Aquastat issue? help!


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Old 09-08-09, 04:11 PM
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Aquastat issue? help!

hey all,

looking for some direction here.. have a boiler -> indirect water tank & radiant heating setup. Havent had any hot water since last week.

From what I can tell, the aquastat on the water tank (which only has 1 dial) is wired into a Taco SR504 which I assume trips the boiler.

I've tested the two other zones on the Taco, the radiant heating in the basement and the garage. Both work fine and trip the boiler to turn on.

I cannot get the boiler to trip from the aqastat on the water tank - which is where my assumption that it is dead comes from.

Can any one provide more insight? possibly a way to test the aquastat or a way to trip the boiler?

thanks!
 
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Old 09-08-09, 09:09 PM
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If the indirect aquastat is wired to the Taco relay, remove those wires from the taco control and insert a jumper to those terminals in the taco relay. If the unit fires it is the aquastat or wire to the aquastat. I would meter the wire ends through the aquastat to verify an open aquastat. If jumping the taco relay does not bring on the boiler it is the taco relay.
 
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Old 09-09-09, 07:06 AM
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Originally Posted by rbeck View Post
If the indirect aquastat is wired to the Taco relay, remove those wires from the taco control and insert a jumper to those terminals in the taco relay. If the unit fires it is the aquastat or wire to the aquastat. I would meter the wire ends through the aquastat to verify an open aquastat. If jumping the taco relay does not bring on the boiler it is the taco relay.
rbeck - thanks for the reply. good idea. stupid question - can i work on the taco unit live, or should i kill power to everything?

(sorry.. I don't normally work on these things, but finding someone to come out isn't as easy as i thought!)
 
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Old 09-09-09, 08:09 AM
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Shut it down until the wires are disconnected and jumper installed. You will be working on the 24v side (top of control) but it may chatter alot while disconnecting and installing jumper.
 
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Old 09-09-09, 03:11 PM
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OK.. so I got home and tried jumpering the relay terminals.. sure enough it fires up the boiler.

next issue!

it appears the wrong circulator is running so the hot water tank is still not getting fed. The aquastat wiring runs to Zone2 on the Taco, but when it's jumpered the circulator on Zone4 runs.. errr..

any ideas?
 
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Old 09-09-09, 03:49 PM
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I can't think of any way that is even possible... unless it's wired wrong, and from what I infer, it has worked properly until last week... right ?
 
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Old 09-09-09, 03:57 PM
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OK.. so I mis-spoke a touch.

The circulator I can feel running is connected directly to the boiler via some Honeywell box. (i believe the boilers aquastat)

The circulator that is supposed to feed the hot water tank is connected to Zone 4 on the SR504 - it is not spinning - at least there is no heat on the other side of the pipe.

All the circulators are Grundfos.

Does that make more sense?
 
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Old 09-09-09, 03:59 PM
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Originally Posted by NJ Trooper View Post
I can't think of any way that is even possible... unless it's wired wrong, and from what I infer, it has worked properly until last week... right ?
And yes, it worked properly until last week so I assume the wiring is fine, that is unless me jumpering the Zone2 thermostat pins causes a different reaction that when the Aquastat on the water tank is reading low temp.
 
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Old 09-09-09, 06:45 PM
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update for you all..

it ended up that the aquastat somehow is controlling or sending some sort of signal through the Taco to an automatic valve actuator that was causing the water to not flow back to the boiler.

i ended up put the aquastat back into the taco zone relay AND jumpering the zone. By doing this, the valve is opening and the boiler is started - finally - hot water!

this temp solution will keep the wife happy for the night.. she gets a hot shower!

that being said, is this making sense to anyone? Im still assuming the aquastat is shot seeing as it isn't starting up the boiler through the Taco, but how the heck is it controlling the auto valve?

thanks for the input.. learing a lot these past few days!
 
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Old 09-09-09, 06:51 PM
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anyways you can post some pics of the near boiler piping ?
 
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Old 09-09-09, 07:48 PM
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sure.. see link below.. lots of detailed pics, thanks!

Pictures by rbc009 - Photobucket
 
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Old 09-10-09, 02:59 PM
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by chance, looking at the unit today, could it be possible that one of the "ice cube" replaceable relays has failed?

is there a way to tell or test if one of these has failed?
 
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Old 09-10-09, 03:16 PM
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Something is screwball there...

Looking at that wiring... something ain't right...

Can't see the 'big picture', so need to ask some questions:

1. Is the motorized valve (called a 'zone valve') in the return line from the water heater?

2. The pump below that is in the line to the water heater? Is that pump wired to zone 2, which is where you say the water heater aquastat goes?

3. With the jumper in place shorting out the water heater aquastat, is that pump running 100% of the time now?

4. The two red wires from the valve, where do they go? I think I know, but would like confirmation of...

5. The yellow wires from the valve... one is going to a small terminal strip, and there is a black wire coming off the other terminal on that strip... where does that black wire go?

6. The thermostat wires coming in to zone 4, do they come from a heating zone?

If you post a higher res pic of the control panel, I might be able to see for myself... I just can't blow it up big enough to see it ...

