Plumbing, Heating and Pool Repair Guides

Weil McLain Ultra Series 2 Gas Fired Water Boiler


The Ultra Series 2 Gas Fired Boiler is equipped with the patented PhD technology from Weil McLain. The PhD stands for Precision Hydronic Data technology; this technology has a smart system that brings the PhD heating and hot water requirements, while bringing the most efficiency by determining the data parameters of your home heating system.
Weil McLain Ultra Series 2 Gas Fired Water Boiler

The Ultra Series 2 Gas Fired Water Boiler has a cast aluminum heat exchanger, a burner that is made with a high quality stainless steel construction, and the burner uses a factory mixed air and gas, which offers a wider assortment of firing rates. This will save money as you won’t need to fire up the boiler as much as you would on any other boiler system. It also has an Ultra Control Mode; this means that the control module answers to the signals from the thermostat, water supply, return water sensors, and the flue gas sensor. Almost all of the sensors in the Ultra 2 Series answer and respond to the Ultra Control Mode. Everything is kept neatly in this package.The boiler transformer installed in the Ultra Series 2 is designed to decrease the amount of electrical voltage used in the line. It has a range of 120 vac to 24 vac.
Weil McLain Ultra Series 2 Gas Fired Water Boiler
The 24 vac controls the gas valve and the blower signal. The front door of the boiler is designed to be sealed to the boiler assembly around the whole boiler. Some other boilers are designed partially around the boiler. The Ultra 2 Series Boiler has a P/T temperature sensor that is installed on the pressure temperature gauge, and can be installed into the outlet water pipe. Some other standard features on the Ultra Series 2 are the Boiler Drain Valve, the Data Port, the Air Intake Adapter, and the Venturi, which is designed to act as a vacuum when the air comes through the venturi. This device is used to help with the quality of the airflow.

When you are working with the operation of the boiler, there are just some things that you should know. You should not block the flow of combustion or, any ventilation to the boiler. The heat exchanger is constructed with aluminum and needs the pH system, which should always read between 7.0 and 8.5. The water chemistry should always be checked when the boiler is serviced. There are easy to read electronic display buttons on the Ultra 2 Series Boiler.

The display has a 4 number display where you can access the heating temperature setting, you can see the outlet water temp, and all other operating conditions. You can also see the boiler status, shutdown, and any lock out codes, which makes troubleshooting problems easy. When you have someone install these boilers, you will need to know that the clearance for hot water pipes is 1/2″ from all combustible materials. For the vent pipe the clearance has to be at least 0.20″. You should have 12″ of maximum ceiling enclosure and a 12″ maximum above the floor enclosure. By ensuring the proper clearances you can look forward to a stress free installation.


  1. I have a Mcclain ultra. The boiler seems to short cycle, can not hold a temperature, and displays an error 37 code. Where do I go to crack these codes? I also would like to know some beginning parimeters to set the boiler temps just as goog starting point and can adjust from there.

    Thanks, Jim

  2. My Ultra 150 is 5 years old and has been nothing but problems, expensive problems. Recently it has started giving me a E – 18 error code. Everyday I have to reset the control. Can’t trust it’s operation, which means someone has to check it twice daily. Thinking about starting a class action because I am not alone and Weil Mc Clain ignors calls for help. If your looking to conserve energy, it’s great doesn’t cost a thing when in error mode. If your looking to empty your wallet Weil Mc Clain has a bridge for you.

    Fed up and cold


  3. My Ultra is five years old and we just found out that the heat exchanger has corroded in multiple places. WM will only replace this part with the same aluminum part and will not cover any labor. They have not been particularly helpful and do not seem to stand behind their product. Has anyone else had this issue? We are trying to determine if we should take a chance on replacing this part. Even the rep admitted that the same thing will probably happen. Thank you.

    • Had the same problem with the heat exchanger. Corroded and started leaking. The new part is also cast aluminum but has been redesigned. This is obviously a design flaw. Would be interested in a class action lawsuit as this is a common problem according to the heating contractor

      • We have an Ultra 230 that has corroded through severely at the base of the exhaust column. I have patched this a couple of times, but wonder if this is a basic design flaw.

        Other than the corrosion, this boiler has worked great for us… but this problem is severe.

        • I have this corrosion problem, and patched multiple times.
          Was there ever a class action suit?

  4. we had a weil mclain installed 3 months ago, had service rep out and he replace control and other parts. Still have a high pitched sound which they say cannot do anything for. Does anyone else have this proble? Ears are ringing. Also our furnace room is closet sized and it heats the room to 90 to 95 degrees. Told we could put a solid door on room to muffle noise now they are saying we need to vent the door for heat. Does anyone have this problem. Wish we woul’ve found this web site sooner.

