I'm in the process of doing some remodeling in our house, and I need to replace one our our baseboard hot water heaters in a bathroom that I'm remodeling. I plan on buying the new unit and soldering the new unit in place. I'm pretty comfortable with this part.

Where I could use some help in on is the process to drain and refill the boiler. I'm planning on turning off the unit, connecting a hose to the drain valve and draining out the unit. After I've made my plumbing modifications, I am planning on opening the fill valve on the boiler, and while keeping the drain valve open, running water through the system until no air bubbles are coming out of the drain valve. I'll then close the drain and fill valves and turn the unit on again.

Is it as simple as this or have I missed any steps?

While I'm not completely familiar with the boiler system, here's some additional information. We have 2 zones - one has been shut down for now due to remodeling - so I'm only working with 1 zone. The system does have an "airscoop" or device to purge air out of the system. I'll check the pressure on the system - when it is running and when it is cold. Once the system is back up and running, I'll double check the pressure to make sure it is in the same range.

I also have an expansion tank - not planning on doing anything to that during this process. I appreciate any advice anyone can provide! Thanks!

 

Is the remodeling of the bathroom part of the zone that has been shut down

If the bathroom is on the second level and the boiler is on the first or in the basement, you wouldn't need to drain the whole system.

Just need to drain it down below the baseboard you are working on. Open the bleeder on that piece of baseboard to see when it is empty and to assist in removing the water from that section(venting).

 

When you have the boiler pressure down to zero to do the work is an excellent opportunity to check the pressure in the expansion tank if it is a diaphraghm type, or drain it if it's a conventional type. Do you know which type you have ?

Diaphraghm type has a "tire valve" on the end opposite the connection to the system, while the conventional is strapped into the ceiling joists above the boiler.

If you have the diaphraghm, use a tire gauge and check to see that there is 12-15 PSI of air pressure in the tank, but ONLY when the boiler is at zero pressure. You will get an inaccurate reading otherwise. If it's not enough, use a small compressor or bicycle pump (if you feel strong) and add air until you have enough.

 

NJ Trooper:

The expansion tank is brand new, as is the furnace. I had these replaced about 2 months ago. It's a new diaphram type of expansion tank. I'll check the pressure when I drain the boiler.

Brewaholic:

The work is not in a zone that has been shutdown. Even though the section of baseboard that I'm replacing is on the second floor, I'll need to drain the system all the way down so I can move some of the lines in basement - to preprare for a basement remodeling.


Once I've drained the system and refill it, how do I adjust the pressure in the system? I'm assuming that I close the drain valve, and open the fill valve when the system is running to get to the right pressure level. Anything more to it?

I'll check the pressure before I start the project, but what is the appropriate pressure level for a 2 story house plus basement?

Thanks for your help!

 

You don't want to fill the system while it's running.

If your system was installed with proper valves, you may have 'purge stations' on the piping, usually on the returns from the zones. There will be a drain valve and a ball valve in line with each other. Do you have those ?

Ya know what, best thing to do is to post pictures of your system, showing all the near boiler piping.

Install air bleeders on the new baseboard when you put it in.

12-15 PSI will usually 'do it', but if you wanna know exactly, take the elevation from the bottom of the boiler, to the top of the highest radiator/baseboard. Multiply that by .433 and add 4 .

If you are say 28 feet, that's 16 PSI, but 15 would be fine.
Remember that's the COLD pressure, it will go up when heated.