Another Hoffman differential loop, few rads don’t heat well

GW

1930s with a peg262. This lil fella need more vent? 

I didn’t measure all the rads, 262 seems kinda big though. Ain’t a big house 

Hoffman loop seems good? Looks like a guy that had a clue piped it, just not sure about the small main vent 

2 1/2 header, Utica says they prefer 3”

each of the two mains have their own crossover trap to grab the two dry ret mains 

Homeowner says just 3 rads don’t heat up well

add vents or fiddle with the traps first? 

Thanks, I’ll be a two pipe man someday 😀

Jamie Hall

That's cute, @GW . Don't add vents out in the system anywhere -- you'll defeat that Hoffman Loop, and that you don't want to do. However... that vent is probably too small, but I'm not sure -- without putting a hole in the overhead there -- that I can see how to put in a bigger one. Like a Gorton #2. Have to admit that if it were mine, though, that's exactly what I'd do: a hole in the overhead and a Gorton #2.

On the radiators which aren't heating well. Are they on the same dry return? If so, might take a look see if there is a trap stuck open on that return It can be subtle... otherwise, are they heating the space? Just not hot all the way across? Might be meant to be that way... check that the throttling valves are fully open.

Steamhead

Jamie Hall said:

That's cute, @GW . Don't add vents out in the system anywhere -- you'll defeat that Hoffman Loop, and that you don't want to do. However... that vent is probably too small, but I'm not sure -- without putting a hole in the overhead there -- that I can see how to put in a bigger one. Like a Gorton #2. Have to admit that if it were mine, though, that's exactly what I'd do: a hole in the overhead and a Gorton #2.

Me too. Is that ceiling just plaster or sheetrock?

GW

Jamie i was referring to the small vent on the Hoffman, you thought I was gonna pop some vents into the mains? Not sure what is Cute

I didn't hang around to fire things up, was just breezing through and paid a quick freebie visit. Based on their explanation, other rads on the same loop do get hot (yet, all three trouble rads are on the same main)

GW

Steamhead it's Plaster, good old stuff.

GW

oh maybe the Hoffman is cute, LOL

Steamhead

Open up the plaster and replace that cute little Vent-Rite on the Differential Loop with a Gorton #2. Then watch how much better it works.

GW

Oh the lil vent  was cute. Wow I’m a little slow 

ok will do

are these traps easy to get cages for? Just in case the rads still don’t heat 

GW

Better view 

Jamie Hall

Hoffman 18 -- should be. Try Tunstall or Barnes & Jones. https://www.statesupply.com/bd1340

GW

Ah yes I’ve been googling, 2211. 

The Hoffmann 18 wasn’t the best invention ever or is the google machine pulling my leg 

Jamie Hall

https://www.statesupply.com/bd1340 , Gary

Steamhead

Jamie Hall said:

Hoffman 18 -- should be. Try Tunstall or Barnes & Jones. https://www.statesupply.com/bd1340

This.

Gordo

Do you have any pictures of a typical radiator valve on this system?

GW

Yes, are they user friendly and easy to repack? 

GW

Gordo and Steamhead are the same company? 

Gordo

Yes we are.
Thank you for the picture of the Hoffman #7 valve.
The one pictured is a pre-1925 version.
Please look up the #7 on YouTube for more info on it.

Steamhead

GW said:

Gordo and Steamhead are the same company? 

Have been for over 16 years.................

Jamie Hall

You don't repack those Hoffman valves, @GW -- they are packless. There are several good YouTube videos on taking them apart, and they really are fascinating inside. Not that hard -- if I can do it (and get them back together! you can!) They have an inner calibration sleeve which can be adjusted to the size of the radiator, and then the valve handle can be turned on and off as the occupant desires without messing with the setting.

GW

Thanks Jamie I’ll check it out. 

Gordo

@Jamie Hall : I beg to differ with you on the "packless" aspect of the Hoffman #7 valve.
In my experience, they are all too "packed". Generally, I find you have to grind out the old packing with a mini hole saw to get them unstuck and then re-pack with your favorite material. Many like the old-style graphite impregnated string as re-packing material. Others prefer PTFE packing.

Jamie Hall

You have more experience than I do, @Gordy !

delcrossv

Steamhead said:

Open up the plaster and replace that cute little Vent-Rite on the Differential Loop with a Gorton #2. Then watch how much better it works.

@Steamhead Why a Gorton #2 instead of a B&J Bigmouth in this application? I think a B&J would clear. Another reason?

Jamie Hall

A Big Mouth won't close on water. There shouldn't be water there, but it's not impossible (in fact, when the Differential Loop trips, there will be water where it attaches; whether it gets to the vent or not...

GW

Question, so with this Hoffman loop in place, no need for a float and thermostatic?

Jamie Hall

GW said:

Question, so with this Hoffman loop in place, no need for a float and thermostatic?

Shouldn't need one anywhere... I'd have to check the whole piping, though.

GW

I guess I get it. The boiler is in the middle of one end of the house, the two supply mains and return mains are parallel to each other, pitching down towards the other side of the basement. At the other end of the basement, they drop in to the wet return. Crossover traps at the ends of the mains. 

