Radiator not heating

Bridgestone

I have a radiator that is slow to heat and only gets lukewarm. It is next to the last radiator on a heating zone, yet the last radiator on the zone heats well. All pipes above the boiler are 3/4" copper with most entering larger steel pipes that narrow going to various radiators. It's an older house with 3 zone valves and and 3 thermostats.
The piping going to the 1st floor problem radiator goes from 1-3/4" to 1" to 3/4". The radiator size is 20x20x6. The pipe going to the 2nd floor radiator at the end of the zone stays at 1-3/4". The radiator size is 28x34x8. I'm thinking that the samller radiator is not heating because water is flowing past it through the larger pipe feeding the larger radiator. Could that be the problem? The radiator does not accumulate air. I drained a quart of water from the radiator while the pump was running and that added heat, but the fix was temporary.
Using 1/2" expansion pex I could tie the probem radiator to a different zone that serves 3 steel panel radiators. All 4 radiators would then have separate 1/2" loops with parellel piping. I'm wondering if that would be a good solution for heating the problem radiator? Any thoughts would be appreciated.

mattmia2

Some pictures especially of where the radiators tie in to the main would be helpful. Is this a monoflow system?

Bridgestone

Photo attached of where pipes go up through the basement ceiling. Somewhere above the ceiling the 1" steel pipe ties into a 3/4" copper pipe feeding the problem radiator on 1st floor. I don't know about a monoflow system.

hot_rod

you would need a balancing valve on the larger radiator. Reducing flow to that one would increase flow to the smaller one. Assuming they are both on that 1' line?
are there valves on the radiators? Round handle type that can be turned to reduce flow?

mattmia2

could be worth taking apart the valve on the problem radiator o make sure it hasn't come apart and is not opening properly when you open it. if it is heating when you remove water from the bleeder it could be water from the return flowing in to the radiator as you let water out the bleeder.

Big Ed_4

Gravity system with a direct return converted to a pump . What type circulator is used ? If it is a three speed , try setting to a low setting . Just enough to lift the flow check ...

mattmia2

How is the radiator connected? Does it heat at all? If it is connected bottom tapping to bottom tapping too much flow can cause it to only heat the bottom, it needs to be slow enough for convection in the water to heat the whole thing.

Bridgestone

To answer questions - The pipe to the larger raditor is 1 1/2" with a handle turn valve. The pipe to the smaller radiator is 3/4" with a lever valve. The radiator is fed from the top, leaves from the bottom. It gets lukewarm. The circulator is a Taco 007e, don't know about speed. The radiator is under a desk fastened to a wall, not easy to access. I'd be more inclined to cut into the ceiling of the unfinished basement and try putting the radiator on the Pex zone I mentioned earlier, if I thouht it work. Any thoughts on that?

mattmia2

if there is a problem with the valve opening properly then rerouting it isn't going to help you. Try closing the valve on the hottest radiators part way and see if that forces enough flow in to the cold radiator.

Big Ed_4

That circulator is for a zone valve system . Is the old system being controlled by a zone valve ??

Big Ed_4

That zone I would recommend to have it's own circulator and a full size flow valve . All you need to make it work is to feed the main and let the hot water rise , the way it was first designed to do . Forcing the water though you will get bypass . The flow valve is needed to prevent over heating . I wouldn't trust a spring check .

Bridgestone

Ed - The house has 3 zone valves and three thermostats. The radiator in question is on the main house zone with 7 radiators. A later-creatd second zone feeds one large radiator on the third floor (office space). The third zone was established for a 30 year-old baseboard heat additon. The baseboards on that additon are being replaced with steel panel radiators. The cost of adding a new valve and circulator is not a realistic option for us. On the coldest days we can put a space heater within 3 feet of the radiator in question and get enough heat. That's why I thought tying the radiator to the steel panel zone would be a reasonable, but not perfect solution, if it would help. I'm unfamiliar with a "spring check", but researched it. There's a valve right above the boiler connectiong the supply and return pipes. I assume that's the spring check you mentioned. It's halfway closed and I don't know if that is good or bad, and I don't understand what you mean by not trusting it.

mattmia2

The valve between the supply and return is a bypass to attempt to prevent prolonged cold water return to the boiler. If it is zoned by circulators then each circulator needs a flow check, possibly built in to the circulator. If it is zoned by zone valves then it doesn't need flow checks.

Big Ed_4

You are dealing with different animals The set up you have is piped and set up for baseboard , The panel radiators should be piped either using diverters or home run and should have its own circulator to work right.

The older system is a gravity system and was piped without a circulator . The rising hot water once it starts moving could pull on the spring check . The flow valve has a heavy weight and better choice on a gravity system .

If you want to hook up a radiator from the main house to the addition zone it will get warm but it would be erratic . Best to keep it on the main house .

Its cheaper to do it right grasshopper, good luck