Hot water radiator bypass and efficiency

Anneg2307

Hello everyone,
We bought a house from 1930's and it has a hot water radiator system, one zone, with the boiler in the basement. As expected, our 2nd floor is colder than the first floor and the basement. The radiators are only mildly warm and we just changed the circulator to improve efficiency. When the plumber bled the radiators he was surprised to find that all of them have a bypass (see picture attached). The bypass gets really hot but not much heat comes from the convector. Why is there a bypass in the first place in all of the radiators, including on the second floor? How can we improve efficiency (switch to european radiators?)? Thank you in advance for your help!

Jamie Hall

The single most important question is: how is the system piped? The second, on looking at the picture, is... are you and your plumber quite sure this is a hot water system? I ask, because I see something which looks alarmingly like a steam trap on one of the pipes going into that convector, If it is a steam trap, what is it doing on a hot water system? Otherwise, what is it?

Any further comments -- other than one -- will depend on the answers to those questions.

The one comment is that no, switching to European radiators will not do anything for you in terms of either efficiency or balance.

I might add, pending further answers from you, that there is what looks suspiciously like a bypass throttling valve on the bypass pipe...

Anneg2307

Thank you! My understanding is that the house used to have radiant heat and it was shut down due to leaks. The piping is not the most straightforward system. I snapped a few pictures. the plumber did not seem very comfortable with the system...

Jamie Hall

Well it certainly is a hot water system now... I still wonder, though, if it might have been a steam system at one time.

And, if so, if the device on what I expect is the outlet from the convector is an old steam trap. And, if so, if anyone bothered to take the innards out of it when the system was converted to hot water.

Has this balance (upstairs vs. downstairs) always been there, so far as you know?

And I still need to know what the device on the bypass line is....

EBEBRATT-Ed

The devise on the bypass pipe is nothing other than a key operated balancing valve as far as I can tell. If you blow the picture up you can see the square key.

The "steam trap" looking devise ...... maybe it was a steam conversion and they left the trap and pulled the guts out. But I don't think so as the supply and returns are copper.

But looking close the "steam" side looks like 1" and the "return" side looks like 3/4" so who knows??

Wonder if @DanHolohan has seen this before

DanHolohan

It was a steam system. My guess is that the bypass had a steam air vent where the key vent now is. Why the installer would do this is another question. It shouldn't be necessary.

As it is now, the bypass is the path of least resistance for the pumped flow, and that's why the bypass gets hot and the element doesn't. I'd eliminate the bypass on all the radiators. You'll need a vent on the return side of each convector, of course.

Anneg2307

Thank you all for chiming in. My only worry is that we find the reason the bypasses were added after we remove them. But at this point, it seems like it would be our best option to get more heat out of the radiators. Is this technically a mono-flow system? I am very new to the world of heating systems...

DanHolohan

We’d need to see how the radiators connect to the old mains in the basement. 

EBEBRATT-Ed

@Anneg2307

I can't see how the convectors could be connected in anything other than a parallel connection, especially with the supply and return being different sizes.

I think if you closed down on the bypass (turn clockwise) the convector should heat better if you have a key that fits it.

It could also be possible taht the "steam trap' is failed closed although they usually fail open

DanHolohan

The guys should be out of all the traps. 

bburd

That fitting on the bypass looks like a standard key operated radiator air vent, rather than a balancing valve.

mattmia2

Could you show us a couple closer pictures of what is in the bypass at the right, from a couple angles, like front and top so we can see that fitting in line with the pipe better? I think it is just a tee with a bleeder valve in it, not a throttling valve.

Can you do the same for the device at the bottom lower right underneath?

Some pictures of the piping in the basement where they connect may answer some questions about if this is a steam conversion.(it certainly looks like it)

Anneg2307

A few more pictures



- thank you everyone for your help!

mattmia2

That device underneath is definitely a steam trap, hopefully the guts have been removed when it was converted to hot water.

Really looks like that device on the bypass is just a tee with a bleeder valve on it. You could open the union and cap the bypass but you would still need a bleeder on the high end of the convector.

