Laars Mighty Therm not working with the pilot

Hi Folks,

One of my new customers (school) has a a Laars Mighty Therm  boiler model AP-1200. The boiler is pretty new- not more than 2.5 old, but the installing company no longer exists, so they turned to me. They want me to do the annual service, and when I asked if there are any current issues, they said that the boiler fires up on call for heat, but very often snuffs out pilot. The UT controller is trying to ignite once more within 5 min period, but then unit usually locks out because of ignition failure.

Has anyone experienced similar problems with one of these models? If yes, what should I pay attention to?



Hi John,

I would start as usual from checking the gas pressure and system water pressure, then take it apart and clean the whole including burners, pilot, cleaners. That usually helps for a while. Also if the boiler is only 2 years old then the Laars technical line will be able to advice/help if you find sth that will worry you.


Laars Mascot water stays hot for days


I am taking care of a house of my friend while she is away. She has the Laars Mascot boiler that is being used for both hot water and central heating. She will be away for 3 months, and I found it surprising that the water in the taps are still hot after more than a week since she left. I went to check on the boiler itself, as she told me that a service guy put its operation on hold, and the who room in the basement seemed too hot, for boiler being in stand-up phase. Should I worry or that is normal with this kind of boiler?

Thanks for any help


Hi Matt,

I would advice to first contact your friend asking if boiler was really put on stand-up mode, if not then everything is fine, if yes well, then there is a problem. Laars are good boilers and can keep the water temperature for long, but a week seems a bit to much, also if the temperature in the boiler room is too high I would advice to contact the Laars boilers technician at your earliest


Laars Endurance problem with hot water

Hi All,

I have a Laars Endurance boiler that I have purchased together with the house. The old owner told me that the boiler is approximate 10 years old, but he has no user manuals or service records for it. It wouldn’t be much of a problem if boiler would work normally, but on one hand the hot water is not hot enough, on another I need to wait for approximately 20 minutes with fully open tap to get any hot water. If I want to get the hot water faster I need to manually push up the thermostat. Is that normal, should I do it every time I want to have a bath or wash the dishes?


Hi Tom,

This what you described is not a normal functionality, and you shouldn’t manually push up the thermostat even during the summer mode. It looks to me like there is a problem with the flow switch or the 3 way valve. Because it is pretty old boiler it is best if you can an experienced Laars Endurance technician, who will fix this issue and do the annual service at once.

Laars Endurance shutting itself off

Hi Guys,

I have in my weekend house a 7 years old Laars Endurance, and honestly saying I didn’t have much problems with it during the last years. This year however every time I go to weekend house, switch on the boiler it is shutting itself off. When I switch the boiler on, the LED panel is changes from OFF to ON, but then it goes inactive/blank for 20-30 seconds, and then the LED display turns to OFF. I think that maybe there is a problem with electrical connection and that is why the LED display goes blank, but on the other hand the water pressure fluctuate between 12-24 psi… Any idea what may cause similar problems. Usually boiler starts properly after I restart it manually, sometimes once, sometimes twice…



Hi Rob,

I would vote for problems with the water pressure primarily, then maybe a water pressure switch itself. Water pressure can fluctuate a bit (± 3-5 lbs), but not 12. I don’t think that the control board have any significant effect on the pressure fluctuations. Try re-filling your system with make up water, if it doesn’t work then try water pressure switch replacement and if that doesn’t fix the issue then go for the control board.


Laars Mighty no hot water unless heating is on

Hi Folks,

I have a Laars Mighty boiler, it is 5 years old and ever summer I have a huge problem with it, because after I  change the mode to summer mode- so switch of the heating, the hot water stops working too. Today I give up and put back the heating mode to enable my family having hot shower. Any idea what to do, or what may be wrong. I have enough of calling the same service guys for years as I think he is not able to fix the issue permanently.


Hi Dan,

I would replace the PCB or the control panel- depending which Mighty model you have and check all the connections. From your description it looks like a problem with appliance mode control.