So, it seems like the air is being pushed upstream, and the condensate is draining down stream. Pretty cool

GW

Look at that, you helped me answer my own question. If the Hoffman differential loop goes, we need F and T-s on the other side of the basement.

Steamhead

GW said:

Look at that, you helped me answer my own question. If the Hoffman differential loop goes, we need F and T-s on the other side of the basement.

Actually, you don't. Just replace the Pressuretrol with a Vaporstat set to 8 ounces or so. The Loop was installed to make sure water could return if the boiler pressure got too high. They didn't have Vaporstats in those days.

GW

Thanks, the question I pose was more theory driven. If the loop goes (it’s staying—-I’m just trying to understand), the dinky air vent goes with it. I would need f and t or simple main vents at the other side of the basement? 

Steamhead

No, just pipe a vent where the Loop was and use a Vaporstat.

Jamie Hall

It's all about pressure differential, @GW . Keep the pressure differential between the mains and the dry returns and the wet returns low enough and you don't need F&Ts or anything fancy. The Hoffman Differential Loop (somewhere on the label you will see "Guardian of the Water Line") does just that without any moving parts at all. Other companies had other widgets to do the same thing.

Back in the bad old days without vapourstats now and then someone would get overenthusiastic and put in too much coal and the steam pressure would soar -- and you can't just turn off a coal fire. So, to keep the water where it belonged -- the Differential Loop.

Got to admit it took me a while to wrap my head around all the potentials of the darn things. They're so simple... and elegant... and do so much for the system!

GW

All righty my old plumber-water boiler-skorchy air brain will get it sooner or later😀. Humor me please - if I do “X” and I don’t install f-t, I will have a mad homeowner? 

Steamhead

What is "X"?

FStephenMasek

Gordo said:

@Jamie Hall : I beg to differ with you on the "packless" aspect of the Hoffman #7 valve.
In my experience, they are all too "packed". Generally, I find you have to grind out the old packing with a mini hole saw to get them unstuck and then re-pack with your favorite material. Many like the old-style graphite impregnated string as re-packing material. Others prefer PTFE packing.

Be careful, that old packing may be made with asbestos - just do it right, no need for excessive worry. I've got some nice cans of new old stock asbestos packing.

delcrossv

Sort of on topic, but if one had to replace on of these valves, what could you replace it with and keep the modulation? A plain globe?

Gordo

@delcrossv : The closest in performance and functionality to my beloved Hoffman #7 is Mepco's SWRF valve.

GW

x - like example, like x plus y = z 

if I can understand what would necessitate float and thermostatics, it my help my pea brain connect the dots. Thanks for holding my hand 😀

or, you can run any two pipe without f and t as long as you’re running 8  oz or so? That’s my hang up 

Jamie Hall

You can run two pipe without the F&T. It doesn't even really have to be vapour, but for higher pressure (pound or so systems) the vertical dimensions get more critical.

In some ways two pipe is sort of misleading. Most of them are three pipe! At least partly...

There are the steam mains. When the system is operating, they contain steam -- moving along at a good velocity! -- at a low pressure relative to the atmosphere -- say 4 ounces or so -- and the steam goes to the radiators. Then, usually right alongside them, you have the dry returns. These pipes are at atmospheric pressure (in some very old systems, actually open to the atmosphere). These pipes carry air from the mains and radiators as it is pushed out by the steam; that's important on startup, but much less so when the system has been running for a while. They also carry any condensate from the radiators to a convenient low point. They are separated, in most systems, from the steam mains by the crossover traps -- which allow only air to pass -- and from the radiators either by traps which allow air or water to pass, or, in some very low pressure systems by interesting contraptions which allow air or water to pass, but not steam. Both of those sets of pipes are above the boiler's water line -- at least 28 inches above for every pound of pressure the boiler is expected to produce.

There is usually a third set of pipes -- the wet returns. These are low. Not necessarily at the floor, but, critically, they must be below the boiler's water line. Anywhere there is a low point in a steam main or a dry return there will be a more or less vertical pipe coming down from the steam main or dry return, as the case may be, to the wet return. This allows any condensate in the steam main or dry return to drain freely.
But... because the steam main or dry return is above the boiler water line, the water in the wet return can't back up into them. The boiler pressure trying to do so, can only raise the water level that famous 28 inches per pound.

So there is no need for any kind of trap to keep the steam out of the wet return, and there isn't any steam in the dry return anyway.

It's a lot easier to demonstrate on a live system -- come and visit Cedric sometime!

GW

ah thanks Jamie, that helps a ton, so the f-t is only needed when the pressures are higher? Yes, the B number, I recall that. A is one pipe and B is for two.

Yes once I see and feel all of this, it will sink in. Then my next battle will be condensate receivers and boiler pumps. I'll get there. Like all people trades, I am bound to yank what I don't understand.

Jamie Hall

GW said:

...
Yes once I see and feel all of this, it will sink in. Then my next battle will be condensate receivers and boiler pumps. I'll get there. Like all people trades, I am bound to yank what I don't understand.

Don't we all?