EBEBRATT-Ed

Wrench marks on the trap, it's been apart.

Must have been steam, strange that they fed it with copper. Must have been copper when it was steam because the risers are two different sizes. If they ran the copper when they converted it they would have pulled the trap out

DanHolohan

The piping may have been changed from steam to hot-water. Can you see the pipes in the basement that go up to the radiators? Not the ones near the boiler, in other parts of the basement. Thanks.

Anneg2307

We are getting into the history of the house! I do have the original specifications, with a section on heating. I also followed the pipes from boiler to a room that used to be a garage and was converted to an office. The radiator is quite unique (and different from all the other ones in the house) as it is attached to the ceiling. I also took a picture of the pipes that go to the master bedroom radiators upstairs

mattmia2

someone replumbed part of it in copper either when it was steam(which isn't correct but not uncommon) or not knowing why the pipes were the size they were after the hot water conversion.

Perhaps they did such a poor job of the repipe that they then converted it to hot water because they couldn't figure out why the steam no longer worked well. Might have screwed up the vapor stuff too causing poor operation.

Anneg2307

Is there anything we can do to fix it?

DanHolohan

The spec calls for copper tubing throughout, on both supply and return of the vapor system. 

DanHolohan

I would eliminate the bypasses on those Trane convectors.

Jamie Hall

It would be hopeless to try to convert it back to steam -- too much has been changed, and at least some of the original parts (like radiator valves) are simply not available.

The shame is that it probably worked wonderfully well when it was new, until people started messing with it who didn't understand it.

Anneg2307 said:

Is there anything we can do to fix it?

Well, yes. But the first question I will ask is whether additional insulation has been put into the house since it was originally built, and do you have storm windows -- good ones? Both may be necessary, as the heat output from the hot water system will be significantly less than the original steam system.

Then perhaps the next easy part of the job will be to eliminate those bypasses, as @DanHolohan (who is our senior guru!) suggests.

At that point, I would take a deep breath and live with it for a bit, because the next part of the game is going to be getting a decent balance between the various spaces in the house, and you need to observe it for at least a little while. While you are doing that, though, you can also help yourself (and us, later!) by tracing as much of the piping as possible, making a note of where any valves and pumps and other fittings on it are, and making a good diagram of it. Once that is done, it will probably (says he optimistically) to figure out where to place valves to get better balance, if that is needed -- and possibly even figure out ways to divide the heating into useful zones, should that be desired.

Anneg2307

Yes, it is our second winter in the house and we know in which room we need to put on a thicker sweater! We have storm windows pretty much everywhere and the attic is insulated.

Would the bypasses need to be removed completely or turning of the valve on it would suffice?

DanHolohan

There’s no valve on the bypass. That’s an air vent. 

Anneg2307

Could we install a valve on the bypass?

DanHolohan

Sure. Then close it. 

Jamie Hall

DanHolohan said:

Sure. Then close it. 

Chortle...

mattmia2

Note that you will still need some way to bleed the air out of that convector whatever you do with that bypass, unless you have the right valving to purge it from the boiler.

EBEBRATT-Ed

I find it amazing that they Specified copper tubing that long ago for the original piping.

WHO said copper won't work on steam?? I am sure it;s all 50/50 or 60/40 solder as well.Maybe if you allow for expansion and contraction it's fine. Probably doesn't work well for the near boiler piping

JUGHNE

You could just remove the longer pipe on the left and plug the openings.
You may have to swing the 90's to get the pipe unscrewed.
Those castings could be fairly fragile.
I would almost be tempted to saw a few inches out of the long pipe and then unscrew the remaining pieces, so as not to disturb the end castings.

Leave the air bleeder in place, air will find it's way to the high point of each convector for bleeding.

I would try this in the cold problem rooms first to see for improvement.

Also these are convectors that work on air flow. These fins looks to need a good vacuuming and clean up in general.

These must have the door on them for heat to flow. Air must enter the bottom and exit the top of the door.

The higher the cavity in the wall, the more heat it will deliver. Gravity air flow increases with height....and also unrestricted air flow.