One cool radiator

FranklinD

I have an issue with one radiator in my house, happening to be in my daughters' bedroom.

We had the boiler replaced awhile ago, and ever since then it just doesn't seem to heat unless the boiler has been running for an extended period of time. A LONG time. It heated 'just okay' with our old boiler, but never seemed as hot as the others on the same branch.

Our house has an old gravity system (I think), the boiler that was here before was an ancient WeilMclain with a big pump. Not sure what it was, but it was big. You could hear the water running through Radiator #1 in the drawing below. There are two pairs of main pipes, starting big and gradually getting smaller. One pair goes one direction across the basement, the other pair goes the opposite way. The pair that I didn't draw out is longer and larger, and all the radiators on that branch heat just fine.

On the drawing, Rad #1 and Rad #2 heat just fine. Rad #1 is first floor, and Rad #'s 2 and 3 are both second floor. The supply pipe to Rad #3 gets hot in the basement, but the return is ice cold. The supply is warmish on the second floor at the radiator, and the radiator warms slightly across the top 2-3 inches only (but it takes awhile).

None of the radiator valves turn, so they're the same as they always were.

After staring at it for a long time, i see that the two main branches are tied together at these Tees. They didn't touch any of this piping when the boiler was replaced this time, but it must've been replaced when the older boiler was installed because it's different pipe than the mains (smaller and black steel).

Do I have a flow issue because of the way these tees are plumbed (because the second branch is plumbed into the 'bull' of both tees)? Maybe the old pump had enough power to flow all the way up to Rad #3? We have a Bumblebee running in delta T mode now. I did try running it wide open and it *seemed* to heat up a little more.

Just looking for any ideas before my daughters room freezes for the winter. Thanks folks.

SWEI

What kind of boiler was installed? Do you have a drawing or photos of the near-boiler piping and the circulator are arranged? Have envelope upgrades (new insulation, new windows, etc.) been done on the house?

Paul48

They did you no favor by downsizing the pipe. Considering it was a gravity system....try slowing the circ down.The smaller pipe at the boiler, and to the tees,increases the velocity and essentially bypasses those rads.

nicholas bonham-carter

Have you tried bleeding the air out of the radiator?
It is possible that the boiler piping was incorrect at the time of replacement, and that this has prevented air from being automatically removed from the system. In this case, maybe all the trapped air has ended up in that one radiator.
There are some excellent books in the shop here about hot water heating, with tips on how to gain economy through regular maintenance.--NBC

icesailor

Paul48 said:

They did you no favor by downsizing the pipe. Considering it was a gravity system....try slowing the circ down.The smaller pipe at the boiler, and to the tees,increases the velocity and essentially bypasses those rads.

They didn't do any favors by downsizing those pipes off the 3" mains because they didn't know what they were doing. They threw a huge imbalance into the system.

The system sees those connected radiators as a single radiator that doesn't have the flow capabilities to get into balance with the rest of the system. There's a short cycle by-pass inadvertently connected. If the 3" supply and return is flowing 2 gallons per minute, the water is moving slowly through the 3" pipes. But the smaller piping to the other radiators can't get that high velocity to pass that GPM water. If the system is already pumped, that part with the multiple radiators needs to be separated and have its own pump. You can't marry two different types of pumped systems. One that was gravity once and converted. And another that was pumped from the beginning. They will never balance. Sometimes, you can help it with balancing cocks, but that's a band aid on an infection. It needs more.

If there is no domestic hot water load on the boiler (like a oil boiler with a tankless coil), turn the high limit to 130 degrees and turn up the thermostat. Let it pump for a long time. If all the radiators in the system finally get hot or the same temperature and at a reasonable amount of time, you might be able to install a Taco "I" series 4-way mixing valve and use the ODR feature to keep the water temperature down and the circulator pumping. If all the radiators on the smaller, multiple radiator loop doesn't get hot together, it won't work well, ever.

You may be able to help it if you can find someone with the patience to get all the flow valves on the radiators working properly. You have to know if the valves are operating and where they are. You need to put more resistance through the old radiators/part to get it to equalize in the new multiple radiator zone.
IMO.

Paul48

I can't come up with an easy(cheap) way out. Working radiator valves would make it work, but that's a lengthy job. I'll throw this out there, as a possibility.....Disconnect and plug the supply and return to the 3 radiators at the tees. Run the supply and return off closely-spaced tees on the newer boiler boiler supply, and pump the 3 radiators. Again, not easy or cheap, but maybe the lesser of a few evils.

