Another Boiler Running When Not Calling For Heat


  #41  
Old 12-24-13, 08:21 AM
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is it possible that one of the controls (Fenwal?) is trying to maintain the high water temperature once a given temperature threshold is reached?
I don't think so. Here's why:

Refer to the most recent diagram with all the notations on it.

Follow the 120VAC HOT in from the top left. You see that it should go only to the transformer and the left side CR2 RELAY contacts. Follow the wires down from the RIGHT side of CR2. You see that wire goes 2 places, to the HIGH LIMIT control and to L1 on the Fenwal. When there is no call for heat, there should be NO POWER on these wires because CR2 is supposed to be OPEN.

This means that with no call for heat, there should be NO POWER to the Fenwal, thus it CAN NOT OPERATE!

If there is power at that point, it means one of two things:

1. RELAY CR2 contacts are 'stuck' closed.
2. Some hack miswired the unit when they replaced the Fenwal and ran a CONSTANT supply of 120VAC to the L1 and L2 terminals.

Let's go a little further and try to understand the function of RELAY CR1 and the PRESSURE SWITCH. This is going to get a little tricky to explain the sequence of events, but bear with me while I try.

First thing to note is that the transformer terminals R and C are a CONSTANT source of 24VAC when the boiler is turned on.

Note also that the C terminal is connected to one side of the CR RELAY COIL, AND to the GND terminal of the Fenwal.

When the Fenwal is powered by 120VAC at L1 and L2 it won't do ANYTHING until there is a 24VAC signal present at the TH terminal, with the GND being the 'return' for this signal.

So there are TWO conditions that must be met for the Fenwal to even TRY and open the gas valve and light the boiler. That being 120VAC at L1/L2 AND a 24VAC signal between TH and GND.

When these are both present, the gas valve will be opened, and the 'HOT SURFACE IGNITOR' will be powered. When the flame is 'proved' to be present (this system uses the HSI as a flame sensor) the Fenwal will allow the gas valve to open fully and the burners will light. If the Fenwal does NOT prove the flame, it will stop and might 'lock out'... or it might 'retry' some seconds later. (I didn't read that far into the manual for the Fenwal, but this part is really informational only for understanding the control)

Now let's go back to the 24VAC signal to the TH terminal, how does that get to the control? This gets a little tricky, but here goes:

When NO CALL FOR HEAT, CR RELAY is NOT ENERGIZED, and both CR1 and CR2 are OPEN.

Since the BLOWER is NOT running at this time, the PRESSURE SWITCH (PS) is in the position shown in the diagram with the internal switch connecting the PS terminals C (common) and NC (normally closed). This places 24VAC on the Y terminal through the PS contacts and allows the CR RELAY to be pulled in when there is a heat call.

When there IS a call for heat from one or both of the 832 relays, the X X terminals which are wired to the Y and G terminals CLOSE and complete the circuit to the CR RELAY COIL.

This pulls the relay in and CLOSES CR1 and CR2.

Now a couple things happen somewhat simultaneously:

When CR1 CLOSES, the Y terminal is connected to the R terminal through the CR1 contacts, which puts a SECOND path to 24VAC there at the Y terminal.

This is important to note, because soon the BLOWER will be up to speed and the PS switch will move from the NC position to the NO (normally open) position which will connect the TH terminal in the Fenwal to 24VAC.

(The switch in the pressure sensor is a 'Single Pole Double Throw' type. What this means is that the "C" terminal is an 'arm' that will contact either the NC or the NO terminals. Never both at the same time. The 'normal' position is always defined as the 'resting' or 'de-energized' or 'off' position for ALL switches)

Follow the path from TH terminal on the Fenwal back backward... through the ROLLOUT switch, from the NO CONTACT of the PS to the C contact of the PS, back to the Y terminal, through the closed contact of CR1 back to the R terminal. This is the path that the 24VAC TH signal to the Fenwal must follow.

When CR2 CLOSES (at the same time as the CR1 contacts), the BLOWER will start, provided that the HIGH LIMIT switch is NOT satisfied. When the blower comes up to speed, the PS switch changes from NC to NO.

When the boiler water is at HIGH LIMIT, the HIGH LIMIT OPENS and removes power from the BLOWER which will cause the PS to change state from the NO contact back to the NC contact, and the Fenwal will lose the signal at the TH terminal and the burners will be shut down.

If the BLOWER never comes up to speed (through a bad motor for example) or there is a failure of the PS, the signal will never get to the TH and light the burner. This is the SAFETY part! The burner will NOT light if there is a fault with the BLOWER or the PS.

