oil boiler L8148A question....

 
titleist1
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Post by titleist1 » Tue. Nov. 24, 2020 7:41 pm

I'm looking for some help for an elderly neighbor that has an oil boiler that has 3 zones, taco 571 zone valves and a single circulator with an L8148A aquastat.

He called saying his circulator doesn't shut off on one zone when the thermostat stops calling for heat. It only shuts off if he cuts power to the boiler or as I observed, the stat is satisfied & high limit is hit and the burner shuts off along with the circulator.

So he had another taco zone valve control head so I replaced that for him on the zone he says is affected. That was yesterday, he called today and said it is still doing it and it is all the zones, not just the one as he initially thought.

Not being a boiler guy, my first question is how is the L8148A supposed to control the circulator? Is it supposed to keep circulating water after a zone 'stat is satisfied or is it supposed to immediately shut off? Does this change if the boiler hits high limit or if burner is firing? The neighbor is elderly and I am not sure he remembers how it usually operated for him.

If its supposed to shut off immediately then I suspect its the relay in the L8148A not releasing after the zone valve opens the T T contact but would like some input please before just throwing a new aquastat at it.

If I can fix it for him there is a generous batch of home made oatmeal raisin cookies in it for me from his wife and I'll be sure to share them at next saturdays coffee house! :yes:


 
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coaledsweat
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Post by coaledsweat » Tue. Nov. 24, 2020 7:56 pm

The TACO zone valve controls the pump. Once the valve opens all the way, it has an internal switch that starts the pump. The valve operating head probably has a bad switch.
If it's only doing it on one zone, it is probably the zone valve either gone bad or wired improperly. There's 3 wires, if 9ne 8s goofed up it may run all the time.

https://www.google.com/url?sa=t&source=web&rct=j& ... 6265908624

 
titleist1
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Post by titleist1 » Tue. Nov. 24, 2020 8:06 pm

I wasn't clear with my description...
I believe the three zone valves are working properly because they each are opening the contact between terminals 2 & 3 when the stat is satisfied. These are connected to each of the T T terminals in the L8148A. It seems to me the L8148A isn't cutting power to the circulator contacts when the stat is satisfied. Unless it's supposed to keep running?

The wiring is done like the example on page 2, the intermittent operating pump and the neighbors system even has 3 zones like the example.

https://s3.amazonaws.com/s3.supplyhouse.com/manua ... D_FILE.pdf
Last edited by titleist1 on Tue. Nov. 24, 2020 8:15 pm, edited 1 time in total.

 
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coaledsweat
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Post by coaledsweat » Tue. Nov. 24, 2020 8:12 pm

No, it should stop when all the valves are closed.

 
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Post by coaledsweat » Tue. Nov. 24, 2020 8:19 pm

C1 and C2 are the circulator power. Disconnect t and t and see if the circulator still runs.

 
titleist1
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Post by titleist1 » Tue. Nov. 24, 2020 8:26 pm

I will have to do that tomorrow, old people don't want to work late! :D

I did check voltages on 2 & 3 on the valve controller when stat was satisfied versus when stat called for heat and the contact between them did open when the stat was satisfied. But I did not pull wires off the T T 's figuring if the contact on 2 & 3 was open the T T's were open as a result.

 
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Post by Holdencoal » Wed. Nov. 25, 2020 5:58 am

Ok, from the sounds of it. If the zone heads are cool to the touch and can operate manually ( the black lever) easy then you might have a bad control. The zone valve wiring should replace the thermostat shown on the diagram.

My guess is the relay is sticking.

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coaledsweat
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Post by coaledsweat » Wed. Nov. 25, 2020 7:11 am

Never operate the manual lever with power to the valve! Wait two minutes with the power off before moving the lever. It will damage the operator.

 
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Post by Holdencoal » Wed. Nov. 25, 2020 7:31 am

coaledsweat wrote:
Wed. Nov. 25, 2020 7:11 am
Never operate the manual lever with power to the valve! Wait two minutes with the power off before moving the lever. It will damage the operator.
Well that’s a new one, I guess I damaged a lot of zone valves. What’s the point of a manual override if you can’t use it while the relay is powered? 🤪

 
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coaledsweat
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Post by coaledsweat » Wed. Nov. 25, 2020 7:36 am

I have no idea. I was always puzzled by it but it is stated clearly on the box and valve. And you shouldn't remove the head when under power, same two minutes off routine.

 
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Post by Holdencoal » Wed. Nov. 25, 2020 7:47 am

This is the only warning.

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coaledsweat
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Post by coaledsweat » Wed. Nov. 25, 2020 7:50 am

Read the box they come in and I'm pretty sure there's a decal on the operator.
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titleist1
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Post by titleist1 » Wed. Nov. 25, 2020 7:50 am

My understanding .....

The wax heating up and expanding moves the piston and subsequently the valve. The spring in the valve pushes the piston back up as the wax cools and loses its expansion 'push'. If you remove the control head before it cools the piston is set in the wrong starting point by the cooling wax because the spring didn't push it back up. I guess you could damage something by putting the control head back on with the piston too far in the 'open' position.

 
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Post by Holdencoal » Wed. Nov. 25, 2020 8:03 am

Interesting....did you read both warnings? Warning label says to disconnect terminal 1, then the box says terminal 1 and 3!?

 
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Post by coaledsweat » Wed. Nov. 25, 2020 8:38 am

Yes, I've read them. Whatever it says they don't want the head powered when you monkey with it.


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