Air Block in Home Heating Radiators

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anjutg

Guest
Hai, I wonder someone could help. Two heating pads (radiators) in my house is not getting heated properly. I opened the air unblocking screw to bleed and there is no water and only a little air escaped.Bottom part of the radiator is heating properly. I tried these two alone by closing all the other radiators. Please advice. Thanks Tom
 
Did you have the heating running full blast when you did this? Is the air vent at the highest point on the radiator?
 
I tried low and full blast. Still no result. Also i tried while the bolier is on and off position. Air vent is at the higest point in the radiator.
 
Anjutg, Is there water in the expansion tank (small tank) in the attic, check the outlet pipe for a blockage? There mightn't be enough water in the system to fill all rads.

Did you bleed all rads? Are all the other rads and the pipes into and out of the hot water cylinder hot? Are the 2 rads that not heating properly upstairs or downstairs, are they the only 2 in either upstairs/downstairs - if downstairs then it might be your pump.

Finally, you may have to drain the system as there might be sludge clogging it up.
 
I am having a similar problem. I Bled the upstairs rads while heat was on. Two of the rads bled air and then the hissing stopped, but there wasn't the expected trickle of water. They seem to heat OK though. However there were then gurgling noises from the pipes and the rad downstairs closest to the boiler stopped heating. There is no heat on pipe into it or out of it. Is it possible for air to be in the system? if so can I bleed it myself, or will I need an expert?

Secondly, I cannot find the expansion tank. Would this be inside the larger tank in the attic, or could it be elsewhere? How full should it be?

Finally, would it be recommended to remove and drain the rads yourself (I have another probelmatic one), to remove sludge or should I get an expert. Seems to me to be a case of closing the values, readying a bowl, remove the nuts and lift, then replace the nuts and thred them over a bit of plumbers tape?
Any advice appreciated as always!
 
Get the radiators adjusted . Every radiator has two valves , one letting in the hot water and one letting out the the water back to the circuit . These outlet valves have to be adjusted. Which means that they let out the water at a similar temperature. The procedure is done by using a thermometer measuring the temperature at the outlet. Only when ALL radiators show the same temperature at the outlet of every radiator the heating system is delivering what it had been paid for.
 
Gimme, Thank u very much, i don't know about the expansion tank, will check find out where it is in the attic
I just bleed the rads which is not heating properly
All the other rads and the pipes into and out of the hot water cylinder is hot
The two probem rads are upstairs, also there is another 2 upstairs which is working fine.
Please advice
 
I don't think the outlet temperature of all rads should be equal, most references say you should measure the difference in temp between the inlet and the outlet, this should be about 12C.

Open all inlets and outlets fully, start with the rad closest to the boiler and almost close its outlet. Turn on the heating, and open the lockshield on the first rad until you get the 12 degrees difference, then continue on to the next closest rad, and continue with all the other rads.

Leo
 
The thermostat at the boiler gives a signal to the boiler.The signal is "fire" or "stop". Therefore ALL radiator outlet temperatures should be the same. Otherwise the thermostat at the boiler would only receive an average return temperature which is of no good to the resident. The very problem that anjutg has described would occur: some radiators would be hot while others would be only luke warm. Plumbers refer to that problem as "heat robbing". This term is not logical but it sticks to the mind.
To give a " hands on " sample for better understanding : The standard setting is 60 degrees C flow temperature and 40 degrees C return temperature . So when the return temperature shows less than 40 degrees the boiler starts firering . Until the return temperature has reached 60 degrees C. Now it will get the signal from the boiler thermostat "stop" and it stops firering accordingly .
The return temperature that the boiler "gets" is the average return temperature. That is the combined average outlet temperature of all radiators ending in the one and only return pipe leading to the boiler (and includes some leveling caused by temperature losses during transport via the pipes ) .
So sensing a return temperature of 40 degrees C does not at all mean that the outlet temperature of the radiators is 40 degrees C - unless they have been hydraulically adjusted .
If the radiators had not been hydraulically adjusted then the outlet temperature of half of them could be 50 degrees C and the outlet temperature of the other half of them could be 30 degrees C - giving a temperature at the boiler thermostat of 40 degrees C . And that would cause exactly the problem that anjutg has described:
As soon as the boiler gets the "fire" signal it will fire untill the temperature of 60 degrees C is reached .
Which means in our hands-on sample that half of the radiators have an outlet temperature of 70 degrees C and the other half only 50 dgrees C.
Note: This hands-on sample is is just a sample. Far wider temperatur differences at the outlets can occur - see anjutg's post.
So unless there is really sludge in the two radiators which are staying cold in anjutg's heating system this is the only solution that comes in my mind. Sludge is a rare problem found but it can happen. The only other problem could be wrongly set - or damaged - radiator thermostats . So my question to anjutg is : are your radiators equipped with individual (automatic) thermostats -esp.the two that are not working ?
 
anjutg: Have a look in your hotpress (or possibly in the attic) to see if there is a small tank (maybe ball shaped) in addition to you hot water tank. If there is then there should be a water pipe running from the small tank up in to the attic and there should be a closed valve on this pipe. If this is the case then try this . .

1. turn the heating off 2. open the valve to the small tank to let the water in from the main attic water tank 3. bleed each rad in turn and the pressure of the water should force the air out 4. having bled the rads close the valve again and test your heating.



This is how my system works anyway.
 
Thank you heinbloed, now i got some idea how the boiler works. There is no individual automatic thermostat for the radiators which are not working properly.Also how can i hydrolically adjust the radiators...
 
I did not explain how the boiler works but why. See my post above from the 26th of October. Hydraulic adjustment means that the different pressures at different parts of the heating system have to be made to fit the demand. The further away a radiator is from the pump the more friction is aplied to the water in the pipe. This in turn makes it slower circulating. What causes it to be cooled down.
So in a system with all valves (at the radiators;there are two on each) open the water would flush trough some of the radiators and trickle only through others.The idea of hydraulic adjustment is to have enough water going through all radiators , not more and not less.
This is achieved by setting the outlet valves at the correct setting.The correct valve setting is choosen by the temperatur loss, measured at the outlet of each radiator. When all radiators have the same temperature at the outlet than the system is hydraulically adjusted.
The "standard" temperature on the radiator outlet is determined at the radiator with the highest output demand - usually the one in the largest/coldest room. Lets say the inlet temperature at radiator "A" is 60 degrees then the outlet temperatur could be 50 degrees . These 50 degrees are than aplied to all other radiators by opening or closing the outlet valves. Work from the largest room/radiator to the smallest .
If the outlet temperature is similar or near the inlet temperatur than the water is flushing through the radiator , all the hydraulic pressure is lost on this one. The pump spends all it's energy/potential (the plumber's slang is "head")on this radiator instead of supplying all radiators with the same pressure.
After adjusting the system you might find that the pump speed/power can be reduced without compromising on the heat delivery. Most pumps are set at full power because the plumber is either incompetent to adjust the radiators or she/he simply is to lazy. Reducing the speed of the pump increases it's life time, reduces it's noise and - most important- safes on energy,money.
 
It sounds from all this I need to open that valve to repressurise my system. What does the valve look like? Where would I most likely find it?

I have a gas boiler (Baxia). The house is no more than 4 years old. I have lloked in the hotpress, there is a pipe into the cylinder with a handle on it. Don't think thats it.

Apologies for being so clueless
 
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