Circulator pump control question

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Old 03-10-15, 07:54 AM
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Circulator pump control question

With the spring weather approaching, my boiler has begun to act up again in terms of very loud banging noises. After some investigation I have discovered this is only happening when the boiler is cold (i.e. has been off for several hours). When the thermostat first calls for heat, the boiler comes on but the pump does not. It is during this period that the banging is occurring, once the pump activates all is well again.

Just as a quick side note, at the beginning of winter I re-plumbed the system when I moved into the house. The system has a compression style tank, and someone had put a bunch of automatic bleeders in the piping. I removed these and installed a new water separator at the outlet of the boiler and plumbed it directly to the expansion tank above. This solved all of the continuous noises I was having during regular operation. In fact, the system has worked flawlessly and quietly until now.

Digging into the wiring a little, the heart of the control is a White-Rodgers relay that I cannot seem to find a part number on. The boiler is activated by this control box and the pump is run off an aquastat mounted on the outlet of the boiler. I'm thinking if I wire the pump so it runs directly off the thermostat, then I won't have this latency period between the boiler coming on and the pump beginning to circulate. Is this a bad idea for any reason?

In reference to the wiring diagram for the White-Rodgers unit (see picture in link below), it appears I can connect the pump across terminals 3 & 4 to be activated by the thermostat. Is it okay to do this? Currently, 'L' terminal is jumpered to 3, to which all hots except the pump are connected. The neutrals connect to the other (lower) 'L' terminal and 4 is not connected to anything. The boiler runs off terminals 1 & 2.

Obviously, if I wire the pump this way, it will turn off when the thermostat stops calling for heat. It would be nice to have the pump continue to circulate until the temperature in the pipes begins to decrease below a certain value. I know this is do-able with a temperature limit switch, but I'm not familiar with the terminology to find the hardware I need. Would this be the recommended way of doing things? If so, can someone recommend an inexpensive hardware solution.

BTW, the system uses a single pump and has 4 zone valves. There is an extra zone with no valve that I have yet to figure out where it actually runs.

Pictures here:

Hyrdonic Wiring Photos by ice4me | Photobucket
 
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  #2  
Old 03-10-15, 08:54 AM
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removed these and installed a new water separator at the outlet of the boiler and plumbed it directly to the expansion tank above
You surely meant AIR separator, yes?

Which model did you use? Was it one that allowed you to run the pipe to the tank from the TOP of the air separator? If it's working, I presume it is piped that way.

I don't think the question should be one of how to rewire, but rather one of why is the boiler 'kettling'... you have a symptom and are suggesting a cure that is a 'band-aid' to the real problem.

Let's start by getting more information on the system itself such as the boiler make/model and any other information regarding the boiler controls.
 
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Old 03-10-15, 02:49 PM
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Yes, sorry about that, I meant air separator. It is a B&G IAS-1-1/2, with a 3/4" top outlet plumbed vertical all the way to an Airtrol tank fitting. The feed water line is also tee'd into this vertical run of pipe.

The boiler is a Raytherm Model 168-T. Circa 1978. Both the relay and aquastat are White & Rodgers but I have no further info on them, other than what you see in the pictures. The zone valves are also W&R.

One thing I was curious about, there are a lot of one-way valves in the system. See here:

http://i42.photobucket.com/albums/e3...psidyx8pse.jpg

The picture is old, so it does not show the new air separator, but the check valves remain the same. Are they really necessary? Could they be causing localized boiling by preventing natural convective circulation? (assuming the water naturally wants to flow backwards when the pump is off)

Let me know if there is any other information that I can provide.
 
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Old 03-10-15, 03:13 PM
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Great... the IAS is the right thing to use for this, but I'm sure you know that already!

It is my understanding (but I can't be certain because the manual for your boiler is not on-line at the Raytherm website) that all of their boilers are copper heat exchangers. As such they have a MINIMUM FLOW requirement that must be met at all times.

What this means is that I am questioning why the pump would be connected to an aquastat that holds off it's turning on for some period of time... (this aquastat is generally called a 'reverse aquastat')

I'm going to study the pics a bit more, and your first post to try and determine:

"What were they thinking?"

Standby...
 
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Old 03-10-15, 03:14 PM
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Do you have the manual for the boiler by chance?
 
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Old 03-10-15, 03:25 PM
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Unfortunately, I do not think there is a manual for the boiler. I will double check when I get home tonight. I do have the cover off, since I was checking the wiring last night - Is a picture worth anything?
 
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Old 03-10-15, 03:56 PM
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The endswitches of all the zone valves are operating the W-R relay on the wall.

Terminals 1 and 2 of that relay are calling the boiler to heat.

That part is easy...



There appear to be FIVE armored cables entering that relay box.

One must be power from the electric panel.

One is going to the pump.

One is coming from the a'stat on the supply pipe.

One must be going to the boiler to power the 24VAC transformer inside it to operate the gas valve.

That leaves one unaccounted for, where does that go to / come from?

It appears they've simply used that relay box as a 'junction box'.

Next, the a'stat on the supply pipe has a cable coming from a box to the right. There are two more cables heading out of view to the right. Where do they go to / come from?

There is another box above that one that appears to have nothing in/out. What is that box?

What is the black object between those two boxes? Is that the 24VAC transformer for the zone valve power?
 
