L8148A Aquastat relay - Burning out transformers

Dustin

Hello!
Here's the story:
1. 2 weeks ago I blew a Taco zone head. I replaced the zone head and all was well....until
2. This past Friday I had no heat. I manually turned on the zone valves and got heat. I thought the problem was the transformer and replaced it. All was well for 10 hours or so. Got back home and smelled the smoked transformer. Replaced with another one
3. 5 hours later, this transformer was smoked. Note that I tested the zones for 2 hours and all appeared well.
4. I replaced the transformer and all 3 Taco zone heads. The transformer blew within 2 hours.
5. I had an electrician check and test all wires. He confirmed all appeared to be properly connected and suggested replacing the L8148A controller.

During all of this, there has been 28V coming off the "TT" contacts on the L8148A. I currently have them jumped so as not to blow another transformer. I am trying to remove the controller from the picture.

My heating person says there should be no voltage going through the TT terminals. I've been reading postings on this forum that state the L8148's are kind of junky.

I need to get my system back running "automatically" again. It was running for two years without issue. All started once the zone head was blown. Any experiences or help that you can share will be truly appreciated. Essentially, my electrician and heating guy are stumped.

jp_2

no fusing?

why are the transformers not fused to protect them?

along with the zone valves?

transformers burn out cause you overload them, too much current on the secondary(zone valve side). like a shorted zone valve or shorted wire.

MIke_Jonas

Then you need a new heating guy. A good one would have fixed this by now, without the danger of you burning your house down over trying to save a couple bucks.

AND.. there's nothing wrong with the L8148..millions of them in use with no problems. Ask Carol Fey if they're "junky"

Norm Harvey

What are you geting for voltage out of the transformer?

What are you getting for voltage between terminals 1 and 2 on each zone valve when the thermostats are turner up? (1 and 2 being the terminals farthest from the valve body)

What are the heat anticipators on each thermostat set on? With the taco 3 mire gold zone valves the anticipators should be set on .9 amps




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Bob Bona_4

Taco's can be

tricky. Make sure they are wired EXACTLY per mfr spec. Could have a short in the wiring or you are backfeeding power sources. Possible ZV plunger seizure? Stat problem?

There should be 24VAC at TT no load on the 8148.

Unknown

Dustin

Sounds to me like a classic example of what happens when using 2-conductor (Red and White) wire with 3 wire zone valves. Inevitably polarity more often than not gets crossed within the wire nut connections between the transformer, zone valves and thermostats resulting in exactly what you just described. Here is a simplified diagram of how to wire three Taco 570 series zone valves. Follow it to the letter and I'll be willing to bet you won't have any more problems. You may also want to check real close for water dripping on the zone valve heads or even the end of one of the wires attached at the zone valve touching or shorting out to another terminal or ground. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Dustin

All the voltages and amps are checking out. All wiring has been verified at the boiler side as well as the thermostats and zone valves and controller. The Air Handler wiring as also been verified for both air handlers. This is as perplexing as it gets! If you can recommend a professional in the Exeter, NH or Portsmouth, NH area, I would be glad to have a 3rd pair of eyes involved.

eagle

sounds like your putting voltage directly through 1 and 2 terminals,must go through a t-stat first.TT terminals do have voltage through them.If your using taco zone valves,TT should go through 2 and 3. from each zone valve,

Dustin

Everything is per spec. All wiring specs from MFG's have been double checked and wiring confirmed. We initially thought of a backfeed problem but thus far cannot prove there is one. No one involved has mentioned a ZV plunger seizure or stat problem to date. Thank you for the info on the TT no load as that is helpful. As I mentioned in an earlier post, if you can recommend a professional in the Exeter, NH or Portsmouth, NH area, I would be glad to have a 3rd pair of eyes involved. Thank you for replying!

Dustin

I am not a heating person and thus don't know the answer to your first question. During this whole ordeal, no one has mentioned fusing transformers or zone valves.

Agreed on the burn out, but cannot trace any source. Also, current is normal and steady everywhere...which is what makes this highly strange and difficult to figure out. As mentioned in my previous posts, if you can recommend a professional in the Exeter, NH or Portsmouth, NH area, I would be glad to have a 3rd pair of eyes involved. Thanks a bunch!

