Boiler - cold temps = brief banging?

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Old 02-19-11, 08:45 AM
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Boiler - cold temps = brief banging?

We have a Teledyne Laars Mini-Therm Hydronic Boiler, Model JV, gas fired. Periodically, when we have cold nights, we'll hear a brief clanging in the basement (enough to wake me up). The boiler then fires up, and the noise stops. Any idea what this might be? It only happens at night during cold temps. I turned the thermostat up slightly, thinking this might help, but it doesn't seem to have done so. We run it fairly cool - about 60F.

We had some louder banging earlier this year, and the boiler would shut down. This was diagnosed as a pump failure, which was replaced - problem solved. I checked the expansion tank, and as far as I can tell it seems OK (warm on the bottom, cool on top; hollow sounding in the top half). The valve on the top of the tank is also open.
 
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Old 02-19-11, 08:51 AM
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To check the expansion tank you need to take the pressure off the boiler and test the tank with a pressure gauge. You may possibly have an air issue also.

What is the pressure and temp on the boiler gauge say? Could you take pics? Possibly the air vents are not working. What type of heat emmiters? How many zones?

http://www.gogeisel.com/geiselonline...I_Model_JV.pdf

Mike NJ
 
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Old 02-19-11, 09:55 AM
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To check the expansion tank you need to take the pressure off the boiler and test the tank with a pressure gauge.
Probably a good idea to verify which of the two types of expansion tank are installed first!

One is a large steel tank strapped into the floor joists above the boiler, the other looks like a gas tank for a bar-b grill. Which do you have?

Teledyne Laars Mini-Therm
This type of boiler is very sensitive to having correct flow through the boiler. Sadly far too many of them are improperly installed. Do you know if this is piped up with a proper SYSTEM BYPASS pipe? If not properly piped, these boilers can and will make all manner of disturbing sounds, and eventually the boiler can/will be damaged.

See also pages 8,9,10 in the PDF file that Mike posted a link to.

We can tell by looking... can you take pictures? If so, set up a FREE account at Image hosting, free photo sharing & video sharing at Photobucket and upload the pics there. Come back here and post a link to your PUBLIC album. Be sure to take clear, well lighted, and large enough for old dudes to see... take a number from a few angles and far enough away that we can see the whole system, in addition to closer detail shots.
 
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Old 02-19-11, 05:34 PM
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Thanks for your reply. Do you mean the pressure and temp when it's banging? I haven't checked that yet (middle of night - less appealing!!). It's not running at present - pressure is 15 psi. Two zones. Sorry - what do you mean by heat emitters? It's a gas flame. Pics at Pictures by blomley - Photobucket (sorry - cramped space: hard to get a wide shot)
 
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Old 02-19-11, 05:38 PM
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Photos at Pictures by blomley - Photobucket
I think the expansion tank is the 'gas tank' version.
Sorry - I don't know if it has a system bypass. We've had lots of problems with the system, and have had many components replaced, including the pump as earlier mentioned. As far as I know (which ain't much) we've got good service people.
 
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Old 02-19-11, 06:30 PM
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In pic 6 is the vent cap loose?? Looks like it was leaking at on time.

heat emitters means cast iron radiators, copper aluminum finned basboard...ect.

Mike NJ
 
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Old 02-19-11, 06:59 PM
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There's some rust spots on top of the expansion tank, but it seems snug on the pipe, with no evidence of new leaks.
The heat emitters are baseboards, with metal fins.
 
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Old 02-19-11, 07:58 PM
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I don't see anything in the pics that I can positively identify as a system bypass... but I can't 'follow' all the pipes.

Take a look at the diagrams in the manual. Note where they show a pipe running from the inlet to the outlet... compare to your boiler. Follow the inlet and outlet pipes and see if you can locate a pipe with a valve that appears to connect the inlet to the outlet, AFTER the circulator pump.

Chances are pretty good that the absence of that bypass is at least part of your trouble... if it is absent after all...

What puzzles me is that the installers went to the trouble of installing temp gauges on both in and out... and that would seem to imply that they were at least aware of the requirement for not more than 30 difference between the two... so why no bypass? hmmmmmm.
 
