Gas Boiler not starting in 1 zone at times

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Old 12-03-19, 05:02 AM
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Gas Boiler not starting in 1 zone at times

Have a three year old crown Aruba 4 boiler. In upstairs zone at times the thermostat will call for heat, I have checked taco sentry zone valve at boiler and it opens. But boiler does not turn on and it does not heat, temperature can drop well below setting in this zone

If I turn on other downstairs zone boiler starts and both zones satisfy thermostat.

This only seems to happen when boiler is cold, as in this zone with tempature set at 70 on hold setting it maintained and turned boiler on to do this. However if it is set back like at night to 62, the tempature will drop below this on thermostat and checking boiler zone valve is open but boiler doesn’t start unless another zone causes it too

Any ideas would be very appreciated.



 
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Old 12-03-19, 05:27 AM
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Hi, sounds like the end switch on the valve is not closing to fire the boiler, check this link
http://www.taco-hvac.com/uploads/FileLibrary/100-82.pdf
Geo
 
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Old 12-03-19, 06:18 AM
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Hi

thank you. So does that mean the head needs be replaced? Any idea why it would fire when boiler is hot but not on setback when boiler cold?
 
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Old 12-03-19, 06:48 AM
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Hi, not sure what you mean by, would fire when boiler is hot, do you have a multimeter,if so, with the zone calling for heat test between the end switch terminals on the valve, I like to remove the conductors and test for continuity.
Geo
 
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Old 12-03-19, 07:01 AM
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The zone will not fire boiler independently.

It will heat once other zones call for heat and then heat is sent to satisfy thermostat on upstairs zone. There are 3 zones heat upstairs, downstairs, and hot water indirect.

Right now valve is open but thermostat on upstairs is set at 69 and temp is 68. It will drop until one of other zones opens and then it gets heat. I think I was wrong about boiler hot and it firing on that zone
 
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Old 12-03-19, 08:14 AM
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I contacted taco and then suggested checking wires into end switch as it would be very odd for a valve to go bad at only 3 years. They wanted me to loosen screws on end switch piece and check this

Does this make sense?
 
  #7  
Old 12-03-19, 11:33 AM
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F,
It is definitely an end switch problem weather it be from wiring or a bad head. Terminals 1 & 2 on a Taco open the valve on a call for heat that make an end switch and 2 & 3 turn on the boiler.

What you can try if you don't have a meter is switch the head with one that is working and check the results. If the problem head does not work on the new zone then change the head. This will eliminate checking all your wiring and other possible problems between the valve and the boiler.

Hope this helps a little.
 
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Old 12-03-19, 07:03 PM
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I appreciate it

im going try switch the head and hope that fixes it. The wires seem fine into valve, maybe end switch part of valve is bad like others said
 
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Old 12-06-19, 04:58 AM
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Taco sentry zone valve starts boiler only when Pipes going to zone are hot

Taco sentry zone valve starts boiler only when Pipes going to zone are hot. Can anyone explain why this would be. If the boiler has not run and this zone calls for heat, valve will open and not start boiler as it should

If however boiler has run and is hot and has thrown heat to this zone it will start and run to thermostat setting then close. At other times when it is cooler it will open and not start boiler.

It makes connection when hot to start boiler and run. I have tested this by running heat to other zone which then throws heat to this open zone which did not start boiler independently. After other zone closes the problem zone will then run boiler to setting on thermostat
 

Last edited by PJmax; 12-07-19 at 07:54 PM. Reason: Two threads combined
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Old 12-07-19, 10:25 AM
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So like was said in the other 2 threads you started it is probably the end switch. AGAIN switch the head with another and see if the problem follows the head. One cannot tell you why a micro switch behaves in a certain way under certain conditions without extensive testing that cannot be done on a computer screen. It is a simple job to switch the heads to get closer to an answer
 
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Old 12-07-19, 07:54 PM
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We are going around in circles and starting new threads is not helpful.
Have you changed out the head ?
 
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Old 12-08-19, 07:39 AM
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Thanks Pete, I feel the same way.
Geo
 
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Old 12-08-19, 11:45 AM
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Am waiting on new head.. it has been working fine with heat coming on more frequently as pipe stays hot and it will then trigger boiler. It makes no sense why it works when it’s hot but will not if it gets cooler
Going change head and see. Appreciate all help from people
 
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Old 12-08-19, 12:09 PM
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Fall,
It makes all the sense in the world which is why changing the head from one that is working to the defective one so you could see what we are trying to explain to you.

What will happen once to swap heads is that the defective zone will now work properly and the good zone will now be defective.

