Thermocouple Replacement-50+ Yr Old Boiler - HVAC - Page 2 - DIY Chatroom Home Improvement Forum


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Old 12-30-2008, 04:26 PM   #16
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thermocouple replacement-50+ yr old boiler


Well they didnt really make a smaller boiler, and i'll be expanding the house to roughly 1500sq ft in the next year or so... Which is why i priced that boiler. What is a tempering loop, and is there a way to test physical GPM?

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Old 12-30-2008, 04:32 PM   #17
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thermocouple replacement-50+ yr old boiler


Also, my aquastat has a lo diff & hi diff... I set both to 15. Is that where they should both me set to?
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Old 12-30-2008, 04:39 PM   #18
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thermocouple replacement-50+ yr old boiler


High 10.
Low 15 or 20, once the mixing valve is installed.

(BTU divide by temp rise divided by 500 = GPM).

Measure the return temp and teh supply temp, then use above formula.

Other manufacturers, have smaller boilers.

A tempering loop/system bypass.
Would be another pipe connected from the supply to the return.
To allow the 10 plus GPM the boiler needs, and keep the baseboard throllyed to its 4 GPM.
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Old 12-30-2008, 04:41 PM   #19
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Is there a controller needed for a bypass? Or can i just put a Tee on the supply & return (Similar to an H pipe equalizing exhausts on a v8?)? How do I measure the temps? Can I just use a laser temp gun on the copper pipes?
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Old 12-30-2008, 04:45 PM   #20
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thermocouple replacement-50+ yr old boiler


Laser guns aren't accurate enough on shinny pipes.

The loopp has to be piped not to interfer with the flow check.
And needs a balancing balve of some sort to control flow.

And it needs to be piped to bypass the system, not the boiler.
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Old 12-30-2008, 04:51 PM   #21
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thermocouple replacement-50+ yr old boiler


So how does one check the temp of a sealed system? Here is a picture of my boiler. The pipe going vertically to the expansion tank is before the flow control (Flow Control is horizontal just before the Expansion tank), is straight out of the boiler. Can I tee into that line, then tee into the line coming directly out of the Circulator pump before it turns into Pex? I can put another flow control in line, but I dont understand how i'm suppposed to know how far open/closed it needs to be.
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Old 12-30-2008, 05:02 PM   #22
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thermocouple replacement-50+ yr old boiler


First, it looks like you have the water flow reversed through the boiler.
Double check which way the arrow is pointing on the circ.

The loop would be tapped in on the discharge side of the circ, when the cisr is in teh supply line(top of boiler is supply side).
Then it would tap into the return pipe.
A butterfly, or ball valve can be used for a balancing valce in the tempering loop.

I find Type K thermister probes work the best for check temp on pipes.

Also, you need to pipe in thermal traps on the domestic water, or the mixing valve won't last long.

Just run the pipes 6" down, and then back up.


Also, shorten the vertical flue pipe, its too long. Flus pipe shouldn't have to run or curve down hill to enter chimney. Doesn't matter how short of a run it is.
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Old 12-30-2008, 05:17 PM   #23
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thermocouple replacement-50+ yr old boiler


The arrow on the circ is pointing down.... That kinda confused me a bit because the old circ was pumping up. I made sure all arrows point in the same direction for the expansion tank, flow control, & circ pump. So where should i add the loop in? Raise the Circ pump and put a Tee under that, then run it to the line on the other side? I'll borrow my Temp Datalogger from the office next week and check the pipe temps... I am a little confused by what you mean by thermal traps. Do you mean re-run my lines so that the cold (in) and hot (out) go down 6" then back up? And I will shorten the flu pipe. That makes sense, didnt think the 1/8-1/4" slight angle it has would be an issue, but i'll cut an inch off the top to make the angle better.
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Old 12-30-2008, 05:26 PM   #24
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The arrow belongs pointing up.

That boiler is not designed for reverse water flow.

Correct it, and all the other direction devices that are flow direction sensitive.
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Old 12-30-2008, 05:31 PM   #25
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well then... this is gonna be fun.... Since i'm going to have it all apart anyways, should i put a loop in there like you recommend? The circulator pump came installed on the boiler when it was delivered.... grreeaatttt.... I'm not about to tackle it tonight... looks like Friday is gonna be the earliest I can get to it... Its not going to hurt it to run a few days like this, right? Just not as efficient?
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Old 12-30-2008, 05:34 PM   #26
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thermocouple replacement-50+ yr old boiler


did you change the thermal couple it clips in on the pilot mounting and screws into the top of the gas valve
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Old 12-30-2008, 05:35 PM   #27
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Yes, install the loop while you are correcting the piping.

Might want to set your limit temps lower.

It shouldn't hurt the boiler for a fews days.
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Old 12-30-2008, 07:05 PM   #28
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Regarding our original poster it probably is a powerpile/pilot generator/thermopile that needs replacing. Most old conversion burners were millivolt systems. That is why the whole burner needs removing. A pic of it would be the answer.

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