How accurate are stap on temp sensors

Reply

  #1  
Old 12-10-13, 12:35 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
How accurate are stap on temp sensors

My high limit aquastat is set on 163. My gauge reads around 165 at 24 lbs when limit is reached. Depending on heating conditions I have seen it overshoot.

Yet my intellicon sensor reads 182 and a strap on oven digital probe reads usually 8-12 degrees less on the return pipe at the boiler.

Do strap ons usually read higher????

Both sensors have insulation covering them.

Just trying to figure out witch one to believe in order to set my high limit. I kinda always felt it might be somewhere in the middle.
 
Sponsored Links
  #2  
Old 12-10-13, 01:42 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
I don't think you have to be all that precise - there are natural variations. But I would be concerned with 26 psi (if correct) at 165 deg. What is the pressure when the boiler is cooled down to room temp?
 
  #3  
Old 12-10-13, 01:54 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
Has domestic coil so never completely cold and pressure ranges from 18 to 24. Old type expansion tank I could let a little water out.

Thanks
 
  #4  
Old 12-10-13, 03:20 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
Has domestic coil so never completely cold and pressure ranges from 18 to 24. Old type expansion tank I could let a little water out.
No. With a conventional expansion tank that may have lost some of its air cushion, letting out a little water won't replenish the air. You're going to have to check the air in the tank, which may or may not require cooling down and depressurizing the system, depending upon your valving and piping - we need some good photos of the tank, boiler, and surrounding piping.

In addition, you should verify the boiler pressure gauge ...

http://www.doityourself.com/forum/bo...ure-gauge.html

... and maybe just replace it.

To cool down the system to room temp, you have to completely shut down the boiler and let it cool - domestic coil or not. Your situation doesn't sound urgent if you are in the middle of a cold snap.
 

Last edited by NJT; 12-10-13 at 04:00 PM.
  #5  
Old 12-10-13, 03:33 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,962
Received 37 Votes on 32 Posts
Old type expansion tank I could let a little water out.
No. With a conventional expansion tank that may have lost some of its air cushion, letting out a little water won't replenish the air. You're going to have to check the air in the tank, which may or may not require cooling down and depressurizing the system, depending upon your valving and piping
With old style in the ceiling you need to drain all the water out to restore the air cushion...
 

Last edited by NJT; 12-10-13 at 04:01 PM.
  #6  
Old 12-10-13, 03:45 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
With old style in the ceiling you need to drain all the water out to restore the air cushion...
Yes, and maybe the whole system will have to be depressurized. If there is a Bell & Gossett airtrol tank fitting and a valve in the line to the tank, the air can be checked and replenished w/o depressurizing the system. We need photos.
 
  #7  
Old 12-10-13, 04:03 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
With old style in the ceiling you need to drain all the water out to restore the air cushion...
I should probably write up a 'sticky' on how exactly to do that... been meaning to for quite a while now.

As long as there is the valve in the line which Gilmorrie mentioned, it's not too difficult... the hardest part is breaking the 'suction' that forms in the tank that makes you think the tank is empty when it's not.
 
  #8  
Old 12-10-13, 04:18 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
Thanks guys I just double checked and its 23 lbs at Gauge reading 165 degrees. Strap on sensor will read 180. I am not sure if I am in danger. Its an old American standard acroliner with cast radiators. I always thought upto 28 lbs pressure was OK. The gauge shows the red zone at 30 lbs.

With old style in the ceiling you need to drain all the water out to restore the air cushion
Just curious Would I need to drain the whole system or just tank.

I never got to do some plumbing changes I want to do so most likely I will be draining it at the end of winter anyway.

But please chime in if you think its not safe now.
 
  #9  
Old 12-10-13, 04:30 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
the hardest part is breaking the 'suction' that forms in the tank
A B&G Airtrol tank fitting takes care of that issue, and also allows confirming the water level in the tank with no fuss.
 
