Gravity feed boiler/ american standard model#g27dpgc

The squealing sound generally comes from a circulator pump, if it has a drive coupling between motor and impeller housing there is an oil cup/or oil hole, add oil until it is full! If it is a cartridge style circulator you may have to replace it.

Sometimes air in a system will cause this squeal noise as well. Purging the air out of system may be required. If you need to know how to purge a system there is a good pdf file at this link for $8.95 The Basics of Purging Air
From your Forced Hot Water System
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Troubleshooting A Leaking Boiler
Relief Valve
Miller Furnace Books Repair

The Expansion tank is factory set to 12 psi and the only way to tell if it remains with 12 psi is to drop the system pressure to zero and check the tank with a pressure gauge. If water comes out the air valvestem when you apply the pressure gauge, the tank is bad, replace it! If there is less then 12 psi on the tank add air to 12 psi and open water valves back up to normal operating pressure. Usually the feed valve will automatically stop at the preset setting.If the boiler is leaking water out any relieve valve drains, the feed valve, relief valve and or expansion tank may need to be replaced.

Need to know what pressure steam you are running, and what your water feed pressure is & temperature. If you are using a deaerator with pumps to supply feed pressure, and if there is a stack economizer. @ your altitude, I would de-rate your gas output to 10% less than your rated BTU's. Also need to know the % of oxygen in your flue gas, and if the gas & air intake is staged or modulating.

You did not mention what pressure the boiler displays when not on. It should be between 12 and 15 psi. You could have a bad feed valve, bad expantion tank (tap lower 1/2 to see if hollow).

Is the pressure in the boiler higher than the set pressure of the relief valve? If it is, there is a problem that the relief valve is trying to correct.
If not, did you try making the valve open?
Be careful, but step back, lift the lever and briefly let the relief valve discharge into a bucket of some sort, maybe you could put some old rags in it to keep from spraying out at you. If there is sediment in the valve this may flush it out.

Hello

This is a relief vave,probably rated for 30 psi.You either have air in your heating system causing the pressure to go up.

Or you need a new relief valve,sometimes the springs wareout or rust and iron from the water keep them from reseating properly.

You should have 15 to 20 psi of pressure on the boiler if its 30 or over you need to bleed air from the highest radiator or baseboard,if there is a 2nd floor go up to one and find the bleeder and bleed out air.Be carefull once the water starts coming it will be hot.

Your expansion tank need air. Bladder might be ripped.either u replace the tank or you drain it cometary and add 12 psi of air

If there is no leak anywhere in the system [pipes & radiators] Check the emergency pressure relief valve. It usually is at the base of the boiler and drains to outside [15mm pipe] where, if the valve leaks, water drips can be seen.. Looks similar to the picture with your query
Renew the valve
You can take it apart and clean it but I've never found that to be successful in the long term

Hi, it appears you have a defected relief valve. you can try one solution. lift the handle on the relief valve and let some water out. sometimes that can flush out materials thats blocking the stem in the valve. if it's still leaking it must be replace.

If this doesn’t work for you please write back. Thanks,

So the boiler relief valve is leaking? What is the boiler pressure when the relief valve leaks? The relief valve will have a pressure rating on it. If the relief valve leaks when the pressure in the boiler is lower than the relief valve setting then its just a bad relief valve. If the relief valve is leaking when the boiler pressure gets above the relief valve pressure setting then the relief valve is doing its job and there is another problem. Several things can cause the boilers pressure to go higher than the relief valves setting. It could be a bad expansion tank or one that needs to be drained and re-charged. It could be a bad cold water fill valve that isn't shutting off and is over filling the system, rasing the pressure above the relief valve setting. If this boiler also does your domestic hot water, I have seen where the domestic hot waters heat exchanger has a hole in it and the domestic hot water is mixing with the boilers water and over pressuring the boiler.

Check the pressure guage. Typically the pressure in a water boiler should not be more than 20 psi. If you are approaching 30, the relief valve is doing it's job. I would replace or adjust the automatic water feed if the pressure is high. Always replace the boiler relief valve. Tap on the expansion tank, it should sound hollow. Replace it if it is full of water. If you have one of the old expansion tank that has no bladder in it, drain it.