Dustin

The Taco's have 3 wires going to each (Red White and Green). This diagram which you've attached was downloaded earlier today from Taco. My electrician just left and I'll be forwarding this off to him for confirmation. Page 3 of the following link from Taco was confirmed while my electrician was here: http://www.taco-hvac.com/uploads/FileLibrary/ZoneValveBroch.pdf

Thank you for your help!

Norm Harvey

Not to bust electricians, but Ive seen alot that cant seem to wire a taco 3 wire.

So long as you only have 1 transformer providing the voltage to the system, and its at 24 ish volts,..

As best I can explain the tacos operation in words,..

The load from the transformer send power to each and every thermostat. When the thermostat makes, it sends power to therminal 1 on the ZV.

The neutral from the transformer connects to all the #2 terminals as well as one of the TT's on the 8148

Once the thermostat makes and you have 24v between terminals 1 and 2 it starts the ZV head working and in a minute or so when the ZV is fully open, and end switch is made sending power down #3 to the other tt on the 8148 to start the burner and circulator.

Once you can imagine how it works, I think its easier to check the wiring and see if its correct.

Also,.. new taco zone valves will smoke on initial start up.

I would check each wire for independent continuity to make sure you dont have any bear wires or anything.



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lchmb

Why not

By the sound's of it, you've spent quite a bit to try and locate the problem. Why not make it simpliar and install a Taco ZV400 series control? It make's it nice and easy to see and follow what is going on with the zone's. And the end switch is just that, a switch.

http://www.taco-hvac.com/en/products/Zone+Valve+Control/products.html?current_category=141&PHPSESSID=444a0ded186149292be57ff7ac84bca6


Good luck

Norm Harvey

Theres an idea! It's got its own fuse to!

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Dustin

I'll mention it....but if there's a deeper problem, my guess is that this won't help. But worth asking about...thanks!

Dustin

The electrician appears quite competent and has looked at all schematics and compared to what he saw (I downloaded all schematics from appropriate MFGs). I can't ask for much more than that. If anyone has any Heating experts is the Seacoast area (south east) of New Hampshire, please forward them on!

Darrell

OK here's a couple of things to check...

How many Taco Zone Valves? If you have more than three then you need more than one 40va transformer. If you have more than one transformer...they absolutely have to be wired on both sides of the transformer the same...L1/L2...it is polarity sensitive. If you cross the leads on either side...when the right combination of zone valves open you will get 48 volts for a very brief time and then smoke. Check this visually...the primary side has colored wires and the secondary side has colered screws it is easy to miss with a voltage tester and I've only run across a couple of electricians, (or servicemen for that matter), who know to check. Do not assume that the power from the wall is correct.

Obviously the operating control is working...until you connect the zonevalves...so...odds are the problem is in the zonevalve circuitry.

Next, if the boiler, (and thus the operating control), is powered from a different source than the zonevalves, the polarity has to be the same, or you'll get smoke. Ideally, all of the heating equipment is powered by the same circuit...I hate burning up my equipment in cross powered situations...but I digress.

Next, the Taco Powerhead has leaf springs that make or break the circuits at different times. They are moved by the plunger moving down or up and the bevel pushing against the little plastic tits on the leaves. If the little plastic tits are broken, tilted, worn, or missing, then the 24v will shunt directly to ground when that particular zone valve opens...and you'll get smoke. You have to check visually...pop it off and look.

Next, look for a burned low volt wire that is tied to a hot pipe. It is common to tie them up that way and eventually they burn through...when that particular zone opens...you get smoke.

If you do not have a Taco Zone Valve Controller...it is worth the trouble to get one. The daisy chain wiring is always suspect...and when I go on a call like yours the first thing I do is strip all the zone valve wiring and start over.

Taco makes great stuff, don't let anyone talk you out of it, and the 8148 is the workhorse of the industry. You have a "peripheral control wiring issue."

Dustin

Good morning and thank you for the informed reply. I want to answer your questions and post some comments of my own:

1. There are 3 zones. Two heating and one for a 50 gallon indirect hot water tank. We only have two people in the house in case there is a thought that the hot water tank is always running (because of 4 kids or the like).

2. We have one transformer. My heating person, as a test suspecting some possible issues with huge voltage, put two transformers in tandem....then both were smoked.

3. Last night, we jumpered the T T lines and left the original thermostat lines off. Heat for both zones and the indirect hot water tank were left "manually open" and worked great last night with no problems. It always happens once we connect the TT lines.

