Hey all-

I was just over at a friends (turn of the (last) century) house- w/ an upgraded (in the 70s-80s by the look of things) hydronic system + fin tube baseboard radiators.  They were complaining of no heat on the second floor.  Easy, right?  =bleed the radiators on the second floor.

Except there are no bleeds on the second floor.  I even hand-over-handed the whole system (except for the risers in the wall, of course )

Am I missing something big picture here?  I've always, always found bleeds in a hydronic system at the high point/furthest point.

The boiler has an auto bleed, but I don't think that that little pump is going to be able to move enough water to push air down to the basement to let it out there.

Thanks-

BobH

Almost all systems have vents located in the discharge piping of the baseboard heater that you can see when you take the cover off of the heater.  I assume you looked there given your knowledge level.

That said, there are a few systems out there with no vents.  What are the safeties set at (normally 30 psig)?  What do you normally run the pressure at?  I would try the easy way first:

###1###

Run the pressure up as high as you are comfortable.  This might be 25 or 26# or so.  I wouldn't run it up this high if I suspect corroded piping in the system that may not take the abuse. 

Running the pressure higher will squeeze the air bubble in the baseboard heater and possibly allow some water flow through the unit.  If you can make this happen, the water will entrain the air and carry it down to the vent in the basement regardless of the size of the pump. 

If this is working, you will run the pressure up and then come back later.  The pressure should have come back down on it's own somewhat because of the air that has left the system.  If you still have no heat, run the pressure back up.

If the pressure stays high and this procedure doesn't restore heat, then:

###2###

Check the zone valves.  Push the manual open lever.  Do you hear flow?  Does the unit provide heat? (this will only work if the circulating pump is running)  Problems related to zone valves can be the zone valve motor, the valve itself may by locked up, the transformer used for control power may be bad, the thermostat could be bad, or there could be a bad circuit board.  Replace part as necessary.

I've listed the zone valve check as #2, but you could do it before trying to run the pressure up if it's easier with your system.  Do whichever you suspect or what is easiest first.

When you are done, put the pressure back to normal.  Normal pressure should be 0.433 X the height of the system in feet.  Then add 3 to 5 pounds for a margin for error.

If that doesn't work:

###3###

Check the vent in the basement.  Are you sure it's working?  If it isn't, the air in the system will accumulate at the top of the system.  This air may normally be entrained and carried down to the automatic vent.  If the automatic vent doesn't work, the air will just be carried back to the top of the system.

If you aren't sure, replacing this will probably involve unscrewing it and screwing a new one in, which would be easier than sweating new manual valves in at the baseboard heaters.

After replacing the automatic vent, repeat step #1.

If this doesn't work:

###4###

Is there only one circulating pump in the system?  My house has 5, and they aren't all right at the boiler.  Make sure you know how many there are and that they all work when they are supposed to.  Make sure you are hearing flow when any of the pumps are on.

Or:

###5###

Give up and sweat in manual bleeders.  Hopefully one of the above procedures will save you from this, although sweating in the bleeders isn't that difficult anyway.

-Reed

Thanks, Reed--I knew I could count on you.  I couldn't for the life of me find a bleed up high...as there are none.   I've been trying to force the bubble down to the boiler, and it ain't going.  There's no real 'zones', there is  just an upstairs loop, and a downstairs loop--with balance valves.  I've tried just running the upper loop (Isolating the other with the balance valves..as well as producing a bit of hydraulic shock by slamming them... )--in hopes that that would push the bubble...but...no.  From the pieces of equipment scattered about the floor in the basement, they've replaced the original B+G pump with what looks like a little Taco.  I suspect that the replacement pump may have been chosen based on $, not specs.

I am thinking that a real nice, easy solution for this is going to be to just cut in a high point (auto) bleed. 

Thanks again-

BobH

Has the system ever worked properly in it's current configuration?  The fact that you isolated the lower loop rules most things out and makes raising the pressure less likely to be a successful strategy. 

If you are going to put an autobleed in the top of the system, I would suggest replacing the one downstairs, and if that doesn't fix the problem, swap them back out and sweat the new one in upstairs.

What kind of exspansion tank do you have on this system is it a bladder or and old tank. If it is and old tank make sure the system isn't isn't water bound.

Thanks for the replies--I should state up front that the bulk of my real world experience is not in residential hydronics.

I was told that the system did, after the last time it was 'serviced' (several years ago), work.  For most of one winter.

There is an auto bleed on the boiler...encased in a mountain of lime--I hesitated to touch it, as I'm looking at this as a favour and don't need to be snapping corroded brass fittings off of the boiler at this point...

FWIW--The boiler fill valves lead down to the deck where a l'il expansion tank (?) 3-5 gals or so sits.  There's a complicated looking ball of brass that tees into the end of this tank.  I assumed that the ball o'brass is a check, but...who knows?  I didn't check them closed, as they too, are corroded...and look suspiciously like they are open...

I got about this far into it (no bleeds upstairs, and a quick look at the boiler), when I got a call from home and had to run.  If I (have to) go back, I'll report more.

I think that I need to check to ensure that the tank isn't waterlogged, and I need to replace the boiler bleed.  I'd like to add a high point auto bleed so  that I never have to go back there, too.

BobH