Radiators in One Zone Constantly On

DoctorAngelicus

We just bought a new house. Has 5 zones of heating. One of the zones is constantly on. I disconnected the thermostat and it was still blasting. What should I check next?

GroundUp

Perhaps a bad zone valve and/or end switch? We'll need a little more information about the zoning and controls to get an accurate depiction of what may be the issue. Pictures would be great

DCContrarian

A quick primer so we're all speaking the same language:

Radiators produce heat because hot water is flowing through them.

A device in the basement called a boiler heats the hot water.

A pump called a circulator makes the water flow.

Devices called a zone valves control which radiators the water flows to.

Each zone valve has a device called a thermostat which turns that zone valve on when the area that the thermostat is in is needs heat.

Each zone valve has a switch that turns on when the zone valve turns on. Those switches are connected to the circulator.

So that zone is heating because the zone valve is open and the circulator is on. The first thing I'd check is that most zone valves have a lever on them that allow you to manually open the zone valve, I'd check to see if someone has thrown that lever. Since this is a new-to-you old house, the next thing I'd check is whether someone connected a second thermostat to the zone valve somewhere that you don't know about, or even just wired it so that it's always on.

It's possible that the zone valve is just stuck in the on position. But since it's a new-to-you old house, I'd look real hard into the possibility that someone wasn't happy with the way the thermostat was working and just rigged that zone so it's on all the time. The fact that it's June 3 today and you're just coming to us now with this problem makes me suspect that for most of the winter having this zone run continuously isn't an issue.

DoctorAngelicus

We just moved in the week before last week and noticed the bathroom of the zone in question was particularly hot (it's the only room of the 4 that doesn't have AC so I am guessing that's why we didn't notice in the rooms as it's counter acting the heat in those rooms). Notes on the definitions:
Radiators in all three rooms are experiencing very hot water flowing through them;
Boiler shows outflow temp ~250F,
Pump circulators are the blue units seen in these photos I believe?,
Zone valves, I'm not sure which part is the zone valve (originally thought it was the blue grundfos things) or where I might find them, my previous house had a taco powerhead value that had the manual switch you are speaking of but I haven't found that yet here - it wasn't at the radiator level or in the boiler room. Any suggestions where else to look?

Boiler into the circulators from the bottom. Flocheks after each circulator. Taco zone relay lights up the red light next to "zone 3" when I turn on the thermostat for the zone in question. Then the light turns back off when I set the thermostat to off again. All the while the radiators blast the heat via the hot water flowing through them. The zone in question is the second from the left, blue grundfos. Let me know if other/closer/further photos are needed and I'll get them.

EBEBRATT-Ed

If you boiler is really putting out 250 degree Hot Water you should shut it off and call for service. The boiler output temp shouldn't exceed 200 under any normal circumstances…..most would say 180.

If all your thermostats are turned down you could have a defective relay, zone valve or some shorted wires.

Do you get domestic hot water from the boiler??

hot_rod

you have zone pumps, at least on some of the zones. On the green Taco boxes, what lights are lite up?

DoctorAngelicus

https://forum.heatinghelp.com/discussion/comment/1803140#Comment_1803140

Only the power light unless I turn on the thermostat to heat (AC is a separate unit installed later not connected into this system).

DoctorAngelicus

https://forum.heatinghelp.com/discussion/comment/1803139#Comment_1803139

We have hot water through the faucets/showers (although I've diagnosed the circulator that goes to the water heater as faulty - it won't open all the time - tapping it immediately gets it to open and hot water flows to the water heater tank; I just got a replacement to install asap). With a pregnant wife and two year old, I can't really just cut off hot water for the house. I'm trying to get an outfit to come to the home but the unit was just serviced less than two months ago before we bought the house.

DoctorAngelicus

https://forum.heatinghelp.com/discussion/comment/1803139#Comment_1803139

Hot water goes from the boiler to an indirect water heater which is set to 130F. I believe that takes the hot boiler water, heats the water in the tank indirectly with the hotter boiler water. So not getting +200F out of pipes throughout the house.

hot_rod

Above the blue circulators are green colored flow control valves. Those are intended to prevent unwanted flow when that zone circulator is off. If the pipes get warm beyond those green valves, with the zone off, it could be the flow valve is not holding, or has been manually opened?

