Grooved end pipe

Discussion in 'Plumbing Forum' started by Nestor_Kelebay, May 9, 2009.

  1. May 9, 2009 #1

    Nestor_Kelebay

    Nestor_Kelebay

    Nestor_Kelebay

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    I had a pair of Weil McLain high efficiency boilers installed in my building in August 2006. The boiler control isn't operating them properly, and my plumbing contractor thinks the problem is that the boiler outlet temperature sensor is strapped to the OD of the pipe rather than being in a well.

    The piping is put together with groove end pipe and Anvil Gruvlok Rigidlok 7401 couplings that are 1 7/8 inches wide. I'm wanting to take out one of these 7401 couplings, and put in a Victaulic outlet coupling that's 2 3/4 inches wide:

    http://www.victaulic.com/docs/lit/06.10.pdf

    That means I'm going to have to also replace one groove end pipe with a shorter pipe as well simply because the wider outlet coupling will require the groove to be in a different location.

    I've been told that the standare specification for groove end pipe is a 1/4 inch groove located 5/8 inch from the end of the pipe.

    Is this true of ALL groove end pipes, or only for 2 1/2 inch mild steel pipe?

    Does anyone know where I could find that specification so that I can confirm for myself?

    And, how strong are the seals that fit in those grooves? If I get the location of the groove wrong by 1/8 inch, will the seal be strong enough to hold the piping in place if it's wanting to spread apart or come together? All the piping is hanging from pipe hangers and it's about 12 feet between where the ends of the pipes come out of the walls.
     
    Last edited: May 9, 2009
  2. May 9, 2009 #2

    glennjanie

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    Hello Nestor:
    Fire sprinkler installers use that method frequently. Perhaps you could find a local company that would cut and groove the pipe for you.
    Glenn
     
  3. May 9, 2009 #3

    Nestor_Kelebay

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    I was told that no one would groove anything less than a 4 inch piece of pipe because it's apparantly "dangerous"(?)

    Apparantly, someone has to hold the pipe at an angle to the rollers so that the rollers pull the pipe toward the machine as the groove is being rolled. and, that also means that someone's fingers and hands have to get close to a potentially nasty machine. So, I think they've arbitrarily set 4 inches as the minimum safe length of pipe to groove.

    On Monday I'll phone up some places that install sprinkler systems here in Winnipeg and see what they do if they need a shorter piece of grooved pipe.

    If push comes to shove, I'll have two short pieces of pipe grooved, cut the grooved ends off, and then have the grooved ends welded together. I don't see that being dangerous, and the local welding instructor at my local trade college has offered to do it for nuthin. If I go that route, I'll buy him a bottle of whiskey for doing that. I'll just give it to him after he does the welding. I don't want it to turn out crooked.
     
  4. May 11, 2009 #4

    edlank

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    If the problem is the temperature sensor is on the pipe outside, then the temperature difference between the pipe contents and the outside of the pipe can be minimized by insulating the pipe and sensor to minimize heat loss. The closer to no heat loss you get, the closer to inside pipe temperature the sensor will sense. Will this be possible as a much less intrusive solution?
     
  5. May 11, 2009 #5

    Nestor_Kelebay

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    Ed:

    The pipe was already well insulated. After I had the heating system installed, I spent close to a week and $700 ($Cdn) on 1 1/2 inch pipe insulation to keep my boiler room cool.

    That sensor was covered with 1 1/2 inch of fiberglass pipe insulation that had a silvery IR reflective coating on the inside of the jacket.

    And still, what happens is that my boiler control tells my boilers to come on at 100% to reach the target water temperature, and the boilers fire up at their maximum rate and stay that way until they kick themselves out on a high temperature soft lockout. Then they cool down and fire up again.
    And then the boiler control tells them to modulate up to a 100% firing rate to reach the target water temperature, and the same thing happens, over and over and over again all winter long. The boilers are knocking themselves out trying to achieve the target water temperature, and the temperature sensor keeps telling the boiler control that the water supply temperature isn't high enough.

