Why does the pressure on my sears kenmore boiler keep rising above the safety pressure?

Question

I have a hotwater baseboard system and the pressure keeps rising to the point where the pressure releif valve always kicks on. I bleed the system often. The boiler has 3 zones. It is about 12 years old. I recently replaced the expansion tank. What could be wrong?

Answer 1

not sure but you had better call a qualified repair man unless you want the boiler to go Thur the roof,

Answer 2

You have controls on the boiler called an aquastat and limit control. You didn't say if you get hot water for the house (tankless) On the outside of the boiler you will see the limit control. This tells the boiler when to turn on and off to heat the water., It may be that the limit is set too high. If its above 180 degree mark you will have to turn it down to around 170, The lower control should be at around 150. If the boiler shuts off when the inside water gets to about 190 or so the heat still in the fire box that was absorbed will still give off heat bringing the temp up to the boiling point, at this stage it will start making steam and the pressure builds up opening the pressure relief valve. Are all the circulating pumps working? when the system is on feel the pipe just above the pumps. The pumps pull the water out of the boiler and through the baseboard/radiators and back to the bottom of the boiler. after a few minutes they should get real hot, make sure all the thermostats are above room temperature so the sysytem is calling for heat in that zone. If you find one not getting warm means that the thermostat in that zone is telling the boiler that it needs heat and the furnace keeps turning on and off. If the circulator doesn't get hot means it will have to be replaced Hopefully you have Taco circulators. This shouldn't matter if the limit control is set at 170. If you do have a tankless check the aquastat which is usually in the same control box or very near the limit. Make sure this is set at 160-165. as this will tell the boiler to turn on and heat domestic water. Doesnt matter if the boiler is gas or oil the controls will be the same Take a look at the pressure gauge. This tells you the water temperature and elevation, On a two story house the elevation should be around 24 feet give or take. the water temp should be around 180. Usually the red needle is elevation and black is temp. I think I covered most to get you started. Happy Thanksgiving

Answer 3

First 1.5 is really too high as a start pressure, 1 bar is quite adequate. If your pressure is rising quite rapidly from start it is most likely a pressure vessel problem, either its busted or needs to be pumped up again. You dont actually say what model you have as they do vary but if you have the instructions for the boiler locate the pressure vessel and look for the inflater valve. Its exactly the same to look at as on a car wheel. Remove the screw on cap and depress the little core nipple carefully. What you should get is air but what I think you are going to get is water. I would suggest that you are probably going to need an engineer to sort the problem unless you are a very capable DIY person. If its busted depending on the model it may well be a cheaper option to abandon the onboard vessel and fit a piggyback vessel on the wall along side the boiler. That will obviously depend on where the boiler is located as its not pretty on the kitchen wall. EDIT I would take issue with the comment that the hot pressure is academic and the gauge is only to cold fill correctly. The pressure gauge can be a very useful aid in finding some boiler problems such as a faulty pressure vessel. How would you know that the pressure was rising quickly if at all if it wasnt there and to be able to say from that there appears to be a pressure vessel problem. Also to say if it goes over pressure its ok it will discharge the excess pressure off via the safety valve, why did it go over pressure,there has to be some reason for that to happen.

Answer 4

Here is how you test that problem. Fill the boiler to the correct pressure and run it. Turn off the valve that supplies the water to the boiler. With the valve off, if the boiler heats and it still pops off, then it is the expansion tank. If the boiler works correctly and the pressure stays good and doesn't pop off, then it is the fill valve or pressure reducing valve. If the boiler doesn't pop off, go ahead and run it until you get it fixed. Just check the pressure once in a while and fill accordingly if it needs it! Hope this helps! Good luck!

Answer 5

William H. has sound advice, also look at your make up water feed line, there should be a pressure regulating valve it might be installed upright or upside down doesn't matter. Turning screw clock wise will increase water pressure coming in and counter clock wise to turn pressure down, sometimes they get out of adjustment or have sediment holding them open slightly over coming boiler valve pressure setting. so it's either pressure or temp that's lifting it. The water pressure reg valve is there because your city water pressure is higher than the operating pressure of your boiler and it would lift the vlv continuously without it.Mine gets out of whack sometimes because my city does a lot of water main work all the time by my house and I get sand jammed in it, so it stays open a little bit or it gets crusted shut and doesn't let any make up water in and then I have a gurgling sound in my baseboards.Easy fix, I would bet that's it since you just replaced your expansion tank. Hope that helps

Answer 6

check that there is NOT a valve closed before your expansion tank. If you have a tankless coil on your boiler for making hot water, close the valve to the domestic water in and then check the pressure. This is to make sure your coil doesn't have a hole in it. Also make sure your boiler feed valve isn't stuck in the fast fill position.