  #10  
Old 12-10-13, 04:32 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
If there is a Bell & Gossett airtrol tank fitting and a valve in the line to the tank
Whats in line below the tank is an old shut off valve with drain. Which is unfortunately stuck open.
I will have to google that fitting and hopefully add it after winter.

should probably write up a 'sticky' on how exactly to do that... been meaning to for quite a while now
.

I know one person that will read, so I hope you do.

Again let me know if I am crazy high in pressure. Thanks
 
  #11  
Old 12-10-13, 04:45 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
A B&G Airtrol tank fitting takes care of that issue
Yes... and there is also the "Drain-O-Tank" ( DT-2 ) drain valve with similar vacuum breaking ability:


image courtesy pexsupply.com

113041 - Bell & Gossett 113041 - DT-2 Drain-O-Tank Air Charger

If one had a bad drain valve that was going to be changed, or even if they just wanted to make it SOOOOOO much easier to drain tank when time comes, this is a 'must have' item.

Pressure should not go too much closer to the rating of the relief valve than 10%, so for a 30PSI relief, the max OPERATING pressure should be 27 PSI.

The only real 'danger' to operating that close to limit is that your relief valve may spew...

Do you own a small air compressor?
 
  #12  
Old 12-10-13, 05:12 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
A B&G Airtrol tank fitting takes care of that issue
Yes... and there is also the "Drain-O-Tank" ( DT-2 ) drain valve with similar vacuum breaking ability
That looks to be the equivalent of my Airtrol tank fitting. Besides breaking the tank vacuum, it can be used to verify the amount of air in the tank: crack open the valve - if water comes out, the air is above the top of the fitting's tube outlet in the tank; if air, vice versa. Best used with a valve in the line leading up to the tank from the boiler to the tank.

The Airtrol fittings used to come in various tube lengths, depending upon the diameter of the tank. Otherwise, trim the Drain-O-Tank's tube to extend about 1/3 into the diameter of the tank.

Essential device with a conventional expansion tank.

We still need to see photos.
 
  #13  
Old 12-10-13, 05:13 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
Do you own a small air compressor?
Yes the small $25 portable type for tires and such. Is that what you mean??

You got me curious now!!
 
  #14  
Old 12-10-13, 05:29 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
We still need to see photos.
gilmorrie hopefully in early am I will post some.
 
  #15  
Old 12-10-13, 06:22 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
OK camera had enough juice for a few pics.

Not sure I want to mess with where that new valve would go. Everything looks welded.

Name:  expansion.jpg
Views: 413
Size:  33.4 KBName:  expansion 2.jpg
Views: 422
Size:  34.6 KBName:  exspansion3.jpg
Views: 413
Size:  30.1 KB
 
  #16  
Old 12-10-13, 06:29 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,962
Received 37 Votes on 32 Posts
Shut the valve going to the tank. Drain tank and open side bleeder on valve you shut... Should drain right out...
 

Last edited by lawrosa; 12-10-13 at 06:42 PM. Reason: spelling...........
  #17  
Old 12-10-13, 06:37 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
open side bleeder on valve you ****...
Thankfully, the forum's website security edited Larowsa's potentially gross and sexually explicit post. I think he was suggesting opening the screw fitting downstream of the valve.
 
  #18  
Old 12-10-13, 06:41 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,962
Received 37 Votes on 32 Posts
Larowsa's potentially gross and sexually explicit post.
LOL... Typed an I instead of U in "SHUT"......

I have fat fingers and am trying my homemade beer.... Its like rocket fuel....
 
  #19  
Old 12-10-13, 06:42 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
Shut the valve going to the tank. Drain tank and open side bleeder on valve you ****... Should drain right out...
Thanks Mike
only problem is that valve sure seems to be stuck open. Scared something might break if I put to much force.

Might have to keep an eye on this till after the coldest part of winter. Then at least replace that shut off valve.

I was wondering why there were *** in post
 
  #20  
Old 12-10-13, 06:58 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
only problem is that valve sure seems to be stuck open. Scared something might break if I put to much force.
Try loosening the packing nut a half-turn or so - the nut surrounding the stem.
 