    Seems the more technically advanced they make these boiler controls, the stupider the way they control the boilers. It's a Tecmar 265 controller, and
    it's got an input parameter for darn near everything imaginable, but there's no way to tell it that the input parameters it's using are wrong.

    We're hoping that putting the temperature probe in a well is gonna help.
     
    Last edited: May 11, 2009
  6. May 12, 2009 #6

    majakdragon

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    There are two types of "grooved" pipe installation. One is a cut in groove and the other is a pressed in groove. Fire sprinkler installers use the pressed type. I have used both. Getting the groove (either type) into short pices of pipe is difficult. Your idea of welding two short pieces will work as long as the weld does not interfere with the coupling. The groove spacing and depth is typical and exact. When the coupling is tightened down, it compresses the rubber seal. Being off 1/8" would not work.
     
  7. May 12, 2009 #7

    Nestor_Kelebay

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    Well, my understanding is that the grooved end to fit a Victaulic coupling is exactly the same as the grooved end to fit a RigidLok coupling.

    I have two RigidLok couplings; one at each end of a 4 inch long by 2 1/2 inch diameter grooved end nipple. I need to replace one of those two 1 7/8 inch wide RigidLok couplings with a Victaulic "outlet coupling that's 2 3/4 inches wide.

    That means the Victaulic coupling will be 7/8 inches wider than the RigidLok coupling it's gonna replace.

    And, that means the length of the nipple I need has to be 7/8 inch shorter than the 4 inch nipple that's there now.

    Which means I need a 3 1/8 inch long piece of 2 1/2 inch pipe grooved at both ends.

    That makes some kinda horse sense to me. Does it seem right to you?
     
  8. May 13, 2009 #8

    edlank

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    I don't mean to be a pessimist, but I fear sinking the sensor in a well will not solve the problem. It may improve it. Having no pipe between the heated water and the sensor will improve the response time, and keep the measured temperature closer to the actual water temperature. My read of that controller is that it is a PID controller, not a bang-bang controller. It appears to me that it is set with too high a gain, and attempts to overcontrol due to an unstable gain setting. I assume you can adjust the parameters? Have you tried?
     
  9. May 13, 2009 #9

    majakdragon

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    In the past, for short pieces of grooved pipe, I have tack welded a short piece of pipe to a longer piece to cut/roll the groove. When done, we just cut and ground down the tacks. Since the grooves are not right at the end of the pipe, there was no problem.
     
  10. May 13, 2009 #10

    Nestor_Kelebay

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    Ed and Majak:

    Ed: I've been on the phone to Tekmar and Weil McLaine Tech Support over and over so many times that they know my voice now. The problem is mostly the temperatures being too low, and the long response time to get those temperatures. The "heating expert" from my local plumbing supply wholesaler has come out and set the boiler supply temperature much lower on the controller to try to get the system to work as it should. Instead of having the supply temperature set at 185 degrees on the Tecmar for domestic hot water generation in my Amtrol indirect fired heater, he's set the boiler outlet temperature at 150 so the Weil McLain boilers reach that temperature before knocking themselves out. He's telling me that the water inside the piping is probably about 170 degrees or more, but the strap on sensor is only reading about 150 degrees because of heat loss both from the pipe and along the steel pipe.
    I don't know if the Tecmar 265 is a good controller or a bad one. I just know it's got a lot of bells and whistles, but I'd trade all of them for a heating system that worked like it should. Mine works, but not like it's supposta.

    And, the funniest part is that this is about the dozenth high efficiency heating system my local plumbing contractor has installed (Abco), and I'm being told by my plumbing wholesaler that they were all installed the same. That is, the first 12 don't work any better than mine, it's just that I was the only one who took the time to stand there and watch the operation of the heating system to realize that it wasn't "modulating" the way it should. The boilers were just firing up, going he11bound for leather until they overheated, kicked themselves out (soft lockout) until they cooled down, and then fired up again. And this dance would continue until the building thermostat stopped calling for heat. All the other similar installations are doing the same thing mine is, it's just that no one either cares or noticed.

