Taco Flo Chek valve stopping water flow from boiler?

Nsherman2006

Hi all,

I went to my parents’ house because they told me it wasn’t heating. Thermostat wasn’t turning on heat but domestic hot water was still working (it’s a tankless coil).

I was thinking bad circulator pump (single zone), but when I took out the pump it was spinning freely, so I reinstalled, fired up the boiler, and found that the boiler side of the check valve was hot but the other side was cold.

After a little reading, I unscrewed the top, hoping to bypass the valve. It worked and there is now heat flowing. So now, should I replace the check valve? Try to clean it?

Thanks!

HVACNUT

I would say the pipe is hot one one side and cool on the other because the flo check is doing its job. By loosening the top you're raising the weight and allowing for a gravity heat rise. It seems more likely there's no power to the circulator or there's air in the loop preventing flow.
Is there a diaphragm expansion tank and air eliminators or a steel compression tank in the ceiling rafters?
Is the pipe one continuous loop or does it branch off to each individual convector?

kcopp

Screw it back down. it may have just gotten gummed up for not being on all summer. Is there glycol/ antifreeze in the system?

Nsherman2006

@HVACNUT

The circulator was removed because that was my first culprit, it spun freely and started instantly upon thermostat connection, so I believe the circulator is good. I then bled the air from the system (there were isolation valves so I didn’t lose much water when I removed the circulator). Upon reinstalling and firing up the boiler, the pipes leading up to the flow check got hot, but past the flow check they did not. As soon as I unscrewed the top hot water began to flow past the valve and the pipes heated quickly, so I’m confident the check valve was causing the obstruction 

@kcopp

I don’t believe there is any antifreeze in the system. I’m inclined to believe it was also gummed up from sitting all summer (the water at this property is pretty hard). If I screw it back down and the heat continues to operate, should I just call it good? I am hoping to avoid a recurring problem, so if cleaning/replacing the valve seems to be a better solution, I’d rather do that then be back in a couple months for a no heat call when it’s actually cold out.

Thanks for the replies!

pecmsg

Nsherman2006 said:

@HVACNUT

The circulator was removed because that was my first culprit, it spun freely and started instantly upon thermostat connection, so I believe the circulator is good. I then bled the air from the system (there were isolation valves so I didn’t lose much water when I removed the circulator). Upon reinstalling and firing up the boiler, the pipes leading up to the flow check got hot, but past the flow check they did not. As soon as I unscrewed the top hot water began to flow past the valve and the pipes heated quickly, so I’m confident the check valve was causing the obstruction 

@kcopp

I don’t believe there is any antifreeze in the system. I’m inclined to believe it was also gummed up from sitting all summer (the water at this property is pretty hard). If I screw it back down and the heat continues to operate, should I just call it good? I am hoping to avoid a recurring problem, so if cleaning/replacing the valve seems to be a better solution, I’d rather do that then be back in a couple months for a no heat call when it’s actually cold out.

Thanks for the replies!

Spinning and pumping are 2 different things!

pedmec

If the loop flows after using the manual bypass then the check has hung up on the seat. Installing new is the best way to stop a recurring failure.

mattmia2

What kind of circulator is it? Is it a wet rotor or a 3 piece?

Nsherman2006

@pecmsg

I don’t know if any way to test how well it’s pumping, but the pipe beyond the check valve heated very quickly once the top of the valve was unscrewed, so it seems like it’s circulating well

@pedmec

Thanks, that’s what I’m thinking as well

@mattmia2

Its a Taco 007 circulator if that helps

Thanks!

EBEBRATT-Ed

depending on which flow check you have pipe size and threaded or sweat they all work the same but look different. They have two positions. 1. Auto the valve is supposed to close when the pump is off and open when the pump pushes it open. 2. Manual you can open the valve externally by a lever or a screw but then the valve stays open all the time and will allow gravity flow even when the pump is off.

picture would help

Nsherman2006

@EBEBRATT-Ed

Thanks, I can’t believe I forgot to post a picture!

hot_rod

Where is the circulator located in the piping? take a pic from a few feet back.

EdTheHeaterMan

HVACNUT said:

I would say the pipe is hot one one side and cool on the other because the flo check is doing its job. By loosening the top you're raising the weight and allowing for a gravity heat rise. It seems more likely there's no power to the circulator or there's air in the loop preventing flow.

Nsherman2006 said:

Hi all,

I was thinking bad circulator pump (single zone), but when I took out the pump it was spinning freely, so I reinstalled, fired up the boiler, and found that the boiler side of the check valve was hot but the other side was cold.

After a little reading, I unscrewed the top, hoping to bypass the valve. It worked and there is now heat flowing. So now, should I replace the check valve? Try to clean it?

