Partially Heated Radiator - 2 Pipe System

benhal

I recently bought an old home built in 1929 with a steam heating system. When we turned the heat on at the beginning of the season all radiators heated up nicely except for one. Upon studying the system a little more, I noticed that this radiator is at the farthest point in the house. Down in the basement, the mains split into 2, one running to one side of the house, the other running in the opposite direction. The main carrying the steam to the radiator that is cold is on the furthest main, so the steam takes longer to get there. I clocked it at approximately 8 minutes for the steam to get to the riser leading up to the radiator (house approx. 2600 sq ft). Initially, I had a plumber come by to take a look, he told me that the steam trap is shot and needs to be replaced. Fine, he replaced it and the steam reached a few additional sections of the radiator. But still didn't solve the problem.

I was reading Dan Holohan's book "We Got Steam Heat!" and it became apparent to me that main vents were an important thing. I then went down to my basement and surveyed the system. At the end of each main I found an air vent. No air was venting from the main that connected to the riser for this particular radiator. So I replaced the vent with a B&J big mouth. The radiator got a little warmer but still not completely hot and still a substantially long time to heat up. I then traced an additional vent by the end of the dry return. Checked that one, air was venting properly. I noticed that the end of this main by the problem radiator continued with a Wye connection. The top of the Wye (facing up) had the vent as mentioned (facing up, of course) and the bottom had a drop to beneath the boiler water line, ran across the basement, connected with another drop from the other main and continued back to the boiler.

I also noticed that nowhere in my system is an F&T trap. According to Dan's book, a 2 pipe system needs to have one (or more) but nowhere in my system did I find anything like it. The only thing I found was by the dry return...an old Tran DIrect Return Trap. Not sure what its function is.

Anyway, need some help! I should also mention that for testing purposes (even though you're not supposed to do this in a 2 pipe system) I put a vent in the mid section of the radiator to help vent any air in the system. The trap is supposed to do that but clearly the steam is not getting there because the sections by the trap are still cold.

What's interesting about this is that you can hear the small vent on the radiator slightly whistle, so you know air is venting. Eventually the whistling stops because the heat from the steam should be shutting the vent. If this were the case though, why are those sections cold? I should be able to feel the heat from the steam by the radiator but I cant!

At this point, the only possible thing I can think is that the radiator valve is shot and not enough steam is getting in. Already ordered a replacement and will be doing that this weekend.

Anyway, if anybody has any insights, I am truly grateful!!! Thank You!

Jamie Hall

@benhal you say "I also noticed that nowhere in my system is an F&T trap. According to Dan's book, a 2 pipe system needs to have one (or more)" Not sure where you read this in The Lost Art, but it simply isn't true. In fact, most two pipe systems don't have one. There are many variations, though, on two pipe systems -- but they all have some way of venting the steam mains (either crossover traps or big main vents) and some way of venting the dry returns (bigger main vents).

You also mention replacing the inlet valve. Pause. Please. Are you aware that the valve is matched to the spud in the radiator? And that the valve may be a special, calibrated valve for that specific radiator? If you do decide to go ahead and replace it, you may find that you also need to replace the spud in the radiator, as the valve and the spud are a matched pair, as I said. You might get lucky and not have to replace the spud -- the union faces might match -- but I wouldn't bet on it.

To go back to the calibrated valve. Many two pipe systems had the valves to individual radiators calibrated to provide enough heat to the space, regardless of radiator size. The proper question isn't whether the radiator gets hot all the way across, the question is does the space get properly warmed? Not too hot, not too cold. Ask yourself that first.

Now a couple of other thoughts. First, is the full length of that main/runout leading to that radiator insulated? If not, it will take a long time for steam to get there, vents or no vents. Second, is it pitched properly everywhere along its length? No sags? At least 1 inch drop for every 20 feet? That can slow steam delivery. Then go and look at that dry return. No sags/ Pitched properly to drain?

JUGHNE

Do you need the rad to heat all the way across, that is do you have a cool spot in the house.
Do all the other rads heat all across while this one does not?

There were some older calibrated valves that had locks to prevent over opening them. Some required a special tool.

Also there was a method of inserting a cup orifice into the supply valve union. You will not see this without opening the union.

Heed Jamie's advice about just changing the valve without change the rad spud.

Could you post a picture of each end of the rad? Especially the valve ?

benhal

Jamie, Thanks for responding. No the room does not get properly heated. The room is pretty cold and we'd like to get it to a comfortable temp.

Currently, the main is not insulated. Should it matter? the other main isn't insulated either. I also have multiple risers on the particular main whose radiators get adequately hot.

When you say 1 inch drop...does this mean that the mains are supposed to be pitched upward or downward? I thought steam rises so they should gradually be pitched upward?