Also, a few pics from further back that allow following the piping around might help also.
 
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Old 09-10-09, 03:17 PM
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Yes, it's possible that you have a failed relay...
 
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Old 09-10-09, 03:33 PM
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hi NJ.. thanks for any help!

1. Not sure.. it just says Wirsbo Motorized Valve Actuator.. it's on a pipe heading right back to the boiler. It has wiring going to Zone4 on the Thermostat area on the Taco.

2. The pump below to the right of the Valve Actuator is pumping to the left to the water tank "boiler in". It is wired to Zone4 on the Circulator area on the Taco.

3. I jumped Zone2 on the Thermostat area of the Taco. With that done, the boiler runs 100% of the time. I turn off the system when I get a tank of hot water.

4. The 2 red wires from the valve go to Zone4 on the Circulator area on the Taco.

5. One of the yellow wires goes to incoming 120V, the other into the strip.

6. See answer 4.. coming from the valve.

Will try and get a better pic up shortly.

thanks again!
 
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Old 09-10-09, 03:52 PM
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1. Not sure.. it just says Wirsbo Motorized Valve Actuator.. it's on a pipe heading right back to the boiler. It has wiring going to Zone4 on the Thermostat area on the Taco.
But, where is it coming FROM? The water heater?

3. I jumped Zone2 on the Thermostat area of the Taco. With that done, the boiler runs 100% of the time. I turn off the system when I get a tank of hot water.
And which pump is wired to Zone 2 on the bottom?

4. The 2 red wires from the valve go to Zone4 on the Circulator area on the Taco.
?? the circulators are wired to the bottom, thermostats and such are wired to the top... those red wires appear to be wired to the thermostat connections for zone 4, is that correct?

5. One of the yellow wires goes to incoming 120V, the other into the strip.
I doubt that... that small strip is 24VAC ... I will look again, but I think your valve is a 24 VAC valve... if you put 120 on that, you will have a schpitzenschparken und schmokinleekin condition at the valve.

6. See answer 4.. coming from the valve.
That's not what I see... those smaller gauge brown insulated wires are not 120 VAC. Those are low voltage wiring, and one of the yellow wires is twisted to the white wire in that pair (without a wirenut... wrong!) ... I think I see the small black wire from the strip that the yellow wire is on connected to the black wire in that same cable... with a red 'butt splice'... where does THAT brown cable go?
 
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Old 09-10-09, 04:05 PM
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1. Yes, sorry.. that valve is coming from the water tank - boiler out.

3. Zone2 is going to the pump at the top right of the wall. I believe it pumps to the garage floor.

4. Correct, my mistake. 2 red wires from the valve actuator go to Zone4 thermostat.

5. My mistake again. The one yellow wire is connected to the furnace (i assume heat exchanger) and the other end to 24VAC on the green slot.

6. Yea, the wirenut broke, dont have one here - will replace it before the cover goes back on! The brown cable goes to the furnace.
 
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Old 09-10-09, 04:11 PM
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just uploaded some higher res pictures as well.

Pictures by rbc009 - Photobucket

can't get a more open shot of the whole room, sorry.. too small of a room.
 
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Old 09-10-09, 04:54 PM
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3. Zone2 is going to the pump at the top right of the wall. I believe it pumps to the garage floor.
And you are absolutely 100% certain that the wire going to Zone 2 T T terminals is the one on the aquastat of the water heater? What I don't understand is why would the water heater activate the pump for the garage floor?

5. My mistake again. The one yellow wire is connected to the furnace (i assume heat exchanger) and the other end to 24VAC on the green slot.
This is one of the areas that I'm not understanding something...

6. The brown cable goes to the furnace.
And this is another...

I also see ANOTHER relay mounted on the wall above the Taco panel... but we'll not think about that today...

Please take a closer look at the brown jacketed wire that is connected to the yellow and black wires coming out of the right hand hole in top of the panel. That hole has TWO brown wires coming out, one pair is going to zone 3 , and is going UP, toward that other relay... but the OTHER wire, the one that is connected to the valve, comes out of the panel, and travels to the LEFT, and from what I can see, disappears somewhere behind the water heater... where is that wire going to ?

Here's what SHOULD be happening:

When the indirect calls for heat, it's control tells that motorized valve to open by switching 24 VAC to the yellow wires to run the motor in the valve. When that valve opens, it pushes on a SWITCH inside the valve body (known as the ENDSWITCH). The endswitch is connected to the RED wires. When the red wires are switched, it tells the TACO panel to operate pump 4, and to turn on the boiler. Since the PRIORITY switch is set to ON, when the water heater calls, the heat zones are turned OFF until the water heater is hot and happy.

But, what you are saying here is that the water heater is connected to zone 2 ? which is the garage floor ? and that's what is totally bizarre...

So, please follow those wires again, carefully, and make sure that you are seeing what you think you are seeing... cuz it just don't make sense.
 
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Old 09-10-09, 05:21 PM
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The wire I highlighted in yellow is the one I'm wondering about... looks like it heads to the water heater.

