A small church needs help

Discussion in 'HVAC Heating & Cooling' started by ges_hu, Nov 13, 2013.

  1. ges_hu

    ges_hu New Member

    Messages:
    4
    Location:
    Wisconsin
    Hello,

    Our church had a Prestige Triangle Tube unit installed a couple of years ago, and we have never been satisfied with its performance. The installer has checked it multiple times and assures us that everything is working as it should. We suspect that he is just trying avoid having to do further work or stand behind the product.

    The reason for our suspicion goes beyond the fact that the church does not heat to a comfortable temperature. If the unit were merely undersized for our church, I would expect to see a slow but steady rise in temperature. It is commonplace to be sitting in a cold church and hear the pump start and pipes start to pop, signifying that hot water is again flowing. This even though the thermostat is set at 68 and the room temperature is in the low 60s.

    Wanting more detail, I created a temperature log last March from 6:30 at night to 3:00 the following afternoon. This was on a night with temperatures in the high teens in the evening, low teens at the coldest overnight, and low 30s for a high on the next day. Some findings:

    6:30 – 9:00: Thermostat turned down as a test. Temperature falls smoothly and gradually from 56.5 to 55.5. No reversals.

    9:00 – 10:06: 55.5 to 58.9 steady rise

    10:06 – 11:45: 58.9 to 59.9 steady rise

    11:45 – 6:51: 59.9 to 60.9 some fallbacks

    We gained nearly 3½ degrees in the first hour. It then took almost 2 hours to gain one more degree and over seven hours for the next, even though the outside temperature was not changing significantly.

    The next day:

    9:52 – 10:46: 63.8 to 65.3 one fallback

    10:46 – 1:04: 65.3 to 65.3 up and down

    1:04 – 2:13: 65.3 to 67.3 up and down

    We gain 1½ degrees in less than an hour. Then, with full sun and significant warming outside, we gain nothing for the next 2¼ hours. Then we gain 2 degrees in 1¼ hour. We gained 12 degrees over the full 18 hour test, never reaching the thermostat setting of 70.

    Before the purchase the dealer told us that it would heat so rapidly that we wouldn’t have to turn up the thermostat until Sunday morning. His latest recommendation is that we leave the thermostat setting up all of the time, so we are now expected to heat the church to 65-70 degrees for 168 hours a week just so that it will be comfortable for one.

    It appears to me that the operation of the pump is sporadic. I have asked if there is some kind of shutdown control to protect the pumps from overheating that might be malfunctioning. However those that should know tell me that there is not.

    I find it very hard to believe that this is normal operation and would appreciate any insight or suggestion as to action we might take.

    Thank you.

    Gary
  2. Reach4

    Reach4 Active Member

    Messages:
    2,127
    Location:
    IL
    In the area of easy stuff, I would determine if the thermostat was calling for heat during the whole process. Depending on the thermostat, there could be an indicator for that. You could also monitor the AC voltage between the W and the R or Rh wires. No voltage would indicate the thermostat was calling for heat, and ~24 VAC (typically) would mean that the thermostat was not calling for heat.

    I know this is unlikely to be the problem, but it is simple enough for me to understand and explain.
  3. DonL

    DonL Banned

    Messages:
    3,977
    Location:
    Houston, TX
    What kind of T-Stat is it ?

    If you have a learning thermostat then select your temperature then select HOLD.

    You may be running on a built in program.

    Or set the program times and temps properly.


    Good Luck.
  4. Dana

    Dana In the trades

    Messages:
    2,812
    Location:
    01609
    In most hydronic heating systems the pumps only run when the thermostat is calling for heat. If the pump is turning on & off it's likely that the thermostat is "anticipating", and somehow doing it incorrectly, or there are issues with the zone controller/pump relay. The pump relay/zone-controller or thermostat are separate from the boiler, but have to be set up correctly for the system to work. If that stuff was all new when the the boiler was installed, the installer is on the hook for making it work. If it was a boiler-swap into an existing system with legacy zone controls, there may be minor incompatibility issues to be resolved, or something is failing or intemittent.

    If the pumps were running and the system isn't keeping up you might need to adjust the "outdoor reset" curve, which adjusts the temperature of the output up & down based on the outdoor temperature (assuming that function is enabled, and the outdoor temperature sensor is wired up correctly), but the description of the problem doesn't sound like that is what is happening.

    Figure out exactly which model you have (there are several), and download the manuals. It should be pretty easy to tell if it's the boiler that is malfunctioning once you grasp how it's supposed to work. From the symptoms it sound far more like a thermostat or zone relay problem than the boiler, but knowing what the boiler temp is doing when the pump is cutting in or out can help rule out or in some other issues with the system.
  5. ges_hu

    ges_hu New Member

    Messages:
    4
    Location:
    Wisconsin
    Hello,

    Thanks for the responses.