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Old 03-10-15, 04:04 PM
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I do have the cover off, since I was checking the wiring last night - Is a picture worth anything?
Yes, a thousand words! (and probably at least 10 questions! )

If there is a wiring diagram of the boiler on the inside cover, take a clear pic of that also.

The boiler should have a 'high limit' water temp control inside it. Probably set to 180F ?

Continuing with the wiring above...

I believe that the cable coming into the a'stat on the supply pipe from the box on the right is going to turn out to be 120VAC feed.

I think that the pump hot wire USED TO BE connected to terminal 4 of the W-R relay box, but that wire was removed at the time that the a'stat was installed for some unknown reason, and wire nutted to the hot wire from the a'stat. Is that what the YELLOW wire nut is?
 
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Old 03-10-15, 04:21 PM
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One more thing to take a pic of...

Slide the cover off the a'stat on the pipe and let me see the guts.
 
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Old 03-10-15, 07:22 PM
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I,
That aquastat on the pipe might be used to turn on the pump for some strange reason.
Just a thought. Turn down that dial as low as it goes and I bet your pump will come on almost immediately.
If that turns out to be the case you can leave it that way or remove the wires from that control and just wire nut them together so the pump will come on the same time as the boiler which is what it should be doing anyway.
 
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Old 03-11-15, 07:47 AM
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Okay, I have uploaded a slew of pictures in the hope that there will be some clarity as to what is happening here. I also omitted some information before, thinking it wasn't important, but I realize now that may or may not be the case.

It appears there is a heating loop that runs into the back of the fireplace. I believe the previous owner was using heat from the fire to supplement the hydronic system. The pump is now gone (only flanges left) and the valves to the circuit are closed. Devices labelled A,B, and C in the picture album appear to be for control of this circuit, which had its own aquastat (Honeywell) mounted on the wall and the probe hanging below it. The junction box 'A' gets power from the current A'stat.

Updated album: Hyrdonic Wiring Photos by ice4me | Photobucket


Is that what the YELLOW wire nut is?
Correct. The yellow wire nut is for the aquastat.

There are two more cables heading out of view to the right. Where do they go to / come from?
I'm guessing you meant to the left... one goes to the main 120VAC power, which is switched near the doorway to the boiler room. The other goes to a 24V transformer that appears to be powering the zone valves. I didn't have much time to trace the wires this morning, but I can find out definitively tonight.

There is another box above that one that appears to have nothing in/out. What is that box?
See my photo album - I have labelled it C. Looks like some kind of contactor but I really have no clue. It is recessed into the wall, which is kind of strange.

What is the black object between those two boxes? Is that the 24VAC transformer for the zone valve power?
Correct. This is powering the zone valve for the fireplace, which is no longer used.
 
  #12  
Old 03-11-15, 09:38 AM
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ICENG,
When the thermostat first calls for heat, the boiler comes on but the pump does not.
From Raypak I&OM

CAUTION: This heater requires forced water
circulation when the burner is operating. See
minimum and maximum flow rates. Severe damage
will occur if the heater is operated without proper
water flow circulation.

Your Raytherm has A Finned Copper Tube Heat Exchanger. It must never ever be fired without water flowing in the heat exchanger.
 
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Old 03-11-15, 09:54 AM
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HeatWorm:

Thanks for your input. Can I ask where you found a copy of the owner's manual? I'd love to have a copy in hand for reference.

I suppose the question now is, what is the best way to control the pump? Simple on/off using thermostat call and existing W/R relay? Or is there a better method, something along the lines of 'on with thermostat call, off with thermostat+aquastat'?

I'm looking forward to cleaning up the rats nest of wiring and eliminating all the 'extra' bits.
 
  #14  
Old 03-11-15, 10:31 AM
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The standard way is to have a relay on the boiler that starts the pump when there is a call for heat.
I do not have a manual for that boiler but it is obvious that it has NO controls other than high-limit.
The pump should always run on a call for heat, burner on or off.

Form the Raypak RaythermTM Manuals Raypak Pool & Spa, Residential and Commercial Hydronic Products

CAUTION: . . . The pump must be
interlocked with the heater to prevent heater
operation without water circulation.
A Flow switch as a safety device installed at the heat exchanger
outlet to prevent the burner from firing without adequate flow
is a good choice.
 

Last edited by HeatWorm; 03-11-15 at 10:57 AM.
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Old 03-11-15, 12:59 PM
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Provided that the W-R relay on the wall is functional on the second pole (terminals 3 and 4) you should just be able to connect the hot lead from the pump to terminal 4 and the pump will run whenever there's a heat call.

Delaying the turn off of the pump is another matter though, not as easy to accomplish because you have zone valves.

Once the heat call ends, the zone valve will close and if you set up for a delayed turn off, you will be pumping into a dead head...
 
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Old 03-13-15, 04:00 PM
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ICENG,
Can you transcribe the model and Max,Min firing rate from the boiler, I can't make it out.
A Picture of the gas train to the right of the gas valve would help.

You have a balancing (butterfly) valve next each zone valve.

I will need more time to look at the piping, yikes . . .
 
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Old 03-13-15, 04:21 PM
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yikes . . .
Oh come on now, it's not that bad. You know you've seen WAY worse!

Why are you worrying about the piping anyway? The question was about the circulator operation and that's been covered... hasn't it?
 
  #18  
Old 03-13-15, 07:29 PM
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I looked behind the curtain . . .

Boiler
Model 168-T. Circa 1978
missed that.
 
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