When the HEAT CALL ENDS, the X X contacts on the 832 OPEN, the CR RELAY is DE-energized, CR1 and CR2 BOTH OPEN, there is NO POWER to either the BLOWER motor through the HIGH LIMIT SWITCH, OR to the FENWAL terminal L1.

The BLOWER spins down, the PS changes from NO to NC and the 24VAC signal is REMOVED from the TH terminal on the Fenwal.

The system is at 'rest', waiting for the next heat call.

I'm telling you all this complicated crap because if you can understand the sequence of events that SHOULD be occurring, it will be much easier for you to understand why I am asking for the readings that I'm asking for... which I will now continue in following posts...
 

Last edited by NJT; 12-24-13 at 08:54 AM.
  #42  
Old 12-24-13, 08:35 AM
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If you've managed to wade through all of that, good for you! Even GOODER for you if you understood it! If not, don't worry too much about it... you can still troubleshoot this by following the steps.

So let's start from the beginning and take some more measurements. These are key pieces of data I need to solve this issue.

First, remember that there is 120VAC line voltage present, and you must be VERY CAREFUL that you don't short anything out or fry your butt... YOU CAN BE KILLED!

Remove cover from HIGH LIMIT control.

With boiler ON and NO HEAT CALL and NOT RUNNING ON IT'S GHOSTLY OWN...

Measure from 120VAC NEUTRAL or any unpainted boiler metal part (which is GROUND) and EACH of the two terminals on the HIGH LIMIT switch.

You should NOT have 120VAC on EITHER of them at this point, but I suspect that you WILL have 120VAC on ONE of them.

If you wait until the boiler is doing a 'GHOST' run and still with NO HEAT CALL, I believe that you will see 120VAC on BOTH of the HIGH LIMIT terminals.

Please report your findings.
 
  #43  
Old 12-24-13, 08:41 AM
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Can you get me a close up of the FENWAL control so that I can read the labels and see the terminals please?
 
  #44  
Old 12-24-13, 09:10 AM
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Preliminary results:
When not calling for heat and system has stopped since high water temp has been reached: 1 terminal on the high limit switch measured 120 volts, the other terminal measured 0.
Waiting for the system to cool down to the point where the ghost takes over and kicks on the system to reheat the water (takes about 20 minutes). Will test both terminals again at that time.
 
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Old 12-24-13, 09:19 AM
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As you suspected, when running in ghost mode, both terminals have power: 118 volts.
 
  #46  
Old 12-24-13, 09:19 AM
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1 terminal on the high limit switch measured 120 volts,
I was afraid of that...

Of course, turn power off first! Good thing to do while waiting for boiler to cool.

To verify that it is a wiring error and not a 'stuck' relay contact, flip the wire bail that holds the relay in place and unplug the relay. Turn power back on and test again.

While the relay is unplugged, if contacts are visible, inspect for burnt and pitted contacts and replace if it looks really bad. Because again, this whole problem could well be a STUCK RELAY!

Thanks, great pic of control!

After this testing, we are going to do similar with the signal at the TH terminal.
 
  #47  
Old 12-24-13, 09:26 AM
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Hmmmmmmmmmmmmmmm....

On the Fenwal, there is a yellow wire on the ground terminal.

Where does that yellow wire go?
 
  #48  
Old 12-24-13, 09:41 AM
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Pulled the relay. It looks clean. With the relay pulled, there is no power reading on either terminal of the high limit switch.

It looks like the yellow wire coming out of the Fenwal is leading to the C terminal on the transformer.
 
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Old 12-24-13, 10:42 AM
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It looks clean
Can you see the contacts on that relay?

If there is no reading with the relay pulled... then I have to conclude that the contacts are stuck...

Get another relay and try it before we pull more hair out of the beard...
 
  #50  
Old 12-24-13, 10:44 AM
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Let me ask another question though...

Have you noticed if that relay 'clicks' when there is a heat call?
 
  #51  
Old 12-24-13, 10:46 AM
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It looks like the yellow wire coming out of the Fenwal is leading to the C terminal on the transformer.
"Looks like" ? or IS ?

I don't see any yellow wires on the C terminal in this photo:



Don't know why it's yellow and not green... but OK, if it's going there then it's a ground wire.

Where is the wire on the TH terminal of the Fenwal coming from? Should be from the 'rollout switch', down near the burners.

