New single pipe steam heat owner - Oversized Boiler

1920cottage

Hi,
I am a new homeowner and with that a new single pipe steam heat system owner. I've read "we got steam heat" and many posts here that have helped me understand the system, thanks! I'm an engineer and have really gotten into trying to make the system run as best as it can.

The primary issue has been that the first few radiators in the line get fully hot fast and the boiler generally shuts off before the last radiator receives any steam. There is a single 2 inch main that is 115 ft. long (this seems long compared to other systems I've read about here). There was a single Gorton #1 main vent at the end of the main that I have replaced with a Gorton #2. I'm thinking I should put in two more Gorton #2's (for three total) but have been holding off on that until budget permits. There are 11 radiators in the system with Gorton vents of various sizes that seem reasonable, but could be tweaked for better balance. Some of the vents whistle or have a whooshing sound, I believe more main venting would help. There is a subtractive pressuretrol set to 1.5 on the main and 1 on the differential.

Most of the main and runouts to radiators have .5 inch fiberglass insulation. None of the joints are insulated. There was an addition put on the house and the runouts to three radiators and some of the main line there have no insulation at all. My next planned step was to insulate all pipes with 1 inch fiberglass insulation (I've already purchased this), which I hope will help get steam reach the last radiator during a cycle. I did not purchase joint covers yet, I was planning to hold off on that until next year for time/budget reasons.

However, I calculated my radiator EDR today and got 355. The house has a Burnham IN6 boiler, rated at 450 EDR, it is oversized! Now I am concerned that if I improve the insulation significantly, I could cause other problems like short cycling, etc.

So, should I proceed with the 1 inch insulation project? Would it make any sense to leave the joints uninsulated to leave some load for the oversized boiler? Any other tips on coexisting with the oversized boiler or this system in general would be appreciated.

Thanks!

Hap_Hazzard

Are the vents on the radiators nearest the thermostat #4s? How close to the thermostat are they?

Where are you located?

1920cottage

I initially posted this in the wrong category and in moving to the correct category, the following informative reply by Jamie Hall was deleted, thanks for the info Jamie!:

"Yes indeed -- proceed with the insulation. The insulation does two things, not one: the obvious one is it reduces the heat loss from the pipes which. The much less obvious thing is that in the process it reduces condensation in the pipes as the system is starting. This excess condensation in the pipes slows the speed at which the steam front can travel along the pipe -- regardless of how much venting you have. Therefore, it can only help. The excess boiler capacity isn't affected by that, one way or the other -- where that is going to show up as cycling (which you can't help much) once the whole system is up to temperature.

Don't worry about the joints at least at the moment. They're pretty minor in the overall scheme of things.

Your 115 foot main is indeed longer than usual. One does wonder sometimes what the pipe fitters were thinking... But before you go out and plunk down much gold for a couple of Gorton #2, go out and plunk down very little gold for a good 0 to 3 psi pressure gauge and a few fittings and hook it up to the same pigtail as the pressuretrol, and then spend some enjoyable time watching it when the system fires from a cool start. This will tell you -- far better than our fancy charts -- whether you really need more main venting or not.

If your main venting is adequate, as the burner starts up you will see a small pressure rise on your new gauge -- the exact pressure it gets to really doesn't matter, but it will probably be around 4 ounces to perhaps half a pound. Then, if your main venting is adequate, the rise will slow down or almost stop and the system will perc. along until most, if not all, of the radiation is getting steam. Then it will start to rise again as all the vents close. On the other hand, if the venting isn't adequate, the pressure will just keep on rising."

Hap_Hazzard

I agree with Jamie about the joints. You find them very useful while you're working on balancing your system, because you can feel them or hit them with a non-contact thermometer to tell when the steam gets to them.

1920cottage

Thanks for the tip on the joints. I've occasionally been timing heat flow from the boiler to the main vent and was curious how I would do that with everything fully insulated.

The radiator in the room with the thermostat does have a number 4. The radiator and thermostat are on the same wall, maybe ten feet apart, with a large open doorway between them. The other downstairs radiators at the start of the line that heat up fast have number 5's and one has a 6. Downstairs radiators toward the end of the line have 6's and these don't get much heat during a steam cycle. The upstairs radiators have C's and D's.

I am in New York and have been keeping the digital thermostat at 65 degrees full time (I don't mind it a little cooler and was thinking I'd save fuel with a lower temp). The house gets a lot of morning sun and the system hasn't run much during the day. From reading other posts here, it seems like the system would probably run better at a higher temperature, especially when all the pipes are properly insulated?

Jamie Hall

The system really doesn't care what the numbers on the thermostat say -- the only thing of significance to the system as a whole is the difference between the interior temperature and the exterior temperature (well, within reason!). What most steam systems do care about is setbacks: there are differences of opinion, but it seems to me that most folks find that setbacks of more than about 3 degrees F aren't helpful in fuel savings.

Running the house cooler all the time will indeed save fuel.

On the venting -- once you are more or less happy with the main venting, you can start balancing to suit. It usually works better if you slow down spaces which get too warm, or heat up to fast, rather than trying so speed up spaces which are chilly or laggard, at least at first.

Fred

The Main is 115 ft. long. How long is it up to the last radiator run-out? Anything past that really doesn't need to be vented and you can get a lot of benefit out of putting your main vent as close to the last radiator run-out as possible.
Also, your Pressuretrol is set correctly but when was the last time someone took the Pressuretrol off of the pigtail and cleaned the pigtail out? They get clogged and the Pressuretrol can't see the system pressure. The higher the pressure, the slower the steam movement through the system.

Hap_Hazzard

Also, if you flip the vent on the radiator nearest the thermostat upside-down, you can temporarily turn it off so you can see how long it takes the other radiators to get hot.

1920cottage

Thanks all for the tips. The last runout is about 5 feet or less from the main vent. Unfortunately, when an addition was put on the house, the main line was extended by 50 feet to add three radiators at the far end of the addition. The first 7 runouts in the line are within the first 50 feet of the main, then there is a 30 foot gap to the three radiators at the back of the addition spaced along a 15 foot section. Then another uninsulated 15 foot gap to the last runout, plus 5 feet to the main vent.

I have no idea when if any maintenance was done by the previous owner so I'll definitely take a look at the pigtail. Thanks

Fred

1920cottage said:

Thanks all for the tips. The last runout is about 5 feet or less from the main vent. Unfortunately, when an addition was put on the house, the main line was extended by 50 feet to add three radiators at the far end of the addition. The first 7 runouts in the line are within the first 50 feet of the main, then there is a 30 foot gap to the three radiators at the back of the addition spaced along a 15 foot section. Then another uninsulated 15 foot gap to the last runout, plus 5 feet to the main vent.

I have no idea when if any maintenance was done by the previous owner so I'll definitely take a look at the pigtail. Thanks

That 50ft. extension is likely where the issue came into play. I would certainly make sure all the main is insulated (in particular the 15ft section that is not insulated) and I would do as you suggested in your original post and add two more Gorton #2's or one Barnes and Jones Big Mouth (has the venting capacity of about 2.5 Gorton #2's). The big Mouth is available from Supplyhouse.com and costs about the same as one Gorton.
https://www.supplyhouse.com/sh/control/search/~SEARCH_STRING=Barnes Jones Big Mouth?searchText=Barnes+and+Jones+Big+Mouth

gfrbrookline

I have seven Big Mouths and two Gorton #2's on my mains, placed on my dry returns. You get a lot of bang for your buck with the Big Mouth, the venting capacity and build quality are outstanding.

coelcanth

is the thermostat shutting down the boiler when it has reached its true set temperature ?

if not, you might want to check the settings for cycles per hour or anticipator