    I apologize for the delay, but it took a few days before I got a chance to get in the church.

    The boiler, a Prestige Solo 250, replaced a 40 year old unit, so it is indeed a swap with the other parts remaining the same, including the programmable thermostat. Thinking that the latter might be the source of our problem, we had it replaced with a White Rodgers 1E78-140, a very basic, manual thermostat. The problem persisted.

    The outdoor temperature sensor control has been disabled. This seemed to offer minor improvement.

    The technician says that the temperature delta has been adjusted to the desired 20 degrees.

    Anti-freeze has been added to the water. We were told that this would have a negative effect on the fluid's ability to radiate heat, but that the effect would be minor.

    All of these things don't address the most glaring symptom, the erratic nature of the heating curve. If we could maintain the 3½ degree/hour rate of the first hour, we would be tickled pink. The programmable thermostat could have been turned on at around 4 in the morning and the church would have been comfortable at service time.

    For years with the old boiler, the church was set at 45 degrees during the week, and we never had this problem. The new boiler was supposed to be better, so this is extremely frustrating.

    I will be glad to at least try to answer any other questions. The help is greatly appreciated.

    Gary
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,927
    Location:
    New England
    First, make sure that they've purged all of the air out of the system...the water won't circulate properly, or through all of the sections, unless they are air free. Depending on how they are laid out, that can sometimes be tough, and take more than one attempt.

    Are some radiators or sections warm when others are not?

    Antifreeze decreases the ability of the fluid to release heat, making the boiler look smaller than it is, but your boiler may or may not be oversized (they tend to do that). It also now adds a new layer of required maintenance - if the system is not checked periodically, it can turn acidic, and eat the boiler up.

    If the old boiler was the same size, the new one should be able to heat the place.

    If the controller is not setup properly, it may not be able to heat at full capacity.

    Does the boiler stay on when trying to turn the heat up? Or, does it cycle? If the temp is below the set point, some boilers have a maximum burn time, then shut off for a short time, then restart. Not all do this and can handle running 100% if it needs to. You'd have to read the spec sheet.

    What temperature does the boiler get to when it is running? If it is way below the setpoint, it probably should get up to around 180-degrees (maybe a bit higher) and stay there until the building gets closer to the desired set point. With the outdoor reset hooked up and working properly, it would adjust the boiler output based on several things, including how cold it is outside. This can lead to higher comfort and efficiency, but you need to figure out why it's not heating in the first place.

    If the wiring from the thermostat to the boiler is intermittent (loose connection, maybe a nail or screw, or a mouse?), it won't keep the boiler on...it should be simple to determine whether it is requesting heat all of the time or not.

    A simple thermostat may only have two wires...the thermostat just connects them together like a light switch. As an experiment, you could add a jumper back at the boiler, connecting those two terminals together. This should force the boiler on, and stay on until that connection is broken. On most of those things, that's controlled by a 24vac circuit.

    Lots of basic troubleshooting should isolate the problem...any good tech should be able to do it, and many DIY'ers, as well. A multimeter and some understanding of how it works should be enough.

    First, verify the boiler is actually firing, and at what temp.

    Then, see if the circulator(s) are working, and if you can follow them, see how far the hot water is going. If it cools off fast past the circulator, they either aren't running, or they can't pump the fluid (likely air in the system).

    If the system pressure is marginal, the safety shutoff may be shutting the system down as things cool off.

    There should be an expansion tank in the system, and it must be properly precharged with air, and the right size, or the pressure could get too high, and dump some from the relief valve.
  7. Dana

    Dana In the trades

    Messages:
    2,812
    Location:
    01609
    If you're starting out at a low temp the degrees per hour will always be higher, but slows as the place comes up to temp, since the heat transfer rate between the radiation & room is a function of the temperature difference between the radiator & room. A 150F radiator in a 45F room has a 105F delta, a 150F radiator in a 65F room has only an 85F delta.

    Without knowing any of the particulars of your radiation, or what the output temperature of the boiler is set to, it's hard to really speculate. But a Sole 250 operated at a higher-than-condensing temperature puts out about 215,000 BTU/hr which isn't a whole lot of burner for bringing the entire thermal mass of a building up to temp, even if it's enough burner to keep the place at temp on the coldest Sunday AM of the week. If the boiler is isolated in a boiler room not fully inside the conditioned space, you have maybe 190K-200KBTU/hr being delivered to the space you care about.

