Runaway circulator pump

WhirlingD

No, it’s not literally running away… But it’s running nonstop, with unknown origin.

So… I’ve had all kinds of disasters here in my 250 year old house in the last 10 days. Two frozen heating pipes, due to failure of zone valve and stupidity on my part… well, lack of knowledge and awareness…

When the oil company technician came over earlier in the week, we blocked off the areas that were burst so the rest of the house could get heat and hot water (tankless hot water). He’s going to do an estimate and schedule the work shortly.

All good… Seemingly… Until I notice over the last couple of days that my circulator pump has been running nonstop, despite no heat being called from any thermostat. In fact, I went as far to take all the thermostats off the mounting, which should close each circuit, and the circulator pump is still chugging away.

I talked with the heating guy this morning, and we thought about removing one wire from the top of the Taco zone valve, to see if it’s a zone valve that is malfunctioning. I did that, and the circulator pump didn’t miss a beat.

So, is there anything else I can do to diagnose this, before I get the guy back here and pay the coin for him to diagnose why this circulator pump, which would easily be older than 18 years old, since that’s how long I’ve been in the house and it hasn’t been changed…? If I can figure it out on my own and save the cash, I’d rather do that. Maybe it’s something obvious?

I thought maybe he might have tinkard with something in the system that made this happen?

I read yesterday that there are some places that have the circulator pumps running 24/7 to prevent freeze ups… I hear every sound in my house, and have listened for that circulator pump over the years, and it definitely doesn’t run 24/7. It turns on when I call for heat, turns off when the function is complete.

Thoughts about what’s going on?

Also… I just got a call from him and he is saying it’s going to be in the multi thousands to do what I want him to do… Here’s what he’ll need to do:

- replace a kickboard heater and replace about 10 feet of copper piping with Plex, hopefully.

- replace a second kickboard heater using Plex, with perhaps 25 feet of Plex

- fix a heat pipe that is hard to access, but about 2 inches from where it comes out to meet the baseboard radiator.

If I had to guess, I suspect he’ll be here for about five hours. But what do I know.

It seems like his three grand initial estimate seems astronomically high. I could get something like a 7200 BTU kickplate, as almost an exact match, for about 350 at Home Depot… Times two, that’s still only 700 bucks… even with the Plex pipe, it seems like an awful lot for labor.

I do know that it’s only an estimate. I think he thinks it’s going to be harder than I think it’s going to be, but he’s the pro.


Thoughts?

Alan (California Radiant) Forbes

You will have to follow the voltage to the pump backwards to find out what's stuck. There is a relay somewhere that's closed.

Is the pump wired to the boiler or a zone valve control? Some pictures of how that pump is wired would help.

We can't talk pricing here. Remove the $$ and we can talk about it.

Grallert

The endswitch on that Taco ZV could be stick on the closed position. I other words calling the circulator. Or as Alan said above.

WhirlingD

Grallert said:

The endswitch on that Taco ZV could be stick on the closed position. I other words calling the circulator. Or as Alan said above.

Thanks for the thought… If that were the case, wouldn’t there be hot water running through the zone? There isn’t any hot water in any zones while the circulator is pumping.

WhirlingD

Plus, I took all of the top wires, one at a time, off of each zone valve, and the circulator kept purring away.

Would this be a way to determine whether it is a zone valve problem? I would think that if they were run in series, disconnecting the top wire, which is supposedly the hot wire, that would close the circuit and turn off the circulator.

HomerJSmith

The pump runs on 115V ac. Zone Valves and thermostats run on 24Vac (most often). Some ZVs and thermostats run on 115V or 220V ac. You have to determine what is controlling the pump, it is most likely a relay. What is controlling the relay, a ZV or aquastat? You have to find out where the power to the pump is coming from.

WhirlingD

OK, here is more information… And I have a hunch…

In the photos, you might be able to see that the wiring from the pump goes into this box, presumably an electronic hub, that’s on the right… On the left, one set of wires goes to the switch for the entire burner, and the other set goes up towards the 24 V transformer mounted on the ceiling, which you can’t see… But I can’t tell if it goes to that first or the ZV, because there’s just a ball of wires. If I have to I’ll unravel it.

However, I took the cap off that box, and if you notice, there is a gray push button up near the top center, a bit to the right, and I pushed it, and it turns the circulator off, before it Springs back out and the circulator resumes.

