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Nestor_Kelebay 05-08-2009 06:18 PM

Grooved end pipe
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:

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.

glennjanie 05-08-2009 08:00 PM

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.

Nestor_Kelebay 05-08-2009 09:21 PM

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.

edlank 05-10-2009 05:57 PM

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?

Nestor_Kelebay 05-10-2009 10:46 PM


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.

majakdragon 05-12-2009 09:18 AM

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.

Nestor_Kelebay 05-12-2009 03:47 PM

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?

edlank 05-12-2009 08:23 PM

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?

majakdragon 05-13-2009 10:12 AM

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.

Nestor_Kelebay 05-13-2009 03:54 PM

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.


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.

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