How to drain a single zone in my closed loop hot water system

Draining a single zone in my closed loop hot water system

As part of a rennovation project I need to temporarily remove some baseboard fin radiators. Like an idiot, I'm doing this during the winter so I'd like minimize the likelihood of disaster by consulting the experts.

I'd like to drain only the zone that I need to open up and continue to run the boiler and remaining zone as normal. I have ball valves on both the supply and return side of each zone, so it looks easy to isolate one zone. There's also a drain spigot in the shared return line that looks like where I'd want to attach a hose to drain a zone. What's not clear is how to ensure that all the water is out of the zone since the drain is higher than most of the piping and rads in that zone. (I'm draining the basement zone and the spigot is about 3 feet off the basement floor.)

A related question is if running the system with one zone isolated but "open" (i.e. a section of pipe and baseboard missing) for a few months is likely to cause any long term harm. After the rennovation is over I plan to connect the loop together again open the zone back up for operation.

Thanks for your advice!

draining

> 1) You can cut where needed after bleeding off

> the pressure from the drain you described, and

> have a shop vac ready...

Ah, yes. For some silly reason I was thinking I'd sweat the fittings apart, but I could just hacksaw it and clean up the result. Thanks!

> 2) You can leave the

> hose attached, and loosen a union on the supply

> side and blow compressed air from a compressor

> through the loop and drain it like a sprinkler

> company does it.

That would be particularly nice, if only I had a union on the supply side

> Do you have zone valves or

> pumps for each zone?

I have zone valves on each zone. If fact, here are a couple photos of the business end of the system. http://www.kroptech.com/~adk0212/pics/furnace/

I may cut at the boiler as you say, since there is an air vent (I think) that looks very corroded and probably should be replaced. Photo here

I'll turn off the t-stat, and maybe even disconnect it to ensure there are no accidents. Just read the article about running a circulator pump with the zones valved off. Ouch.

Thanks again for your advice!

You win the prize for most intriguing reply. I heard from the prev owner that there is antifeeze in the system, though I'd forgotten that until now. First question, how the heck did you know that from the ballvalve? Second question, does the existence of af change the course of action I should take?

The relief discharge ends just behind the water heater off the left side of the shot. There's a floor drain on the other side of the room, but it would be unpleasant if the relief blew (though not as unpleasant as if it didn't).

Antifreeze

Honestly, I was thinking of not replacing the af. I don't see a compelling reason why this system needs it, but I may need education on the matter. I have emergency backup heat in the case of extended power failure. There are a couple spots where the basement piping goes thru the slab under doorways and such. Those are about the only places I'd be worried about a freeze, and that seems unlikely during normal operation. Is there a reason to have af that I'm overlooking?