Hi
So I had a contractor removed and installed a new steam boiler.
He is supposed to come back and do a skimming on the system after 2 weeks, but he never came back.
My urgent question:
- The automatic feeder that he installed along with the boiler keep (re-feeding) even after it reached max level
Remaining Concern:
- The thermostat never reached what was set. The room temperature is always below the thermostat temp by 2 degree. I showed it to the contractor, but there was nothing he could do. (our old heat, the room temp reached the thermostat)
- The heat/room seems to take so long to achieve or reach the thermostat. (old system, set to 72 degree, and it took like 10-15 minutes to reach it). The new system takes forever (1-2 hour), is it normal? Is the system too small for the house or just an efficiency design for the new system?
What is your thought?
I have and HVAC license and without being there it sounds like it is taking too long to heat because the feeder is letting too much water into the boiler and it is taking too long to make steam. The feeder should be wired into the low water cut off mounted near the sight glass usually. Once the lwc is satisfied it should let the feeder know to stop feeding. Check out the Btus on the boiler and look it up online with the square footage of the house to see if it is big enough. It sounds like a wiring problem with your installation.
Hi
@John Knight, @Tom W., and @Jeffrey VanGilder I am sorry for the delay response. Thank you for the input.
I want to wait until the contractor got here before responding.
Yes, after he went through the skimming process, it appears that the gauge glass remains stable when the heat is on. I checked the low water cut off, and it seems to work OK now. I drained the water, and after the water went below a certain level, the re-feed kicks in.
Initially before the skimming, water keeps coming into the gauge glass and bouncing around like crazy.
Does anyone have a formulas to calculate how big of a system I need?
My house is 1520 sq ft ish. I have 5 active radiator steamers. I think they range from about 5-10 columns.
My current replacement system is a Slant Fin, Galaxy (Gas Fired Steam Boiler) GXHA-100 *.
CSA Input BTU/HR = 100,000
DOE Capacity BTU/HR = 81,000
Net Ahri Steam sq ft = 254
Net Ahri Steam BTU/HR = 61,000
When we are talking input and calculation, which one of the above numbers is important?
FYI: To be honest I had no idea how/why the contractor pick this system with this input ... etc
Thank you
When it comes to sizing replacement steam boilers, the Net Steam Sq Ft is the important number. This relates directly to the size and quantity of the radiators. Each radiator has a specific free internal area to hold the steam. There are charts that show various types and styles of radiators that give the calculated area per radiator section. This number is multiplied by the number of sections to give the area per radiator then multiplied by the number of radiators for the total sq footage of steam required. The replacement boiler must be sized so that it's net steam square footage output is at least as large as the calculated number. If the boiler's output is too low it will run out of water before the radiation system is completely filled with steam. This will cause the autofeeder to kick on and add additional water. When the steam in the system condenses back to water and makes its way back to the boiler it will flood the boiler.
Unfortunately, I don't know what your radiators look like so I can't really help you on the sizing at this point. If your contractor didn't take a walk through the house and inspect each of the radiators then he probably did not size the replacement boiler that way. Very often contractors will size the replacement boiler based on the size of the old one. This will usually not cause any operational problems but sometimes results in the new boiler being larger than it needs to be. Back in the day when these old boilers were installed, energy efficiency was not a prime concern so the thinking was that bigger is better.
From your description it sounds as though the skimming procedure has solved your problem. With a 1500 sq ft house, which I assume is older with less than ideal insulation, a boiler with a net 61,000 BTU steam output is probably just about right. If the water level in the glass remains fairly stable during operation and does not continually drop low enough to activate the autofeeder when firing then I think its safe to say you will be ok.
@Tom W. look online for the burnham heating helper. You can find the info in there. Look for the steam radiator edr