Reverse Flow Purging

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Old 01-26-14, 11:58 AM
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Reverse Flow Purging

Hi,

New home owner here, the house that needs a fair amount of work but I am very comfortable with most projects so no big deal. However I have never had any experience with hot water heat before and have a few questions about purging air from the system.

From the direction arrows on the pump and zone valves and the boiler manual the system is as follows:

Boiler → expansion tank → main shut off valve → spigot (A) → split into zones → zone shut off values (A) → radiators → zone shut off values (B) → honeywell zone values → merge into single pipe → grundfos pump → Tee with supply line that also has drain spigot on it → boiler

Everything is currently working and I have heat but one zone has air in it that I would like to purge out. From what I can tell purging will require closing the main shut off and using supply pressure to push water the reverse direction through the pump and zone valve and then out spigot (A). The honeywell zone values and zone shut off valves (A) could be used to control which zone is being purged.

My questions are does this process seem right, and will verse flow cause damage to a grundfos ups15-58fc pump or honeywell V4043 or V8043 zone valves?

Any help is appreciated.
 
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Old 01-26-14, 12:37 PM
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Welcome to the forums....

IMO dont purge anything if you have heat at the moment... If you have air its most likely your air elimination device is not working..

That should be replaced, but we need pics to see what you have...

Also could be a water issue...

Whats the make and model of boiler?

What does the pressure and temp gauge read on the boiler...

Lets start there....
 
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Old 01-26-14, 12:57 PM
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It could be the air elimination device it looks original.

The water comes straight form the well and always has so just about anything could be in it.

The boiler is American Standard GPM-8 of 1974 vintage.

The pressure gauge reads about 17 to 18 psi but it has never moved so I'm not sure if it works or not. The temp gauge holds about 180 and will drop to 140 when a zone opens. At 140 the boiler fires and will bring it up to 190 before it turns off again.
 
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Old 01-26-14, 01:07 PM
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Generally you would have a drawoff (spigot) on each zone before the shutoff (B).
Since you have just one on the return you have to shut both A & B valves on the zone that's good and leave the other zone to be bled open.
Manually open your zone valve to allow flow. Get your boiler up to about 25 lbs or so using your fastfill lever on your feed if you have one and open spigot on return line after pump. Keep pressure up until water flows steady.

Shut drain and fastfill if used and drain excess water to about 15 psi on boiler. Open all valves and fire up.

If you still find a liitle air left you can bleed it after the water heats a little.

As lawrosa said it is good to do this hot but get the lions share cold first.

Good Luck,
 
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Old 01-26-14, 01:15 PM
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Pictures are attached

The first shows the outlet of the boiler, pressure relief value, air elimination device, main shut off value and spigot (A)

Second shows the main shut off value, spigot (A), the zone split and zone shut over values (A)

Third shows the zone shut off valves (B), honeywell zone valves and zones merging on top of the pump.

Fourth shows the pump, supply line and drain valve, and the gauge with the pressure on the left needle and temp on the right needle.

Fifth shows the supply line (including regulator and drain spigot) merging with pump outlet and entering the boiler.

Edit: corrected picture order.
 
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Old 01-26-14, 01:40 PM
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Hi Blake,

I'm going to change the course a bit for starters... first, read the following two threads. I recommend that you at least check the air pressure in the expansion tank. It appears recently replaced, so it MIGHT be OK, but it should be considered a MINIMUM of bi-annual preventative maintenance. Service techs seem ignorant to the fact that these tanks lose the 1-2 PSI per year and are basically clueless about the proper method to recharge them for the most part. That tank will last a LOT longer if the air charge is maintained. There are step by step instructions in this first thread.

http://www.doityourself.com/forum/bo...sion-tank.html

If you don't know the pressure in the system, you are running around blind. MOST boiler pressure gauges are pure crap.

http://www.doityourself.com/forum/bo...ure-gauge.html

That air vent on top of the boiler... is that little cap on top TIGHT or LOOSE? For it to operate properly the cap MUST be loose. If it's closed and leaks water when opened, it needs replaced.

After taking care of these items, THEN you can go ahead and purge if needed... but with the new air vent installed and the proper charge in the expansion tank, and proper pressure on the boiler FIRST.

Although, if the heat is WORKING, my advice is to LEAVE IT ALONE until the weather warms up in a month or so.

Mid-Winter is NOT the time to see exactly how steep the learning curve is!
 
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Old 01-26-14, 08:38 PM
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The expansion tank, main shut of valve and spigot directly above it were added/ replaced in early November as part of the house inspection when I was buying it. It was all done by a heating and cooling company that has techs that are pretty familiar with hot water heating since about 20% off houses in this area have it. But to have them come out is about a minimum of $200 (between service charge and an hour of labor) and I feel that I should be able to do most of the work on my house myself.

I'll get a gauge put together in the next couple of days and check the pressure on the spigot above the main shut off.

The little cap on the top of the boiler is actually a schrader value covered in rust and hard water strains. With some straining around it from having water come out of it at some point in the recent past. So my guess is I should start looking for a new air vent.

I'm probably not going to touch anything for at least the next few days since it seems to be working well and we're looking at highs in single digits. But I'm concerned that leaving the air in the system could eventually allow it to make its way into the boiler and cause bigger problems.
 
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Old 01-26-14, 08:46 PM
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So my guess is I should start looking for a new air vent.
Yes change that and when the air comes around to the boiler it will be removed....

To change kill power to boiler so no zone valves open... Close yellow handle valve on feed. Turn off valve for make up water to boiler.. Drain water out of boiler drain ( Down at bottom of boiler) just enough so the gauge goes to 0.

Remove air vent..CCW... Put 2 wraps of teflon tape on new vent wrapping with the threads and install.

Reverse all of above and run boiler...
 
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Old 01-26-14, 10:07 PM
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Seems simple enough. On an unrelated note what is the normal position for the supply line valve, fully open, or only partially or closed? Just asking because I'm pretty sure mine is only cracked open or may be closed. I will confirm in the morning.

Just so I have a full understanding of how everything is supposed to work together. Under normal conditions you would purge the line to get it to almost full of water and then the air vent would slowly bleed off the rest as the system operated and moved the air around. The regulator would then flow water into replace the air until the system was full and at pressure. Correct my if I'm wrong.
 
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Old 01-27-14, 05:50 AM
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what is the normal position for the supply line valve,
All should be fully open... unless you have some sort of bypass then it may be throttled...

Need other pics to see if you have a bypass..

What type of heat emitters? Radiators? Copper baseboard?

Correct my if I'm wrong.
That statement is correct..........
 
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Old 01-27-14, 07:48 AM
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Put 2 wraps of teflon tape on new vent
On that fine thread, 1 wrap is probably enough IMO, but do NOT put ANY on the first 2-3 threads, you don't want those teflon slivers getting into the new air vent.

As long as the air does not stop flow in the zones it's really nothing more than an annoyance. It won't hurt the boiler.
 
 

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