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We have a two pipe low pressure steam heat system. one of our radiators is not working.

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You probably have an airlock condition and need to release the vent to let trapped air escape but be careful when doing this steam can cause severe burns.

Posted on Nov 15, 2008


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Posted on Jan 02, 2017


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I have a lot of noise coming from the pipes i have bleed the air valves from the registers and still have the noise

you can not bleed air from a air con system like you can a radiator in your home its against the law the system will need to have the gas removed checked for leaks put on a vacum then recharged bleeding will not work

Jan 21, 2011 | Heating & Cooling


What are the differences between a steam and hot water radiator

If you have a steam heating system and want to convert it to hot water or if you have a hot water system and want to go steam, you need to first find out if the radiators are compatible with the new system. If you are buying used radiators for your hot water or steam system, how do you know if they will work with your system?


The first rule to remember is that hot water will ALWAYS take two openings into the radiator. Usually they will be in the bottom, but I have hooked up radiators with the supply going into the top of the radiator and the return out the bottom. A small taping will also be needed for an air vent. This will release the air from the radiator so that it fills completely with water.

For steam it will depend on the type of steam system that you have. If you have a two pipe steam system you will need two openings and they do need to be in the bottom. For two pipe systems you will also have to fit a steam trap on the return side of the radiator. A valve on the inlet is a very good idea also. For one pipe steam systems you will need only one opening at the bottom. However you will also need to have a tapping for a small vent towards the top of the radiator to release air from the radiator. There is no trap on a one pipe steam system, but an inlet valve is still a great idea to be able to control the heat output of the radiator.

There are many styles and configurations of radiators made. Many can be used for both hot water and steam heating. Some cannot be used for one or the other. You do need to checkout the radiator to make sure that it can be used for your intended heating system.

I have already drilled and tapped radiators to make them suitable to use for the style of system that I want. Make sure if you do this that there is a space where they can be drilled and taped properly. Many radiators already have a spot for the tapings that you need.

on Jan 30, 2010 | Heating & Cooling


Steam System Steam Radiator Air

If you have a steam heating system you know how great the heating is from that type of system. You also know that there are not many people left that have a quality knowledge of what it takes to trouble shoot these systems.


One of the most common problems is getting the air out of the radiators effectively so that the steam can replace the air and make heat for your home. This steam flow needs to be properly controlled. If too much steam flows through it is wasted and efficiency drops. If not enough steam is supplied then the radiator will not heat to it’s fullest capacity.

If you have a one pipe system then you will have a vent on the side of the radiator near the top. The job of this vent is to release the air out of the radiator till it is full of steam. Once the heat from the steam hits this valve it will then close until it cools enough to allow more steam in the radiator again. If this valve does not do this properly then you will either loose steam out of the vent, and make a mess from the condensation or you will not get the air out of the radiator and you will not get enough heat. These valves also can be sized to allow more of less air out depending on the size of the radiator and the distance from the boiler.

If you have a two pipe steam system then you will have a trap on the return pipe of the radiator. This trap is on the side opposite of the valve. The top of the trap is screwed tightly on and can be removed with a pipe wrench. It is advisable to use two wrenches so that you do not break the piping when turning on the top of the trap. Inside the trap you will find a disc that has a thermostat in it. This disc snaps open and shut as the stem heats it up and it cools down. These discs are specific to each brand and size of trap. For proper operation of the trap you will need to match the replacement to the specific make and model of your trap.

Most of the time when you have a heating problem with one of you radiators, the trap or venting will be the problem. Very seldom does a pipe become clogged or there is some other problem that causes you not to have heat in one radiator.

on Jan 16, 2010 | Heating & Cooling

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We own an apartment building that has the old radiator steam heat powered by a gas bolier .. It heats 11 apartments and 3 store fronts. recently 1 of the apartments called and said that they were not...

the steam is not flowing to that radiator because of a blockage in the pipe or radiator, the valve may have an obstruction or the radiator is water bound. Remove the vent and see if the heat improves. If not, you have a blockage in pipe or valve.

Jan 08, 2011 | Heating & Cooling

1 Answer

Hhow to set the pressuretrol??

I assume you are talking about a steam heating system...
There are two screws on the top of the pressuretrol...

turn the pressure screw down to the lowest pressure at which you still get heat to the farthermost radiator...make sure the vents are working...or steam does not flow to displace the air...
Then just give the differential screw enough difference so the boiler cycles on and of a bout three times and hour...when making steam...
That's all there is too it...


Oct 08, 2010 | Heating & Cooling


Hot Water Steam Efficiency Plus Comfort

Steam heat is a great warm, wonderful, and absolutely fabulous way to heat your house. Steam heat is almost always created from water in a boiler fueled by gas, oil or electricity. It then passes through pipes and radiators or convectors to heat your home. A steam heating system uses steam that is generated from a boiler. When the water boils, the steam rises through the pipes and into the radiators to heat them. The hot radiators then heat your home.

Steam is a great heat distribution medium because it moves easily through your system and it has an extremely high heat-holding capacity. The heat-holding capacity of steam is much greater than that of water. Steam heating systems often operate at very low pressures and usually under 220°F. Steam heat is usually distributed by either one or two pipe systems. In a case of a one-pipe steam heating system, a single main serves the dual purpose of supplying steam to the heat exchanger and allowing condensate to run back from the radiators also. A two-pipe system has two connections from each heat exchanger or radiator. In this system, steam and condensate flow in separate piping from each other. With a steam system all pipes must be well insulated and you must use pipe insulation rated for steam piping. If the insulation is removed the system will no longer work as designed. Noise and all sorts of problems will come from uninsulated piping.