 
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Old 09-10-09, 06:08 PM
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NJ,

bah.. im a total goof. I went down there again and traced everything back by removing tie-wraps, staples etc. Man, i feel like a dummy.. my wiring scheme was wrong, im sorry to waste your time. here is the CORRECT setup.

#1) That wire you highlighted IS the aquastat.

Z1 TT -> Mars 24VAC Relay (the one to the left of the switch)
Z2 TT -> Garage flooring
Z3 TT -> Basement flooring
Z4 TT -> Red Wires on Actuator Valve

Isolated End -> Honeywell Box on Boiler
ZC/ZR -> Closed
Z1 Pump -> Empty
Z2 Pump -> Garage flooring
Z3 Pump -> Basement flooring
Z4 Pump -> Water tank
120V -> To wall switch

Aquastat
White wire -> Yellow wire on Actuator Valve
Black wire -> 24VAC on Taco green board

other yellow wire on Actuator Valve -> COM on Taco green board

Bottom wires on Mars 24VAC Relay -> Furnace


Now.. i was listening closely to the Taco box and noticed that the "ice cube" relays (or one of them) was making clicking noises like it was tripping, but no boiler action. while doing that, it actually did start the boiler once on Z4, but then shut off right away. I tried switching the "ice cubes" around, not toucing the 1st one which is 120V, but no difference.

So, does this paint a clearer picture now?
 
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Old 09-10-09, 07:34 PM
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So, does this paint a clearer picture now?
Si Senor, much clearer now! Actually, that's kinda what I thought, but had to be sure before making diagnosis.

OK, let's back up to the test that rbeck had you do early on with the jumper.

What you can do now is that same test, but on zone 4.

Remove the RED wires from the TT terminals and install the jumper on those. When you power back up, the boiler should fire up and the pump should run. BUT! the valve won't be open, so don't run it for more than a few seconds like this, because it's not good for the pump to try pumping into a closed valve.

What you are doing here is isolating the problem to either the Taco panel, the zone valve, or the aquastat.

If jumpering zone 4 on the Taco runs the boiler, then you can eliminate the Taco as the problem.

My gut feel is telling me that the ENDSWITCH (which is connected to the red wires) in the zone valve is 'flaky'. It probably isn't making contact when the valve opens.

Do you have a multimeter? and know how to read OHMS ?
 
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Old 09-10-09, 07:46 PM
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testing on Z4 using the jumper, the boiler starts. that being said, the valve seems to be opening from what i can tell because there is hot water on either side of the valve and the water tank is heating.. can that be?

i do have a multimeter, and yes I know how to use it. kind of. what do you suggest?
 
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Old 09-11-09, 02:51 PM
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OK, this sounds more and more like the endswitch in the zone valve is flaky...

If you set your multimeter to OHMS scale, (is it a digital? or analog display?) and touch the two leads together, you should read a very low value... this is to verify the meter is functioning properly...

now, when you are sure that the valve is OPEN, the endswitch should be CLOSED. That's the two red wires... with those red wires still disconnected, and the valve OPEN, connecting the test leads to the red wires, you should read very close to zero on the meter...
 
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Old 09-11-09, 04:12 PM
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NJ - thanks for the advice. Will try that tonight when I get home from work.
 
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Old 09-11-09, 06:21 PM
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ok.. checked the wires when the valve was open.. no change on the meter..

tested it with a straight wire, it reads 0.6 or so.

so looks like your diagnosis is right?

if that is the case, can the endswitch be replaced or does the whole unit need to be replaced?
 
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Old 09-12-09, 08:58 AM
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To start, ALL zone valves eventually have problems with the endswitches, so this thread from another forum probably shouldn't be taken to mean that only this brand/model suffers:

WIRSBO UPONOR Motorized Valve Actuator MVA A3020522 Failures - Topic Powered by Eve Community

And it talks about 'other' design issues affecting the switch failures also... since you aren't using their control panel, that issue which seems to drive that discussion doesn't apply here...

Read down in the thread and there are a few sources mentioned for a replacement switch. Once you get a part number, also look at places such as ' Digi-Key ' and ' Mouser ' as possible sources for the part. If you've got an electronic part store in your neighborhood, you may even find one locally that will work.

The switch may be held in by a rivet... so it may have to be drilled out and a screw used to reattach (discussed in that thread).

All this said, it may be easiest to just replace the power head for about $60 or so.

BTW, there are also mentions of the plastic parts inside becoming brittle and breaking, and if that's the case, of course replacing the switch is useless...
 
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Old 09-21-09, 10:02 PM
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Just an update for you all.. got a new MVA and sure enough the system is back to normal. NJ was correct in his bad end-switch diagnostic.

NJ - thank you so much for your guidance and help. Very much appreciated. Let me send you some wine or something!
 
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Old 09-22-09, 04:03 PM
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Thanks for the update, and you're welcome!

While I would love to take you up on the offer of gratuity, I would much rather you 'pay it forward'... (watch the movie of the same name if you don't know what that means!)
 
 

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