Yes, if you have valves on the supply side it is no problem. You isolate the boiler from the distribution piping, hook a hose to the boiler's drain, loop it over something a little lower than the air valve, and you'll only empty down to the crown weir of the hose.

Having valves on the supply side will also make swapping the relief valve easier. On my boiler I have the circulator valved off but that is it. And if the relief drips, it's into the corner where I cast a 5gal bucket-size pit into the floor while pouring a new slab, twenty years ago.

It is fairly common to loop a hose over the highest pipes to empty a system just enough to move radiators etc.

Keeping a dedicated hose, cut down to a manageable 10' or 15', by the boiler, makes service work easy and cuts down on floor clutter. My go-to is 15' and works for most work.

Just go ahead and valve off all the zones and drain the boiler to change the A/V and relief at the same time.

Then refill with water BEFORE opening them back up.

Might as well make it easy and get them out of the way now, since you have to bleed the system anyway.

And while the boiler is drained and there's no pressure on the boiler (expansion tank), check the pressure on the expansion tank.

OK... took a look at the tank. Appears there is a typical valve stem on the bottom, so I guess I check it with a tire pressure gauge.

YouTube tells me 12psi - is that right?

quote:

Originally posted by motor59:

YouTube tells me 12psi - is that right?

Very important, you can only check it when there's no water pressure on it!
Yes, standard air gauge.

12 psi is the factory setting.
Actual setting is dependant on boiler piping. What the distance between the boiler and the top of the highest radiator?

I’ve never had to service one, only replace when a bladder ruptured. You’d get water out of the Schrader instead of air. Plus, your relief valve would begin regularly discharging every time the boiler brought the water up to temperature.

Here’s a typical spec sheet:

https://www.amtrol.com/wp-cont..._19-Fill-Trol-IO.pdf

It's weird... both ends of the expansion tank have schrader valves in them. I expected the cap on the auto vent to be covering a hole, based on what I've seen in videos so far - but there's a valve in there. Played with it a little bit before bed last night, since it was cool for a change. Let a buncha air out, but I'm sure there's more in there.

The one on the little air vent on top ["float vent"], you push in until water comes out to test it. It is supposed to vent air automatically as collected by the air scoop. Only the expansion tank is pressurized with air.

Excam mentioned height. A pound of water pushes roughly two feet, so setting your autofill for 12psi water pressure should be enough to push water into 2nd floor radiators.

https://www.amtrol.com/product/air-elimination/

Air Vents. Float vent automatically removes air from a closed heating system that can affect performance and cause corrosion. Available with 1/8” or 1/4″ connections. Quick-Change model available.



I was buying a whole lot of Amtrol pressurizers for a while; they sent me a couple nice camo hats with their logo; but besides that, it is a great company with a great line of products.

quote:

Originally posted by motor59:
It's weird... both ends of the expansion tank have schrader valves in them.

Uh, no. Tanks have one air fitting. The other end is a 1/2 MIP to screw into the boiler piping/air purger.

Obviously, you are correct. I misspoke.
What I meant to say was that there's a schrader valve under the tank, and another in the vent atop the air scoop. I didn't expect to see one there. I thought the cap just covered the hole for the air to vent.

As to your previous question, the furthest baseboard from the boiler is somewhere around 90' away... 20' vertical and 70' horizontal.

Schrader on the tank is for the air in the bladder. Which compresses when the water expands from heating. Lowering the overall increase in pressure due to the heating cycle.

The Schrader port on the air vent is to vent any air which is in the boiler piping. Inside is a float, as the float drops the air is vented, as the water fills it up, the float rises and covers the port to keep water from leaking out.

Given your measurements, 12 PSI is where you want your bladder and boiler pressure set at for your system.

BTW, make damn sure you get a pressure relief that is set at 30 lbs (used for boilers) and NOT 150 lbs (used for water heaters).

Relief Valves 101:

Your typical boiler relief valve, like a residential series Watts 335, is a pressure-only relief valve factory set to blow at 30 psi.

https://www.watts.com/products...me-safety-valves/335

A water heater relief valve is designed to protect against both excessive temperature and pressure, hence is commonly referred to as a "TP valve". A fine example is the Watts XL100 series. I *believe* the supply house usually tosses a 150psi-210˚-rated TP valve on the counter if you tell them you're replacing one on a residential WH. Note the long temperature probe. Your boiler piping is configured such that a TP valve cannot be installed.

https://www.watts.com/products...-relief-valves/100xl

I've noticed that many residential boilers come with an accessories piping kit of threaded steel fittings which permit only a boiler relief valve to be installed. Although if you do not read the directions or even look at the pictures, anything is possible.

If the discharge is horizontal, I'll hand-tighten a ¾" steel street elle into the relief valve to move to vertical discharge, then a short piece of ¾" copper with a male adaptor crimped / soldered to the end. This allows one to unthread the discharge pipe for relief valve replacement without cutting anything. You have no such issue on your installation.