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Old 06-24-2009, 11:07 PM   #1
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Draining furnace, couple questions.


So I spent some time learning about how the furnace system works in my house and then i went and traced the whole system so I understand what does what. My plan is to drain the second zone so I can remove the pipes to remodel the wall so I want to make sure I'm doing this right before I proceed.

My understanding is I need to do these steps.

1.) Shut the return valve off for the zone I want to bleed.(#1 in photo)
2.) Attached hose to spigot and open that to drain the water out the hose(#2 in photo)

So, here is where I have a question.

- Will the pipe empty or will the water just be replaced to keep the pressure the same? I know I have that "thing"(number 4 in photo) that will add water to keep the pressure the same.
- If the heat is off for that zone will water still flow from the zone control(#3 in picture)?
- Should I shut the water completely off to the system(blue knob below the number 4).

If I don't need to shut the water off because it wont flow through the zone valve when it's off how do I force it open when it's time to refill it?
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Old 06-25-2009, 06:13 AM   #2
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Draining furnace, couple questions.


Yes, you need to close the valve on #4 (automatic fill valve). In theory the zone valve would keep water from flowing but I wouldn't trust it with the system opened up. Closing that valve is very cheap insurance. Keep in mind, after you drain the system, you can still expect to get some water to drain out when you cut the pipe. It can be up to a gallon or so depending on where you cut and how many ups and downs your system has. One trick I've used to get all the water out before cutting is to connect a cheap ice maker saddle valve to the pipe and drain the residual water before I cut. FYI, you have a boiler not a furnace. Good luck.

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Old 06-25-2009, 06:31 AM   #3
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Yes, you need to close the valve on #4 (automatic fill valve). In theory the zone valve would keep water from flowing but I wouldn't trust it with the system opened up. Closing that valve is very cheap insurance. Keep in mind, after you drain the system, you can still expect to get some water to drain out when you cut the pipe. It can be up to a gallon or so depending on where you cut and how many ups and downs your system has. One trick I've used to get all the water out before cutting is to connect a cheap ice maker saddle valve to the pipe and drain the residual water before I cut. FYI, you have a boiler not a furnace. Good luck.
Thanks. Here is a closer picture. Should I shut the water off completely(blue valve) or will the auto fill valve have a shut off too?

Since this system heats my hot water I don't want to leave it off, should I plan on capping the ends of the pipe after I remove the baseboard so I can turn the water back on and not have to worry about it?
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Old 06-25-2009, 07:25 AM   #4
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Draining furnace, couple questions.


Ahhhhh. You have an "open system". I'm going to let someone else tell you how to proceed since I have no experience with this type of setup. Basically, you need to isolate the zone you will be working on and in this instance, you don't want to shut off the fill valve because you don't want to risk running the boiler out of water. It might be acceptable to use the zone valve to isolate the zone. Hopefully a pro will weigh in.
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Old 06-25-2009, 12:10 PM   #5
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Draining furnace, couple questions.


Would it be a safe bet if I turn off the power to the boiler, turn off the main water, cut the pipe and solder it back just in a loop without the baseboard and then turn the water and power back on?
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Old 06-25-2009, 12:23 PM   #6
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Draining furnace, couple questions.


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Would it be a safe bet if I turn off the power to the boiler, turn off the main water, cut the pipe and solder it back just in a loop without the baseboard and then turn the water and power back on?
I know basic boiler and closed loop heating systems relatively well, but I don't feel comfortable chiming in on your original question as you have a lot of stuff going on in and around your boiler. But with regards to your last post; you'll still need to drain the loop before cutting into it. Yes, turning off your water main will mean there is no water pressure going into your boiler and therefore no pressure coming out of it, but there will still be water in the system. What I did when I had to work on a radiator on my 1-zone system a few years back was just turn off the water at the boiler's inlet, open the bleed valves on the radiators to establish a vent, then drain the boiler (which drained the entire system). At that point, I did the work I had to do on that radiator.

In your case, with a 2 zone system, I don't know if you can drain just the contents of the pipes in one zone. You may have to to drain at the boiler like I did, which means you'd have to drain both zones...I think. I'm not sure though.
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Old 06-25-2009, 02:01 PM   #7
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Draining furnace, couple questions.


If I'm understanding what I read/see in the pics:

If you can close the zone control (#3 in first pic) manually, and close #1, then that zone is isolated from the system and can be worked on. You would not need to shut any other part of the system down.

Opening #2 will not drain the loop fully; you'll have to break the vacuum at the top of the loop first (either with a bleed valve, or by cutting/disconnecting the pipe). Like Joe F said, you might still have lots of water come pouring out when you disconnect the pipe anyway (I like the saddle valve idea!)

As for how to close the zone control manually, I have no idea. If you take the cover off, you may see something to turn. Otherwise, it's probably normally closed so if you disconnect power to it, it should not come on (it's summer, so it probably won't come on anyway if you have your T-stat set really low or off). You'll know if #3 isn't closed if when you open #2 you have lots of pressurized water coming out.

Don't turn off the main water supply to the boiler unless the boiler is off also (using the emergency cutoff switch).
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Old 06-25-2009, 02:41 PM   #8
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As for how to close the zone control manually, I have no idea. If you take the cover off, you may see something to turn.
The zone valve will be manually closed if you remove the motor (1/8 turn CCW) or put the lever in the up position. I am not sure if a zone valve provides a true water tight shut off.
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Old 06-25-2009, 02:50 PM   #9
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Draining furnace, couple questions.


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The zone valve will be manually closed if you remove the motor (1/8 turn CCW) or put the lever in the up position. I am not sure if a zone valve provides a true water tight shut off.
Well, I guess one way to find out is to hook up a hose to the out, close the connection that feeds back into the system and let it rip. If it's shut off the water should stop coming out...if not then it wont. :-)

Actually, will the water flow if there is no hole on the other side? Is that was the bleeder is for that I'm not sure is there?

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Old 06-25-2009, 07:50 PM   #10
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Draining furnace, couple questions.


I wouldn't be too concerned about a great deal of water coming out and causing a "flood". If water goes past the zone valve it should only be a trickle. However, a trickle could be enough to prevent you from being able to solder it back up.
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Old 06-25-2009, 08:15 PM   #11
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Draining furnace, couple questions.


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However, a trickle could be enough to prevent you from being able to solder it back up.
Could always keep a pipe with a compression coupling on one end and a pipe cap on the other handy for a quick solder-free seal-off.
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Old 06-26-2009, 04:28 PM   #12
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Draining furnace, couple questions.


okay, after mastering "sweating" over the mast couple of days I feel confident I can repair the pipes now. So, I hook up a garden hose to the outlet, shut the outlet valve off and slowly turn the spigot .... nothing.

After thinking about it for a while it hit me (duh) there is nothing to take the place of the water so it wont move..same thing if you put your finger over a straw with liquid in it. So, how do I put a small hole in the pipe to allow air in so the water can flush out? I don't just want to cut the pipe completely because the water will pour out, I figure a small hole is more controlled or is there a better way?


Oh, and side note. How long does it take the water in the pipes to cool down? I found how to override the thermostat and I ran the heater accidently for a few minutes. :/
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Old 06-27-2009, 08:42 AM   #13
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Draining furnace, couple questions.


Might try a saddle valve at the point you're going to cut into. That should get the flow started.

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