Home>Discussions>PLUMBING>Bleeding non-standard hydronic heating system
9 posts / 0 new
Last post
Joe99
Bleeding non-standard hydronic heating system
Joe99

I recently purchased a home with a boiler/baseboard heating. The problem I was having was that only one zone worked. On other forums, it was suggested that I "power purge" the 2 zones that were not working, but I didn't get any info on how to accomplish that. I have attached links to pics of the system here:

http://www.imageno.com/n3hicq2i0tctpic.html
http://www.imageno.com/6tit7ul0g3wipic.html
http://www.imageno.com/tuee6ygavshnpic.html

The problem is that all the links/tutorials/youtube videos of purging a boiler system show the automatic boiler fill valve coming in on the supply side. With this one, the fill valve goes in right with the 3 return valves, just prior to the air scoop.

I have tried adapting the bleeding process by closing all supply and return valves, except one supply valve. I then manually open corresponding solenoid. I then run the system all the way up to 30PSI with the manual lever of the boiler fill valve. The intent is to push the cold water through the boiler, and out to the zone.

I then close the supply spigot, open the return spigot from the zone, and open the blue upside down spigot. I tried that about 10 times, and all I appear to be doing is pressurizing the big gray tank, and bleeding that pressure off when I open the blue spigot. The boiler is still hot, and if the cold water was flowing through it, I would think it would start cooling off.

Does anyone have any insight on how to bleed/power purge this system? Thanks.

brewster
Re: Bleeding non-standard hydronic heating system
brewster

Joe99:

1) I have serious doubts that your problem is with the lack of water in the zone pipes---more likely it is related to a loose low-voltage wire or a dead solenoid inside the zone valves (those round silver things on the main supply pipes)---I can't see from the angle of the excellent photos you posted, but there is usually a tiny neon red or orange light on each of the zone valve housings that light up when something happens to the wiring or a solenoid dies that shuts down the zone valve for a particular zone---by all means temporarily shut off the main power switch & take a screwdriver and tighten all the screws that hold the little wires to the zone valves---make sure that all terminals of the zone valves have the same number of wires, & that they are all firmly attached to the screw terminals.

Just 3 zone valves makes a real "rat's nest" of wiring that is very hard to follow just by looking at it; there are wiring panels that can be installed to eliminate this problem; also, each zone valve mfgr issues a diagram of color coded wires and to which terminal they all go to----follow the colored wiring scheme for now with the one zone valve that IS working if you cannot find the applicable wiring chart on-line.

Check to see if there are any tiny neon lights on the zone valves, which would indicate which zone valve solenoid, or one with the loose wire is stopping flow in that particular zone---green lite means the ZV is ok; orange or red lite indicates there's something wrong with that particular zone valve.

This should be a low cost repair if you call in a service person that is EXPERIENCED WITH HOT WATER (HYDRONIC) HEATING SYSTEMS.

To briefly review the PROCESS of how zone valves work: First, the THERMOSTAT in a particular zone (room) CLOSES contacts when the room gets cold & this initiates a call for heat to the ZV (for that room) & boiler; SECOND, the T-stat wire is connected to the zone valve for that particular zone & electrical energy heats up the little solenoid inside the zone valve to open it; when the zone valve is completely open (takes approx 2 minutes) the opened ZV sends a 12v voltage signal to the boiler AQUASTAT (control switch on the boiler) to fire up the boiler, turn on the circulator pump, & circulate hot water thru that particular zone to heat the room; when that zone (room or floor) is warm enough, it shuts down the T-stat in that room (the T-stat opens from the added heat), which shuts down the boiler as the zone valve slowly closes.

2) To check & address any low water condition in any of the baseboard zones you can remove the end parts of the baseboard housing in any of the zones/rooms & take a screwdriver to OPEN UP THE LITTLE BLEED VALVES that are used for this purpose (they always have a little metal slot to accommodate the screwdriver)--hold a small paper cup near the bleed valve to catch water coming out----close the bleed valve with the screwdriver as soon as water comes out of the bleed valve; the pressure reducing valve (PRV) at the boiler (usually set to 12 psi) will automatically maintain aprox. 12 psi of water pressure throughout the system.

Joe99
Re: Bleeding non-standard hydronic heating system
Joe99

Brewster,

First, thanks a ton for the in-depth reply. The valves have no lights on them. The valves are Honeywell Synchrons, running on 24VAC, similar to this:

https://hdsupplysolutions.com/shop/p/honeywell-24-volt-replacement-zone-valve-motor-p212747

I'm an Electrical Engineer, so the electrical system is the first thing I checked. 24VAC is good, and making it to all the thermostats. When you turn the thermostats on, the boiler does come on and heat up, and the Synchron valves open up as commanded. All wiring is consistent, all valves are responding, and the boiler is heating fine. It looks like everything works!

To give you a sample troubleshooting sequence, I'll turn on the upstairs and downstairs thermostats to the max, and make sure that all "to" and "from" valves are open. The boiler turns on, and the Synchron valves to both zones open. Within a few minutes, the one upstairs gets hot, the one downstairs shows no sign of heat. I'll turn off the upstairs thermostat so that only the downstairs zone is open, and still no hot water flows.

