Thermostat stopped triggering heat, technician came rewired taco valves and fried aquastat. Help.

GhostProtocol

I have an American Standard Gas Boiler from the 1970s, 3 zone system with taco valves. The upstairs thermostat would call for heat and the boiler wouldn't turn on. I could manually open the valve and run heat to the upstairs, other zones worked fine. While I was trying to diagnose the problem I was trying to examine the wiring on the taco valves and a small piece of wire broke off.

Technician came and said it seemed like a wiring problem and spent a few hours rewiring the taco valves. They came up and told me that after the tried to run the heat "the aquastat fried" and they smelled burning wire. They want to come back with their manager and replace the aquastat for additional fee. From the estimate- "Returning with another Technician to perform a major diagnostic on the boiler wiring & replacing the failed Aquastat."

*Additional charges may occur due to the issues & age of this boiler.

I feel like the issue was with the Taco valve wiring but is it possible they did it wrong and that is what "fried the aquastat?" I know originally the taco valves had wires going to each other and now they don't. Not sure if that matters. But how should I proceed at this point?

I can still manually open all 3 taco valves and manually fire the boiler even without electricity. So I can supply some heat to the house.

I would appreciate any insight or guidance in navigating this issue.

GhostProtocol

mattmia2

The burner fires and the circulator runs if you close t-t on the aquastat?

I suspect that they don't know how those taco zone valves with the common between the heat motor and end switch connections are supposed to be wired. You can burn them or other components out if they aren't wired correctly.

and please edit to remove the price.

GhostProtocol

mattmia2 said:

The burner fires and the circulator runs if you close t-t on the aquastat?

I suspect that they don't know how those taco zone valves with the common between the heat motor and end switch connections are supposed to be wired. You can burn them or other components out if they aren't wired correctly.

and please edit to remove the price.

I can do exactly what this guy does in this video at 3:47 to fire the boiler. It also works like this during power outages.

https://youtu.be/WV6QUrobbF4?si=bAGF1Xib4xpCrmqw&t=229


Yes, my concern is that it wasn't wired correctly and that is what damaged the aquastat. Should I be made to pay for that, if that is what happened?

I feel like the wiring on one of the Taco valves was damaged and the technician made the problem worse with the rewiring.

mattmia2

does the aquastat close if you jumper t-t? Do you have a picture of the schematic for that aquastat from the cover? I assume those terminals are TR and TW. if it does the aquastat is ok. there are ways the second transformer for the zone valves could burn out the transformer in the aquastat if it was miswired.

don't do what he's doing in that video, it bypasses the safeties.

pecmsg

Just find a more qualified service provider and move on. 

mattmia2

(for those that didn't deal with the video, he jams a screwdriver in the armature of the relay)

GhostProtocol

GhostProtocol

mattmia2 said:

does the aquastat close if you jumper t-t? Do you have a picture of the schematic for that aquastat from the cover? I assume those terminals are TR and TW. if it does the aquastat is ok. there are ways the second transformer for the zone valves could burn out the transformer in the aquastat if it was miswired.

don't do what he's doing in that video, it bypasses the safeties.

Sorry, I don't know what jumper t-t means.

I do what the guy does in the video twice a day for 15-20 minutes to get some heat to the house. Although it is warmer now so maybe not necessary. Is it unsafe to do ever do it, or ok sparingly like that?

mattmia2

I don't recommend doing it, but you have to watch the temp carefully, do not leave the boiler because it bypasses the aquatstat, there is nothing to shut down the burner if it gets too hot.

the 2 terminals on the right of the aquastat, one is labeled Tv and the other T. The thermostat (or the end switch on the zone valves in your case) shorts those terminals together to make a call for heat. If you jumper those the circulator and the burner should come on if everything is good in the aquastat. Is that a reset button or a fuse holder on the top of the aquastat sort of behind the thermostat connections?

GhostProtocol

mattmia2 said:

I don't recommend doing it, but you have to watch the temp carefully, do not leave the boiler because it bypasses the aquatstat, there is nothing to shut down the burner if it gets too hot.

the 2 terminals on the right of the aquastat, one is labeled Tv and the other T. The thermostat (or the end switch on the zone valves in your case) shorts those terminals together to make a call for heat. If you jumper those the circulator and the burner should come on if everything is good in the aquastat. Is that a reset button or a fuse holder on the top of the aquastat sort of behind the thermostat connections?

I turned on the electricity to the boiler to try to jump them and there was immediately a component burning and smoking. I drew an arrow in red on this picture to the component. I shut off the breaker to the boiler now. What is this component and why would it burn if the electricity was on?

mattmia2

That is the relay. unhook the wires to the zone valves and try again. maybe they put the 2 transformers in series so that it is getting 48vac to the relay instead of 24vac from the built in xfmr.