    Majak:

    One of the "old hands" at my local plumbing wholesaler was able to groove a 3 1/8 inch piece of 2 1/2 inch diameter pipe for me. We're waiting for a #72 Victaulic "Outlet Coupling" to come in so we can install it and see if the heating system works better with the sensor in a well.
     
    Last edited: May 13, 2009
  11. May 14, 2009 #11

    edlank

    edlank

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    Nestor,
    I am not sure which sensor is the problem. It is a Weil McLaine boiler and an Amtrol water heater? It looks like the Weil McLaine has threaded inlet and outlet pipes. Is it the lines between that and the Amptrol that are the grooved end pipes? If the Weil McLaine pipes are threaded, you have simpler options to get a temperature probe in the flowing water stream, so I am guessing that is not the problem location. Is the controller like
    http://www.weil-mclain.com/downloads/ug3_wiring_diagram.pdf?
    Is each connection made to an appropriately placed sensor? I have a hard time believing that water at 170 degrees would allow an insulated pipe to measure only 150 on the outside without a lot of air blowing across it. Water and steel are much better heat conductors than air or insulation. I suspect a sensor from the "system supply" and "system return" is reversed with the "exchanger inlet" or "exchanger outlet" sensor. I think something else is wrong. Is the rate of burn above specs? Can you lower the gas supply pressure? That wiring diagram above does not show any gain adjustment. I assume it exists. Right?

    I know the above is way off the original question.

    How will you seal the probe in the new pipe coupling? Could you have bought another coupling like the one you have and have a port welded to one half of it and get a small access hole without shortening your existing pipe?
     
  12. May 15, 2009 #12

    Nestor_Kelebay

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    Ed:

    I'll see if I can answer your questions:

    I have two Weil McLain Ultra 310 boilers and an Amtrol 100 gallon indirect fired water heater. The two Ultra 310s are used for both space heating water and are used to indirectly heat the domestic hot water in the Amtrol water heater.

    Because of the fact that the boilers are used for both space heating and domestic hot water supply, the boiler outlet temperature sensor has to be in the water path both during space heating and domestic water heating.

    This was the first problem I encountered as the heating contractor that installed the system originally had the outlet temperature sensor downstream of the heating system's main circulating pump. So, in the summer, when that pump was off, the boiler supply temperature sensor kept reading room temperature throughout the domestic water heating cycle. Thus, the Tecmar 265 controller was being told that the boilers were producing water of room temperature and kept ramping both of them up to 100% modulation to reach the target temperature. And so, they kept knocking themselves out trying to reach the target temperature (but never doing that since the @#$%ing sensor was in the wrong place.

    So, we moved the boiler outlet sensor into the DHW loop, and that helped, but the boiler's own water temperature sensors detect the outlet temperature more quickly and accurately than the sensor strapped to the pipe that provides that temperature information to the Tecmar controller. So, in a couple of minutes, the boiler's temperature sensor is hitting 190 degrees F, but the strap-on sensor that the Tecmar controller is listening to is still only reading 170 deg. F, say. The result is that the Ultra still kicks itself out on soft lockout cuz of that 190 degree temperature, and when it cools down and fires up again, the Tekmar is telling it to modulate up to 100% again to reach the calculated target temperature of 180 degrees, say. And that kept happening over and over again, too.

    So, the heating expert at Wolesley (formerly Westburne) came down and lowered the target temperature for domestic hot water generation from 185 deg. F down to 150 deg. F so that the boilers would achieve that target temperature and be controlled by the Tecmar. His thinking on this was that the water temperature inside the piping was higher than the strap on sensor was detecting, so even though the target temperature was lower, the actual temperature inside the heating coil in the Amtrol would still be at or above 170 deg. F. After doing that, the boilers would only knock themselves out about 5 or 6 times. But, typically, it was more common to see the DHW demand be satisfied after those 5 or 6 cycles than it was to see the boilers actually be modulated by the Tecmar.

    So, now the gameplan is to install that temperature sensor in a well to get a faster and more accurate temperature measurement of the boiler water outlet temperature.