There are many times over the history of living here

, when I could hear a buzzing sound coming from that box… And it’s been for years… And when I press that gray button, it starts buzzing like that before it goes all the way in, and it buzzes coming back out.

I get a hunch that my problem may be related to that switch, or something in the box. I really have no idea, though. That’s an armchair theory.

WhirlingD

Of course, you guys are probably going to now tell me that you can’t replace components in one of these boxes… Which means I may have to replace the whole box… And they’re going for three and some change at Home Depot, not to mention what the heating guy will want to put it in. Grrr.

Is replacing one of these boxes some thing that a sometimes courageous homeowner could do themselves? I could probably follow each wire and connect it right to where it comes from on the old box, and set it exactly as the old one is.

Is that recommendable? Of course, I don’t entirely know this is the problem, but I wouldn’t at all be surprised. That little switch seems wonky.

Jamie Hall

No, we aren't going to tell you you can't replace those components. We are going to tell you that unless you get an exact functional replacement, it's not going to work.

The other thing we'll tell you is that you need to identify what component is malfunctioning -- and it could be that grey box with a button. Which might be an aquastat (that looks suspiciously like a tankless coil cover plate that the box is mounted on) and it might be 24 volts or 110 volts. Or it could be a relay, with either voltage on either the coil or the contacts or both. You -- or someone who knows something about electricity and boilers -- need to find out what is powering the pump.

And, as an aside, the zone valve end switches should be wired in parallel, not in series, and taking a thermostat off the wall opens the control circuit, not closes it.

WhirlingD

HomerJSmith

The aquastat controls the functioning of the boiler. The diagram show that the circulator is controlled by the aquastat relay. That relay is a two pole relay. One pole turns the circulator on and one pole fires up the boiler thru the safety circuit. In other words, one set of points is 115V and the other set of points is 24V. The boiler's not firing but the pump is running? The boiler's not firing is different than the thermostat not calling for heat. Is the boiler firing or not?

This is what I would do.

Disconnect the one wire going to the TT terminals on the aquastat. Did the pump stop?
Short the TT contacts together. Did the boiler fire and the pump turn on?
Turn off the power to the boiler and turn the power back on, did that correct the problem?
Sometimes the point on the relay stick or pit and cone (especially 115V points) to a condition where the points touch. With the power off to the boiler I use a diamond fingernail file or wet and dry sandpaper to carefully clean the points.

If the relay is energized both the pump would operate and the boiler would fire. Examine the reeds with the points closely and see if they're making contact with the power off to the boiler.

WhirlingD

HomerJSmith said:

The aquastat controls the functioning of the boiler. The diagram show that the circulator is controlled by the aquastat relay. That relay is a two pole relay. One pole turns the circulator on and one pole fires up the boiler thru the safety circuit. In other words, one set of points is 115V and the other set of points is 24V. The boiler's not firing but the pump is running? The boiler's not firing is different than the thermostat not calling for heat. Is the boiler firing or not?

This is what I would do.

Disconnect the one wire going to the TT terminals on the aquastat. Did the pump stop?
Short the TT contacts together. Did the boiler fire and the pump turn on?
Turn off the power to the boiler and turn the power back on, did that correct the problem?
Sometimes the point on the relay stick or pit and cone (especially 115V points) to a condition where the points touch. With the power off to the boiler I use a diamond fingernail file or wet and dry sandpaper to carefully clean the points.

If the relay is energized both the pump would operate and the boiler would fire. Examine the reeds with the points closely and see if they're making contact with the power off to the boiler.

Thank you. This is really helpful. I’ll take a look tomorrow morning and see what I can see…

You have to understand, I am a DIY homeowner, and not familiar with the electronics of a unit like this…

Where am I finding the TT connector you are describing? And the points?

But, yes, the boiler fires up for the hot water, and seems to be operating normally when the thermostats call for heat.

EBEBRATT-Ed

The boiler could be cycling on high limit what is your water temp. The "grey pushbutton" is the relay that controls the boiler and the pump. That relay should only pull in when the thermostat that is connected to T & T is calling for heat (or in your case a zone valve end switch is probably controlling it.

I would suspect a stuck zone valve, a shorted wire etc. if the grey relay pulls in the control is probably ok.

WhirlingD

EBEBRATT-Ed said:

The boiler could be cycling on high limit what is your water temp. The "grey pushbutton" is the relay that controls the boiler and the pump. That relay should only pull in when the thermostat that is connected to T & T is calling for heat (or in your case a zone valve end switch is probably controlling it.