GhostProtocol

mattmia2 said:

That is the relay. unhook the wires to the zone valves and try again. maybe they put the 2 transformers in series so that it is getting 48vac to the relay instead of 24vac from the built in xfmr.

Unhook the 3 wires that connect to each of the 3 zone valves? Or is there an easier way to disconnect the zone valves?

mattmia2

Disconnect these 2 wires:


see if the relay stops getting hot when you do that. If that part goes ok, jumper the 2 t terminals together and see if the relay closes and the boiler fires without the relay smoking.

They may have already damaged the relay so the relay-aquastat needs to be replaced or rebuilt but it smoking because of some defect that developed on its own is unlikely.

GhostProtocol

mattmia2 said:

Disconnect these 2 wires:


see if the relay stops getting hot when you do that. If that part goes ok, jumper the 2 t terminals together and see if the relay closes and the boiler fires without the relay smoking.

They may have already damaged the relay so the relay-aquastat needs to be replaced or rebuilt but it smoking because of some defect that developed on its own is unlikely.

When I disconnected the wires and turned the power on, it seemed fine, not smelling like smoke. When I jumped the terminals it immediately started smoking.

hot_rod

A meter and proper training on how to use it might be a better way to troubleshoot the issue. Safer too

Alan Welch

That boiler is around 50 years old. Might make more sense to get a few estimates on complete system replacement, instead of spending a lot of money on it.

Jamie Hall

Honestly, you really need to find a new technician who actually understands how to wire this up. It isn't that hard -- if you know what your are doing, but if you don't you can very easily burn things out. There are a variety of ways to do that, but only one way to do it right.

If you jumper from T to TV in the upper right corner of the aquastat, does the relay close and the burner fire? You could run it that way

GhostProtocol

I will be talking to a manager today about the situation. It is a well known and respected company that I've only had good experiences with previously. My hope is that someone more qualified can come figure it out and we can make a compromise on the price for repair. My feeling is that I don't mind paying for the new part but the full estimate seems unreasonable if they contributed to the demise of the aquastat.

mattmia2

If the 2 zones were working but the 3rd zone wasn't after you did what you did but before they touched it then it isn't they contributed to the demise of the aquastat/relay, they destroyed the aquastat /relay.

You need to replace the aquastat/relay (they should pay for that and the labor if 2 zones were working when they touched it), then they need to get the wiring for the zone valves and second transformer right such that it doesn't power t-t, so it only closes the contacts between t-t, then they need to find the original problem which was either a broken wire or the end switch on the zone valve was bad or the actuator or valve is sticking so it doesn't move far enough to close the end switch.

if both transformers have a grounded end then that end needs to connect to the common terminal on the zone valve from both transformers.

GhostProtocol

I spoke to them today and they are going to send a new technician out. They will replace the aquastat and fix the original problem for a much lower price than originally quoted. I thought it was reasonable. I appreciate the help here, it gave me the confidence to insist on a better remedy on their end. Thank you.

EdTheHeaterMan

I can be 98% sure that the first technician made a wiring error the caused the aquastat failure. The Taco 570 series valves ( the three wire valves) are not fully understood by many technicians in the industry. I have a detailed comment here on the subject.
https://forum.heatinghelp.com/discussion/comment/1785090#Comment_1785090?
Since there are more ways that work than the one in the zone valve diagram, it is common to get someone to make the mistake.

It is quite possible that you have a defective zone valve heat motor part number 555-050RP. If you find that this is the case, then you might ask that if the 555-050RP was replaced originally without rewiring the entire system, then perhaps the Aquastat would not have failed. They should just include that in at no charge!

Mustangman

Who ever wired the zone valves broke one of my rules. Don't land 2 red wire on the zone valve. To me it seems like you are getting 24v from the zone valves, tangled up with the 24v transformer on the aquastat. I always run, red ( top screw ) white ( center screw ) and blue on the ( bottom screw ). Its really easy to land the wrong red on the zone valve.

GhostProtocol

EdTheHeaterMan said:

I can be 98% sure that the first technician made a wiring error the caused the aquastat failure. The Taco 570 series valves ( the three wire valves) are not fully understood by many technicians in the industry. I have a detailed comment here on the subject.
https://forum.heatinghelp.com/discussion/comment/1785090#Comment_1785090?
Since there are more ways that work than the one in the zone valve diagram, it is common to get someone to make the mistake.

It is quite possible that you have a defective zone valve heat motor part number 555-050RP. If you find that this is the case, then you might ask that if the 555-050RP was replaced originally without rewiring the entire system, then perhaps the Aquastat would not have failed. They should just include that in at no charge!

Yes, I think this is what happened. Thank you for linking that comment. The total price they are charging is about the same as the retail price for the aquastat part. So it seems fair to me if they fix the original problem and I have a new aquastat replacing a decades old one.