  #21  
Old 12-10-13, 06:58 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,962
Received 37 Votes on 32 Posts
only problem is that valve sure seems to be stuck open. Scared something might break if I put to much force.
Loosen the nut where the shaft goes into the body....( Packing nut)..

You should be able to turn. Once you loosen it will move freely.... Sometimes a water pump plyers on the handle to get that initial turn is all you need...

Edit:...........LOL...Gilmorrie beat me to it....Great minds think alike.
 
  #22  
Old 12-10-13, 07:07 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
Ok I will give it a shot. Most likely on Friday. Like to do it when I have time just in case

Ya never know when something will go terribly wrong

Thanks!!
 
  #23  
Old 12-10-13, 07:20 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
Ya never know when something will go terribly wrong
Good thought! Never rip into something unless the hardware store is open.
 
  #24  
Old 12-10-13, 07:32 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
in line below the tank is an old shut off valve with drain. Which is unfortunately stuck open.
Shut the valve going to the tank.
No can do if it's stuck open.

Do you own a small air compressor?
Yes the small $25 portable type for tires and such. Is that what you mean??

You got me curious now!!
In lieu of being able to close the valve leading to the tank, here's something you can try to get you through the season...

First, you need to rig together some kind of an adapter with a schrader valve that you can screw onto the drain valve.

These should be available at automotive stores (speed shops):


image courtesy teopro.com

The thread is 1/4" NPT.

Get one of these:


image courtesy plumbingsupply.com

and screw the schrader into the fitting and onto the tank drain valve.

Drop the boiler pressure to zero by shutting the water supply and letting some water out. (COOL BOILER, under 100F)

Using your tire pump and add air to the tank through the drain valve until you have about 12-15 PSI on the boiler.

Run for a few days and see how much difference that air charge you added has made. If it helped, but not enough, repeat the process.

I can't say how many times you can do this before you empty the tank (which is something you do NOT want to do. You DO want that tank about half full of water) because we have no idea how much water is in it now. You don't want to start pumping air down the tank pipe back into the boiler, but I bet you could repeat this process several times before there is any danger of that.
 
  #25  
Old 12-10-13, 07:38 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Loosen the nut where the shaft goes into the body....( Packing nut)..
And if that is corrosion I see on the stem, take a strip of emery paper and polish up the exposed part of the stem before you try to close it. That corrosion can 'scar' the packing material as it goes past.

Some silicone spray might not be a bad idea...

Speaking of obscenities, it's unfortunate that we can't call a drain **** a drain ****. We need to call them drain ROOSTERS!
 
  #26  
Old 12-10-13, 07:42 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
trim the Drain-O-Tank's tube to extend about 1/3 into the diameter of the tank.
I think that 1/3 is going to put the tube underwater under NORMAL conditions. As I recall, TWO/3 is recommended, but it's been a while since I've read the instructions.

Under normal conditions, that tank will be at LEAST half full of water when pressurized to 12-15 PSI.

I guess "one size fits all", just read instructions and they don't mention trimming the tube at all.
 
  #27  
Old 12-11-13, 08:16 AM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
As I recall, TWO/3 is recommended,
Yes, you are correct: http://documentlibrary.xylemappliedw...07/S10300H.pdf

During normal operation, the tank would be about half air and half water, I believe. When an empty tank (filled with air at atmospheric pressure) is pressurized with water, roughly the correct amount of air will be in the tank. In the compression process, the absolute pressure of the air will approximately double, from 1 atm to 2 atm, so the volume will be reduced by half.
 

Last edited by gilmorrie; 12-11-13 at 09:00 AM.
  #28  
Old 12-11-13, 11:15 AM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
I guess the first plan of attack would be the traditional way?? Using shut off valve and opening drain port.

I should not drain it completely?? But half way??

My biggest fear is it will get stuck closed or leak after touching it. But I guess there is no way around that. I will do the emery and spray thing first!!