I would suspect a stuck zone valve, a shorted wire etc. if the grey relay pulls in the control is probably ok.

Thanks… The boiler seems to fire up when the water temperature in the coil goes below the threshold… And it is set at a High Point of just under 200°, and a low point of just under 180°, with a slightly under 10° differential.

The circulator pump seems to not be affected, whether I disconnect the main positive wire going to each valve head, or even turn all the zones off at the ball valves. That thing still chugs away. The only thing that stops it is turning off the main power to the boiler, or pushing in that little gray button.

I also just went down there when the boiler was fired up, and that little gray button also turns off the burner when it is depressed.

I still think it may have something to do with that little button, because it kind of was stuck in between full in and out, and making this annoying buzzing sound… Which makes me think that something in there isn’t fully engaging and disengaging.

Could that be part of the points consideration that was mentioned earlier?

HomerJSmith

There isn't any low voltage circuit on the L8124AC or the L8151A aquastats except the 24V circuit going to the thermostat and ZVs. Both poles of the relay are at 115Vac and operate the circulator (one pole) and the burners (other pole). 1K is the 24V relay coil, 1K1 is pole one on the relay which turns on the burner, 1K2 is pole two on the relay which turns on the circulator.
Diagram below

The only way that power could get to the circulator is thru the low limit switch or ZC, then thru 1K2 points. I think the 1K2 points are stuck closed. There is no connection with ZR or ZC, but ZC isn't very visible in your photo. So...

The burner wouldn't turn on because it gets it power thru 1K1 points, so if 1K2 points were closed it would have no effect on the burner. It would just effect the circulator.

Check the points on the relay and clean them if you can. The alternative is a new aquastat$$$.

The foregoing is my considered under educated opinion. Looking back on life I seemed to be more wrong than right.

HomerJSmith

With the power turned off to the boiler you might try rapidly tapping on the relay bar. The thingy (relay) the red arrow it pointing to. That might free up the stuck points.

WhirlingD

HomerJSmith said:

With the power turned off to the boiler you might try rapidly tapping on the relay bar. The thingy (relay) the red arrow it pointing to. That might free up the stuck points.

Thanks… Interesting thought. I was actually pushing the button in and out rapidly while the thing was going, both circulator and boiler… I thought maybe I could jarred something loose.

I will try tapping on it a little more with it off.

Is there any way to open that little switch box… To clean the points?

EBEBRATT-Ed

That is the 1K relay in the drawing. If you disconnect one of the T T wires the relay should drop out and shut down the circulator. It will also shut down the burner unless the low limit is calling.

If that does not shut down the circulator replace the aquastat it is unreliable and not safe.

HVACNUT

@WhirlingD, this is TT.Shut off the power and remove one wire. Don't let it touch any metal and turn the power on. If the circulator is running, it's a bad aquastat. If the circulator is off, it's a bad end switch in one of the Zone valves.
We don't know what type of zone valves you have but the wires from TT go to the end switches. You can remove one end switch wire at a time to see which one turns off the circulator. 

WhirlingD

OK boys and girls… I think I have figured it out. With your help.

I was about to remove a wire from the T connector, when I thought… Maybe I’ll start with removing the bottom wire of the taco ZV head, which is part of the end switch of that device. That was easier to get out.

I had a hunch that a zone valve which was failing before may have been the culprit, but I had taken the top power wire off of that one before, which was suggested by my heating guy, and the circulator still ran.

One of your helpful fellows suggested I try removing one of the bottom wires, and on the first try, the circulator stopped. The gray relay switch also clicked inward, which was a good sign.

I also then called for heat, because I thought maybe breaking that connection might disable the circuit to all of the other zone valves as well, but lo and behold, about three minutes later, the system fired up and began running heat to that zone…

Wonders never cease!

So, for the time being, I am just going to leave that wire off that particular zone, and the head off of the valve.

I will check the other zones, as well, just to make sure…

After I discovered this, I quickly called the heating guy off, who had just scheduled to come over this morning… And as I sat to write this, I saw his van pull away off of my property, so he must have just gotten the message from his office to cancel… He was probably mighty pissed… ooopppsss.

I saved the service call, with the help of you guys, and since I am a considerably poor bloke, that is very meaningful, and I really appreciate all of your input.

Is there anything I am missing here, or anything that I should be concerned about given what you’ve read so far? If so, please let me know. I am at your mercy… 🤣😂