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Weil Mclain ultra gas-fired water boiler 399

RTR
RTR Member Posts: 2
I have a Weil Mclain ultra gas-fired water boiler 399 that was installed last year. It replaced a huge 1925 old cast iron boiler, and I'm saving very  little therms.



Last year I installed plastic on the windows and insulated drapes on the floor where the thermostat is located and still didn't see a change in usage.



Before turning it on this season, the technician came and checked the system. I've been monitoring the control panel and since the colder weather, there is a large discrepancy in the outdoor temp. For example, this morning the outdoor temp was 16 but the boiler says it is 27 (water supply 172 -target 182). Previous reading were similar when is was 11 the boiler readout was 27 (supply 180 -target 182) and another day it was 26 outside and but the boiler readout was 42 (water supply 88-target 145). I reported this to the HVAC technician a week ago and haven't yet heard back. He said he'd have to check into it and get back with me.



Could this outdoor temp discrepancy be causing the boiler to run more often thereby not reducing the gas usage and not  reaching the set 67 degrees set on the thermostat on days when the outdoor temp is in the teens?

Comments

  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    there is a large discrepancy in the outdoor temp.

    If that controller is like the U-control in the Ultra 3 boilers, there is an adjustment accessible from the control panel where you can correct it. Mine is 2 or 3 degrees off, I forget which way. But the location of the ODR sensor and the outdoor thermometer is a little different. Both are in the shade at all times in the winter.



    " For example, this morning the outdoor temp was 16 but the boiler says it is 27..."

    "Could this outdoor temp discrepancy be causing the boiler to run more often"



    I would think it is the opposite: that it thinks outside temperature is higher than it is, so it would make the boiler run at a lower temperature than need be. To maintain the required inside temperature, I would think your boiler would run longer, but less often.



    " Previous reading were similar when is was 11 the boiler readout was 27 (supply 180 -target 182)"



    Those temperatures seem awfully high for a condensing boiler. I would assume you get no condensing at all. Hence the high fuel consumption.



    Was this system designed? Was there a room-by-room heat loss done? What is the nature of the emitters? Baseboard? What size? radiant? In slab? panels on walls or ceiling? etc. If you have enough emitters, you should be able to run lower temperatures. Are the reset curves set right?
  • RTR
    RTR Member Posts: 2
    edited December 2013
    Weil McLain 399 details

    "Was this system designed?"

    To determine the size boiler to replace the 1925 one, all radiators were measured to determine the total radiation in square feet and that was multiplied by the conversion factor for hot water (185) which resulted in a BTUH load of 303,159.



    "Was there a room-by-room heat loss done?" No



    "What is the nature of the emitters? Baseboard? What size? radiant? In slab? panels on walls or ceiling? etc. If you have enough emitters, you should be able to run lower temperatures."

    There are a total of 30 cast iron radiators on three floors.



    "Are the reset curves set right?"

     I don't know. Attached is that section of the manual.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    "Was this system designed?"

    "To determine the size boiler to replace the 1925 one, all radiators were

    measured to determine the total radiation in square feet and that was

    multiplied by the conversion factor for hot water (185) which resulted

    in a BTUH load of 303,159."



    For any given water temperature, that would give you the amount of heat that could be delivered to the load. But that would not tell you the amount of heat needed by your load to maintain the desired indoor temperature with a given outdoor temperature. You will still need a room by room calculation of the heat load, preferably at two different outdoor temperatures. One should be at the design day temperature and one could be quite a lot warmer, say 50 to 60F.



    From that you can determine the supply water temperatures needed. And with that, you can calculate the required reset curve(s). I did all that and it worked, but for my system, the heat loss calculated exceeded the actual heat loss by enough that the reset curves I calculated were too high. So I reset one end or the other by trial and error until I got them right. I had a plan, though, it was not at random.



    For my system here in New Jersey for a small Cape Cod type house, design temperature is 14F and I run between 76F and 120F in the radiant slab, and between 110F and 135F in the baseboard zone.



    If you are running around 180F in your system you are almost certainly getting no condensation, which costs you a fair bit of efficiency. Also, the outdoor reset will save you even more efficiency than the condensing feature does because it matches the heat supply to the heat need. And except for outdoor temperatures at or below design temperature, if the system is asking for 180F supply temperatures, your resets are almost certainly wrong.
  • Rich_49
    Rich_49 Member Posts: 2,607
    Delta T

    What is your Return Temp when 180* is going to radiators ? 
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • RobG
    RobG Member Posts: 1,850
    One other thing

    This is not related to the outdoor sensor issue. I don't know about your area, but here in Virginia it has been colder than in many previous years for the months of November and December. This will obviously affect your comparisons to previous years.



    Rob
This discussion has been closed.