Steam boiler pressuretrol differential dial setting

RuffinoVino

I have a Weil McLain EG steam boiler 1 pipe system located in the basement The house is single family, 40' long and 20' wide and has 2 floors in addition to the basement. The first floor has 1 radiator in the back kitchen/dining room approximately 30' from the boiler and 1 in the front living room about 10' from the boiler. The 2nd floor has 1 radiator in the master bedroom above the living room, 1 radiator in the bathroom directly above the boiler, 1 radiator in the bedroom directly above the dining room and 1 small radiator in the smallest bedroom adjacent to the previous bedroom. 

I have the Honeywell pressuretrol cut in set to .5 psi(the screw is turned as far as can go) and the differential dial indicator at just about halfway between the numbers 1 and 2. ( Halfway between the 1 and 2 and lined up with the black line above it).

The issue that I'm having is when I turn the thermostat up 1 degree from the set temperature or when the first run of the morning (2-3 degree increase) occurs the boiler will run for approximately 30-35 mins and shut off for 4-5 mins even though the thermostat is not satisfied. After 4-5 mins it will fire up again and run for either the minimum run time I have the thermostat set to which is 5 mins or it will run until the thermostat is satisfied usually 10-15 more mins).  All of the radiators are heating and heating pretty well balanced.

I don't understand why the boiler shuts off after only 30-35 mins and I'm wondering if I should increase the differential to closer to 2? I know articles have suggested to set the differential dial to 1 but I'm assuming this will further shorten my boiler cycle run time from where it is now so I haven't done this. Isn't the boiler supposed to run non stop as long as required to satisfy the thermostat unless the pressure reaches the cut out? Or should the boiler shut off and restart more than one time a heating cycle by having the pressuretrol differential set closer to 1 to have the cut out lower and allow the boiler to shut off prior to the thermostat being satisfied then restart a few minutes later until the thermostat is satisfied or again the pressure builds to the cutoff?

When the thermostat is at it's set point throughout the day it will turn on every hour and a half or so(depending on how cold it is outside but example in mid 30s) and within 4-6 mins the steam has hit the end of the runs on both sides of the house evenly so it's operating efficiently from the last stand point.

The house has all new windows, new doors new insulation and has very little draft so when the thermostat is satisfied even when it's 30 degrees outside the inside heat retains for more than an hour and a half. 

Does this seem like any issue or something I should try and tweek?

Additionally, the only other odd thing is the smallest radiator which is furthest from the boiler gets hot at the bottom opposite end of the valve before the top and side where the steam enters the radiator. I have a D vent in this one. Has anyone seen this radiator issue before?

EdTheHeaterMan

With your description of the situation, there is no proof that the pressuretrol is the reason the burner is going off or if the thermostat has a timer that stops the call for heat for 5 minutes once it times out. (unless you have the old mercury bulb switch controls, you can't see the position of the switch inside the control.

To be sure the pressure control is the reason the burner stops, you will need a meter that measures voltage.

By your description of the timing for burner ON burner OFF and how the steam reaches the radiators, there is nothing you need to do. Your steamer is working just fine! Call me when you have a real problem! LOL

Jamie Hall

As @EdTheHeaterMan implies, your boiler is working just the way it is supposed to work. It's just that it can make more steam than your radiators can absorb -- so it has to quit for a while to let them catch up. You'll do just as well -- if not better -- on fuel usage if you turn the differential to 1. Less stress on everything, too.

RuffinoVino

I guess I'm wondering if it's more efficient to have the differential dial lower set to 1 and have the boiler hit the pressure and shut off after 15 mins or so then restart rather than run the full time needed to satisfy the thermostat in 1 run. Also in response to Ed regarding how I know the minimum run time setting is because I have a Ecobee thermostat that allows you select how many minutes you want the boiler to run at a minimum. I set this to 5 minutes.

Jamie Hall

Significantly more efficient to have the boiler shut off when it has made enough steam! Any extra run time after the pressure has gotten even to a pound or so is just wasted fuel.

Now in an ideal world the boiler would be just the right size to make just the right amount of steam to heat all the radiators, but no more, and would never make much pressure and would never shut off on pressure. Right. Happens rarely. Much more commonly the boiler is bigger than really needed, like yours, and so it gets to take a rest from time to time.

RuffinoVino

Ok. Just so I'm understanding correctly if the pressuretrol differential dial is set to 1 and the boiler fires up from a call for heat from the thermostat and shuts down after 12-15 mins without being satisfied and then restarts 5 mins later for another 15 mins to then satisfy the thermostat your saying this is more efficient then having the boiler run for 30 mins straight?

Jamie Hall

No -- but you're forgetting that during that 5 minute shutdown the radiators are still heating, even though the boiler isn't burning any oil. So you have a total runtime to satisfy the thermostat of say 35 minutes. If the boiler doesn't shut down on pressure, you have a boiler run time of 35 minutes also. If it does, however, to let the radiators catch up, it only runs for 30 minutes -- a 5 minute savings, or some 16 percent or so on the fuel burn.

In other words, as long as the radiators are hot, it's going to take 35 minutes to satisfy the thermostat, whether the boiler is running all that time or not.

RuffinoVino

Ok thanks. Any thoughts on the one radiator that is heating first on the opposite side of the inlet and the bottom up?

Jamie Hall

Whimsy?