Grallert

Is it that the boiler shuts off before that radiator heats up fully? Or is the boiler still running? Are any spaces over heating?

benhal

Yes, the boiler shuts off because the thermostat on the main floor is satisfied. The radiators on the first floor work well. The radiator we are talking about is in a room on the second floor and is the farthest point.

Jamie Hall

@benhal you say "I also noticed that nowhere in my system is an F&T trap. According to Dan's book, a 2 pipe system needs to have one (or more) but nowhere in my system did I find anything like it." . I'm not sure where you read this, but it is simply not true. Most two pipe systems do NOT have F&T traps.

They work very simply. The steam goes out in steam mains. These are vented either with crossover traps -- which are NOT F&Ts -- or big main vents. Any condensate is taken care of by drips to wet returns. The radiators accept steam in accordance with their valve settings (more on that later) and the air and condensate goes into dry returns. The air from these is vented by bigger main vents, and the condensate is dropped to wet returns. The wet returns return the condensate to the boiler.

Now you mention replacing the valve on the problem radiator. Are you aware that the valves on two pipe systems are often adjusted so that the radiator puts out the amount of heat required by the space -- and may not necessarily fill the radiator with steam? The appropriate criterion for a radiator is not does it get hot all the way across, but is the space it is heating at the right temperature. You might want to consider that.

If you do decide to replace the valve, which I don't recommend unless it simply can't be repaired, you should also be aware that the valve and the spud in the radiator are a matched pair. You might get lucky and not have a leak at the union with a mismatched valve and spud -- but you might not, and find you have to replace the spud as well.

Now bac to the problem radiator. If, in fact, it is not heating the space adequately, you might check and see if the steam main and runout feeding it are big enough and that they are pitched properly. Then make sure that they are insulated for their full length. Poor or missing insulation can slow steam delivery considerably.

Jamie Hall

I wondered what happened here -- I just replied to your other thread.

On insulation. Yes the main must be insulated. Most of the time delay which you mention in you initial post is due to the time it takes steam to heat up the uninsulated main to the point that it can get to your radiator (example: on the main place I care for, the mains (three of them) are 75 feet long, and take around 3 minutes for steam to get from starting at the boiler to the ends; uninsulated it would be more like 10 to 15 minutes).

On pitch. It doesn't matter to the steam which way the mains and runouts pitch -- steam isn't moved by rising, but by pressure differentials. What does matter is that they do pitch enough for the condensate which forms in them to drain. Some -- perhaps the majority -- of systems are parallel flow; that is, the mains pitch away from the boiler and are dripped at the far ends to a wet return. Some -- and most runouts -- are counterflow; that is the condensate and steam move in opposite directions. Counterflow piping requires more pitch than parallel flow.

Again, before you replace that valve, insulate the runout and mains -- and check that the valve is really fully open.

benhal

Jamie, ok I will insulate over the weekend and see what happens.

Amazing, that explains why I have a drop at both ends of the mains that connect to each other and ruin back to the boiler. I was wondering what those pipes were for but couldn't understand.

Thank You so much! if nothing else, I've learned a big lesson today.

In terms of valve...the valves are actually frozen...no wrench will move it and there is no information on what the previous owner of this house did. You wouldn't believe the type of rigging we found in this house so far. Unfortunately, he joined the Dead Men now and took all the knowledge with him...

One question I have: how great of a pitch should the mains be? how large of a pitch for the return lines?

Grallert

If the room in question is cold this sounds like a balancing issue to my ears. Are any rooms over heating? You could slow the room with the thermostat down a bit. In other words partially close the supply valve to the resident radiator causing the boiler to run a bit longer.

Jamie Hall

Pitch is covered in The Lost Art... my recollection is that parallel flow is fine at 1 inch in 20 feet, but counterflow mains should be 1 in 10 feet. I have seen some less than that and be OK, but they have to be really straight to survive...

Erin Holohan Haskell

Since this was posted in two different categories, we've merged the two threads into one and posted here. Thanks!

benhal

How do I measure the pitch to make sure I don't have any slopes or sagging?

Jamie Hall

The first step which I do is sag. And all this assumes that either the insulation is very uniform -- or not there (you've got an advantage!). Anyway. The simplest is to simply tie a string to one end of the pipe and just go to the other end and hold the string tight against the pipe there. It should be, you hope, close to the same distance from the pipe all along. Easiest to spot sags if you are as close to the centre of the top as possible. Hangers get in the way. But that's the principle.

Having checked that, just put a good reliable carpenter's level along the pipe anywhere handy I use a 4 foot level, but a shorter one will do if you don't cheat.

Or you can use a laser level if you have one.

nicholas bonham-carter

Check your thermostat for having been setup for steam as well. What sort do you have?--NBC