Pressuretrol Question

James W.Stamo

Marc_3

Pressuretrol Question

I'm renting a cottage (garage with apartment over it) with (mostly) one pipe steam heat, and after reading alot of the material here, I've learned an awful lot. The system is a one pipe steam system in the upstairs, and there are radiators in the garage section that are two pipe with an air vent. We've cleaned all the air-vents by boiling in water/vinegar, and the main vent (hoffman 75) was replaced by a local plumber/heater. He also turned the cut-in pressure down to .5 pounds. It was much higher when I moved in.

We installed a Honeywell CT3500A thermostat, and have the setback on it to go to 63 overnight, 67 in the morning, 62 in the day, and 68 in the evening.

In the morning, the thermostat kicks on, and the radiators fill with steam, and the air vents on the radiators seal. However, the boiler continues to fire for 10 minutes past this point, as the thermostat is usually still calling for heat. So we get these periodic "blow-offs" from the radiator vents as they vent excess steam. The thermostat then shuts the boiler down, and everything is fine. There is overshoot, but thats why we only set it up to 67 or 68. I'm concerned that this last 10 minutes of boiling time is unnecessary, and that it's really a waste of fuel when the boiler should be off. I'm under the impression, having read stuff here, that the cut-out on the pressuretrol needs to be lowered. I know my cut-in is .5 pounds, which is where it is supposed to be, but I don't know about the cut-out or differential. I can't find it on my pressuretrol.

The pressuretrol is a blue/gray box made by Honeywell. On the left side of the front face, there is a meter for the cut-in, with the adjustment screw on the top of the unit. There is another screw on the bottom of the front face, in the center. I don't know where to find the cut-out or differential.

The side of the unit has 8150 PA404A 1009 2 stamped on it.

I don't want to mess anything up, but I'm a fairly technical and handy guy, and figured it would be worth at least finding out whether my cutout is too high, and if so, lowering it slowly.

Any help would be appreciated. This site has been very helpful. Thanks in advance.

chuck shaw

the screw

on the bottom center removes the cover, inside, you will find the diff pressure wheel. set this to one. That will give you a cut out pressure of 1.5 pounds.

hope this helps.

Chuck Shaw

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Unknown

As Chuck stated

the CutOut pressure is determined by setting the CutIn and the Differential and adding them together. The Differential dial is inside the control to the left side. But I would be more concerned with your thermostat Heat Anticipator setting and not the boiler pressure. If you are overriding room temperature, you need to adjust this. I'm not so sure about the CT model, but most of the digital Honeywell Setback tstats have two or three screw terminals that you have to adjust for the type of system you are controlling. If my memory serves me right (and sometimes it does ;-)) the thermostat normally comes set for a Warm Air system. You probably want to set it for a Gravity Water Setting. Take a look at your thermostat owner's manual as it is described in there. Hope this helps.

Glenn Stanton

Burnham Hydronics

David Efflandt

I have

> I'm renting a cottage (garage with apartment over

> it) with (mostly) one pipe steam heat, and after

> reading alot of the material here, I've learned

> an awful lot. The system is a one pipe steam

> system in the upstairs, and there are radiators

> in the garage section that are two pipe with an

> air vent. We've cleaned all the air-vents by

> boiling in water/vinegar, and the main vent

> (hoffman 75) was replaced by a local

> plumber/heater. He also turned the cut-in

> pressure down to .5 pounds. It was much higher

> when I moved in.

>

> We installed a Honeywell

> CT3500A thermostat, and have the setback on it to

> go to 63 overnight, 67 in the morning, 62 in the

> day, and 68 in the evening.

>

> In the morning,

> the thermostat kicks on, and the radiators fill

> with steam, and the air vents on the radiators

> seal. However, the boiler continues to fire for

> 10 minutes past this point, as the thermostat is

> usually still calling for heat. So we get these

> periodic "blow-offs" from the radiator vents as

> they vent excess steam. The thermostat then

> shuts the boiler down, and everything is fine.

> There is overshoot, but thats why we only set it

> up to 67 or 68. I'm concerned that this last 10

> minutes of boiling time is unnecessary, and that

> it's really a waste of fuel when the boiler

> should be off. I'm under the impression, having

> read stuff here, that the cut-out on the

> pressuretrol needs to be lowered. I know my

> cut-in is .5 pounds, which is where it is

> supposed to be, but I don't know about the

> cut-out or differential. I can't find it on my

> pressuretrol.

>

> The pressuretrol is a blue/gray

> box made by Honeywell. On the left side of the

> front face, there is a meter for the cut-in, with

> the adjustment screw on the top of the unit.

> There is another screw on the bottom of the front

> face, in the center. I don't know where to find

> the cut-out or differential.

>

> The side of the

> unit has 8150 PA404A 1009 2 stamped on it.

>

> I

> don't want to mess anything up, but I'm a fairly

> technical and handy guy, and figured it would be

> worth at least finding out whether my cutout is

> too high, and if so, lowering it slowly.

>

> Any

> help would be appreciated. This site has been

> very helpful. Thanks in advance.

David Efflandt

I have CT3500 on steam

You should set the 3500 for steam/gravity (1 cycle per hr). It has to go through a learning period to learn how long to run, and what it needs to do to arrive at set temp at set time (Smart Recovery). That may take a few days to a week (whatever the manual says). After that it should seldom overshoot unless the weather turns mild.

You might want to make sure the pigtail the pressuretrol is attached to is not plugged. Mine was cranked way up when I bought my home, apparently due to a faulty vent damper (that would not reopen while hot). My pressure gauge was also faulty and snubber it was on was blocked.

Air vents should just vent air, not steam or water. It is normal for them to stop venting when the radiator gets fully hot (or pressure gets too high), and then possibly vent more air if the boiler starts pressure cycling (some only vent up to 1.5 psi).

Marc_3

Honeywell

The CT3500A is 5-1-1 digital setback thermostat with "adaptive recovery"... I set it to steam the day I got it. I recently changed the morning program, so we'll see if it learns slightly quicker. I feel like every time I hit the "Run Program" button, it resets the memory. Not sure though. Also, the weather has been up and down lately in this area (CT).

The vents don't purge water. They do let loose some steam on these "blow offs" and I'm not sure why. They used to let loose a lot of steam (weren't sealing) so I pulled them all off and boiled them for a while. They all seal now, except they do this blow-off thing periodically, if the system runs for a long time.

How would I know if the pigtail on the pressuretrol is clogged? (Keep in mind, I'm not a plumber. I'm a 23 year-old with a technical mind. I'm reluctant to play too much, especially in a rental.) I figured I would try lowering the pressure, just to make sure that's not causing any problems.

So, all I have to do is unscrew the screw on the bottom center of the front face of the pressuretrol and pull off the cover? Inside, what will I find? A screw to turn to change the pressure? (Someone said a "wheel"..?)

Thanks alot for all the help. While people are responding, does anyone care to explain what the cut-in setting really means? What's physically happening here? Cutting out at high pressure makes sense, but I'm not sure the cut-in makes sense.

Thanks.