edlank

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?

Nestor_Kelebay

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.



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.

edlank

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.

Nestor_Kelebay

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.

kok328

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).

Nestor_Kelebay

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.