Troubleshooting Baseboard Heater

Problem

Baseboards in one zone (basement) stopped heating up. Suspect the zone is air-bound.

Here's the configuration of our natural gas boiler and hydronic heating system. Zone 1 is not heating up. Wiring is not shown.

What We Know Now...

- Valve motor/switch receiving calls for heat just fine (switch responds), but no hot water flows to zone.

- Supply pipe from boiler is cold after first few feet. Return pipe to boiler is cold (luke warm). Pipes for other zones are hot. - There are 3 zones in the house, one for each floor.

- 3/4" copper pipe used on 2nd and 3rd floor zones. 1/2" copper used on basement zone. - Approximately 18 vertical feet from boiler in basement to 3rd floor baseboard registers. - Water pressure gauge on boiler reads 10-12 psi with 2 of 3 zones currently heating (hot pressure reading). - Natural gas boiler.

- Pressure tank w/ butane bladder (100 psi max) is mounted atop boiler unit on its side.

- We are on well service (our own well).

- Its winter and temps are in the single digits (Anchorage, AK in December). - Basement thermostat appears to be working fine; 24v metered at boiler when call from tstat was made.

- There are no purge valves on baseboard emitters.

- You can hear bubbles in the pipes at boiler when its running.

Symptoms Leading Up to This Problem

- Heat in basement stayed on despite tstat no longer calling for heat. Then zone stopped heating altogether.

What We've Tried So Far...

1.) Replaced Honeywell Parts for Basement Zone

- New zone valve motor (silver cylinder on top)

- New end switch (springs and lever in the middle)

- New ball valve (brass thing below)

>> Result - No effect.

2.) Checked wiring connections. Removed wire nuts, re-twisted all connections and reinstalled nuts.

>> Result - No effect.

3.) Attempted to bleed air from system following these steps...

a. Shut of power switch for boiler

b. Shut off all 3 return valves

c. Connect hose to basement zone drain valve

d. Grab 2 buckets

e. Push basement zone valve lever to Open (to the right), make sure it hooks in and stays put

f. Slowly open basement zone drain valve to let water start to flow

g. Let water flow until no air comes out (we got less the 1 gallon from basement zone)

h. Shut off drain valve to hose

i. Repeat process for next zone (valves, hose, lever, bleed)

j. Pull up on pressure value to increase pressure (no effect, no change on dial)

k. Return pressure valve back to original position

l. When all successfully(?) purged, open valves, return valve lever to Auto, and turn on boiler switch again. >> Result - Purging air from basement zone yielded less than 1 gallon before water stopped flowing. Purging other zones next yielded almost no water. We suspect we are either doing it wrong or too much air is in the lines to allow purging this way.

4.) Replaced batteries in Thermostat

>> Result - No effect. Batteries are OK.

5.) Swapped Thermostats Upstairs and Downstairs

>> Result - No effect. Both appear to be functioning properly.

6.) Checked voltage at the End Switch.

>> Result - No effect. 24v received from tstat. Switch responds to call for heat.

7.) Messed with Sasquatch. Without doing anything else, I lifted the lever on top of the Pressure Reducing Value (PRV) and observed the water pressure gauge.

>> Result - No change over several minutes. No noise or other change by lifting lever. Lifting PRV lever resulted in no response of any kind. Boiler switch was on while doing this.

8.) Poked the Bear. Connected bike pump to small pressure tank. Pump has a pressure dial on it, so we pumped it up to ~25 psi at which point the relief valve began to empty some water.

>> Result - No effect on main problem.