FranklinD

That's what gets me on it...that it all worked for 30 years. Must've been that the big pump made enough flow to create enough back pressure in the 3" supply to push up to the last radiator on the second (2") circuit thru that tee. I joke not, it DID work before.

Maybe if I do as in Dan's book, and connect the supplies and returns into one big loop and pipe the boiler in p/s. If I did that, I know it would involve a second pump for the main loop, but don't I have to also provide boiler temp protection then since it's a cast iron boiler? It should have it anyway, I think, but it doesn't. Boiler bypass and system bypass are the two terms I see tossed around a lot.

FranklinD

I actually do have a big box 'o' new radiator valves...they've been on the 'to-do' list. They're all 3/4" valves except for the living room and kitchen which are 1". 9 total, one has a new valve already.

Paul48

I was proposing a secondary loop off the boiler, maybe a 1 day project. The valves, on the other hand, would be a much harder job. If you've ever changed one, you know what I mean. Getting the spud out of the old radiator can be a pain in the arse. Not to mention the fact that the house has probably settled considerably. When you disconnect the radiator, the pipes may go "Boinnng". At which point, you are left wrestling to reconnect them, and usually you create leaks elsewhere in the system. Ain't plumbing fun!

icesailor

Being the cheap, lazy critter that I am, I'd be carefully loosening up the packing nuts on the radiator valves and giving them the Kroil Treatment. If they weep, some graphite packing and some water pump grease. If there's paint on the stem, carefully remove it, sand it smooth with sand cloth, and get the valves to turn. If they are originals, there must be at least one that is working and can give you an idea of how they turn and work.

Most of those old gravity radiator valves only turned a half turn and often had a hole in the plug for slight circulation when closed. Gentle is the operative word. I can gently pat my cat. She'll just lay there and enjoy it. If I pat to hard, she jumps up and goes and hides under the couch.

If you have ten radiator valves that you say won't turn, carefully try each one. They are not all equally tight. Find the loosest one. Learn on that one. Then try the next easiest one and fix that. By the time you get to the last one, you'll be proud of yourself.

Go gently pat your cat.

Paul48

The least intrusive way is the best way, and that's it.

FranklinD

In my case it's a dog, gentle old Sydney the blue heeler. She just gives me an offended look should I pat too hard.

I was curious about loosening the packing nuts...I should wonder where I could find replacement packing to have on hand just in case.

I guess one benefit of the work that's been done is that now I have a boiler drain valve and boiler fill valve that work. Always a plus.

For all I know the valve to that radiator is turned mostly off. I know the pair at the opposite end (on the end of the 'East' mains) get hot as all bloody heck. Maybe at one point they had a similar issue with this cool radiator at the end of the 'West' mains.

I can only speculate what this all looked like with the original boiler, possible 2 separate supplies and returns on the boiler, one set going East, one West. That's how my relative's house is. He still has the coal behemoth boiler (with an oil burner on the front) and no pump.

Perhaps after work I'll chip a little paint and spray a little 'Liquid Torch'.

FranklinD

Well, a lot of chipping paint, a little penetrating oil, and a lot of patience, and I managed to turn the valve about 45 degrees. I did get a few beads of water at the packing...I'll have to find some new packing or replace the valve soon. Fortunately this valve is at the top of the system.

But now the radiator heats all the way to the bottom! The other two don't heat up as fast, but do still heat completely (the other two are piped bottom to bottom and the third *trouble* radiator is top to bottom). I'll take it as a win for the moment.

Thanks for the assistance!

icesailor

That wasn't all that hard, and you learned something.

Try to get a roll of graphite packing. Cut off a piece 6 to 8 inches long. You can unravel it into smaller pieces. Wrap them around the stem individually. Push them down with something small, flat and pointy. Its OK to have some sticking up. Just be sure to always be able to easily engage the packing nut. Slide the grease inside and tighten the nut. Not too tight. But if you get it turned down a lot, add more packing by backing the nut out and repeating. You want it so that there is always soft resistance to tightening the nut. Once you have it so that there is plenty of new packing, work on turning the stem all the way around.

If they are all the same brand, see which way they turn on and off, closing the flow.

Glad we could help. Keep trying. Its worth it.