Why your defective valve works sometimes as you think it does is because another zone is calling and heating the boiler so when the defective zone calls the valve opens to let the hot water flow into that zone also. If you run the defective zone ONLY, because of your BAD end switch the boiler will NOT come on to reheat the water in the boiler like the good zone does.

What you have to realize is that by using the process of elimination if you don't want to do anything else is think about this.

Your boiler, circulator, transformer are all common to both zones. Your t-stats are separate but you can eliminate your stat because the ZV is opening and it is not air bound because you DO get heat occasionally. That leaves ONE final thing which is a DEFECTIVE END SWITCH which you could verify very easily just by switching the heads.

Hope this long winded post has at least made a little sense to you.
 
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Old 12-08-19, 12:19 PM
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Actually no if the pipe is hot the other zones can be off and it will run zone. I have observed this
If it is cool valve opens but will not trigger boiler. It will trigger independently at times specifically when pipe is hot going to valve
 
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Old 12-08-19, 12:22 PM
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I am going change head and see if that works. I do appreciate all the help
 
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Old 12-08-19, 12:26 PM
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With the temperatures in 20’s and zone coming on frequently it has worked fine l. However if temperature is set back and it cools pipe to valve. The zone will not trigger independently. Thermostat temp will drop and zone remains open but boiler off. If another zone kicks on yes it will throw hot water into that pipe and it will then run independently even after other zone closes
 
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Old 12-08-19, 12:33 PM
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The pipe being hot has no bearing on the valve at all. The valve has no idea if the pipe is hot or cold. If the valve does work intermittently then it can still be a bad end switch that also works intermittently or loose or defective wiring going from your ZV to the boiler. Make sure all connections are good. This can also be determined by switching out the heads though.
 
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Old 12-08-19, 12:38 PM
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Ok I’ll switch it out. Thanks. Thought maybe could’ve be an air in lines problem and when it is hot don’t see this. I agree it shouldn’t matter but it consistently works if hot. Thanks
 
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Old 12-08-19, 12:59 PM
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I wouldn't worry about air. If it was air it would be the same every time. Air is consistent until removed. It doesn't allow the zone to heat one time and not another.
 
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Old 12-08-19, 04:53 PM
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Things expand when they are hot, it could be simple as that causing it to sometimes work and sometimes not. I would think the important thing is trouble shoot the issue to find the defective part as it it s still defective if it works some of the time or none of the time. In the time it took to make the posts you could know for sure if it was the end switch and continue trouble lm shooting if is not.
 
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Old 12-08-19, 05:47 PM
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Your right. I am going change the valve and see, Thanks
 
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Old 12-11-19, 08:01 AM
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Well I am guessing he switched the head and it followed or put a new head on and it is fixed due to no responses
 
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Old 12-11-19, 11:21 AM
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Didn’t change yet am waiting on head and help to do it
I am hoping it fixes it, works only when pipe hot which would not point to valve
could it be something in pipe keeping valve from opening and then when it gets hot it expands and allows connection to be made
 
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Old 12-11-19, 11:29 AM
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I will post here once valve changed
 
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Old 12-11-19, 01:26 PM
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What you can do until the new head arrives is to put your valve in the manual position so when any other zone calls you will get heat to that zone also.

Remove the top wire on the zone valve and push the lever all the way down. This will open the ZV and take the t-stat out of the equation.
 
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Old 12-11-19, 02:48 PM
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A blockage that large would impeded flow all the time. It could be a hot only electrical thing with contacts touching when hot. I am no expert and it took me longer to type this post than it did to change the last head I did. FWIW the last one that went bad only misbehaved when the pipes were hot failing to shut the call for heat cleanly and it cycled on and off several times before finally shutting off.
 
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Old 12-11-19, 05:44 PM
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Ok. I just got new head and am going get it changed. I appreciate information and hope your right. Thanks
 
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Old 12-15-19, 09:54 AM
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Since we have not heard back I guess the issue has been solved.............
 
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Old 12-16-19, 08:07 PM
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I am changing valve on Saturday with family help. Will post if it solves issue of zone not turning on boiler at times
 
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Old 12-21-19, 06:43 PM
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Changed the head and seems be working properly now. Thanks to all for help, seems to have been end switch on taco valve. Talking to taco valve company thought would never have believed that as they make you believe could not be valve
 
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Old 12-22-19, 09:39 AM
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Thank you for the update. Glad things worked out.

Merry Christmas.
 
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Old 12-23-19, 05:38 PM
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Thanks to all for help. Is working normally now and triggering boiler at all times when call for heat

Merry Christmas

thanks again
 
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Old 12-23-19, 06:37 PM
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Great to hear there was an easy fix
 
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