    I fully expect the Ultra 310's have threaded outlets. However, somewhere between the boiler outlets and the piping that was installed in the boiler room they switched to grooved piping and RigidLok couplings. Where they did that, I don't know. And, as long as it doesn't leak, I don't care either. To me, grooved piping is as good or better than threaded piping.

    I just reloaded Windows XP on my sister's computer, and I'm using it now. She doesn't have Adobe Acrobat reader, so I'll download that .PDF file and look at it once I'm back using my own computer.

    So far as "sealing the probe" goes, we're planning to install a Victaulic #72 Outlet Coupling. Victaulic's "Outlet Coupling" is 2 3/4 inch wide, an that's 3/4 inch wider than a normal Victaulic coupling, or 7/8 inch wider than the 1 7/8 inch RigidLok couplings I have now. That outlet coupling holds the pipe ends 3/4 inches apart, which is enough to accomodate a well between the pipe ends.

    [​IMG]

    The outlet coupling has a 1/2 inch female pipe thread, so if the sensor isn't close to the middle of the 2 1/2 inch diameter pipe, we can thread a short iron nipple and iron coupling into the port on the outlet coupling to move the location of the sensor 1/2 inch at a time.

    And, cuz the Victaulic outlet coupling we're adding is 7/8 inches wider than the RigidLok standard coupling it's replacing, the 4 inch grooved nipple the RigidLok currently clamps around needs to be replaced with a 3 1/8 inch grooved nipple for the grooves and gaskets to all line up.

    Does this makes sense to you? I hope so cuz we've already got the 3 1/8 inch grooved nipple and the Victaulic outlet coupling is on it's way. I also have two new EPDM rubber gaskets for the RigidLok coupling on the other end of that grooved nipple we're replacing.
     
    Last edited: May 15, 2009
  13. May 15, 2009 #13

    edlank

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    I understand.

    Have you checked all the temperature probes? Do they at least seem to change their properties (I have not gone back to see if the controller needs thermocouples, RTD, or thermisters to see how you would test them), but they need to be checked, too.

    I would try one other thing before doing that installation. Put the problem temperature probe in a hot water bath that you control and keep its temperature at 190 degrees or whatever specifications suggest. If your problem persists, I think you can avoid an unhelpful job, because what you propose, I think, will not help.
     
  14. May 15, 2009 #14

    Nestor_Kelebay

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    The wiring diagram you provided was the controller for a Weil McLain modulating boiler.

    In this case, I have two Weil McLain modulating boilers, and both are controlled by a Tecmar 265 controller. So, my 265 controls the boilers, and so far as I know, the controller on each Ultra 310 isn't even used.

    The heating expert at my local plumbing and heating wholesaler has been talking to both Weil McLaine and Tecmar tech support, and there seems to be a concensus of opinion amongst them that the first thing to do is to put the boiler outlet water temperature sensor in a well in order to get the most accurate temperatures and the shortest response times possible. Who am I to argue with these guys? I figure it's worth the time and effort to do it, and if it still doesn't work properly, then checking and/or replacing the sensor will be a trivial matter. The existing sensor is connected with wire nuts, and it'll just be a matter of removing the old sensor and installing a new one.

    I'm hoping it works. This stupid heating system cost me $45,000.
     
  15. May 16, 2009 #15

    kok328

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    Any possiblity of just drilling a hole, tapping it and screwing in the temp probe?
    I also noticed the type of well your have, has threaded ports. The alternative is a closed port well. This type you would fill w/thermal conductive paste and then just stick the temp probe into that (sorry, don't have the tech specs on what I'm referring to, perhaps you've dealt with that type before).
     
  16. May 16, 2009 #16

    Nestor_Kelebay

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    I may be wrong on this, but my understanding is that the temperature well is only a tiny bit larger in diameter than the temperature sensor.

    So, I expect the gameplan is to simply slide the temperature sensor into the well without any form of heat conducting media between it and the ID of the well. There may be plans to do that, but no one has said anything about it to me.

    Since the sensor can be pulled out of the well without draining any water, that's something that can be done if the sensor still doesn't read the temperatures quickly and accurately.
     

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