    That's probably enough boiler to keep a ~5000' church building with 18' ceilings at temp in a WI climate, depending on the R-values & window area. It's probably not enough burner for a 10,000' church building. It would have to be a pretty small building for it to raise the temp 25-30 degrees in a short amount of time. Both the amount of radiation and the boiler temp affect the ultimate ramp rate too. So, how much radiator (& type), and what is the programmed (and measured) output temperature on the boiler?

    Tracking the curve of the ramp with the air temperature inside the conditioned space is pointless- there are many many factors that can keep it from being a monotonic ramp- wind speed, changes in solar gain, changes in ventilation rates, etc. all have effects on ramp rate that can be bigger than mere changes in outdoor temp. Tracking the boiler's input & output temperatures and it's behavior during a long sustained call for heat are more useful. If the flow rate isn't sufficient to get the full high-fire BTU output into the radiation it might become evident by the system behavior. Knowing how the near-boiler system is plumbed can also be key. If the same pump is driving both the the radiation flow and the boiler flow it could be a real problem limiting the boiler's output, or not, it depends on what the actual flows and temperature differences are.

    Assuming the boiler is actually operating correctly and is perhaps undersized for rapid recovery you could start recovery from setback 16 or 24 hours in advance rather than leaving it up all week. There may be errors in the system design limiting ability of the boiler to deliver full-fire output into the system though, and if that's the case a change in the plumbing & or pumps might make all the difference. That can only be addressed by a competent hydronic heating designer after all the radiation & flow conditions are known.
  8. ges_hu

    ges_hu New Member

    Messages:
    4
    Location:
    Wisconsin
    Hello again,

    Some updates:

    I printed the thorough responses that I got here and passed them on to our church trustees. Thanks again for the great information and your donation of time.

    I found the original architectural drawings for the church, specifically the sheet dealing with heating. The church proper had a rating of 74 MBH. Am I right in assuming that this means they figured 74000 BTUs per hour would be sufficient to heat this space? The basic structure has not changed in the 45 years since the church was built.

    A trip to the church at 11 p.m. last Saturday, with the thermostat set on 68 and the room temperature at 62 led to some observations:

    (1) The pipes were very hot all around the perimeter of the church. I couldn't begin to hold my hand on them.

    (2) I am not confident that I can tell when the pump is working. Even the pumps for the other zones that are not being heated are hot and vibrating. It sounds like water is flowing through the pipes, but there was still a period when the pipes started popping as if there was a significant temperture change. If I can reach the point where I can differentiate on and off without a doubt, I will allocate the time to do a multihour, precise documentation.

    (3) A potential problem. The water temperatures ranged from 172 to 188 but the temperature delta from 2 to 6. Examples: water at 186, return at 182; water at 172, return at 170; water at 184, return at 178. It sure looks to me as if the water/antifreeze solution is not giving up its heat to the room. Our water has a lot of minerals. Could the antifreeze react with that to further weaken the heat radiating ability?

    (4) Another problem. At one time the display said the the burner had shut down due to the set point being reached, This even though it also said that the temperature was 176 and the set point was 184. It didn't stay down for long.

    This is really more in the province of the trustees. However I am determined to find a way to get the hard data that I need to take advantage of the knowledge on this forum.

    Gary
  9. Dana

    Dana In the trades

    Messages:
    2,812
    Location:
    01609
    If the architectural drawings specified 74MBH, yes, that is a presumptive heat load of 74,000BTU/hr. If the radiation is ow mass fin tube sized to emit 74,000BTU/hr at an average water temperature (AWT) of 180F or 200F, the boiler is ridiculously oversized for the load-it'll short cycle like crazy when the boiler output is in the condensing temperature range. (The Solo 110 would have been a better choice.) The minimum fire input is ~65,000BTU/hr, and it's entirely possible that there isn't suffcient radiation to deliver that much heat from the water to the room at ~170-180F AWT with the pre-existing radiation if it was designed to deliver 74K @ 200F AWT with water, not anti-freeze. At temps where the thing can actually condense the radiation emits more slowly, and it's likely to short-cycle. I assume you've set the water temp to the max.

    If the radiation is all full of 170F+ water, the pumps (and boiler) are definitely working, but if it's at a 2-6F delta it's probably over pumping (and by quite a bit!) or you don't have enough radiation for the size of boiler to shed enough heat to a big enough delta-T (likely.) What type of radiation, and how much? (Fin tube baseboard? Finned convectors? Something else?)