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Old 02-19-11, 08:44 PM
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In pic 6 the air vent should probably be changed, And as Trooper said what is the inlet and outlet temps read??? Post them. It may make a difference if we get these #'s Like 180 out and 160 in???? When running and when first start.

Mike NJ
 
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Old 02-19-11, 09:16 PM
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I'll check. What is the function of a system bypass?
 
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Old 02-19-11, 09:47 PM
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What is the function of a system bypass?
In the case of your boiler, it is to protect the boiler by assuring proper flow through the boiler at all times. Read the section in the manual about it... may help to understand a bit better.

Your type of boiler is of a type that is called 'copper tube heat exchanger' and they are very sensitive to having proper flow.
 
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Old 02-20-11, 04:34 AM
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The saving grace here may be the B&G 100. Even though he does not state which one he has the head losses are not terrible. The head loss is not terrible on the boiler and the B&G moves a ton of water. At 7 ft of head it can move almost 20 gpm. Way more than this system requires. We do not know the ft head requirement for the whole system but most residential systems not utilizing mod/cons will work on less than 7 ft head. I think if they would have went to a wet rotor pump when it was replaced the problems and noises would be a lot greater.
 
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Old 02-20-11, 07:47 AM
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True... I do wonder what the diff is on those temp gauges when it's starting up cold and running after a while...
 
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Old 02-20-11, 10:25 AM
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By 'starting up cold' do you mean that the boiler has been deactivated for a time? I checked the temps this morning after the furnace had warmed up, but was not running (1), and then called for heat and checked again after it had run for about 5 mins (2). The temps are Celsius

1) Inlet: 50 (122 F)
Outlet: 60 (140F)

2) Inlet: 62 (144F)
Outlet: 79 (174 F)

I looked for a system bypass, connecting inlet and outlet after pump, but could not find one.
 
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Old 02-20-11, 10:50 AM
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'starting up cold' do you mean that the boiler has been deactivated for a time?
Yes, if that is what would be typical of the conditions in the middle of the night when you hear the noise.

I do wonder though if the boiler actually is making the noise all the time, but you only hear it at night when the house is ultra quiet?

2) Inlet: 62 (144F)
Outlet: 79 (174 F)
Presuming accurate temp gauges, the 30F qouted here is pretty marginal. Manufacturer wants <30 ... 20 is probably preferred. It indicates marginal flow through the boiler. The heat isn't getting out to the system as fast as it's being put into the water.
 
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Old 02-20-11, 11:33 AM
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Let me check the temperature differential again when the boiler is closer to night time conditions. The manual indicates I should measure this with the longest (highest head) zone calling for heat alone.

As far as I can tell, the banging only occurs at night - prime time is 4 - 5 a.m. when the house is presumably at its coldest. No noise last night, though (and it was cold outside).

Should I talk to my technician about the bypass? The pump is new.
 
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Old 02-20-11, 01:42 PM
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For a system bypass the pipe would have to be to the left (before) the pump in picture #4. It is not there.
 
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Old 02-20-11, 03:53 PM
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Should I talk to my technician about the bypass?
He'll look at you like you've got two heads, I guarantee. Won't have a clue what you are talking about... but I hope I'm wrong about that.
 
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Old 02-20-11, 04:44 PM
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Originally Posted by NJ Trooper View Post
He'll look at you like you've got two heads, I guarantee. Won't have a clue what you are talking about... but I hope I'm wrong about that.
I'm used to that! Thanks for all your help - it's greatly appreciated. I learnt a lot.
 
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Old 02-20-11, 06:18 PM
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Yeah, me too!

I just want you to keep in mind that it's not absolute certainty that the flow issue is what's causing the noises, and I don't want ya cursin' me if I'm wrong... so take it for what it's worth!
 
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Old 02-20-11, 06:56 PM
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Noises aside, will a bypass increase efficiency?
 
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Old 02-20-11, 07:11 PM
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No... wouldn't have any affect on efficiency... sorry.
 
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