2 zone system: one of the 2 return pipes in one zone is cold

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Old 01-04-12, 02:58 PM
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2 zone system: one of the 2 return pipes in one zone is cold

My two story, two zone hydronic system has been acting funny lately. Last week I lost hot water circulation upstairs (pipes stone cold) while the downstairs belted out heat (seemingly ignoring thermostat setting which should not have been calling for heat). I shut everything down, let cool, restarted and was fine. This week I have almost the opposite problem: heat upstairs (also ignoring t-stat), sending heat downstairs, but one of the two downstairs returns is cold (it's one one zone, but with two return pipes).

I've shut down and restarted, bled the system (various permutations) but ultimately it returns to the situation described above. I have also drained the cold return until it drew hot water from elsewhere in the system so I don't think it's a blockage issue. I'm guessing the 2 Taco circulators (one for upstairs zone, the other for downstairs) are good because of the hot send pipes. The only other anomaly is I seem to have a nearly constant - though low level - flow out from my expansion tank (so much so that I ran a hose to a drain). Oh, and my boiler is slightly cracked and has been for several years (so it seems) resulting in another small leak.

Sorry in advance for the lack of parts details. Any thoughts to get me through this winter?
 
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Old 01-04-12, 04:00 PM
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I seem to have a nearly constant - though low level - flow out from my expansion tank (so much so that I ran a hose to a drain). Oh, and my boiler is slightly cracked and has been for several years (so it seems) resulting in another small leak.
Flow from the EXPANSION TANK? You sure? Do you mean the pressure relief valve perhaps?

And that crack in the boiler? not a good thing...

Any thoughts to get me through this winter?
Dare I say... new boiler?
 
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Old 01-05-12, 03:38 PM
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update

Thanks. The leak which the technician indicated was from cracked boiler was 90% remedied by sealing an elbow joint in the exhaust system. I'm going to do a major remodel on this house soon so am not eager to do anything to the heating system. I can live with some drips. I guess I do mean pressure relief valve (though my system pressure seems to be a constant 18), and should have pointed out that this drip predated the situation I'm currently having.

From a cold start this morning it operated normally for a few hours, then reverted to the situation described above. I discovered by manually adjusting the flow rate on the two hot return pipes I can force the cold water from the faulty loop. Is is safe to operate the system with the two hot return values partially closed? Thanks again.
 
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Old 01-05-12, 04:33 PM
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The leak which the technician indicated was from cracked boiler was 90% remedied by sealing an elbow joint in the exhaust system.
Exhaust system? Post a photos of where the crack is - and where the drips are.
 
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Old 01-05-12, 04:49 PM
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(though my system pressure seems to be a constant 18)
Never trust a pressure gauge, particularly one that doesn't move!
 
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Old 01-09-12, 04:32 PM
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second update

Whatever I did or did not do resulted in normal operation of the system for a few days. Then it reverted to a version of the original malfunctioning state: ignoring the thermostat downstairs while belting out heat, normal heat upstairs! This is better than no heat downstairs, but not a long term solution.

To clarify:
- pressure gauge does move (a bit) but always within acceptable range
- "exhaust" leaks: should have said flue. It's either a lot of condensation or water is escaping through there somehow (in the aluminum not the PVC)
- drips are from the side with the two flues, some of which I catch in that drip pan
- related/unrelated issue, the vent on top of the air purger drips if I leave it open, as does a similar device on the side of the housing

Pictures at
Pictures by mjc20005 - Photobucket

Thanks again!
 
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Old 01-09-12, 04:58 PM
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MJ, show us more... get some wider shots of the whole system, and I would like to see the air inlet and outlet piping all the way to where they exit the building.

I don't think you told us boiler make/model...

Just because the gauge moves a little bit doesn't mean a thing. Still could be toast.

The leaking from the flue connections has me a little concerned... let's get this fixed so nobody dies from CO poisoning! That may be fairly serious, ya think?
 
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Old 01-09-12, 07:28 PM
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Disturbing to say the least. I installed a few of these GV units. (Weil Mclain) First off a starter tee is supposed to be purchased seperately. This catches the condensate and a drain hose gets attached.

Apparantly the installer never read the instructions. Why weil mclain did not supply these tee I may never know, but I have seen these on many occasions.

Second, and I am checking my records for this unit, the flue is supposed to be vertical so many ft I beleave off the unit before any turns are made. I am looking up that info now.

third I would say at a minimum that extrol expansion tank should be replaced. I would feel more comfortable with a regular fill valve and backflow preventer installed and a regular expansion tank. Or you need to check the air charge in that tank. The air charge dictates the fill water pressure.

Note: Get a CO detector asap. That system flue is not correct. I know its probably been there a while but why take the chance of waking up dead.....


I may be wrong, but like I said I am checking and will post back more info.
Mike NJ
 
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Old 01-09-12, 07:51 PM
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Geez.... I wont even get into it.

Here is the install manual.

http://www.weil-mclain.com/en/multim...ler_manual.pdf

Look the flue tee has a flange and is sealed to the boiler. Its mated to the boiler flange on the flue with a gasket. I see no way that the elbow you have is sealing anything.


Just want you to be safe my friend, thats all.

Mike NJ
 
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Old 01-09-12, 08:25 PM
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That boiler install manual doesn't have all the information on venting... the supplements that cover it... there are whole manuals for the purpose... this is one of them.

http://www.weil-mclain.com/en/multim...structions.pdf

Seriously... this boiler WILL eventually kill you if you don't get that repaired... stat!
 
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Old 01-09-12, 08:40 PM
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Troop I was looking for that. I have an old hard copy but still cant find the minumum vertical length off the tee.


Looks like this brand of flue just shows as high as the boiler before a turn. No specific # of ft.

