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Hot Water furnace

steve from staten island

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I need my suspicions confirmed
The safety lifted on the furnace today
The unit was running and the water temp was were it should be but the pressure was to high
I drained some water brought the pressure down and shut off the water supply
Since I have a indirect hot water heater I gave the unit about two hours to see if the pressure rose, indicating a leak in the heater coil
No raise in pressure
Opened up supply valve and another two hours later pressure is still ok
The only thing I can think of is the expansion tank is saturated with water
I know the old style tanks were the best
Drain at the start of season and you were good to go
This is a bladder type of tank
It’s not close to new and I know the bladder can go
If I have a repeat of this problem I thinking expansion tank
Thoughts are appreciated
 
You have a bladder problem:D.

Seriously though, time for a new expansion tank. I don't know if bladder types or diaphragm types are better. Your locality might have rules on what you use, or your furnace system in general. That is, they might hit you up on other necessary upgrades in the name of safety.
 
You can usually tell as it will feel and sound like it weighs a ton.... if empty like it should be, it will feel light and sound kinda tinny.
 
Does sound like expansion tank. But could also be pressure regulator at inlet where back flow preventer is.
 
You have a gauge on it? If so, what was the reading? Don't know much about the system you are using but when a safety valve opens, I like to know at what point it's opening. Used to machine seats and nozzles for large safety valves at work so I know a little bit about them.....small ones ain't all that different except you just replace the parts....
 
If you can give the tank a shake, that will help you determine if the bladder is busted. You shouldn't hear any water sloshing around. I replaced mine, and I agree, the old tanks were the best.
 
I need my suspicions confirmed
The safety lifted on the furnace today
The unit was running and the water temp was were it should be but the pressure was to high
I drained some water brought the pressure down and shut off the water supply
Since I have a indirect hot water heater I gave the unit about two hours to see if the pressure rose, indicating a leak in the heater coil
No raise in pressure
Opened up supply valve and another two hours later pressure is still ok
The only thing I can think of is the expansion tank is saturated with water
I know the old style tanks were the best
Drain at the start of season and you were good to go
This is a bladder type of tank
It’s not close to new and I know the bladder can go
If I have a repeat of this problem I thinking expansion tank
Thoughts are appreciated
 
Tap on the tank with something metal like a screwdriver. The bottom half should sound hollow the top solid. If it sounds solid all the way the bladder is shot.

A new should be sized to your system and the air pressure checked when the system is in a static state.
 
Welp...sounds like you got a clinker Steve-O

 
Mine lasted 7 years and then odd pressure problems. It’s heavier than it looks when it’s full of water that’s for sure.
 
On top of the tank should be a plastic cap covering a schrader valve, looks like a valve stem on your car tire.
If you press down on the pin and water comes out your bladder is shot.
 
Actually the schrader is on the bottom. If it’s on the top your tank is upside down.
 
Sounds like a different type of system. I have hot water heat here with a Weil Mclain energy efficient boiler and 4 zone pumps. It works well.
 
I agree with your comment, tank can also be mounted horizontal
yes, technically you are correct but if the bladder were ever to fail, the weight of the tank could not be supported by itself and fall or break away.
 
Your PRV could be overfeeding. This time of year, there can be long off cycles during the day, then it has to run at night. Most residential bladder expansion tanks are pre-charged to 12 psi. If the PRV is set higher or overfeeding, the air charge will be higher due to the increased pressure. Good procedure on your testing so far Steve. I would watch the pressure at a long off cycle, then at night or early morning after it runs more. It should by fairly steady if the expansion tank is in good shape. Did you unscrew the plastic cap and check the air charge w/ a tire pressure gauge?
 
Thanks for all the replies
The tank sounds like it is full
I pushed the bottom S valve and got some air mixed with water
Looks like expansion tank is shot and I got a new one this mourning
The make up auto water feed could be leaking past it’s diagram, ever so slightly and increasing pressure over the course of a few days
I am confident it’s not the coil in the domestic hot water tank
Thing is as we all know it can only be one of a few things
All I know being a old school type of guy is those tanks strapped between the floor joists were the way to go
Figure this my bro house was built in 1959 and it’s still the same tank all those years
Drain it at the beginning of the season hook up a garden hose into the slop sink drain it and that’s it
We’ve become a people who want convince only , no fuss no maintenance
That comes with a price but that’s a topic for another day
Thanks again
 
If you plan on partially draining the system, consider replacing the water feeder and the pressure relief valve.

Be careful that tank will be much heavier than you think. If possible, support it with a strap or rope, if you’re working alone.

The tank will come pressurized but you should check the pressure while the boiler is in neutral state, nothing running. That pressure should match the water feeder psi.
 
If you plan on partially draining the system, consider replacing the water feeder and the pressure relief valve.

Be careful that tank will be much heavier than you think. If possible, support it with a strap or rope, if you’re working alone.

The tank will come pressurized but you should check the pressure while the boiler is in neutral state, nothing running. That pressure should match the water feeder psi.
The tank was almost full of water so I think thats the problem but im going to keep a eye on the water feeder as well
 
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