Pressuretrol

mcp1

I have a single loop system with 1 zone in a old 1600 sq ft colony. What should the pressuretrol be set at? My 2nd floor gets incredibly hot.
This is what it is currently set at.

adambnyc

Everyone is going to need some additional details. Changing the Pressuretrol isn’t going to solve the issue of the second floor being hot. Your Pressuretrol is set a little bit high, but it’s not horrible. You can turn the main down to 2 or even better 1.5.

I have a similar issue as you. On freezing days, my second floor is very hot. This is because the first floor of my house is harder to heat for a variety of reasons, insulation, open floor plan, not enough radiators, etc.

If your house is like mine, the thermostat is located on the first floor. Your boiler will not stop pumping out steam until the thermostat is satisfied, which on very cold days can be challenging if your system isnt balanced.

You can change all the vents on your second floor radiators to a vari-vent and slow the steam and prevent the rads from going full hot. There are downsides to this as I’ve found. Adjusting the vents down leads to more pressure and higher rates of boiler cycling.

You can also look into TRV style vents but I hear mixed things on those.

Also, when the weather returns to something a bit more normal, you might find yourself messing with the vents again.

My next project is to add 2 additional radiators to my first floor to increase the heat and start sealing up air leaks in the house.

mcp1

Thank you, I have changed most of the vents to TRV and the rest to Vari-vents. My downstairs is an open floor plan with an open stair which most likely acts as a flue. I've tried a lot of different things but not much has worked. I read on someone's post that dialing down the pressuretrol might help. I'm a real novice when it comes to steam heat; learning as I go.

adambnyc

With the TRVs and the varivents, are your second floor rads getting completely hot all the way across?

mcp1

Yes, all the radiators are hot to the touch all the way across.

Fred

@mcp1 , Turn your "Main" scale down to 2 and the Differential Scale down to .5. That will cap your Pressure at 1.5PSI which is the most you want, if the boiler short cycles at all or for a normal safety setting. It might help your second floor a little. I had a similar problem with my second floor at one time. I found that good main venting helped a lot, in that it allowed the boiler to run shorter cycles and it also prevented some of the second floor radiators from starting to heat as the back pressure from poor main venting caused the steam to take a path with less resistance, that being some of the second floor and first floor radiators. Do you have good main venting on your system?
Also, if you have a programmable thermostat, make sure it is programmed for steam heat, being a setting of 1 or 2 cycles per hour. They come with a factory default setting of 5, for forced air systems.
Make sure your thermostat is located in an area where the room temp is representative of the average temps in the house. If it is located in an area that is the coldest room in the house, or in a place that is drafty, like near a door or on an outside wall, it will call for heat more than it probably should. Make sure the hole in the wall, behind the thermostat, where the wires come through, is plugged with insulation. I was surprised how much draft came out of that hole and fed the backside of the thermostat.

Danny Scully

@fred, this pressuretrol is subractive. Diff should be 1.5, main should be 2. Start there and let us know how it goes.

Fred

@Danny Scully , Sorry, my bad!

mcp1

Thank you Fred, very helpful. Yes I have 4 vents coming off my main, which I installed about a year ago; I only notice a slight change with that. I haven't checked my thermostat yet, but it has been acting up and it's on an outside wall. Can you recommend a good thermostat for a gas fed steam boiler? Here a some pictures of the vents coming off the main.

Fred

I have a Honeywell model # RTH7400. It is programmable and has 1,2,3,4 and 5 cycles that you can program. Many thermostats don't have the "2" cycle option and it is nice to have. Sometimes 1 is not enough and 3 is too much for steam. This model does not have WiFi but it has been great for my steam system. If you look at other models, just make sure it gives you the full 1 through 5 cycle option.

mcp1

Thank you. I don't need the wifi. This seems like a silly question, but what do the cycles 1-5 mean and how do I know which cycle to choose?

Fred

Do you have some pitch on that Vent antler to allow water to drain back to the main? If not, the one or two vents towards the end of that antler may not be venting at all.

mcp1

I wil check. If the don't, can I just put a strap on the end of the antler to pull it up some?

Fred

If it has some give. Otherwise you may need to use two 45's into the Tee to give you some swing. You don't need much.

mcp1

There is a slight pitch on the antler back to the main. Should the pitch be noticeable with the nake eye?

Fred

If you have a 1/4" that should be fine.

mcp1

I just noticed Danny's post. Should I set the pressuretrol Main to 2 & the Diff to 1.5? Because I set the Diff at .5 already.

Fred

@mcp1 , yes, set it at 1.5. That will make the Cut-in .5PSI and the total pressure 2 PSI. My mistake!

mcp1

No problem, I really appreciate your help with this issue.