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Old 12-05-2009, 07:49 PM   #16
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At what voltage is a 24v transformer considered too weak?


There still are a LOT of old Neanderthal boilers (80-100 yrs old) in Wpg. with ugly old millivolt burners etc. Fortunately my plumbers do most of them, LOL.

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Old 12-05-2009, 08:52 PM   #17
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At what voltage is a 24v transformer considered too weak?


Problem solved - At least for now.

I checked the transformer at the leads and it was 28v without load. Under load it showed 21v. So all was good with the transformer.

I just crawled back up there and started the furnace cycle. When the voltage was applied to open the valve (a period of 9 seconds), I tapped on the valve case and the combination of the motor trying to open the valve and me tapping on the case let it open up again.

Hopefully it closes! I'll have to check that as soon as it finishes this cycle.
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Old 12-06-2009, 09:10 AM   #18
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At what voltage is a 24v transformer considered too weak?


Quote:
Originally Posted by beenthere View Post
Yoz.

Study how solenoid valves/coils work.
My library couldn't get "Fundamentals of Gas Utilitization". I am SOL.
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Old 12-06-2009, 09:21 AM   #19
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At what voltage is a 24v transformer considered too weak?


All solenoids work the same(coil wise).

Look how they work on cars, water lines, refrigerant lines. or any thing else.
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Old 12-06-2009, 09:27 AM   #20
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At what voltage is a 24v transformer considered too weak?


Quote:
Originally Posted by beenthere View Post
All solenoids work the same(coil wise).
Look how they work on cars, water lines, refrigerant lines. or any thing else.
You know I can't do math!
http://ocw.mit.edu/NR/rdonlyres/4775...0/solenoid.pdf

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Originally Posted by philp View Post
Hopefully it closes!
Valve stuck open and you knew it might = Darwin Award
and
". . .a duty of care is a legal obligation imposed on an individual requiring that they adhere to a standard of reasonable care while performing any acts that could foreseeably harm others."

Last edited by Yoyizit; 12-06-2009 at 10:14 AM.
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Old 12-06-2009, 04:24 PM   #21
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At what voltage is a 24v transformer considered too weak?


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Originally Posted by Yoyizit View Post
I thought you should get 24.0 vac at the rated VA load with the rated voltage in.
Open circuit voltage might go 10% to 50% higher, because of poor voltage regulation.

What current are you pulling?
A 24v 40 VA 'frmr with 26v open circuit voltage, at 21v, is delivering ~4A.
If Voc = 28v, @ 21v, I = 3A.
YOY are you human? am I questioning a Martian or computer or human or other??

YOU CRACK ME UP!!!!!!!!!!!!!!!!!!!!!!
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Old 12-06-2009, 04:29 PM   #22
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At what voltage is a 24v transformer considered too weak?


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Originally Posted by SULTINI View Post
YOY are you human? am I questioning a Martian or computer or human or other??

YOU CRACK ME UP!!!!!!!!!!!!!!!!!!!!!!
Actually, my existence is defined and indeterminate for those regions outside of Cyberspace. . .
http://www.google.com/search?client=...UTF-8&oe=UTF-8

Here, this should keep you busy for a while
http://en.wikipedia.org/wiki/Artificial_intelligence
http://en.wikipedia.org/wiki/Artificial_stupidity
http://en.wikipedia.org/wiki/Turing_test

BTW, Mr. S., can you find yourself in this list of stock characters?
http://en.wikipedia.org/wiki/Stock_character

Last edited by Yoyizit; 12-06-2009 at 05:24 PM.
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Old 12-06-2009, 05:39 PM   #23
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At what voltage is a 24v transformer considered too weak?


Quote:
Originally Posted by Yoyizit View Post
Actually, my existence is defined and indeterminate for those regions outside of Cyberspace. . .
http://www.google.com/search?client=...UTF-8&oe=UTF-8

Here, this should keep you busy for a while
http://en.wikipedia.org/wiki/Artificial_intelligence
http://en.wikipedia.org/wiki/Artificial_stupidity
http://en.wikipedia.org/wiki/Turing_test

BTW, Mr. S., can you find yourself in this list of stock characters?
http://en.wikipedia.org/wiki/Stock_character
Whew I am exhausted and OUT for the night.
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Old 12-07-2009, 02:56 PM   #24
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At what voltage is a 24v transformer considered too weak?


24v transformer VA test

If
Voc = 'frmr open circuit voltage
Rload = load resistor value
Vload = voltage across load resistor
then
a = Voc - 24
b = Voc - Vload
and the rated VA
= 24aVload]/bRload

E.g.
Voc = 27vac, Rload = 12 ohms (a common household toaster), Vload = 25 vac
then a = 3, b = 2 and the VA rating is 75.
or
Voc = 28vac, Rload = 12 ohms , Vload = 23 vac
then a = 4, b = 5 and the VA rating is ~37.

This formula may give VA ratings slightly higher than actual.
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Old 12-07-2009, 03:26 PM   #25
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At what voltage is a 24v transformer considered too weak?


So what is the starting/opening VA of the solenoid.
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Old 12-07-2009, 05:30 PM   #26
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At what voltage is a 24v transformer considered too weak?


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Originally Posted by beenthere View Post
So what is the starting/opening VA of the solenoid.
That is a State Secret for those of us not in the trade, as you well know but if you have a storage scope and a shunt you could tell me.
Or if you know the coil resistance and coil inductance with the solenoid core in the open position?

This formula is only for the 'frmr.

But,
since a solenoid is a "motor", and most motors want a stiff (i.e., low internal impedance) voltage source, these valves may also want a max. value for the 'frmr's internal impedance, which implies a 'frmr with good voltage regulation.
So a 40VA 'frmr with Voc = 48v may not work, even if the VA are sufficient.

Last edited by Yoyizit; 12-07-2009 at 05:58 PM.
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Old 12-07-2009, 08:19 PM   #27
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At what voltage is a 24v transformer considered too weak?


So now do you know why your other post was off base.
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Old 12-08-2009, 06:51 AM   #28
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At what voltage is a 24v transformer considered too weak?


Quote:
Originally Posted by philp View Post
Problem solved - At least for now.

I checked the transformer at the leads and it was 28v without load. Under load it showed 21v. So all was good with the transformer.

I just crawled back up there and started the furnace cycle. When the voltage was applied to open the valve (a period of 9 seconds), I tapped on the valve case and the combination of the motor trying to open the valve and me tapping on the case let it open up again.

Hopefully it closes! I'll have to check that as soon as it finishes this cycle.
Philp
Your statement problem solved - at least for now.
Is a true statement once a valve sticks it will do it again and it will at the time you least expect it 20o outside, holidays, weekends, middle of night.
So the point being replace it ASAP because it will let you down again.
Be prepared.
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Old 12-08-2009, 10:33 AM   #29
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At what voltage is a 24v transformer considered too weak?


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Originally Posted by beenthere View Post
So now do you know why your other post was off base.
What #?
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Old 12-08-2009, 10:53 AM   #30
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At what voltage is a 24v transformer considered too weak?


10.

Apply the math. And you'll see it doesn't work out like you thing.

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