How to bleed the zones in a hot water heating system

jws13

Hello... sorry for the long post but trying to provide as much info as possible...I've read several post on this topic but not exactly clear on which valves to open and close, how and when to add water to the system, and how to adjust system pressure if necessary.  I'm trying to help an elderly friend and long story short he called and said he needed a zone valve replaced because a zone wasn't heating and it has happened several times on his 4 zone system over the past 10 years.  I assumed he knew what he was talking about because when I got there he had a box full of old motors and parts that had been replaced.  So I secured the water, drained as little as possible and replaced the motor and the internal parts of the Honeywell zone valve.  Turned everything back on and all the zones except the one I worked on are working fine just like before, but the one zone isn't.  I placed the zone valve in manual and no change.  So I go to all the baseboard radiators and try to bleed them but out of the 5 I get cold water out of one and no water or air out of any of the others.  And the supply and return for the zone is cold as well.  Thinking that maybe the zone valve wasn't opening I took an old valve assembly and removed the rubber ball valve and reassembled it so basically it was like a straight pipe to that zone.  Supply and return pipes got a little warm but no heat at the radiators and no water or air and now 2 of the other zones are not heating as before.  I'm assuming that I've let air in the system and possibly the system pressure isn't high enough as well. From the pictures it looks like pressure is below 10 psi.  Sorry about the pictures but I forgot to take some before I left so he did his best.  As an fyi the system has a gas boiler and is also tied to an electric water heater with a boiler back up.  Appreciate info on how to go about bleeding the system unless you think it's something else... thanks 

jws13

Here's a few more pictures, could really use some help with this as we are in Colorado springs and weather is supposed to get really cold on Friday... thanks 

EBEBRATT-Ed

Hard to tell the layout from the pictures but I will try. Yes I think they have some bleeding to do. First thing is to get the boiler to 15psi and try and maintain that while bleeding. Leave the circulator and boiler off. Look at the air vent on the air scoop and open the cap on top it looks like it may be shut so that air vent can bleed.

Then close the supply and return valves & zone valves to every zone. Pick the zone you want to bleed first. Put a hose on the purge valve (third picture down) (the drain valve is between the ball valve and the zone valve) run the hose to a drain or into a bucket. Open the drain valve and the ball valve above it keep the zone valve closed. It should start draining and purging. keep the boiler at 15psi. Let the water run until no more bubbles close the drain and the ball valves.

Move the hose to the next zone. Rinse and repeat for each zone. When all the zones are purged open the supply and returns and zone valves to all zones and bleed all the rads.

When that is done open one zone valve and start that zone only run the boiler and pump. If it heats good. If not bleed the rads until it is heating. Then close that zone valve and move to the next zone rince and repeat. When all zones heat open all the zone valves

jws13

Thanks Ed .. now some questions.. can you tell me which picture has the air vent on the air scoop you mentioned, what's the best way to ensure the zone valves are closed, thermostats or does turning boiler power off take care of them, and how do I keep the boiler pressure at 15psi, and do I need to open the specific supply and return valves as I'm bleeding each zone . thanks 

EBEBRATT-Ed

13th pic down shows "American" air scoop with an auto vent on top of it. With the little cap loose, it should vent air but sometimes they leak a little, so the best thing is once everything is blead and working is to tighten the cap.

Alternate:

If you want to try something else is to close all the zone valve except 1 and run the boiler and circulator to heat just that zone. The air scoop and the bleeding of rads may get it going without all the purging. Might be easier. Than do the same thing for the other zones. Keeping only 1 zone open and running the circ pump may push the water and air through that zone. Then repeat for the other zones.

The pipe above the air scoop is the water make up with the backflow preventer and pressure reducing valve on it. The PRV has a "fast fill lever " on top if you pull the lever up and it bypasses the prv to fill water faster. Too much water will open the relief valve though so you have to watch it.

If you don't think you need to go through the complete purging of all zones just keep the zone valves open or closed by using the manual lever on the zone valve actuator. Just open 1 at a time and get 1 zone working at a time. Turn all the stats down to keep the zones closed. Open the zone valve on the zone you are working on.

Clear as mud I know it's confusing when you have a bunch of zones.

jws13

Ed this really helps, so thanks again.  Some more questions before I head back over there...do I use the prv bypass valve to keep the pressure around 15psi as I'm purging each zone, if the simpler method doesn't work and from reading other posts it sounds like keeping the pressure between 15&25 during the process is ok?  

EBEBRATT-Ed

Yes. All you are trying to do is when you bleed you lose water and air which make the pressure in the system drop. You just want to keep the pressure at 15-25 so you can bleed. You can Lift the lever raise the pressure go bleed some and check the pressure repeat repeat.

jws13

Ed .. you're a great guy.  Went back today and bled all the zones as per your directions and presto everything works.  Had to bled the second floor twice but no problem.  Thanks again from me and my friend, he was extremely thankful.