4. The whole system is powered from the same source. We changed brakers just for posterity's sake and because I had a bunch of new ones laying around. That did not solve the problem.

5. Taco powerheads appear to be functioning properly with no issues. Note #3 previously.

6. I will re-inspect (4th time) for a LV wire tied to a hot pipe. This scenario is plausible because some wire is hiding behind the insulation covering the pipes.

7. I have just replaced the original (Honeywell) controller with a new Honeywell controller. I will reinspect all wiring this morning with a rested pair of eyes.

Thank you for your in depth response! -Dustin

Darrell

You have a bad Powerhead or a burned wire. Pushing the Powerheads open manually does not activate the same leaf springs as driving them open with the thermostats, so that test is inconclusive. One 40va transformer is sufficient. Wiring two in tandem is fine but the polairity must be consistent. My money is on a burned wire...especially if they are buried against the hot piping under insulation. If the thermostats are bad, usually the thermostat will burn out and not damage any other controls. Run time with your water heater is not an issue.

Dustin

Hi!

We've swapped the power heads with new ones to test. Same problem existed when this was done. Likelihood of a power head being bad is slim. I have just (literally, just) purchased a new ZVC404 Taco controller and will be setting it up shortly. I purchased it for two reasons: 1) to help troubleshoot the problem I am having and 2) to clean up the rats nest...although I believe the wires to be correctly installed, it will be much nicer and cleaner that before...plus it will be fused.

As for your comment about a burned wire, I cannot fully exonerate the wiring because I cannot see inside walls. However, all the visible stuff everywhere is clean. This will be quite the solution and I'll be sure to post it when all is said and done.

Thanks to you and everyone on the board for their TIMELY assistance. I can't believe how fast responses have come in!

Dustin

Dustin

Narrowed down problem

Hello!

Thanks to the advice on this forum, I've installed a Taco ZVC 404 Zone Valve controller. I've hooked up the unit and performed the following:
1. Turned on all 3 zones and noticed that Zone #1 was tripping the fuse in the ZVC 404.
2. Replaced the fuse and then swapped power head with known good power head. Burned out the fuse again for Zone #1.
3. Replaced the fuse and then replaced the thermostat for Zone #1 with a known good thermostat. Burned out the fuse again for Zone #1.

Please let me know if my conclusion is sound. Conclusion: Wiring in the wall going up to Zone #1 and related Zone #1 wiring must be toast somewhere. Replacing the wiring from the thermostat, air handler and down to the zone head should solve the problem.

Thanks again to one and all for the assist! I will post the result when completed. -Dustin

Mark Hunt

Check continuity


on the wire coming from zone #1 after disconnecting it from both the head and the ZVC controller. Sounds to me like there is a wire that has been crushed either by a staple or something else.

Better yet, run a new wire from the head on Zone #1 to the ZVC control. Terminals #1 and #2 are for the coil in the head and they should not touch each other. That is a direct short and will release the magic smoke.

Mark H

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Darrell

Abandon the old wiring and use new stuff...it's faster than sorting out the old and the cost is nothing compared to what you've already spent. The wiring pertaining to that zone valve head is the problem. If it was the thermostat that is shorted, the zone would come on and never go off...but not short out...Mark is right, wire 1 and wire 2 are shorted together.

Make sure that both of your troubleshooters get all of these posts...

Dustin

SOLUTION: Figured out what the problem was

Hello!

As promised, myself and my buddy the electrician have resolved the problem. Thanks to the Taco Zone Valve Controller (ZVC404) and a voltage tested, we were able to narrow the problem down to a specific cable.

Specifically, the cable that goes from Zone Valve #1 to the Taco Controller was BAD. We stripped the cable and found some "compromise" with the wires. There was a green powder that smelled like something burned badly on the cable at a certain location.

It turns out that the specific location was where a small staple held the wire to the framing. But it was not the sole cause of the problem.

My electrician thinks that, when the original zone valve #1 blew, that a higher amount of amperage and voltage passed through the suspect wire. When that happened, it degraded and started to compromise the insulators around the wiring. It only took around 1.5 weeks for the initial surge, then the on/off of the zone to finally burn the wires together.

In summary, the wire was toast and the new wire has now been working properly for a while now with no problems, no blown fuses, and thanks to the new Taco unit, no more blown transformers.

Thanks to all for the advice, suggestions, insight and opinions. It helped immensely!