Hello!

I have an oil boiler feeding 3 zones (hot water baseboard) and a hot water tank. Each of the four zones has a Taco 007-F5 circulator. This is control by a Taco SR-504.

A week ago one of the zones (upper level) was not getting heat. I figured it's the circulator so I replaced it. Now that zone is getting heat WITHOUT the thermostat calling. In fact, it is getting heat even after I disconnected the power to the circulator. The only way that I can prevent that zone from overheating is to shut-off the isolation valve to that zone. I think I screwed something up but I don't know what.

The hot water has to be pumped by something, right? Now I've noticed the hot water tank circulator is ALWAYS getting power even when the temp at the tank is high enough. The red led on the zone 4 of Taco SR504 is always on. Most of time the boiler stay put and NOT fire up. I guess the hot water tank is REALLY hot enough.

Is the SR504 faulty? Does the hot water tank circulator somehow pump one zone but not the others?

Thank for help.

N.B.

 

Went through the posts here, I learned the term "ghost flow". My system does have Taco 220 on each of the zones. I loosened the thumb screw on the flow-check valve and tapped (with a hammer) on the cast iron body, closed down the thumb screw. It seems to stop the hot water from getting into the zone when the circulator is not running. We'll see.

Assuming that's the problem. What did I do wrong? The circulators are on the return side. The flow-check valve on the supply side after the boiler. I must have done something to upset that zone. This is a system about 9-year old.

And then there is still the problem of SR504 constantly running the circulator of the HW tank. No clue so far on that.

N.B.

 

When you changed the circulator you may also have dislodged some junk in the system. This then hung-up the flow check valve. Which was possibly cleared by your working on it.

The other thing is that the original circulator may have had an internal flow check (IFC) in it. This too would help prevent ghost flow. If you have the old circ see if one end has a spring loaded flow check in it.

As for the indirect circ always running. The indirect tank should have an aqua-stat on it. That would signal the SR504 that the indirect needs attention. Check to see if it is always calling for heat to the indirect. If so then the aqua-stat is the issue. If not then the SR504 is the issue.

Al.

 

As a diagnostic, you can remove the wires from the indirect aquastat to the T T terminals on the 504.

If the call then ends, you know that the 504 is OK, and the indirect aquastat is not satisfying.

If the call does not end, you know that the problem is in the 504.

There may be a 'PRIORITY' switch on the 504 that will shut down the heating circuits when the indirect calls for heat.

 

Now it's time to report my findings:

1) the original circulator was NOT an IFC. So the check-flow valve was working fine, somehow disturbed by my changing the circulator. Now I hope my tapping has solved it.

2) I removed the wires from the tank (actually an L4080B) and the calling stopped. So it is the thermometer. The L4080B was set at 140F. I tried lowering (and raising the temp. dial on the L4080B with no effect. Do I have to wait for the sensor to reset it self somehow?

Thanks for the help.

N.B.

 

No, there's no 'reset' time on the water heater aquastat. It switches based on the water temperature. You might have to replace that aquastat... I believe the one you have is obsolete, and that the functional replacement is a L4006A.

 

The Honeywell L4080B is now constantly shorted (always calling). I pulled the control a little bit to see some green stuff like dried dye in the sensor well. Couldn't really pull the sensor out afraid of breaking the tube trying to get the bulb out. Guess there is no other way to replace it but pull it harder.

N.B.

 

That's probably dried up thermal compound. I've never had one that got 'stuck'... so maybe some of the other guys will have some tips on how to get it un-stuck. Maybe there's some kinda solvent you can squirt down the well? I dunno...

Anyone?

 

The ghost-flow started again. It seem I have to tap it with a hammer everyday to unstuck it. Tapping doesn't seem to be a long term solution. So how to go about it?

The bulb of L4080B is still inside the well. I poke a screw driver into the well a few times and now the bulb is at least loose. I can pull it out about a quarter of an inch. Even rotate it by holding/tuning the tube. I can hear the bulb scratching again the well so it's definitely loose. But a quarter inch is as much as it can go. I though inside of the well is smooth so there shouldn't be anything to stop it, right?

The green stuff doesn't look like dried thermal compound to me. Maybe the tube leaked?

Thank you.

N.B.

 

Maybe! or possibly the bulb leaked whatever juice is inside it into the well. There shouldn't be any 'obstructions' inside the well to prevent removal. Was there a metal 'clip' in there that holds the bulb in? Can you maybe use a wooden dowel to chip away at the stuff? (I hesitate to suggest a screwdriver to prevent damage)

 

The old bulb is finally pulled out. Talk about a tight fit. Thank you for the help. A new 4006A is going in. Hopefully it will get this part solved.

N.B.

 

Great! Let us know how it works out !

 

The sensor is working fine. But the flow-check (Taco 220) still needs some tapping.

N.B.

 

Try manually lifting the disc with the screw-knob on top and back again. Maybe this will 'loosen' the works up. There might be a piece of crud hanging in there that will get knocked off...

 

If exercising the manual lever doesn't help cure the problem, you'll probably have to bite the bullet and replace the flo-control valve. After a few decades, they become leaky, perhaps due to erosion of internals. These are actually "lift-check" valves. They shut off only because of the weight of the disk and stem, so can be touchy if the internals are boogered up.

Edit: sorry, I didn't notice your flo-control is a Taco. Ignore the following.
Is this a Bell & Gossett flo-control? They sell a repair kit that essentially rebuilds the valve. Here's a link: Bell & Gossett Flo-Control Valves - State Supply Company (Check other suppliers, too - these prices seem high to me.)

You should be able to rebuild the valve without removing the valve from the line.

 

I loosen the thumb screw on top of the valve, tapped the body of the valve with a hammer while the circulator was running. Did that a couple of times then tightened the thumb screw down. It seemed to work. And that valve has been working fine for a few days now.

Last time I did tap the check-valve, but NOT while the circulator running. Hopefully this solved that problem. Thank you for your kindly help. I'll report back if anything changes.

N.B.