Vaillant Boiler temperature too high and pressure too low

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Old 01-17-13, 09:19 AM
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Vaillant Boiler temperature too high and pressure too low

We put in a new Grundfos Pump and replaced the Filltrol tank. We cannot leave the pump on as it overheats the water and the pressure relief valve blew. We turn the Vaillant Boiler (which is 24 years old) on only long enough to heat the water maker and then turn it off.

The tridicator is working.

Is there an easy way to check the aquastat? We do not know how to see if the water is turned up too high or if it is working. All the above parts had never been replaced.

Any other suggestions? We cannot afford a plumber.
 
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Old 01-17-13, 09:47 AM
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replaced the Filltrol tank
When you say "Filltrol" I have to ask ... this is what it said on the tank itself, correct?

And this tank was attached to a water valve that fills the boiler, correct?

When you replaced it, you used a Filltrol tank to do so?

The reason that I ask is because a standard expansion tank will not work properly with the valve that you may have.
 
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Old 01-17-13, 09:59 AM
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We cannot afford a plumber
Sometimes one can not afford NOT too! Often it is possible to get one's self 'in trouble' to the point where it costs MORE in the end... just saying...

The tridicator is working.
How do you know that?

In the title, you said that your pressure was 'too low', yet you then go on to say that the relief valve blows.

The relief valve will only blow if the pressure rises to 30 PSI...

Please give us the history of why the pump and tank were changed... tell us the original symptoms from the time you first noticed a problem.
 
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Old 01-17-13, 10:38 AM
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The pump quit working and we replaced it. When we did that the fill-trol "blew" and we replaced it with an Amtrol 110 fill-trol with auto fill valve. Now when the boiler comes on and the pressure comes up to 12 it stays on but the temperature keeps going up and when it hits over 200 degrees the pressure drops to 0.

We have bled all our baseboards.
 
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Old 01-17-13, 10:48 AM
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I am disabled on a fixed income.
 
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Old 01-17-13, 11:19 AM
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when it hits over 200 degrees the pressure drops to 0.
The pressure drops? Why? Because the pressure relief valve opens?

I ask again, how do you know that the tridicator is good?

What model is the aquastat on the boiler?

And what is the model number of the boiler? F70???
 
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Old 01-17-13, 11:30 AM
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The boiler is a GA 92 Series, for propane. The aquastat is a Honeywell Type L8148E.

I assume the tridicator is working because the pressure and temperature change.

The pressure drops to ZERO when the temperature gets up over 200, the boiler bangs and we shut the system down because the burner never shuts off, when it is supposed to at 180 degrees.
 
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Old 01-17-13, 01:46 PM
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Please check to make sure that you have installed the new pump so that it is pumping in the proper direction! This happens more often then we care to admit, even to the pros.

I don't understand why the pressure would drop to zero... does it STAY at zero then?
 
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Old 01-17-13, 01:59 PM
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The pump is installed correct, the arrow points down as the instructions say. It circulates water and it cannot go another direction where it fits in the boiler body.

The burner will not shut off unless done manually.

The pressure stays at zero after being shut off.
 
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Old 01-17-13, 02:12 PM
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If the burner fires continuously, you could have:

1. defective aquastat

2. defective gas valve

3. incorrect wiring

I have no idea why the pressure would build, then make a noise and the pressure drops to zero... not a clue, sorry!
 
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Old 01-17-13, 02:27 PM
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We have wondered about the aquastat. Is there any way to check the gas valve? The numbers we get off the Honeywell are: 03-11.0A and 8645.

Where would the wiring be wrong?

Thank you so much for all the information you haved given us.
 
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Old 01-17-13, 03:23 PM
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If you owned a multimeter and knew how to measure voltage with it, you could attach it to the B1 and B2 terminals inside the aquastat... when the aquastat calls for the gas valve to fire it would send 24 VAC to those terminals.

If there is voltage on the terminals ALL THE TIME, even after the water temperature has passed the setpoint on the dial, then the problem is with the aquastat.

If the water passes the setpoint temperature and the voltage goes away, and the burner keeps firing, then the problem is in the gas valve sticking open.

I put the wiring at the bottom, because it's least likely... but needed to be mentioned.

Sometimes a wire can touch another wire, or maybe the insulation can get worn or melted, and this can cause a short circuit and all kinds of strange things can happen.

Sometimes when work is done on some part, the wiring needs taken apart, and sometimes it doesn't get put back together the right way.
 
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Old 01-17-13, 03:32 PM
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Thank you, we will look at all of it.
 
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Old 01-17-13, 03:38 PM
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OK, I want to place my 'standard warning'...

WARNING! 120VAC EXPOSED INSIDE AQUASTAT! YOU CAN BE KILLED! TURN OFF POWER BEFORE WORKING INSIDE AQUASTAT! BE CAREFUL!

Let us know what you find out! Good Luck!
 
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