See if the pipes are warm beyond the green valves.

It could also be a mis-piped issue. A boiler or system circulator could be causing ghost flow through "off" zones. But that would have been the case from the original install.

DoctorAngelicus

Well last night, my FIL and I swapped out the circulation pump (grundfos 1558) that was getting stuck and not pumping hot water to the water heater and got hot water back to the house (with no leaks after reassembly, woo!). It was a pretty easy change out. If that proves to be all the faulty zone needs to be corrected, could easily do that again. Only concern is these blue ones pictured - I'm not sure if their is any significant difference compared to the red one we changed out other than the obvious difference in color.

Two findings from swapping the dying pump were 1) the boiler power was cut for the process and while it was cut the temp gage on boiler outflow never budged so I think it's old and not working. I tried pushing on the little pointer and it was pretty cemented in place. 2) after throwing the breaker back on, the zone in question is no longer heating unintentionally. I haven't tried to call for heat again because obviously I don't want to have it open up again and not be able to close without cutting the power again (because I'm not confident it will work that way reliably). Takes the urgency off the situation since we're not wasting all the hot water through those rooms' radiators but obviously still want to address the underlying issue asap. I believe this eliminates the possibility that it is just a zone valve manually pushed into always open? Or would that revert with loss of power?

hot_rod

the color can sometimes indicate the age of the circulator. In some cases specific colors are used for OEM customers. Always there will be a date code on the motor, week/year. 2297 would be the 22 nd week of 1997.

The important number is the model number 15-42 and 15-58 are common Grundfos numbers.

15 is the size of the hole in the volute, the second number is the head in decimeters.

Keep an eye on the zone that was over-heating. Ghost flow is a condition that can happen slowly over time if a flow check is leaking past or a mis piped system.

Check it in a day and maybe after a week.

Did the new circulator include a plastic check valve, either in the pump body or in the box?

The gauges on boilers are also a maintenance item it would be good to have an accurate working one installed. Some read pressure and temperature. You can buy strap on temperature and gauges if you want a simple indication until you replace it

Sounds like you are good to go for now

DoctorAngelicus

https://forum.heatinghelp.com/discussion/comment/1803219#Comment_1803219

It did have a white plastic check valve already in the body. We left it in. Was that wrong to do?

I'll definitely be keeping an eye on the zone that was having issues. So far still no warmth to any of those radiators.

hot_rod

Here are the valve deigned to top ghost flow. They can corrode inside and prevent them from ealing tightly. The sheet explain their operation. They could be disassembled, checked and cleaned if needed.

https://s3.amazonaws.com/s3.supplyhouse.com/manuals/1351085006630/85098_PROD_FILE.pdf

I prefer the spring type plastic check, that came with the pump. They seal well and have less pressure drop. You don't need both the green ones and the ones in the pump.

That looks like a GV boiler which has a pump inside. Itb needs to be piped a certain way to prevent that boiler pump from causing flow when you don't need or want it. Is the manual still around? It has the piping method detailed.

GroundUp

It appears as though you have zone circulators, rather than zone valves so my original comment regarding the zone valves is irrelevant. Do you know if any of the circulators in the system are running 24/7? Or is it possible that the flow of water to that hot zone was only taking place while the indirect tank had a heat call? This seems to be a classic case of ghost flow, typically caused by a faulty check valve in a system zoned with circulators. Given that you opened up the system to replace the indirect circ, there is a good possibility that the hot zone in question is now airlocked which is stopping the ghost flow from occurring. You should be fine to leave it alone for now, but at some point before it gets cold again, I think it'd be worth trying that zone again via the thermostat and see if it heats up. Maybe in the interim, check the voltage to the circulator in question. The lights in those switching relays are known to go bad on occasion, as well as the internal relays so there is a slight possibility that the relay was stuck and circ powered up before, just no light to show you that it was running.

hot_rod

Here are two tools to determine if a circ is powered. They read the magnetic force. But they do not always indicate the circulator is actually spinning. Download the app from Danfoss. Hold your phone against the pump motor.

• Does not work on all brands, and not on ECM type circulators.

The gauge or meter will spin just in the presence of electrical energy applied.

Although a volt meter on the pump terminals will give you the same info.