The radiators on the second floor of my house are not getting hot

[thelanx]

What makes radiators make this knocking noise? Metal expanding?

 

[Antisocial Virge]

Originally posted by: mugs

Originally posted by: Antisocial Virge
It sounds like your relief valve is lifting either because its bad or your PRV is letting too much pressure into the system from the city water and its lifting your safety valve. I work on boilers for a living but nothing that small. More like 200hp and up like pic below.
http://www.cbboilers.com/firetube/images/4wi_large.gif

If that is the problem, how do I fix it? (I will try replacing the relief valve first)

Do you have any guages on your boiler at all showing pressure? Most only run like 10 pounds or so. If you open the makeup and you see that pressure spike its your PRV thats bad or out of adjustment. You could also check to see if your relief is lifting early by comparing the system pressure to the relief valve rateing.

 

[Antisocial Virge]

Originally posted by: thelanx
What makes radiators make this knocking noise? Metal expanding?

Water hammer I imagine. Before we open steam headers we have to make sure we drain as much condensate out of the header before the boiler. Condensate water and 150 PSI of steam causes water hammer so bad it can rupture and blow apart 12" steam pipes.

EDIT: Water hammer in a boiler system is basically just the condensate heating to the point of forming a bubble and popping in the pipe. Not the same as the water hammer when you shut off your bathroom tap too quick and here the pipes rattle 🙂

 

[Sukhoi]

Originally posted by: thelanx
What makes radiators make this knocking noise? Metal expanding?

Yeah, I presume so. The radiators in my dorm used to bang like hell when the heat would come on.

 

[dartworth]

Originally posted by: thelanx
What makes radiators make this knocking noise? Metal expanding?[/q

More than likely from water/condensate running into steam.

 

[mugs]

Originally posted by: Antisocial Virge
Do you have any guages on your boiler at all showing pressure? Most only run like 10 pounds or so. If you open the makeup and you see that pressure spike its your PRV thats bad or out of adjustment. You could also check to see if your relief is lifting early by comparing the system pressure to the relief valve rateing.

The pressure is usually less than 5 lbs. I didn't see anything on the valve that indicates its rating, but the furnace said the max relief valve capacity is 96 lbs per hour. Currently the pressure is reading 0 lbs - I guess because it wasn't running at the time? I turned the water on until it overflowed again, the pressure didn't move... should I have done that while it was running?

 

[NascarFool]

mugs,
A normal boiler will range from 12 to 15 PSI. The relief valve should be rated at no more than 30PSI (they are rated at PSI and BTUs) I carry 30PSI/650k BTU relief valves on my work van. Residential boilers seldom exceed 250,000 BTU (most are 200,000 or less). If the pressure is not coming up that's an indication of a bad pressure gauge or a leak in the system. The water should be left on at all times during the heating season. The Fill valve should keep the boiler filled. I use WATTS fill valves. Do you have seperate thermostats for different areas in the house ? *Can you post pics of the system ?

 

[DOSfan]

KISS: Keep It Simple Stupid.

I say that, so you know I am not trying to insult anyones intelligence here... Just starting from the simplest points.

1) Are there shut off valves to the individual raditotors? Are they open? (The house I had that had radiator heat had shut off valves at the feed pipe at every radiator.)

2) How long has it been since you drained the boiler tank? Not necessarily completely, just to "flush" out the rust. If it has been some time, there is quite likely rust clogging something/anything.

3) At the boiler, the water inlet valve should not necessarily be open at all times. It really depends on your furnace. If you have a water sight (glass tube on the side of the furnace somewhere) the tech we had in our house suggested filling the tank until the sight is about 75 - 80% full. (For whatever that may be worth to you.) I am not aware of what a non sighted boiler should have done. By the way, the sight will also hint to you when the water should be flushed.


Unfortunately, that is all I can add... Sorry.

 

[Batti]

More help here - Heating Help

Note that residential steam heating systems run at less than 1 psi, don't go cranking up to 15!!!

 

[mugs]

Originally posted by: NascarFool
mugs,
A normal boiler will range from 12 to 15 PSI. The relief valve should be rated at no more than 30PSI (they are rated at PSI and BTUs) I carry 30PSI/650k BTU relief valves on my work van. Residential boilers seldom exceed 250,000 BTU (most are 200,000 or less). If the pressure is not coming up that's an indication of a bad pressure gauge or a leak in the system. The water should be left on at all times during the heating season. The Fill valve should keep the boiler filled. I use WATTS fill valves. Do you have seperate thermostats for different areas in the house ? *Can you post pics of the system ?

I posted a pic above. One thermostat for the whole house. I thought 5 PSI seemed low since the gauge goes up to 30.

When I turned the water on and left it on until it started shooting out of the relief valve, one of the upstairs radiators started leaking too (from the valve knob). I guess that probably needs to be replaced too. :|

DOSfan - the valves are open on all of the radiators. 🙂