Het its all irrelevent anyway. I wonder if the bottom of that flue is looking like swiss cheese. May not even be pitched properly.

Uggg!!!

Mike NJ
 
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Old 01-09-12, 08:59 PM
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I did a little bit more research also... hit the OLD manuals for this boiler and come to find that the Series 1 and 2 manuals don't specify the starter tee, and DO show pics of the vent and intake exactly as shown.

BUT... whether or not it was 'legal' at the time, these books ALSO show a condensate drain tube, which may or may not be there... but he's got a rubber maid, so... I guess that's catching the condensate.

MJ, these boilers ALL produce water in the flue pipe, that is a NORMAL condition, and there is supposed to be a drain tube connected that directs the condensate down a drain somewhere.

What has apparently happened to yours is that the drain is plugged and missing and that condensate is pooling in the bottom of the pipe. That condensate is mildly acidic and will EAT the metal... perforating it... and causing exhaust leaks into the home. THAT is why we are concerned!

See Figure 13 page 12

http://www.weil-mclain.com/en/multim.../gv1manual.pdf

http://www.weil-mclain.com/en/multim.../gv2manual.pdf

There are also different vent supplements for different vent manufacturers... all here on this page, scroll down to GV.

Residential & Commercial Boilers, HVAC Equipment | Weil-McLain

In any case, W-M revised the design, most likely because of problems such as this one...

I am betting that the condensate drain is completely plugged up with rust and crud, and that the metal down there is 'swiss cheese' as you said. It's still unsafe regardless if it was done right when installed or not.
 
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Old 01-09-12, 09:21 PM
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Good job getting the docs. I am having loading troubles. Computer freezing up some.

Anyway yeah I see the GV 1 or 2 has is piped that way. There is an enternal ell with a drip leg. In the pic you can see a small hose coming out at the bottom near the exhaust. Hmm bottom area looks all rusty down there.

I wonder if it is a metal ell inside the jacket?

Anyway I have to re read this thread because I forgot what the original issue was.

I never did like these boilers and when I see one I kind of cringe. Hated sevicing them.

Mike NJ
 
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Old 01-10-12, 10:20 AM
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more system pics uploaded

Ok, it's safe to say I'm reasonably terrified. I put a CO detector outside utility room this morning and it came back at 213 ppm. System is currently shut down and house is empty.

Visual inspection of the external surface of the flue did not reveal any obvious swiss cheesing. It is side wall vented and at a horizontal point where two sections are joined there had been a long term drip (the floor under this joint had a golf ball size cavern in it. I fixed the join 1+ years back with plummer's putty and no leaks since. (The mild acidity makes a lot of sense here)

Regarding the normal routing of condensate down a drain: when I bought the house there was an inoperable pump system that routed water to a utility drain. I replaced it with the rubbermaid system and a sponge.

I had been thinking of contacting the firm that installed this unit, but after reading posts here am not sure that is in my best interest...

Thanks for the very solid advice given here! I would still like to repair, not replace, this system as I know I won't be keeping it in the long term. Thoughts on components that need to go?
 
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Old 01-10-12, 04:16 PM
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Thoughts on components that need to go?
The system needs to be carefully inspected in order to determine course of action. There really isn't much else that we can do from here.

You've probably already determined by yourself that 213 ppm is quite high... but I found this info on another website:

At what level does carbon monoxide become toxic?
For healthy adults CO becomes toxic when it reaches a level higher than 35 ppm (parts per million) with continuous exposure over an eight hour period.. When the level of CO becomes higher than that a person will suffer from symptoms of exposure. Mild exposure over 2-3 hours (a CO level between 35 ppm and 200 ppm) will produce flu-like symptoms such as headaches, sore eyes and a runny nose. Medium exposure (a CO level between 200 ppm to 800 ppm) will produce dizziness, drowsiness and vomiting in as little as 1 hour. This level of exposure is deemed to be life threatening once three hours has passed. Extreme exposure (a CO level of 800 ppm and higher) will result in unconsciousness, brain damage and death in as little as a few minutes. OSHA guidelines state that the maximum exposure over an eight hour time period is 35 ppm.
excerpt courtesy of A Guide to Prevent Carbon Monoxide Poisoning
 
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Old 01-11-12, 08:55 AM
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Technician inspection today revealed a severely degraded starter tee where it exists the boiler: cracked on the bottom effectively bypassing the condensate drain (hence the leaks down the side of the housing) and a smaller but still significant crack on the top (hence the CO). Technician is looking for the part now and I will post a followup once it's installed and we can safely diagnose the whole system. Thanks again!
M
 
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Old 01-11-12, 03:37 PM
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severely degraded starter tee
I didn't see a 'starter tee' installed on your system. I assume you mean that metal 'box' at the bottom where the flue pipe connects?

Thanks for letting us know that you have taken steps to correct the problem!
 
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Old 01-13-12, 12:35 PM
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repair completed

Right again, Troop! It was actually resolved through a Vent Elbow Replacement Kit, stainless steel instead of the plastic original. I was told that Weil Mclain changed the part to stainless some time ago, probably for this exact issue. I used some of the spare silicone from the kit to seal the next elbow joint and reconnected my condensate pump (though it has nothing like the volume that had been coming out through the crack). No CO detected.

Heat came back in full force, no circulation problems, though I think the downstairs tstat may be malfunctioning (it's calling for heat even after the desired temperature is reached). The worst news of the day was the discovery of a very rusted heat exchanger which leaked when cold, but sealed when it reached normal operating temperature. I think its days are numbered.

Thanks again for all the valuable advice. Cheers,
-m
 
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Old 01-13-12, 06:16 PM
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Well, good news with the bad I guess...

At least you won't get dead from CO poisoning!

Can ya take pics of what was done? I'm curious...
 
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