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When boiler heats water the pressure increases to the point that the pressure relief valve( 30 psi) releases water from the system.What causes the pressure to increase? The system includes an expansion tank( Wilkins-model HXT-30)

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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).

Posted on Mar 16, 2011

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Alpha cd28c boiler loosing water and pressure through pr valve when heating is on,and when then switched off needs repressuring to use heating again.no obvious leaks.new pr valve been fitted.pressure


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

Oct 20, 2014 | Water Heaters

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Expansion Water Tank Boiler Expansion Tank


d186d4f.jpgWhen water is heated the water will increase in volume. The thermal expansion tank in a boiler heating system is there to allow the extra volume of water some place to go. It also holds enough water to fill the void back up when the water cools.

The water expansion tank is a necessary item in heating systems. It also can cause problems if they do not work correctly. Some of the problems caused by a faulty expansion tank are:

  1. The boiler relief valve will be constantly dripping or blowing off if the tank is totally full of water and does not have the air cushion needed to counteract the increased volume of water as it is heated.
  2. Air can be introduced into the system if the tank does not hold sufficient volume of water to keep the system full as it cools.
  3. If fresh water is introduced into the system frequently the tank will rot out from the inside out.

One of the main things to remember is that a faulty boiler expansion tank can make other things like the relief valve look faulty when it reality it is not the problem. A bad expansion water tank or a bad pressure reducing valve can make the relief valve look bad. Or actually cause it to need replacement. Check everything out carefully before deciding what pieces need to be replaced. If go about just changing parts without a through investigation first you may be changing parts for a long time till you find the right one.
http://www.fixya.com/support/r3705970-heating_circulating_water_pump_problems

http://www.fixya.com/support/r3695967-valve_pressure_reducing_or_pressure

on Dec 23, 2009 | Heating & Cooling

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Valve Pressure Reducing or Pressure Reducing Valve


dfef4ee.jpgThe pressure reducing valve on a boiler is the way that the water pressure in the boiler is controlled. The standard pressure for many hot water boilers is considered to be 12 PSI. To keep the boiler pressure at or near the 12 PSI mark a small valve is used for pressure reducing. Most domestic water systems run between 20 and 60 PSI, so the pressure must be reduced for the boiler.

This pressure reducing valve is installed in the pipe that goes from the domestic cold water to somewhere in the piping on the heating system, usually at or near the expansion tank. The valve is mostly maintenance free but will create some problems at times. Some of the things that can go wrong are:

  1. The valve seat can get dirt stuck under it causing water to leak by and increase the pressure in the boiler, causing the relief valve to release water periodically.
  2. The valve can become plugged with dirt causing the boiler to not have enough water pressure, which will cause circulation problems with the boiler pumps.
  3. The valve can leak causing a mess around the boiler area.

Replacement of the pressure reducing valve is not difficult if the installer strategically placed manual valves so that the reducing valve can be isolated from the rest of the system for replacement.
If the water pressure reducing valve fails in any way, it is usually best to just replace the whole valve rather than trying to repair or fix it. I have tried a number of times with only temporary results. These valves are not a high dollar item and the time it takes to fix them is not worth it.

http://www.fixya.com/support/r3696173-expansion_water_tank_boiler_expansion

http://www.fixya.com/support/r3705970-heating_circulating_water_pump_problems

on Dec 23, 2009 | Heating & Cooling

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My boiler has a squeeling sound during the warmu up. I think it is coming from the expansion tank?


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.

Oct 09, 2014 | Amtrol EX-30 Diaphragm Expansion Tank...

1 Answer

Very loud foghorn sound


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.

Sep 06, 2014 | Noritz Water Heaters

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Boiler Leaking Water - The Boiler Leak may not be the boiler


Went on one call today and had another query by Facebook about this so I though why not write an article about it. Both persons were very concerned as they saw water dripping from theirs boilers. A closer inspection for both showed that it had nothing to do with the boiler its self.

There are many things that can make water leak from your boiler. If you know for sure that the water is coming from a hole in the sections then you may have a serious problem. Usually though there is an easy fix for that also, more on that in another article. Both boilers today were leaking water from the relief valve.254c728.jpg

This valve is design to relieve the excess pressure from the boiler in case of a build up of extra pressure in the boiler. The extra pressure can come from a number of different things. A few of the causes may be a bad expansion tank, a bad fill valve or pressure reducing valve, or an open bypass valve. The bypass is easy, just close it and relieve the extra pressure. The others are not as easy.

Your expansion tank is simply a tank that allows water from the system to go in and out according to the pressure in the system.610ab3c.jpg This tank contains about ½ air which acts as a cushion to absorb the extra volume of water that is created as the water is heated. Hotter water takes up more space or volume, so it needs a place to go to when it is heated. If the expansion tank is totally full of water then, it will push water out of the relief valve. Changing your expansion tank will fix the problem.

If the reducing valve or fill valve is leaking by then you can also get extra pressure in the system.8e5ccb4.jpg A normal heating system will only run 10-20 psi pressure. Most well systems or city water is way higher than that. If the pressure in your boiler gets over 30 psi then it will begin to relieve the extra pressure by dripping water.

If you have a drip from your boiler this is what you check. First the expansion tank, the reducing valve, and the bypass valve that bypasses the fill valve. This valve is usually installed to quick fill the system, or purge the water lines of air.

Often there is just a small problem that looks like a big problem. Do not get excited and methodically check through the possibilities. You will usually find that the problem is not nearly as bad as you first thought that it was.

on Dec 06, 2009 | Heating & Cooling

1 Answer

Wickes 102 combi boiler constantly loosing water pressure


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?

Feb 02, 2013 | Water Heaters

1 Answer

Loss of pressure in boiler, no obvious leaks, water pressure switch changed plus pressure release valve


Check that your make up water is on.

Make sure your fill valve is working but it sounds like it is not. Your min pressure should be 15 psig. on the boiler. Fill valve will maintain a15 psig on the boiler. Water and pressure does get out of the boiler when radiators are bleed. When fill valve is not working people will keep bleeding the radiators trying to get heat but only lowering the boiler pressure with no water make up.

Make sure your boiler is getting water and has pressure when running.

If it isn't...SHUT DOWN and have a professional look at it.

Pressure relief valve is factory set ta 30 psig and opens when pressure is above 30 psig. This is a safety valve.

Feb 17, 2011 | Heating & Cooling

1 Answer

Hydronic Boiler relief valve problem?


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.

Dec 03, 2007 | Heating & Cooling

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