When you have radiators on upper floors or radiators that are further from the boiler they should be adjusted to release more air to compensate for the increased air volume in the piping due to the distance from the boiler. If you have a valve that is clogged with mineral deposits or stuck shut, no air will be able to get out of the piping. Because of this no steam can enter the radiator, so it doesn't heat up. This will block the movement of steam into the radiator, or cause a very noisy hammering as pressurized steam tries to get through this water "dam".

Steam radiators need to have a valve that allows air to escape at a controlled rate so that the radiator can heat up. Steam heating systems will also lose a little bit of water all the time, so there has to be water makeup so that you do not run your boiler dry. Steam heating systems without an automatic water feeder are not safe. You will risk serious boiler damage should boiler water be lost. If the boiler runs dry it could also explode if water is placed into it while it is hot. There should always be a low water cutoff installed on every steam system. Therefore on a steam boiler the automatic water feeder serves as a safety device also.

It is very important that you find someone that is very familiar with steam heating systems when repairing or installing steam heating. Incorrectly designed, installed, steam systems and condensate piping is a huge problem in today's buildings and facilities. There are not many qualified to design and install properly operating steam heating systems. Incorrect steam piping will always cause costly premature failure of steam equipment such as steam coils, heat exchangers, and control valves. Not to mention the higher cost of operating a system that is not working efficiently.

on Dec 29, 2009 | Heating & Cooling

1 Answer

Help my poor clogged cast iron steam radiator, we need you back!

If you have a two pipe system, meaning there are two pipes going to the radiator then you may have a trap that is bad, meaning that it is not opening up and allowing the steam to go into the radiator. Look on the side that the steam goes out of. Opposite the valve and there will be a round thing. The trap is inside that and will need to be replaced. This should be done by a propessional or at the least you need to make sure you get an exact replacment for it.

If you have a one pipe system then you may have a venting problem. There will be a silver thing on the side of the radiator that allows the air out of the radiator when it is cold and allows the steam to enter the radiator. This too needs to be replaced properly. Just anyold one will not do. There are many different models with different flow rates. The flow rate needs to be properly figured.
The chances are that your radiator is not plugged, but nees to have the venting fixed.If the air cannot get out of the radiator the stem cannot get in.
Make sure that you radiator is venting and you will probably have heat there.
I hope you have checked that the valve on the radiator is open... :-)


Jan 16, 2010 | Heating & Cooling

8 Answers

What causes high pressure in cooling system?

i can give you a general answer. the cooling sys is a closed system. as the engine warms up pressure is also increased. kinda like how a boiler works, or a pressure cooker. i dont know the figure of how much pressure is produced within an engine that is operating normally. the engine's thermostat. the thermostat of many car engines opens at 195 deg coolant temp, allowing the coolant to circulate. high pressure when considering a car's cooling sys to me is relative. if you try to remove the radiator cap when the engine is at/near/above operating temp you will be burned by the hot coolant under pressure rapidly escaping out the radiator. most pressure that is above normal is caused by an obstruction somewhere in the system. a t'stat that is stuck shut is an example. air pockets within the system will also lead to high pressure within the system. air pockets occur when you refill the system with coolant/water. pouring water/coolant back into the radiator traps air that can circulate throughout the system and you must ensure that these air pockets escape out the radiator, or you risk damaging the engine from excessive heating.

Aug 09, 2009 | 1993 Chevrolet Suburban

1 Answer

My 1990 subaru legacy was running fine-I went to the store less than a mile away and when I got home something was leaking from underneath the car and there was steam coming from under the hood..i don't...

Just because it was not hot to the touch, does not mean it is not a coolant loss problem----if the coolant is so low, there may not be enough to make the radiator hot (though usually the steam in the system will).
...a stuck thermostat can also let the engine overheat while the radiator remains cool (the fluid only circulates within the engine and is stopped from getting to the radiator.
...likewise a hose could have burst below and let the coolant out, over heating the engine, and the steam going out the ruptured/popped off hose; would look underneath..
...when cool, check the level in the radiator (likely empty),
...and less than a mile away, may not have ever heated the radiator, though usually only a mile to heat up the coolant
...of course there is always sabotage
...and water pump failure, (so no water circulated) causing overheating and no radiator heat, and possibly enough pressure to blow off a hose, but usually the radiator cap relief spring would allow pressure to escape (and that steam would heat up the radiator on the way---but if only steam in the radiator, it would cool off quickly after venting, because no more water in the radiator to hold the heat. all depending on climate,temp and further details , symptoms..
hope helps..

Aug 09, 2009 | 1990 Subaru Legacy

1 Answer

Open vent central heating

yes it is possible toupgrade the system to a sealed one using a system boiler as you mentioned. the thing to bear in mind is to upgrade the radiator valves to pressure rated ones 10bar.
The probable cause of the over heating is down to the system being sludged up/cold feed blocked, or possible pump circulating problem?
I would recommend the installation of a magna clean filter to help keep the new boiler clear from system debris.I would definately power flush the system, if the system is a twin two port valve system then a automatic bypass should be fitted, all of this done by a corgi registered gas engineer



Dec 18, 2008 | Protech Systems FasNSeal FSWMKE4 4" Vent...

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