Residential boiler cycling again. House cold.

eclecticmn

In Feb 2023(?) I had an issue with my residential boiler. It was cycling and the house was cold but the radiators were warm. When the boiler temp dropped to 165 it would start up and keep running until it hit 180 then shut off. I figured out that the pump must be bad and replaced it with another Groundfos UPS15-58FC, 3-Speed Circulator Pump, 1/25 HP, 115 volt.

There is only one zone and I put the check valve in. Now the same thing is happening. I think my system is functioning like a gravity system. The pump should last more than 2 years, correct? Any chance the check valve is clogged?

If I replace the pump is there much advantage to the higher efficiency pumps? Any reason to put in the check valve?

I lack the skills to swap out the pump in a hurry and refill the system. My house is warm enough until the temp drops below zero as it has. Now I supplement with expensive electrical heaters for the next day or two..

Any thoughts? Should I wack the pump with a hammer?

EdTheHeaterMan

The limit setting to 180 is supposed to stop the burner so the water does not boil. You don't want boiling steam in a hot water boiler. (12 PSI gauge water boils at 245°F). The differential on your high limit must be near 15°F. If you have baseboard 4/3" copper/Alum fin then that is normal. If you have the old gravity piping in the basement with big 'ole Cast Iron standing radiators then you may not hit the limit because of the large water content. But if you are reaching the limit and you are not getting enough heat for the home, you can increase the limit temperature to 195°F and see if that helps.

jesmed1

What is the water pressure at the boiler? Do you have the old-style steel expansion tank, or a modern bladder tank? Have you bled the radiators?

With a relatively new pump, it sounds more like you have air in the system that's preventing circulation. Post some pics of the boiler gauge close-up, and of the entire system showing the expansion tank and any air eliminators.

eclecticmn

I have no air eliminators. I have no boiler temp or flow gauges. The boiler temp is from the LED readouts on the Burnham System 3. I have horizontal cylindrical expansion tank hung from the ceiling. There is no sight gauge to read the water level in the expansion tank.

I could bleed the radiators again.

tcassano87

you have pictures of the boiler & all the piping?

Have you bled the system or do you have a means to bleed the system of air?
How much pressure is in the boiler?

jesmed1

With no boiler gauges at all (?) how do you monitor your water pressure? I assume you know that you do need to maintain 12 psi or so in the system, or you will have air problems that impede circulation.

eclecticmn

There is a water pressure gauge where the inlet water comes in. There is no automatic fill. I turn on the water until it hits around 15 psi. At 18 psi it overflows. The house is two stories above ground with the boiler in the basement.

I have to leave the house for an errand but will take pictures when I return.

jesmed1

I'm not sure what you mean by "it overflows." Overflows from where? Do you mean the pressure relief valve on the boiler? That's typically set for 30 psi.

mattmia2

is there a tank in the attic? cast iron converted gravity systems can be hard on wet rotor circulators if there is a lot of rust in them. it is possible that it was just air bound when you replaced the circulator before. it will heat better by gravity if you open the flo check.

if the boiler piping isn't right the air will migrate out of the compression tank and in to the system.

eclecticmn

The overflow at high pressure? I cannot remember I only did it once.Yes a pressure relief valve. The water pressure gauge had a red limit mark at 18 psi.

There is no tank in the attic for sure. I will take photos and make drawing later.

hot_rod

What speed do you have the pump set on? You could try upping the speed to move more btus to the system

Increasing the speed can also move an air bubble to wheever you can collect and vent it out. In the radiators perhaps.

techforlife

Should be able to hear if the circ. pump is running. If it quiet but hot, hit it with a hammer, after all he said Grundfos. You could check for power at the 2 wires at the circ. with a meter. I saw Burnham and digital readout. Is it an IQ system? They are notorious for electronic issues. With the boiler in the basement and he bled the rads, I don't think his problem is water, especially if he is getting some gravity flow.

tcassano87

If your relief valve is blowing off at 15-18 psi it’s 1 of 3 things or a combination of them. It shouldn’t blow off at 18psi

1- you have the wrong relief valve, a 15 psi and not a 30 psi relief

2- the relief valve is correct but not functioning correctly

3- your boilers gauge is broken and not reading pressure properly(probably what’s going on if I had to guess)

GroundUp

An ECM circ is not a good choice for a cast iron system without a healthy magnetic separator. The 15-58 is a nearly bulletproof circulator, but the check valve does not need to be there with a single zone system. Was the system working well in the meantime, even during these nasty cold days we've been having (assuming you're in MN, per the screen name)? There seems to be a bit of a pressure issue between the gauge and relief, but that would not be causing the lack of temp. Without a few temp readings, there is no way to know what the issue might be but hopefully you can get us some good photos that may reveal something. If there is still a call for heat when the boiler cuts out, the temp of the supply piping exiting the boiler should be very similar in temp to the piping entering the radiation- do you maybe have an infrared temp gun that you could use to get a baseline on those aforementioned temps? Even just by feel alone possibly?