If I had to guess my tank is not empty and not completely full based on tapping tank.

What pressure am I shooting for maybe 18 - 20 lbs hitting limit on 165 deg.

I will try to get fittings you suggested NJ just in case no luck with valve but also wondering if an air compressor would help if tank is air locked?? Or will the small port on valve help prevent that??

It looks like the valve on my system is closed from in coming water. (Plans to change that valve to a ball valve in future). Not sure if that would change anything but thought I should mention it.

Thanks again everyone!!
 
  #29  
Old 12-11-13, 12:38 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
I should not drain it completely?? But half way??
No... drain all the way if doing 'traditional' method.

When the system is repressurized, the air in the tank will be compressed under system pressure and the air will become appx half the volume.

If you use the air compressor on the drain valve it's a bit different story... if you start with the system at 0 PSI and add air with a compressor until the system is at 12 PSI, you have already compressed that air.

In other words, if you are draining the tank to the atmosphere, drain it completely and allow the water feeding into the boiler to pressurize it.

If you are adding air to the tank with a compressor, the air is being compressed in the tank because the system is closed.

I hope this is making sense...

What pressure am I shooting for maybe 18 - 20 lbs hitting limit on 165 deg
That's reasonable...

also wondering if an air compressor would help if tank is air locked?? Or will the small port on valve help prevent that??
Yes, it would... I have used a garden hose "Y" adapter on the tank drain... drain hose on one of the Ys, air hose on the other. Open valve on Y to drain hose and drain until it stops. Close that and open the other and push air in with compressor... close that and re-open the side with the drain hose on it. Repeat until tank is completely drained.

I don't know why Mike is thinking that opening that little bleeder on the side of the valve will help, I don't think it will... if that tank is locked up with suction, that little pee hole bleeder isn't going to help.

USUALLY, when the tank stops draining, if you close the drain valve and remove the hose, and with a bucket under the drain, reopen the drain... the tank should take a 'gulp' of air and continue to drain. Reattach hose and repeat as necessary.

If you use the largest and shortest drain hose as possible, rather than looping a 1/2" hose 50' long around the floor it will help too... because air has to go back UP the hose in order to get the tank empty.

It looks like the valve on my system is closed from in coming water
You mean the manual feedwater shutoff valve? It DOES work though, correct? I mean, you've got a way to repressurize the system after you drain the tank, right?
 
  #30  
Old 12-11-13, 05:23 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
Ok NJ I got ya. Iím sure I will refer back to reread your posts before doing it. I know I have a Y hose connector somewhere. I most likely will go easy on that shut off valve below the tank to see how it feels, slowly in and out just a bit. Then go from there to decide which way to go.

I have seen the fresh water fill valve work once before. Never tried it again.

Thanks guys truly the best DIY forum out there!!!
Always quick and good solutions.

NJ I hope somebody somewhere is paying you very good!!! Cause you sure give a lot of free info here!
Thanks!!
 
  #31  
Old 12-11-13, 05:58 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
NJ I hope somebody somewhere is paying you very good!!! Cause you sure give a lot of free info here!
Here, we're all volunteers... so no, the gift card we get at Christmas is not nearly enough... but it's my choice to be here, I like helping ppl!
 
  #32  
Old 12-11-13, 06:11 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,962
Received 37 Votes on 32 Posts
I just give trooper one of these on occasion and he seems content... Dont know why????
 
  #33  
Old 12-11-13, 06:19 PM
Member
Thread Starter
Join Date: Mar 2008
Location: NJ
Posts: 113
Received 0 Votes on 0 Posts
Well Then

Here, we're all volunteers... so no
I know, I meant wherever you work. Kinda a Karma thing for helping here so much!!
 
  #34  
Old 12-11-13, 07:47 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Mike, I need to introduce you to my boss, Mr. Scrooge!

Dont know why?
Don't you? Me thinks you do!

Thanks for the beers fellers, right back atcha!
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: