Cold rads and boiler cycle time

sobriquet

Hello, this will be my third winter with steam and I'm still not satisfied with my systems performance. I've done a lot of research and asked a lot of questions here and am constantly trying to make my system more efficient. I have an old 2500 sqft home, 15 one pipe radiators. I have 4 gorton no 2 mains, 2 at the end of each main. All rads have hoffman 1a vents. It's about 35 degrees outside right now and my thermostat is set at 68. It's 68 downstairs and about 64/65 upstairs. There are probably only 3 or 4 rads that are actually warm right now. My boiler runs for about 5 mins, shuts down and restarts every 30-40 min. All upstairs rads are cold except for one that I recently installed a gorton no c in, and that only just gets a bit warm at the bottom where the pipe connects. I have thermometers in the house that say it's 68 but shouldn't some of these radiators be hot? It always feels chilly, especially upstairs. Most of the rads are baseboard style. I believe I have my pressuretrol set to 1.5 cut out with 1 diff. Would replacing the Hoffmann with gortons make a difference? I suppose my problem is rad venting or pressure?

BobC

What kind of thermostat are you using, is it set up for steam (1 or 2 cycles per hour)?

Have you timed how long it takes the steam to get from the boiler header to the end of each main? Do both mains heat up at about the same time?

How long are the pipes that connect the radiators to the steam mains? Does the steam seem to heat those pipes up at the same rate? Have you checked the piping with a levl to be sure the pitch is right? Check that there are no sags along the length of the pipes.

What is the EDR of the boiler and the total radiator EDR?

Bob

Fred

A five minute heating cycle is way to short to heat the rads. It probably takes that long just to heat the mains. What kind of Thermostat do you have? If it is a digital/programable one, it should have the ability to set the number of cycles per hour. Make sure it is programed for steam which is typically 1 cycle per hour. Some like 2 cycles per hour. If you did not change that when it was installed, they come factory programed for forced air which is 5 cycles per hour. If you have the older, round thermostat, they have a heat anticipater that needs to be adjusted to give you a longer run cycle.

Jamie Hall

In addition to what the fellows above had said, two thoughts: first, you say that your thermostat is set for 68, and it is 68 downstairs... if I assume that your thermostat is downstairs, except for the potential cycle interval problem, seems to me that it's working.

Which doesn't help the cold upstairs, eh? Several possibilities there. First, and perhaps most obvious, is to increase the venting on the upstairs radiators and decrease it on the downstairs ones. Second, if there is a big radiator near your thermostat, you may want to really slow that one down.

But the major thought is... if the house is holding 68, as you say, there is no reason for the radiators to be any hotter than they are, is there? Seems to me that the downstairs ones, at least, are doing exactly what you are telling them to do...

sobriquet

The thermostat is an old Honeywell chronotherm. I have no idea if it is compatible with steam. Once the boiler fires up, the ends of the mains are very hot within 2-3 minutes and both mains seems to be the same temp at the same time. The first floor rads are connected with about 3 - 5 ft of pipe from the mains. The second floor rads are obviously a straight shot from the first. I have not checked the mains with a level, but I know the return pipe is correctly pitched. If it's relevant, I recently removed most of the radiators during some major house work. All rads were cleaned, some painted and reinstalled, all pitched with a level, sole maybe pitched more than necessary but I didn't think it would matter. I haven't calculated the total edr of all radiators, I'm not sure how to determine it from baseboard style rads. I believe the boiler btu is 225k, I'd have to double check that though. I can figure out the rad edr soon if that's something you need to know

JUGHNE

So everything is 1 pipe steam? You said most of your rad are baseboard type, are the others cast iron (old school). Which ones give the best comfort?
How long are the baseboard ones and they have to have a fair slope on them if they are connected to a 1 pipe system.

Supposedly cast iron rads and BB heaters do not play well together. CI take a long time to heat up and stay hot perhaps until the next cycle of firing. BB heaters are pretty on and off with not enough meat to hold heat.

I say all this so others above replying are aware of the BB heaters.........Have you tried just setting the T-stat at 70 and see what that gets you?

sobriquet

I'll have to look into the thermostat and find out if I can change the cycle setting. That's my problem, Jamie. I don't know if I even have a problem at all. My house is 68 and the boiler doesn't run too often, but most of my rads stay cold. I have the radiator turned off (vent turned upside down) in the room with the thermostat. The second floor rads are set to vent quicker than downstairs, though these hoffman vents don't seem too precise or reliable.

