Vaporstat vs pressuretrol and leaking juncture

1890ish

Hi, first post here! We've been in our house for about 10 years and as the username suggests the house is from around 1890 with some original single pipe steam radiators.
My question is about the Honeywell pressure trawl connected to our weil mclain boiler. 

The cut-in is at the lowest setting, below half a PSI, and the differential is an internal dial with the lowest setting at 1. I'm presuming this is 1psi differential, and that seems like too much!
The reason I'm asking is that we ( I myself) recently had to reseal the threads on a couple of control valves for the radiators. I always use pro-dope pipe dope, but even with that one was still leaking! I tried again with a combination of pro-dope and plumbers tape. A bit messy, and a bit better, but still leaking today when it's 6 degrees out. Doesn't leak when it's above 30 degrees out.
I know I should probably try to fix the threads and redo the whole thing -- but it's in a very awkward spot and for some reason the steam pipe is copper for this rad, instead of black pipe like it is everywhere else in our house.
This got me thinking that maybe running too much pressure and a vaporstat might help with efficiency and pressure compared to the pressuretrol.
Opinions please? Thanks!

Gsmith

Is there a pigtail between the pressuretrol and the boiler? Is it clean? So the pressuretrol is reading the real boiler pressure. If the pigtail is clogged your pressutetrol will not work properly. Generally your pressuretrol settings 0.5 psi and 1 differential—on the white dial, are good for single pipe steam systems.

1890ish

Thanks for your answer about the pressuretrol, that saves me a lot of money! I've followed this site and bought Dan's binders over the years and it's been both helpful and good to understand how the hydronic system works.
The system was just serviced this fall, and the pigtail was inspected and cleaned as well as a system flush and new oil nozzle and filter.
I didn't watch over the work so I suppose I could double check the pigtail, and maybe I'm being lazy, but I trust the guy who did the annual maintenance. The real problem is that the pipes leaking at the threads on cold days. It's only on this one radiator and I don't want to have to move the entire radiator to fix it properly.
Any other ideas for how to stop this leak? It's at the pipe threads going into the brass valve. Preferably a solution that's not going to cause more problems than it fixes. Permatex? Self fusing silicone tape? Ugh!

nicholas bonham-carter

Post a picture of the leaking joint, and double check the pigtail.
If it is the threaded collar of the union joint, pipe dope, and tape are not needed, as the mating surfaces should be clean to seal.
Rock the rad slightly as you tighten the collar.
If it is between the packing nut, and the valve stem, then some graphite, or Teflon string will seal it up.—NBC 

KC_Jones

Pictures of exactly where the leak is would help a lot, it could influence the recommendations.

1890ish

It is a crazy fitting, I have to disassemble and rotate the valve to get it to thread onto the pipe on the leaking side. Guessing it was probably threaded on first, and then soldered onto the copper pipe before we moved in. Very tight clearances!

Jamie Hall

That is just bizarre. Even with low pressure, once that has started to leak it's going to leak until you take it apart, clean the threads (if they aren't too badly damaged), and reassemble it. And honestly I don't know how you are going to do that.

EBEBRATT-Ed

Unfortunately how could it not leak? Bad place to solder or do anything.

For the time being i would put a pan under it and wait for warmer weather.

If that is unacceptable (and it may be) cut the copper tubing between the elbow and the copper adapter and pull the radiator out.

Sweat a new piece of tubing on a new adapter and screw it in the valve. Then you could slide the rad back and use a copper slip coupling or (and i would hate to do this) a copper union

The only good fix is get rid of the copper and go back to black pipe

1890ish

Yes and yes. But I think I found another culprit at 2am. That rad is badly piped but it's weird that another started leaking. I cleaned the pigtail and have been emptying pans since 11pm. So why not get friendly with the boiler, really my only friend at this hour.

I turned the thermostat up to 75, and the boiler kept going and going trying to heat up this house and didn't cut out until the pressure gauge measured 3psi!! 

Here's a short video of the gauge - at 10x speed. https://youtu.be/WEBNy7_I5cM

I can trigger the cutout by pressing the right spot but methinks there is something awry. 

1890ish

A bit of progress to report! I completely disconnected the screw that holds the spring to set the cut-in at the lowest setting and now my pressuretrol actually works! It cutout pretty quickly. So I'm slowly making adjustments.
What's the optimum cut-in? A certain number of cycles per hour I'm presuming? I'm to to read up on this and fiddle with the right setting. Thanks for your help everyone.

Jamie Hall

Usually with the grey box type pressuretorl they are reasonably reliable with a cutin set at about 0.7 psi. Anything much below that and they tend to come apart. The differential -- white wheel -- should be set at 1