    If the pipes are all 170F+ and blistering hot to the touch, the anti-freeze isn't impeding all of the heat from getting into the radiators, but if the radiation was designed on the margins for 190-200F AWT, and you're banging on the 184F setpoint and only re-firing when the temps drop to 164F, your average temp during a startup ramp is going to be well under the 190-200F number.

    It doesn't take long for the boiler to drop from 184F to 176F when 176F water water is being continuously pumped through it. These systems are designed to wait until the temp has dropped a significant number of degrees (sometimes fixed, sometimes programmable) to keep from short-cycling the boiler into an early grave. Unless you were there and observing the displayed output temp the exact moment when it turned off the burner, that observation isn't likely to be a problem. The fact that you took measurements of 188F at various points means that it may have overshot the setpoint a bit, but that too is not an alarming symptom.

    What methods are you using for measuring the temperatures? Are you only looking at the boilers return-water display, or is that measured at the radiators? (If the near-boiler plumbing is designed for primary/secondary loops- separate boiler & radiation pumps, it's possible the AWT on the radiation is running 10F or more lower than the measured AWT at the boiler.)

    It's entirely possible that you are radiation-limited for being able to use this boiler effectively. It's probably both cheaper & better to add more radiation to help with the ramp up from setback problem rather than buying a different boiler, but it would probably be pretty expensive to add enough to to get the Solo 250 into a high-efficiency condensing range. This is all hydronic-heating 101 stuff- it doesn't matter how big the burner is if the radiation can't dump that amount of heat into the room at the boiler's maximum operating temperature. Without a better description of the type and amount of radiator you have, this is sheer speculation based on the symptoms. Yes, it's a big burner, but no, it can't heat up the place any more quickly out of a fixed amount or radiation unless you can crank up it's output temp. Many cast iron boilers can be set up with a 220F high-limit and be run safely there. At 210F AWT you can get about 25-30% more heat out of the radiators than at 175-180F AWT.
  10. Reach4

    Reach4 Active Member

    Messages:
    2,127
    Location:
    IL
    To work around this until you get more/bigger radiators, maybe you could blow small fans through the existing radiators.
  11. ges_hu

    ges_hu New Member

    Messages:
    4
    Location:
    Wisconsin
    Hello again,

    First off, let me mention that you are dealing with the church treasurer, and not a particularly mechanically inclined one at that.

    Now that's out of the way ...

    I got to the church again last night and sat with the system for 1½ hours, during which time the temperature climbed from 55 to 60.

    First off: the fluid temperature readings are indeed from the display. I would know no other way to do it.

    My best guess is that the pump works full time. I was listening with a small glass pressed against the pump. I had thought that I would be able to differentiate off and on from the sound in the church. However, the organist came to practice, and I had to resort to plan B.

    The burner seems to shut down every 20 minutes or so for around 2-3 minutes. As I reported last time, even though the set point is 184, it will shut down even though the fluid is less than 184. The reading tends to fall to around 170 or so before it starts up again. I assume the fact that it does fall supports my belief that the pump is working constantly.

    The temp delta is still usually in the 2-6 degree range. There were times when it was 0, and I even saw the return temp exceed the boiler temp. I really am at a loss to explain that. However, if shutdown is based on return temp, this could explain why we have shutdown when boiler temp readings are under 184.

    This whole topic of sizing the boiler is a puzzle. The contractor had initially told us that we would need two boilers working in tandem. He later said that this one is borderline. The old boiler, inefficient as it was, was rated around 350,000 and never had these kind of problems heating the space. I would estimate that the sanctuary might be somewhere in the vicinity of 50000 cubic feet. It has no ceiling other than the high roof which is not insulated. And yet, as plain as day on every blueprint I can find, it says 74MBH right in the middle of the room.

    It sure does sound like the heat is just not radiating into the room. The pipes run around the baseboard and, except for a few spots, are surrounded by fins. So I assume the choice of "Fin tube baseboard" fills the bill.

    I think that is about all for this time. If I think of something else or get further data, I'll pass it along.

    Continuing thanks,

    Gary
  12. kcodyjr

    kcodyjr New Member

    Messages:
    103
    Location:
    Chelmsford, MA
    Are there any zone controllers? More to the point, are you positive that all of the baseboards are actually getting hot?

    I'm no expert, but it seems to me the radiating capacity is known to be sufficient by virtue of having worked for many years. That said, do you know with certainty what temperature limit the older system was running at? If they had it at 220 or something, maybe there's a reason.

    Seems to me, if we know the water's getting hot, and we deduce the radiating capacity is sufficient, there's only two possibilities: either the heat isn't getting from the water to the radiators (unlikely, IMO) or the water isn't getting to the radiators at all.

