I have a valliant ga 1000-20 boiler. The pressure relief valve on the output line located near the boiler wore out. i replaced it with a 30 psi relief valve. this valve leaks each time the boiler comes on and heats water. is this 30 psi valve to low? IF so what psi rating valve should i use or is there another fix for this problem?

pressure is one of the variables - other is maximum flow, in case of pressure relief valve (safety valve) if valve was calculated at 50psi and flow of say 10gallon/sec, if you change the diameter, your flow will drop significantly, in case of 1" drop to 3/4" drop will be by nearly 45%! and that is significant drop...

i would suggest do not use reducer but 1" relief valve as required...

if you wan to establish bit more calculations on the subject, go to this site and have play with variations, sele3ct correct calculator and enjoy :
http://www.tlv.com/global/TI/calculator/

reverse engineering will be here:
https://www.physicsforums.com/threads/calculate-water-pressure-coming-out-of-a-pipe.274737/

hope this will help you a bit - do not forget to vote...

I assume losing pressure through the PR means Pressure Relief Valve (PRV) or temperature pressure (TPR). Open in TPR may mean boiler is overheating/overpressurized. Open in PRV means the Pressure Reducer/Fill Valve in the fill line of the boiler is broken.
House Water Pressure in a home is 30/40 PSI min to 60-80+PSI max.
Boiler PRV/TPR are set at 30 PSI open (SYSTEM PRESSURE) so too high a house water pressure will open the PRV/TPR. Replace the reduction regulator on/in the fill valve assembly

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
&
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.

Loud rumbling noises are often caused by either water boiling in the burner or by entrapped air in the system. To help prevent water boiling make sure that the boiler system has a pressure between 15 - 30 psi. Also check for sufficient water flow and remove any sediment from the in-line filter. To remove entrapped air, install an automatic or manual air vent at the highest point in the heating system and also make sure you have a properly working micro-air vent installed. With the unit turned off and cooled down, you can also try flipping the lever on the pressure relief valve to try and flush out any air in the heat exchanger . Hope this helps.

It sounds like your thermostat could be the problem. Have you noticed the boiler cutting off at all, or does it run continuously until it goes out on low water?

You stated, "when boiler is on", so I am wondering how you get the boiler on. If your boiler is controlled by a thermostat, you need to check it for a cold draft possibly from behind the thermostat in the wall where the wires come through. The thermostat should never be on an outside wall. The thermostat could be defective.

An aquastat can also control your boiler. If you have an aquastat, check the setting, typically 175 - 180 degrees. You should also have a "high limit" which should be set at 210 - 220. Some people run that high side limit higher; not a good idea - defeats the purpose. If the aquastat is set too high, the boiler will operate too hot and the problem you have will occur.

"pressure rises and pressure relief valve opens" This could mean that your pressure switch is prematurely venting. Check boiler temperature to see exactly at what temperature the T&P valve purges. If it blows off below the high side setting, either adjust or replace. The T&P valves are usually not adjustable. That blow off temperature is stamped on the head of the valve. So, if it discharges too soon, replace it.

Have you actually seen evidence thgat the T&P valve is opening? You may have a bad bladder in your expansion tank and your system may have air in it. Your boiler should have 12 psi when cold and 20 - 22 psi when operating. Check your boiler pressure guage.

"this eventually drops below the minimum operating pressure" Technically, there is set point for a NO MINIMUM OPERATING PRESSURE. That is a function of the amount of water in the boiler. If the T&P is blowing off, it will vent water from the boiler and the boiler pressure will go down. There is a minimum operating TEMPERATURE.

Your boiler could be low on water. You will have to manually fill the boiler. Be careful of thermal shock to the boiler. Feel the piping, and fill only when the circulator is running. Make sure the water is not going directly into the boiler. The supply water should go into the circulating supply side which feeds the radiators, radiant floor, or base board circuits.

All this will adversely affect your hot water. The heat exchanger for the potable hot water may have scale build up in it. Using the hot water keeps the boiler running, and a scaled heat exchanger will give you cooler hot water and the boiler keeps running. If this is a problem, you will need to replace the heat exchanger. A better idea is to not use the boiler for your domestic hot water. Why run the boiler in the summer?

Even a small amount of crud on the rubber washer/sealer can cause the valve to seep. Some valves can be taken apart and cleaned but it will be better to replace the valve. They can be found on line for around $12 or more. You will have to shut off the water in take valve and drain most of the system unless you have a main line shut off valve so the system wont drain back into the boiler. These valves are usually set at 30PSI.

The expansion tank is located on the header leaving the boiler. If it is a newer style than it will be a cylinder, most likely hanging above the boiler. It will have a valve on the bottom of the tank that looks like a tire or bicycle valve. If you put an air gauge on the valve stem it should read 12 psi, if it reads more, say closer to 30 psi, then the bladder is broke, and it should be replaced. If there is less than 8 psi, then there is probably a slow leak and the tank should be replaced. If it is an older expansion tank, it will most likely be mounted in the ceiling of the boiler room, it will be a large steel cylinder, that is piped into the boiler, and should have a drain valve on on side of it. If this is the case, connect a hose to the valve, and allow all the water to drain from it. This should solve the problem if it is your expansion tank. Hope this helps.

Under the boiler a little right of center there is a blue/other colour knob. Turn this anticlockwise [as you look up] [twist from right to left] This is the mains inlet tap to let water into the boiler and create the pressure shown on the guage 0.5 bar is the absolute nin.
allow the water to flow in until the guage reads about 1 bar then turn off the knob -not too tight as these are plastic
If you allow too much pressure- do not worry, there is an automatic relief valve.
If the boiler persists in loosing pressure, look for a leak in all pipes to & from radiators. If no leak then check the pressure relief valve outlet pipe, it usually goes through the wall to the outside. Look at the end for water drips & if there are drips replace valve

Turn the power off at the wall , wait 60 seconds and the boiler will automatically reset.

Modern boilers are complex re safety and the boiler will only start if the exhaust fan is running and is up to speed .

The vacuum caused by the fan trips a switch and allows ignition to continue

If the pilot light does not come on it does not warm up the thermocouple which turns on the main gas valve.

If you go to the Valliant website they will supply you with a user guide

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,