these piped and wired many different ways all of which were proper in their application.
    I have also seen applications where it was not installed properly. Most common mistake is an aquastat on the tank to maintain tank temp but affects the ODR temp and maintains temp year around.
  12. David1

    David1 New Member

    Messages:
    11
    Location:
    01453
    TK,

    I was not aware that standard buffer tanks need/use an aquastat. I thought that buffer tanks are piped using the four ports and the cavity served as a storage facility. I'm guessing the boiler circ pulls from the tank to maintain flow for the boiler while the zone circs pull from the tank to satisfy the zone stats. I was thinking the aquastat was used when and if the tank functions as an indirect water heater. Am I way off base here ? Thanks.
  13. tk03

    tk03 New Member

    Messages:
    56
    Location:
    Harrisburg, pa
    Depends on the tanks and application as I stated earlier. I personally would not use an aquastat. Check out boiler buddy. They have a pretty good website for buffer tanks.
  14. mage182

    mage182 Member

    Messages:
    64
    Location:
    NY
    I assume this would mean only turning down the fan speed on the heating side and not the DHW side? How would I calculate what to set the new fan speed max to be?

    Also if the rate of modulation is shipped at 3. How do I know if I should lower it? And should I lower it to 2 or 1?
  15. Dana

    Dana In the trades

    Messages:
    2,840
    Location:
    01609
    When in doubt, go lower (for highest efficiency and fewest burn cycles), especially when you think/know it's oversized for the application. Start at 1 and only bump it up if it doesn't keep up.

    David: There are buffer tanks that operate as "reverse indirects", with aquastat control, but that's not what we're after here. (ErgoMax, TurboMax, Everhot EA all make reverse indirects). Any insulated tank plumbed in series would do.

    BoilerBuddy, or ErgoMax buffer tanks are essentially high-mass hydraulic seperators- useful in some system configurations but an expensive way to go for 1-2 zone simple residential systems. In a small primary/secondary system installing an (unpowered) electric tank hot-water heater anywhere in series with the boiler loop an appropriate (and far cheaper) way to add the necessary mass to the system in such a way that it participates in every burn. The electric tank adds only a very modest amount of head to the boiler loop, and won't affect pump sizing.
  16. tk03

    tk03 New Member

    Messages:
    56
    Location:
    Harrisburg, pa
    Normally I use the higher number for modulation. The faster setting is going to react to turn down faster. The fan speed is as Dana stated start lower and work in the direction you need to.
    Remind me what the heat loss and boiler size you have. I can give you a good starting point.

    Dana,
    Does the electric tank have large enough tappings for the system piping? Aren't they normally 3/4"?
  17. David1

    David1 New Member

    Messages:
    11
    Location:
    01453
    Dana,

    I would be interested in looking at a piping diagram for the electric water tank. If a buffer tank sits across the loops, (2) supply outputs and (2) return inputs, how does a standard hot water tank work ? I'm thinking the electric hot water tank has (3) available ports (supply, output and drain). I have watched the "burn cycle" a few times on the boiler at different OATs. It looks like the boiler fires up on average 5-7 minutes. I am thinking that a 10 minute burn would be better, any comments ?

    It does appear that the boiler is oversized but I think the min mod output is even with a one zone call. At a quick look, I have about 300 feet of 3/4" copper. At 2 gallons per 100' that suggest I have 6 gallons in the loop and less than one gallon in the boiler. From what I can gather, copper baseboard (existing) is about as low mass as you can get. I'm thinking the hot water slugging back does not help me out very much.
  18. David1

    David1 New Member

    Messages:
    11
    Location:
    01453
    TK,

    I plotted my way thur a heat loss calc (3 hours for somebody that does not know what they are doing) and came up w/ 70,000 loss. The boiler that was installed is the Alpine 150. From what I read, it has a min mod ouput of 28-30 K with a max of 120 K. I have two loops split evenly.
  19. Dana

    Dana In the trades

    Messages:
    2,840
    Location:
    01609
    David1: The boiler only has one loop- putting the electric tank in series with either the output or return side (between the zone manifold & boiler) would allow the mass to participate in every burn, independently of how the rest of the system is configured. A short section of 3/4" plumbing on the boiler loop isn't going to present enough head to ANY pump to cause issue with operation of the boiler at the flows you'll be looking at. The 1" taps are only necessary to be able to run it on longer runs at full-fire without running out of margin on the safe delta-T. (see discussion below) The tank is a lot fatter than 3/4"- so you're really only looking at the length of the tank's dip-tube.

    300' of fin-tube is capable of delivering ~75KBTU/hr with 120F average water temps, so with your zones are split evenly 150' would still be above min-mod, you should be able to run ~125 or 130F output water without inducing short-cycles, but you may need to reduce the flow (tweaked with a ball valve) to get it to actually RUN at mininum moduation. As long as the return water is ~120F or below you'll be in the 90%+ range. If it doesn't allready have a ball valve in series with each zone, adding ball valves to be able to back off the flow and tweaking each zone to run the boiler at min-mod when it's the only zone calling for heat is much easier & cheaper than adding a buffer tank on the boiler loop- I'd go there first. With that much fin tube in you should be able to achieve continuous burns whenever there's a call for heat (from either or both zones) and stay in condensing mode the entire time.

    Combustion efficiency in condensing boilers is all about the return water temp- if you can get it to run 100-110F return-water into the boiler and 120-130F out you'll be in the mid-90s. I'm not sure what the max delta between output and return the Alpine is speced for, but 20-30F deltas are safe for any boiler. At 2gpm a 30F delta between output & return is ~30KBTU/hr, so that's a decent way to guage when you're balanced at or near mid-mod you are when tweaking flows. Even if you have to bump up the output up 140F out with 110F return for consistent heat in every room that's still fully condensing, but 140F out with 120F water on the return would be a few percent lower efficiency.

    While 6 minute burns aren't exacting terrible toll on efficiency on a low-mass boiler, reducing the number of burn cycles by a factor of 2 or 3 saves considerable wear & tear, and you can probably get there without adding mass with 150' of fin-tube per zone.

    Most heat loss calcs tend to run 25-35%on the high-side of reality- you may actually be closer to 50K. If you have a year's worth of fuel use to work against weather data you can get closer to the true design-condition heat load, but that won't much change how you set up the system. Average water temps still need to be in the 120F range for consistency with fin-tube, and that's more than enough to meet design-day conditions at 120F AWT.
  20. David1

    David1 New Member

    Messages:
    11
    Location:
    01453
    Fin Tube Length


    Dana,

    I may have mis spoke .......

    the 300' is the total run of copper on both zones. The emitters for each zone, (zone 1 = 60', zone 2 = 65') total 125 '. Is that what you understand ?
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