    Were the pumps replaced? Could they be feeding backwards or anything compared to the old setup?

    Could a valve somewhere have been closed during the replacement and not reopened?
  13. Dana

    Dana In the trades

    Messages:
    2,812
    Location:
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    The setpoint on the boiler is the output temp setpoint, but it doesn't have to be at or over the setpoint for more than a second before it turns off the burner. To keep it from short-cycling there is a built-in hysteresis/differential, that keeps it from re-starting until it hits a lower temp. I don't recall if that's programmable in this unit (it might be), but if you can set it up to re-start once the temp falls to 175F you'll get incrementally more heat out of the thing.

    Delta-Ts in the 2-6F range with the burner running and system temp 170F+ is an indication that the boiler is either being over-pumped &/or there isn't sufficient radiation to shed enough heat at only ~180F. If it's plumbed primary/secondary it could be that the radiation loop pumping rate is fine, but that the boiler loop is being over-pumped, or it could that the radiation loop is so incredibly under-pumped that it has a huge delta-T (unlikely) but only very low flow. If it's pumped direct the boil The temperatures of the piping can be measured with an infra-red thermometer, as long as there is paint or some other infra-red emmissive surface to read, not bare copper (which is low-E, and would give a false-low reading).

    With 2" fin-tube baseboard you get about 600BTU/hr per running foot when the average temp is 180F. At 210F you get about 800BTU/ft (~33% more), and at 220F it's about 850 BTU/ft. Most cast-iron boiler can be set up to run as high as 230F, and it's highly likely that the old boiler was doing exactly that. Measure up the total length of baseboard-only, don't count any sections of plumbing between them that don't have fins. That will be one hard-parameter that determines the max heat you can get out of it with a boiler that is limited to 184F. Fatter fins= more heat per foot, so if the fins are bigger than 2", tell me what they are- it matters. Break it down in baseboard length and fin size zone-by-zone, since that also matters when a zone is under-radiated with a low-mass boiler.

    The total enclosed volume is an irrelevant number- it's the square footage of the exterior surface area the U-factors/R-values of the different surface types that are what determines the heat load at the inside & outside design temperatures. An uninsulated building with high ceilings in WI could have heat loads as high as 75 BTU per square foot of floor area depending on the amount/type of window and the R-values of the building materials. But so far the dimensions & description of the construction is being withheld. Descriptives like "small church", "high uninsulated ceilings", and "50,000 cubic feet" are woefully short of enough information to even take a WAG at the credibility of the 74MBH figure.

    With return water in the 170F+ range and the boiler tripping it's set-point it's unlikely to be a problem with functioning of the boiler, but that you don't have sufficient radiation to heat the place with 180F average water. With those low delta-Ts it's probably not even reaching full-fire. If it wasn't enough boiler and too much radiation, the boiler would never be able to reach it's set point even at full fire. The installer most likely didn't do the math on the radiation to determine the water temp required for heating the place before specifying the boiler, and is probably not competent to diagnose the problem correctly, let alone find the most cost-effective solution.

    The likely solutions come in three basic flavors, none of which are going to be cheap:

    1: Replace the boiler with a mid-efficiency cast iron boiler sized with output that balances with with the available radiation at a 220F average water temp. eg: If the radiation can deliver 280,000 BTU/hr at 220F, you don't need to go with a boiler with a D.O.E. output number bigger than that, since the radiation can't deliver it. An 80% efficiency boiler with a 350,000 BTU/hr input would deliver 280,000 BTU/hr out. But it's possible, even likely that old boiler was also oversized for the radiation, and would cycle on/off during recovery ramps. You have to do the real math on the real radiation to know. Oversizing the boiler for the radiation has no benefit, only down side- in both upfront cost and lower operating efficiency.

    2: Add enough radiation to be able to deliver the full output of the existing boiler at 150F average water temp.

    3: Reduce the heat load sufficiently with air-sealing/insulation/window upgrades so that the existing boiler with the existing radiation can heat the place up from setback in a reasonable amount of time.

    (4: A combination of 2 & 3.)

    (5: Add separate auxiliary heating to make up the difference.)

    The financial aspects of each potential solution depends a whole lot on the particulars, but have to be considered in different time frames: Boiler lifespans are a couple of decades, maybe three or four with regular maintenance and repairs, radiation and insulation is usually good for at least a century with no maintenance, windows will vary from 20 years to 100 years, depending on how you go. The economics of low cost low-E storm windows is far better than high-performance gas-filled low-E double-panes, both in terms the lower upfront cost bang/buck, and the century+ lifecycle.
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