Here's another puzzle about that... the TH terminal of the Fenwal has a RED wire, but in the same pic above the rollout switch is visible and clearly there are TWO YELLOW wires on it. How does the TH RED wire turn YELLOW? Or is that RED wire going somewhere else? and where?

If the RED wire is not going to the rollout switch, where is the other yellow wire, not the one from the pressure switch going?

The other side of that rollout switch (yellow wire?) should be going up to the pressure switch. Is it?
 
  #52  
Old 12-24-13, 10:56 AM
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The ground wire is orange not yellow....
 
  #53  
Old 12-24-13, 11:05 AM
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The ground wire is orange not yellow....
You say POTATO

I say SPUD

..............

Yer not just trying to be 'difficult' are you?
 
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Old 12-24-13, 11:40 AM
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Have you noticed if that relay 'clicks' when there is a heat call?
Something in there makes a distinctive click when there is a call for heat. Could be the relay, but I'm not sure. Will investigate further.

"Looks like" ? or IS ?
All of the wires coming out of the Fenwal are going through a connector (see pic). There's a label on the male (Fenwal) side of the connector with the following key: Grnd = Yellow, TH = Red, MV1 = Brn, L2 = White, S2 = Blue, S1 = Grey, L1 = Black. The pins of the male side are also labeled with Grnd, TH, MV1, L2, S2, S1, L1. If I follow these positions on the female side I get a green wire coming off where the ground is supposed to be. This is what's going to the "C" terminal on the transformer. The red wire coming off of the Fenwal matches up with a yellow wire on the female end. That's what's going to the rollout switch.

The other side of that rollout switch (yellow wire?) should be going up to the pressure switch. Is it?
Yes.

If there is no reading with the relay pulled... then I have to conclude that the contacts are stuck...

Get another relay and try it before we pull more hair out of the beard...
Suggestion as to where to go buy another relay.
 
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Old 12-24-13, 11:46 AM
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Suggestion as to where to go buy another relay.
Call Ferguson.... Give them the part # off the one you have... They should have in stock...

They sell to the public...Find one with plumbing sales near you......

Locations Finder
 
  #56  
Old 12-24-13, 11:50 AM
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Edit. Oh wait thats not it..... Trooper had the links....

This one.


510-350-223 - Weil Mclain 510-350-223 - Plug In Relay w/ 24V Holding Coil


[ATTACH=CONFIG]23493[/ATTACH]
 
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Last edited by lawrosa; 12-24-13 at 11:56 AM. Reason: Added Correct info..................
  #57  
Old 12-24-13, 11:55 AM
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This the part if you want to change the whole thing,
Should I change the whole thing? Not just the relay coil that connects to it?"
 
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Old 12-24-13, 11:57 AM
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I edit post #56... That should be the part and part #...
 
  #59  
Old 12-24-13, 12:08 PM
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Suggestion as to where to go buy another relay.
See post #24 ...................... basically anything that crosses to a Honeywell R8222U1079 or to the W-M number and part that Mike posted will work.

Should I change the whole thing?
I don't see the point in that.
 
  #60  
Old 12-24-13, 12:17 PM
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All of the wires coming out of the Fenwal are going through a connector (see pic).
Sure wish I had known that was there from the beginning... That's a Fenwal factory part made specifically for replacing the -21 with the -32 ... would sure have eliminated a lot of speculation!
 
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Old 12-24-13, 12:50 PM
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Sure wish I had known that was there from the beginning.
Sorry. I don't know what I don't know.

It's gonna be a few days before I'll be able to get a new relay. Will get back to you once I have one in hand.

Once again, thanks for your help.
Have a Merry Christmas, a Happy Holiday, or whatever it is you may celebrate!

David
 
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Old 12-24-13, 12:55 PM
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Sorry. I don't know what I don't know.
No problem really... I just need to remember that myself... it's my fault that I didn't press for pictures of every single wire inside the boiler!

Have a Merry Christmas to you and yours also!
 
  #63  
Old 12-30-13, 03:02 PM
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Final Update:

Installed a new relay and voilà, boiler problems solved!
Thanks to everyone for your help!
 
  #64  
Old 12-30-13, 03:15 PM
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Très bon!

It's too bad that for something as simple as that we had to run 60 posts! But that's how it goes when troubleshooting electrical stuff on the net... one false move and POW! something gets blown up.

But I'm glad it was that simple... and now you've got a marked up diagram that you can print out and keep with your boiler for future use.

Download full size here:

http://i224.photobucket.com/albums/d...ps43e85bc1.jpg
 
 

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