BobC

If you take the cover off the cronotherm can you see an anticipator, if so what is it set to? How close is the thermostat to the radiator in it's room? Make sure there isn't a steam pipe running up through the wall the thermostat is on.

If the mains are heating up that fast the pitch must be ok, make sure the pipes that feed the second floor radiators have good pitch. You also might want to try some maid o mist vents that come with multiple orifices on the second floor. On my system I find I need #6's on long piping runs, your system may not be the same.

The radiators should be vented proportionally by the total volume of the radiator and the pipe that feeds it. You have to be careful when adjusting the Hoffman valves to be sure you center the cap before you tighten the screw so you get the venting rate you expect. What do you have the vents set to right now?

http://www.amazon.com/Maid-Steam-Angle-Radiator-Valve/dp/B003DV3AGE/ref=sr_1_2?ie=UTF8&qid=1449368639&sr=8-2&keywords=maid+o+mist+5L

The Hoffman vents at a rate of 0.02 to 0.145 CFM, The Maid O Mist from 0.028 to 0.341 CFM. You should not need the top rate in most cases.

Bob

sobriquet

Jughne - the old school cast rads definitely retain heat and seem hotter than the baseboards. I'd love to replace the baseboards with ci but don't really have the money or time right now. It's definitely on my long term to do list. On a cold start or a large temp change request, the boiler runs longer and the upstairs rads heat up. But once temp is reached, everything eventually cools down.

BobC

If the baseboards are copper pipe/ aluminum fin type you have a compatibility problem because they have a completely different heating characteristic than the cast iron does.

How is the insulation on the second floor?

Bob

sobriquet

The anticipator is set to one end of the scale, believe it says 1.2. are the maid of mists better than the gortons? The farthest bedroom has a gorton c, the other upstairs rooms are hoffmans set at 5 or 6, everything downstairs is set at 2 3 or 4. Thermostat room is turned off completely

BobC

The maid o mist is similar to the gortons, that kit I highlighted is handy because you can swap the orifices. Another war is to buy MOM #5's and drill out the removable orifice to whatever you need. It's a shame Gorton doesn't use the removable orifices.

Bob

sobriquet

The baseboards I believe are cast iron pipe with steel fins, circular. Insulation? Good one! House was built in 1842, solid brick exterior walls with plastered interior. Above the second floor is an uninsulated attic, plaster ceilings, with standing seam metal roof that has original wood shingles underneath. But attic door is weathersealed, if that's worth anything.

Fred

Some insulation in that attic would go a long way towards fixing the problem.

BobC

That type of baseboard is better than the new stuff. If I were you I'd get that attic insulated with blown cellulose, that will do A LOT more than almost anything else for the money it will cost. You are losing huge amounts of heat through that ceiling.

Does the house have any knob and tubing wiring?

Bob

sobriquet

Well I believe some areas of the attic floor have old insulation underneath (maybe mineral wool). Is it typical for a steam heated home to have cool radiators but an acceptable ambient temperature? No knob and tube wiring, updated in the 50s or 60s by the looks of things, I'm slowly rewiring. Should I assume my thermostat and boiler are operating correctly? That my problem is just poor insulation, undersized radiators and maybe some under vented radiators?

BobC

If your downstairs is comfortable I would assume the thermostat is doing it's job. Insulating the second floor ceiling and optimizing the venting looks like the right path. Sufficient radiator venting should help but it's hard to judge with outside temps n the 40's and 50's.

Bob

Mark N

Sobriquet, I would suggest you get yourself a copy of "We Got Steam Heat!". Its a great read for a owner of a steam heating system. I've lived with mine for 27 years. The way you describe that your system is heating is not right. A 5 minute on cycle is not long enough to properly distribute the steam. A proper steam on cycle is around 20 minutes according to "We Got Steam Heat!". From my own experiences that is very true when maintaining temperature and not recovering from a set back. With proper venting the steam should arrive at all the rads at approximately the same time. If the rad was properly sized for the room and they all heat the same, say 1/3 of the rad hot, all rooms will be the same temp. All rads should heat equally every cycle. I suggest you look at the PDF of "It's All in The Venting" thats in the Old Steam section of the Heating Museum here on Heatinghelp.com. You need to determine why the boiler is shutting off after only 5 minutes. Is it the thermostat or another control.

Mark N

Also, you have a thermostat with an anticipator. Does it also have a mercury bulb? If so it needs to be level to operate properly. The anticipator needs to be set properly to set the cycle rate. The manual for Burnham boiler states to set it for 0.8.
I would check the level and try 1.0 on the anticipator. Setting to 1.2 should cause the boiler to run a long cycle with a large temp swing.