Thanks!

Sounds inconclusive to me. The Circulator spins freely according to @Nsherman2006. Nowhere does he say that the circulator is actually operating. Need a electric multi meter to see if there is voltage going to the pump.

Has anyone adjusted the temperatures on the boiler control since the last time the heat worked? There is a reason that it says Set Hi limit 20° higher than Low limit on the L8124A triple aquastats.

Nsherman2006

@hot_rod

I can get a picture, but I’m hoping the next time I go out there can get everything fixed. The circulator pump appears to be right at the return to the boiler (on the opposite side of the piping from the check valve)

@EdTheHeaterMan

I pulled the circulator from the boiler and crossed the thermostat wires. It sounds instantly and smoothly, so I know that the circulator is at least spinning with electrical power, if not working up to spec 

My question would be: is there anything else beside the check valve failing that would cause the hot water to not circulate but then circulate strongly once the valve was opened? Could a weak circulator do that?

pecmsg

Put an amp probe on the motor. 

Air bound comes to mind. 

EdTheHeaterMan

I need to know more about your system to tell if air-bound is the problem or if the flow control valve is sticking. But from the results of your test I might agree with you. The thing about the flow control valve you pictured, It is a very rare occurrence that they get stuck. It is not impossible... Just very rare.

Your circulator test states that you heard the pump operate. Did you actually see the impeller rotate? A motor that turns but is not connected to the impeller will make a noise that sounds like a motor turning.

To actually check the impeller, I would look at it by removing the cartridge. That is done with 4 bolts that have either a 5/16" hex head or an Allen wrench head. When you see the impeller condition and if it actually turns, you will know if there is a problem. That test is free. Replacing the flow-check is more costly, and if the Flow control replacement results in the same problem, you will then replace the circulator. So why not do the free check of the circulator first.

I believe you are on the right track. You have a good understanding of the function of the flow control valve. I would just hate to see you take all that time to drain the boiler, replace the Flow Control, fill and vent the system and find you did all that in vane. Especially when you say the circulator has isolation valves so that test is very easy.

hot_rod

When you force it open does not supply and return get warm? That would indicate flow is moving. Test a few feet w away from the boiler or piping so you aren’t feeling conduction heat

Nsherman2006

@EdTheHeaterMan

That’s exactly what I did, which led me to believe the circulator is fine. I removed it, but when I noticed it was not bound and spun freely, I reconnected the wiring and fired the system up and the impeller spun without noticeable defects, which is when I started inspecting for an obstruction and landed on the check valve. With the system running and the check valve as it was when I arrived, the boiler side of the check valve was hot, and the opposite side of the check valve was cold. As soon as I forced the check valve open, the other side got hot very rapidly.

So I figure it has to be one of two things:

1) The check valve was stuck shut. In which case, is replacement a better option than cleaning? Is it likely that it just stuck from months of idling without use and would likely stay free once unjammed?

2) The circulator is spinning freely but was not generating enough pressure to force water past a check valve that was functioning fine, so the problem is still with the circulator even though the heating system is working fine with the check valve bypassed to open.

Thoughts?

HVACNUT

Get a complete replacement. 
You can just replace the weight portion but you must make sure the brass seat inside the valve body isn't damaged. If it is, then replace the whole thing. 
If you can solder, and have room to sweat in a coupling, changing the whole thing shouldn't be too bad. What could posibliey go wrong?

pecmsg

Possibly the valve between the air scoop and flow check?

Can we get a pic of all the piping?

EdTheHeaterMan

Nsherman2006 said:

@EdTheHeaterMan

That’s exactly what I did, which led me to believe the circulator is fine... Thoughts?

To see if the check valve was just stuck from a season (summer) of being idle, then I would let the system cool, then operate the circulator and see if the problem is resolved or if the problem persists. That is less expensive. If the problem returns, then you (or your customer) knows that replacement is necessary.

OR

if the boiler is more than 10 years old, then sell then a new boiler!

The last statement was sarcasm

hot_rod

If the heat emitter gets hot with the valve screwed open, seems that is the determining factor. The eliminates an air or pump issue.

mattmia2

Replace that leaking automatic vent while you're at it.

Joe Mattiello

Anyway of testing the circulator on a demand? Clamp amp will work, if it’s below nameplate amp, it has voltage, impeller spinning, but not pumping water. Purge that line.
Rule out pump first, and then look at flow check.
flow check is mechanical and doesn’t normally go bad. 

Sometimes simply cleaning seat area of lodged system debris resolves any check issues.
if the problem persists contact Taco tech support at 401-942-8000 for additional assistance.