Steam controllers.....whaaaa?

CuriousDan

Can a medium sized commercial steam boiler (W/M 88 around 1.7 million BTU/hr) ever run on it's own controls like a HW boiler, or does it absolutely have to have some kind of Heat-Timer or TekMar279 type of unit that controls the run cycles and senses outdoor temp etc.

icesailor

What's the function:

What's the function of the 3/4" pressure relief valve coming out of the front of the boiler in the picture?

nicholas bonham-carter

Steam controls

My 55 rad, 1,050,000 btu system runs the old fashioned way, with a Honeywell Visionpro thermostat using a remote sensor in the 2nd floor north apartment bedroom. It senses the dropping temperatures pretty well.

Where the Tekmar/Heatimer controls may excel would be in the application of daily temperature setback, which many here would not use due to the extra fuel consumed by the period of recovery. They may also compensate for bad venting, by establishing the arrival of steam at the farthest radiator, no matter how slow it is.

I feel it is better to spend those Tekmar dollars on generous main venting.--NBC

I would also check your pressure, as it may be too high. Can we see a picture of your supply piping?

CuriousDan

Dawn of the Computer Age in Controls (i think)

IDK why the PRV is right on the front near all the wiring....

I've been to the job twice but the 1st time we decided not to do anything and the 2nd time we were looking for a way to put in a manual switch for servicing when the outdoor temp was higher than the setpoint. But we couldn't communicate with the old floppy-drive controller, which led to the decision being made to scrap the whole control system. It is no longer controlling the actuators correctly at the zone valves anyway. Also the controller is not in the boiler room, it is up in the attic...

Is that Vision Pro sensing outside air temp or room temp at the farthest, coldest point?

SWEI

In that box

used to be some kind of DDC controller on the left?  Looks like a relay board on the right.  No more need for the zone valves at all?  What state are they in?  Were they properly installed and dripped?



I'd be suspicious of ripping it out before I knew exactly what it was doing.

nicholas bonham-carter

Visionpro sensor location

The sensor is inside the bedroom. That room always cooled down more quickly than elsewhere, so it seemed like a good location.

Recently we recovered the old flat roof above and put 4 inches of some foam insulation, under a new PVC membrane, so it may not be feeling the outside temperature it once was.--NBC

CuriousDan

I am suspicious!

The controller and box had no markings or phone number or anything. I dug through our records and came up with the original installer (from 2004) and gave them a call. They identified one of two possible operating systems it could be running but when my field guy got there his laptop couldn't communicate with it, so it must have been the other one.

By the way, this is a highway garage, L shaped bldg with two wings of truck bays and some offices and break room at the middle. No process loads.

The controller relies on outside temp and indoor setpoints which were problematic to get right in the first place. Also the facility was unhappy because they were left without any control to fire up the boiler in warm weather for servicing and maintenance. The controller sends 24v power to the actuators in each zone (I think there are 5), and as of late some of those stopped working too. They had a local contractor come in and fix the valves in the open position and leave them that way. The actuators looked pretty new and solid to me.

To make a long story even longer, the facility wants the controller gone and replaced with something way simpler, as do my field guys, they say the same thing but disagree about how best to go about it. I don't want to just yank it out, and I don't want to upgrade to a new DDC system that in a few years no-one will remember how to operate.

The good news is we went in there originally with the intent of ripping the whole system out and replacing with hydronic but found it to be operating very well over all with little or no complaints. Compared to many other DOT's around the state, this one is still performing very well.

SWEI

Pressuretrols

and/or Vaporstats look like they might be set up for two stage firing.  If that is the case and the system is reasonably well balanced and vented, you may not need anything else.

CuriousDan

I like where this is going

Today i found the manual for the old 88 Series 1 boiler on the W/M website under discontinued models. That is indeed the pressure relief valve coming out the front but I hope its piped off to the side from there.

I think I'll take another trip out to the site in the next week or so and really trace the whole system out, take better pictures, and fill in all the blanks, before I finally decide what the next step shall be. They've got heat so its not like I have to decide right this minute.

BTW here are pictures from an identical garage 30 miles up the road where the old steam system was completely replaced. Much older boiler and bad water problems there too. We found some "deposits"  in the return.

Hap_Hazzard

It's there just in case

the two Pressuretrols and the Vaporstat all fail at the same time?