Weil Mclain Ultra Boiler/HWH Malfunctioning

Discussion in 'Boiler Forum' started by Bob716, Nov 13, 2013.

  1. Bob716

    Bob716 New Member

    Messages:
    3
    Location:
    NY
    I am having two major issues with a 3 year old WM ultra boiler and indirect HWH. The system has seriously underperformed since having it installed and I'm worried something is majorly wrong with the installation. When I first had the system installed the HWH was pumping 180 degree water to our house faucets. They replaced the aquastat then eventually the hwh completely. Well the scalding hot temperatures are back and that's not all. Several people I talked to thought this was a bad aquastat again but I talked to WM rep and tested the one I have and it works properly. Along with the hot boiler temperatures, the boiler will not heat the house well when its 30 degrees. Our house will drop from 70 to 62-63 degrees overnight. I am very worried about these issues with having two, two year olds.

    Today, I stood by the boiler for about an hour and tested a couple things. Firstly, I was able to activate the house zone and HWH zone while the boiler was in the standby setting. But in both cases the boiler just went from "Prepurge to Ignition to DHW/FTB to Postpurge" in a constant 1 or 2 minute cycle. The boiler didn't fire and the circulator pump for the activated zone continuously pumped. This I can remember happening the whole time we've had the boiler (again mainly at night).

    I'm confident this issue along with the system heating the hot water boiler zone to 180 degrees is malfunctioning the entire system. At times it works properly but overall its a big mess. Our boiler worked for a short time today (well it heated the house), which is the confusing thing to me. It seems like the vast majority of the day these two issues arise which is certainly which is causing the unit to underperform.

    Any help you could give me would be greatly appreciated. The installer is not helpful.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,892
    Location:
    New England
    First, while you can heat the water in the indirect that high, it generally isn't required or wanted, but it should have a tempering valve on the outlet to prevent that excessively hot water from ever getting into the distribution pipes...generally, these get set to around 120-degrees. My indirect is set to 140, and then there's a tempering valve which limits it to 120.

    The flame sensor may not be working properly on your boiler. Or, there may be a failure in either the design or operation of the circulation and something (maybe the high-temp limit switch) tripping, which causes the boiler to shut down.

    A typical cycle is:
    - activate the igniter
    - open gas valve
    - sense the flame is on
    - run until either the high-limit is reached, or the call for heat is satisfied

    Or
    - sense the flame did not come on
    - shut off gas valve
    - purge the burner of raw gas
    - try again (i.e., start over, which may have a limit of repetitions before it quits)

    The controls that determine what temperature the boiler runs at is determined by the controller. Often, it will hit that 180 or so when called for heating the indirect. Otherwise, it will only go high enough based on the controller to heat the house. That temperature can be affected by the outside reset, and the programming set points. The type of radiation you have can affect the best temperature.

    So, it sounds like there's more than one problem. Ensure the system water pressure is correct as well, and maybe purge air from the system, as that could prevent the water from circulating. If you have a primary/secondary loop system, and the primary pump fails, the high limit switch will quickly shut things off. If the secondary loop's circulator(s) aren't working, there will be little heat transfer to the heating loops (there may be some convection, but it just won't circulate per design).
  3. Bob716

    Bob716 New Member

    Messages:
    3
    Location:
    NY
    There isn't a mixing valve and the WM rep was surprised by this. I noticed they aren't required in the installation manual although they are recommended. If I get this resolved I'm going to put one in myself.

    The company that installed the boiler pretty much did bare bones installation. They left an old taco air scoop from my old boiler and an old steel water tank that isn't diaphragm or bladder (as required by the installation manual). I was thinking this was causing some issues with my system but I have never heard air in the system and the air vent doesn't seem to ever weep water. The air vent on the HWH does but I believe only because the temperature is so high.

    I wish they installed an outdoor reset. Even after asking they told me it was more trouble than it was worth. Ditto with piping the air intake to the outside.

    The pressure when the house zone is going seems ok 11-12 psi. The pressure when the HWH is going bounces around a little bit from say 13-15 psi.

    I believe the primary loop is the house zone circ (I only have 1) and the secondary is the HWH circ. Although my knowledge is sketchy in this area. Could the issues stem from a wiring issue?

    Not sure if this helps, but here's a link to photos of the install and a diagram.
    http://ringo311.wordpress.com/boiler-photos/
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,892
    Location:
    New England
    Where I live (and I think it is a fairly widespread plumbing code thing) you must limit the outlet of the WH to 120-degrees, and the only safe way with that type of system is with a tempering valve.

