During my current bathroom renovation I had to drain my boiler to remove a radiator. I have since put the radiator back in it place but my boiler is still off and mostly drained of the water it once contained. The pressure is 0. I need to get the boiler back up and running and I need some advice on how best to do this. Is it as simple as just turning the water back on that supplies the boiler and flipping the electrical switch to turn it back on. And then setting the thermostat to on and wait for it to refill, while bleeding all the radiator of air as the water starts to circulate again. Please let me know as I don't know what the operating pressure for the boiler should be or if there are any special steps I need to take.

Thank you!

Is this a hot water or a steam system? You should be able to just open the supply and it refills on its own. Are these baseboard radiators of cast iron stand ups?

It is a hot water system with cast iron radiators that stand up. They have a supply and return and the water is circulated by a pump.

This doesn't sound like what I am picturing.

Please explain

This is a typical hot water boiler with circulator pumps that pump heated water to a radiator. The radiatror give off the heat and then the water returns through another pipe on the other side of the radiator back to the boiler. It uses gas for the burners. It has 3 zones only 2 in use.

I don't know why I did this but I assumed you had a single pipe steam radiator. From what youtell me it's a 2 pipe water recirculator, my fault for assuming anything. You will need to bleed each radiator starting with the one closet to the boiler.

Thank you, so, I should first turn on water to the boiler, then turn on heat, via thermostat, then begin bleeding each radiator? How long should I wait before there is enough pressure to bleed all the air and what is the target pressure for the boiler.

I would bleed first before turning on the heat. I assume you also have any expansion tank, right? Drain that too.

How would that work? If the heat is off there would be no pressure and nothing would come out of the bleed vavles. Or am I wrong. I had the radiator off is that not just a really big bleed valve? That ius where I am not understanding. Thnak you

You said you have a recirculation pump, that will push the water hot or cold. The big valve is not the bleed valve, there should be a small screw type bleeder on the side of the exit pipe. Can you post a picture of your radiator showing the valves?

But if the heat is not on then the circulator pumps would not be on and therefore no water would be circulating. So if I open the bleed valves at this time I really would not be getting the air out. My confusion is around you saying to bleed the system before I turn on the heat, there would be no pressure. I know which vavle is the bleed vavle. I was saying that having the radiator disconnected from the pipes leaves them open. I was using this as an extreme analogy to bleeding the system with the heat off. In both instances the pumps are off and the air reamains in the pipes. So my question is if the heat is off and therefore the pumps are off how does bleeding at this time help. Wouldn't the air just sit there. It seems to me the heat would need to be on so the pumps start and the pressure would build so that when the bleed vavles are opened the air would come out until the water starts to come out then close the valves. Am I totally off base??

There is an auto fill valve on most systems that fill, pushing the water, an air, out of the radiator. This should help you how to bleed a hot water radiator - Google Videos

No need to fire up boiler to bleed. Just turn on incoming water, go to each register and bleed them till you get water. Even with the pumps off, the water pressure coming into boiler will force the air out the bleeders. Now, once you get water out of every bleeder, you can fire boiler (pumps on) and go around and bleed the bleeders again to make sure no air comes out. It important to bleed the system without boiler fired at first, because the pumps will not circulate air, so if there is any air in the system, it may not circulate the water that is in the system. Hope this makes sense. Also, on a hot water heating system, the pressure reducing valve is factory set at 12psi, not need to let it get up to 12 before bleeding, just turn water on and bleed. Once system is filled and bled, the operating pressure should be no lower than 10psi, and no higher than 25psi max. If pressure exceeds 25, there is a chance of pressure relief valve blowing off. Pressure relief valve is factory set to blow off at 30 psi. And if pressure is to low, water will not circulate properly, if at all. Please let us know how you make out. Lee.

I know there is a pressure-reducing valve of some kind that has a lever on the water supply line as it enters the boiler (The lever let me add more water and increase the pressure faster). Will this cause a problem?

I remember a long time ago I had to fix a hole I put in a pipe once, I soldered on a repair coupling. When I did this, I had to drain the system a little to empty that pipe which was on the top floor. When I tried to restart the system, I turned the system on, put the thermostat on 90, and opened the bleed valve. It took hours before water made its way into that radiator let alone began to come out of the bleed valve ( the other radiators were hot). I kept on having to open the valve until air stopped coming out, but no water. I then closed it for an hour and then opened it again with the same results. It took almost all day to get water back up to this radiator.

Was the pressure-reducing valve preventing the water from getting up there fast as the pressure reduced when I bleed the radiator and took a long time to get back up?

Alternatively, was the problem that I was bleeding with the system on? Let me know so I fully understand.

Thank you.

Was my video of any help to you, it gives complete directions on how to do what you ask. MGD and I both say to bleed with the heat shut off. Thanks Bob

Yes, I saw your vid, and I am trying to get you to focus on my particular situation instead of giving generic advice. In my post, I am asking if you think the pressure reducing valve may have caused a problem with bleeding in the last situation. I don't know and that is why I ask. The video was overly simplistic and did not address any items beyond the local radiator, I have always known that aspect of bleeding a radiator if it is cold. But, I am trying to get a boiler back up to the correct pressure after having emptied it almost completely. The video did not discuss that, I am just trying to get a total understanding prior to beginning and while I have yours and mgd's ear.

MGD was very helpful in given advice specific to my question and I was trying to follow up with him, to understand my previous situation and understand if my bleeding while the pumps were on may have caused my past problem. That would useful learning experience for me for this and other tasks with my heating system, if that was the cause of my problem. I will be bleeding the radiators prior to turning on the system, as per all the suggestions, no question about that. Nevertheless, I am trying to see if the prv on the boiler will prevent the water pressure from getting high enough to make it to all the radiators and expel all the air with out the pumps, seems like that is true, but I wanted to share my past experience where I could not get all the air out even when I opened the bleed valve all the way and had the screw in my hand. Simple question, your answers and video did not deal with pressure and MGD began to answer that for me and I found that interesting.

Unless I misread something the first mention of a PRV came after my video posting. The PRV should not affect the bleed process.

Sure prv was first mentioned in mgd post, and I asked about pressure requirements for the boiler in my original question. Only he talked about that and in that discussion PRV came up, as it should. I found that helpful. I would hope that I would be led through the process and made aware of things that I may not know about like mgd did. I found that very useful and made me feel like I was getting a complete pict from him. But I appreciate your opinion that it should not affect the process. Thank you.

My video was post 13 and prv was talked about by MGD in post 14. Let us know if you run into any difficulties. When we first answer a question we try to keep it just to the basic steps since long, involved answers are a turn off for most folks. We get a dialogue going and answer one question at a time. Sorry if I was detailed enough.