Temperature Control

JohnnyComeLately

I'm looking for a bit of advice.  I sold a pair of vertical fire tube boilers, with modulating 3:1 burners on them.  These were installed in a 90 year old building.  After selling and installing, I read Dan's greening steam book.  I checked on my installation yesterday when it was 27 degrees outside, and everyone was happy with the boilers.  However, they're cooking people out of the top floor at night time.  The building holds so much heat that they're only running the boiler in the morning and then shutting it off in the afternoon, and then letting it run again some at night.

The steam risers go to the attic, then down to the 2 pipe radiators.  All of the traps were inspected and rebuilt during the summer when the new boilers were installed.  The attic was also insulated with blown in insulation, which is obviously doing it's job. 

The client here has limited funds (don't they all).  Zone valves are probably not an option because they might cause water hammer, and finding a common steam supply pipe could be tricky.  I think the best solution is to install some TRVs in the problem spots on the fourth floor.  Does anyone have a better idea?  Is there a more cost effective TRV than the Armstrong RV4?

nicholas bonham-carter

cooking the top floor

see if the steam arrives at all floors at the same time. of course it will tend to arrive at the top first, but with some means to get the air out more quickly from those mains/risers, the heating should be more even, which it seems not to be, as it favors the top floor. maybe some massive vents on the bottom of the risers will fill the whole riser with steam before the steam begins to flow through the radiators.

let the boiler run all the time under some form of thermostatic control as it is during the recovery of temperature that these imbalances are most pronounced. you may have to keep the control locked up, not even allowing the occupants access to it!

another factor may be the pressure-keep it low in the ounces range. high pressure equals higher radiator surface temperatures which make people feel hot instead of comfortable.

and for a client with limited funds, the reduction in fuel use will be just as attractive as the increase in comfort. how do the ratings of these boilers compare with the total amount of radiation? after these problems are worked out, you can begin to stage the burners, and save more fuel money.--nbc 

JohnnyComeLately

cooking

Turning the pressure down makes sense, we can try that.  I think we're running at 5 psig right now.  As I've learned, we should be able to run 1 psig and get steam everywhere it needs to go.

We have a heat timer multi-mod platinum controller which is enabled by a thermostat on the first floor.  The T-stat is not in an ideal location (inside the operation managers office).  I'm trying to get them to move it to an interior wall.

I believe that the boilers are over sized.  We replaced a 2000 mbh input cast iron sectional with atmospheric burners with two each 1600 mbh vertical fire tubes with 3:1 turndown on forced draft burners.  I don't know if the system is calling for two boilers to fire or in the morning or not, I need to be there early one morning to witness the action.