    The programming of the controller may be all off, and the thing was designed, and (I think) came with an outdoor reset sensor. If the installer didn't understand how to make use of it, I'd not have much faith in their capabilities. You are also losing LOTS of efficiency by not plumbing the outside air to the thing...It takes a lot of fresh air to heat up, and guess what, that air is coming through cracks in the house, drawing in cold air, and you're throwing that heat out the vent pipe. If the room where this is is fairly tight, that in itself could be causing running problems...there are sensors that look for the proper air movement (pressure/vacuum) in the supply and vent pipes. It may not get that when it isn't plumbed properly.

    The pumps work best with a proper expansion tank, and it must be installed in the proper location - it also keeps the pressure much more even. If the old air scoop isn't gummed up, it can work - depends on its condition and where it is.

    You may end up needing to call WH or a local distributor to find someone who is both trained and is selling and installing these things. Unfortunately, it may cost some money to get it sorted out...it doesn't sound like the original installer did you any favors.
  5. Bob716

    Bob716 New Member

    Messages:
    3
    Location:
    NY
    Ok, so a serviceman from the installing company (not the person who installed it) came over to the house today to diagnose.

    Firstly, he took out the igniter and cleaned it off and the boiler started firing.

    He also checked the programming and there appeared to be an issue. The system is set up as primary secondary with 2 zones and 2 circ pumps - 1 zone being the hwh and 1 zone being the house radiators. When the house zone fires the primary pump and zone pump are both activated. For the HWH, only the zone pump was set to activate when the HWH demanded heat. He turned that setting to activate both the zone pump and the primary pump.

    He said this would probably fix the malfunctioning hot water heater. We shall see. The house is heating and I am happy for now. I am thinking of replacing the igniter.
  6. Dana

    Dana In the trades

    Messages:
    2,805
    Location:
    01609
    Current code requires that tempered water be distributed to sinks & showers (but untempered is allows for dishwashers & laundry). That is true independent of the water heater type. Though pre-existing installations grandfathered-in, any replacement heater would require upgrading the hot water distribution at that point. In most homes the tempering valve is installed at the output of the water heater to avoid the complexity of having separate tempered/untempered hot water distribution plumbing. Whatever else you do with the system, it needs a tempering valve.

    Even if you're running the boiler fixed-temp, there's no need to set it as high as 180F (which guarantees that it literally never achieves condensing temp.)) And it may have been set to some lower temperature so that it condenses, but possibly too low for the amount of radiation you have to deliver the full boiler output at minimum fire. When the boiler is oversized for the radiation you may not be able to run it at condensing temps without short-cycling, but there are ways to deal with that if that is truly the cause. An fixed output temp set too low would also make it not be able to keep up during colder weather. If the boiler trips over it's setpoint during a call for heat it's normal for it to re-start when the temp has fallen sufficiently, but it shouldn't be jumping directly from a pre-purge to a post-purge without firing at all, but the burns could still be pretty short.

    It's possible to figure out how to set it up to a pretty-good degree with napkin-math (or a spreadsheet tool, if you MUST. :) ) We'd need to know the actual model numbers (the Ultra has a handful of sizes), the amount & type of radiation. A Zip code and the amount of fuel you burned between two winter meter-reading dates along with the radiation numbers would be able to determine the maximum temp requirements.

    It's normal for the system pressure to bump around a bit when a high-volume pump is actively running, and vary in pressure a bit with the system water temp. The fluctuations between 13-15psi when the indirect zone is running is of no concern.

    In wet-head hydronic heating terms the "primary" is the loop that is pumping water to & from the boiler, and the "secondary" is the water that pumps to the radiation. Where the loops intersect is either a component called a "hydraulic separator", or in your case, a short section of fat pipe with closely spaced tees at the primary/secondary branch points. This allows the the designer to set different rates of flow for the boiler and for the radiation, which is sometimes necessary (but often not, on single-zoned systems like yours. The loop to the indirect appears to be independent, and agnostic of the state of the heating system (it'll run even if there is currently a call for heat from the house thermostat), unless both the house thermostat and the tank's aquastat are wired to a zone-controller rather than pump relay.

    [​IMG]

    It's possible that the check valve on the loop to the indirect is letting water bleed through, or if the primary pump is pumping away from the boiler (flow direction isn't indicated on your diagram for either the primary or secondary pump, but direction is indicated by an arrow in the casting on the side of Taco pump body) it would always be pumping some hot water through the indirect whenever the space heating was active (just at a lower volume than when the indirect's pump is active.) If that's happening and the boiler is delivering 180F water the indirect would slowly heat up even with it's aquastat set to 120F. From your pictures it looks like the black Taco on the primary is pumping toward the boiler, but I'm not 100% on that.

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