With everything cold this morning, I started from scratch and tried to "trick" it. I turned the thermostat downstairs all the way up, and the boiler kicked on and the downstairs zone Synchron opened (as it should). I manually opened the Sychron to the upstairs zone, and sure enough, it heated up. I closed the manual control on the upstairs zone, and still, nothing to the bottom zone. So the hot water supply is available at the manifold, and is proven to be capable of circulating through the upstairs system. Even when you manually open the downstairs Synchrons, the water does not flow. I would have thought the upstairs zone would be the problematic one, since it has to fight gravity!

I have checked the majority of bleeder valves you were talking about - as soon as you crack them, water comes right out with no sign of sputtering air. The PRV is maintaining pressure at about 20PSI cold, and when it heats up, its about 21-22 PSI and 180 degrees.

So to put the problem in its simplest form, I can have the boiler heated up and ready to go. By manually controlling the Synchron valves, I can get water to flow to the upstairs zone, but I can't get even the slightest sign of heat to the downstairs zones. It's like there is some hidden shutoff valves blocking flow to the bottom 2 zones, but I have looked everywhere I can think of. There must be something else I'm missing.

Joe

dodsworth
Re: Bleeding non-standard hydronic heating system
dodsworth

The only thing I can think of to try is to check the copper supply/return lines (usually 3/4" or 1" throughout the cellar wherever visible-usually near the boiler) to see if there are any brass hydronic BALANCING VALVES present in any of the piping---these are often installed to provide balanced HW flow thru the system when more than one zone is calling for heat---but they almost look like regular brass soldered piping connections---except that they have an almost inconspicuous screwdriver slot---horizontal is full open----vertical is completely closed.

Sometimes even when they are set to "partially open" they can accumulate internal crud over the years & completely shut down a given zone.

To view an image of a brass balancing valve: Google Watts HBV 1" balancing valve SKU 3095 (Plumber's Stock).

Joe99
Re: Bleeding non-standard hydronic heating system
Joe99

I googled that valve, and I cannot find anything like it in the house. We are on a bed of ancient lava, so there is no basement.

I took some pics of the radiators to see if that sparks any suggestions:
http://www.imageno.com/eg91ehpx09qlpic.html
http://www.imageno.com/aljzfinby010pic.html

Also, it was suggested to put valves on the return elbows, and I drew a picture to try to explain it:
http://www.imageno.com/x4l7sf0evy9tpic.html

I can't purge it, because there is only point of exit for the system (blue spigot) which is co-pressure with the supply line, so I can't create a pressure differential. I'm still trying to figure out how they even filled the system in the first place. The only way I see to fill/purge this thing is to open up the "hygroscopic disc" valves all over the house and let water squirt all over the place!

von_steuben
Re: Bleeding non-standard hydronic heating system
von_steuben
Joe99
Re: Bleeding non-standard hydronic heating system
Joe99

I'm still trying to find a solution to this. I found a bleeder on one of the radiators on the far side of the house with a good clean 2" hole in the concrete around the copper pipe, which allowed me to just let the water flow down in to the ground. Yes, I know that is probably a bad idea with cold weather coming up, but I'm desperate to figure this out.

I turned on the heat, made sure the boiler was warmed up, and closed the return valve to that zone to ensure the water that was coming out was coming from the boiler and not the cold supply line. I let it sit for a good hour with the bleed fully open, and still just cold water was coming out. That leads me to believe that it is definitely a flow problem. Am I right in assuming that is one of 2 problems - air in the system or a partial blockage? I opened up all the bleed valves to make sure only water is coming out, which points to partial blockages.

That leads to the question of what now? I can't exactly snake the system out. Possibly re-plumb the cold water supply on the "supply" side of the boiler, and install valves on the return side that I can drain them individually?

Or could the circulator pump be dead? Like some strange phenomenon where the upstairs works due to rising hot water and gravity, and the downstairs needs a circulation pump??

johnjh2o
Re: Bleeding non-standard hydronic heating system
johnjh2o

Check the valves on both the supply and return side to be sure the stem hasn't broken. It's quite common with gate valves. If the handle spins without coming to a stop the stem is broken with the valve in a closed passion.

Joe99
Re: Bleeding non-standard hydronic heating system
Joe99

I don't know what I did, but all zones are working. I went around and re-bled a few random valve locations. I had went around and bled them all last night, so I don't know what the difference was. However, somehow, when I was messing with one of the valves, I heard the radiator start to crackle and the water started flowing. My only guess is that I "nudged" the water along somehow, and once the water was flowing, the air scoop started taking extra air out of the system?? I really don't like it when things start working and you don't know why.

For anyone else with those "troublesome" bleeder valves, the following valve was suggested to me on another forum:

http://www.supplyhouse.com/Webstone-41685-1-8-FIP-x-MIP-Full-Port-Forged-Brass-Mini-Ball-Valve?gclid=CKH7jczsycgCFQwXHwodCEgCLA

I plan on ordering a bunch of them and replacing every bleeder in the system. Those things are nothing but trouble, and once you crack them open, they don't like to shut off again.

Anyway, thanks everyone for the help!

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.