    • Hi Judy, I have had the exact same problem with my weil mclain series 2 boiler. Even though the boiler was in the basement, you could hear it screaching on the first floor. The boiler was initially installed 4 years ago. I was told that it was not installed properly and was set up to always run on high speed rather than modulate (disabling the high efficiency aspect of the boiler’s operation.) So, I paid this company 2K to repipe it. That is when the screaching began. The screaching became higher as the boiler modulated higher – so was very loud last winter. I put fiberglass insulation in the rafters above the boiler and had the piping attached to the wall rather than the ceiling. That did help, but the noise was still annoying. Everyone said there was nothing they could do about it. The screaching has not recurred yet this season, but I am now getting b 19 soft lock outs and E 19 hard lockouts every day. Currently troubleshooting to see if I can resolve without dumpying yet more money in this boiler

  5. My ultra went into lockout —do to a power outage –out in the street—
    thus no heat until the reset button on the boiler is pressed—
    thus if it was in winter — all my pipes would have frozen and burst —
    if I was at work or on vacation

    Weil McLain said for me to install a Time Delay Relay as a fix.

    of course f something happens to the time delay relay they could blame that
    instead of there boiler should my heat system go introuble again

  6. The unit fails to generate a piezo buzzer type of low beeping or audible alarm noise when in E lockout ofn the Ultra 105’s if it did one would no a trouble existed sooner — currently the only way to know is when room temperature in the hous edrops down –thus
    one doesn’t have the time one could have to get the plumber and emergency parts in the winter months —one could have been home and not known the trouble existed and then left for the day —- an audible alarm at and inside the boiler could be heard through the floors and would be of value on something like this that has so many problems — relative to things that can go wrong with it


  8. I have had nothing but 5 years of headaches with this unit. There isn’t a service man with 10 miles that will help me and they all state because fo the poor response from WM and that they won’t honor their warranties or deliver replacement parts timely. At this time I am sitting here with no heat and no hot water because no one is willing to work on this unit, not even WM. I do not have money to replace the unit and cannot get assistance.

    As for clearing up your water to help stop the build up, I have Culligan and it doesn’t assisit preventing the corrosion at all.

  9. I’ve bougth my Weil Mclain Ultra 2 boiler 2 years ago and have had to call for service 4 times. Now the boiler has stopped twice in 2 days and I was able to resstart by removing some water in the condensation hose. I do not have an idea why this is happening. The hose is not clogged.

    Thanks for any advice


  10. Hi there, I am having a new problem with my weil mclain series 2 ultra boiler now. I am getting constant b 19 soft lock outs. Sometimes the soft lock out seems to resolve itself, but generally it is followed by E 19 hard lock out (indicating return water tempature too high.) I verified that that all of the parameter settings are as recommended in the manual. I had adjusted the aquastat setting on the honeywell aquastat on my superstor ultra indirect fired hot water tank. I thought i had set it back to what it was before, but am not sure. I do not see a model number on the honeywell aquastat. It just has a single dial. there is a “pointer” on the dial part that moves, and a similar indicator/pointer on the fixed frame that the dial moves within. I have re-aligned these “pointers”, which is how I believe it was before. It does not seem to have changed the soft/hard lockout 19 problem. The boiler is also “leaking” a fair amount of water from the relief valve. An engineer told me that is because we have such “dirty/rusty” water in my city, and it is normal, so not worth changing the relief valve as it will only start leaking/relieving again. He said it should be doing this… Any suggestions for what I should try/do next? I have a limited support plan on the boiler, so most likely will have to pay if I call to have it serviced. I will call if there is nothing else I can try to adjust first to resolve. thanks for any suggestions you can provide. K

  11. I am a plumber in N.Y.C and around 3 Years ago I installed a Ultra 80 series boiler in a artist loft down on 23street in Manhattan. This is the third heating season that it is operating and other than a lock-out that required a reset 3 times the boiler has been working fine thank GOD. I recently bought a house and decided to convert from oil to gas and was considering putting in a ultra 80 series which led me to look at reviews about the lock out problems and trying to reset the system which was complicated which was a total turn off to me. I like simplicity. After reading your reviews and I thank you all for posting them. I purchased a slant fin bobcat boiler that’s been running for a few days now. Before buying the bobcat I read good reviews and most importantly slant fin stands behind there product unlike Weil McLean.

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