Thermostat or not?

Unknown

I run an 30's model steam boiler 2 pipe system in an older courthouse.

There is a thermostat on the second floor.

Each cast sectional has standard old hoffman control valves.

With a pressuretrol at the boiler why is there a thermostat?

Should not the temp. be controlled by the user at the radiators themselves?

The pressuretrol with a press diff is supposed to be the control, is it not? and the diff is to be responsible for the cycles, true?

I can not express my dismay and I am being told by a "boiler co." that the tehermostat is to control the temp and the pressuretrol is to be the "limit" control!!!



Can I get confirmation or denial either way???

Thanks!

J.P.

Alan (California Radiant) Forbes

Unless

the boiler is perfectly sized to the heat loss of the building, you need a thermostat.  Without the thermostat, the boiler has no way of knowing how warm it is inside the building.  Without the thermostat, the rooms will overheat.



The heat loss of the building is dynamic; low heat loss when outdoor temperatures are mild and a high heat loss when it's freezing outside and the thermostat (in your case) is the only way the boiler knows what it's like out there.

Ted_4

Steam Control

You don't say whether your question comes because of problems you have heating the building, but I can imagine that there may be comfort problems with a single thermostat controlling the boiler, plus individual radiator controls. 

 A single thermostat can sense temperature only in the zone where it is located, thus the cycle length is dependent on what is happening in one zone only.  Others zones may not get the right amount of steam.

The pressuretrol controls the burner, and keeps the steam pressure between high and low limits during a steaming cycle.  It has nothing to do with the length of the cycle per se.

Where you have many independent zones,  controlling the boiler  with a device such as a "Heat TImer" may serve better.  A device like this is a cycling control that bases the steaming cycle length on outdoor temperature: the colder it is, the longer each heating cycle is.  The radiator controls will then vary the steam to the radiators to control indoor temperature. 

With a cycling control you can get additional goodies, like night setback and morning boost.  Make sure the installer knows how to set the unit up properly, and you'll be all set.  It will be helpful if you understand the control basics as well, to be able to make adjustments to tune the control to your building's characteristics.

http://www.heat-timer.com/En/ProductDetail.aspx?Id=5

.

nicholas bonham-carter

courthouse boiler

what are the settings on the pressure control? if they are too high, then the system will tend to overheat, and/or be noisy.

if you could describe to us any symptoms, we could better advise.

"the lost art of steam heating" from the shop here would explain much better than i could the functions of the entire steam system, and in particular pressure control, and thermostat anticipation settings. basically, the boiler is fired on command by the thermostat, as the room temperature falls below the set-point, and while it runs to make steam, the pressure of the steam is kept lower than a set pressure by the pressure control. as it only take a few ounces per squ. inch to get the steam up into the radiators, there is no use in allowing the steam pressure to rise much above that. 

quite likely an outdoor reset control [tekmar 279, or heattimer] would give you  better comfort and economy, however they are no substitute for a well vented, balanced, and low pressure system.--nbc

Dinosaur Whisperer

pressures

I have the pressure set at 12oz. w/ a diff of 4oz.

There are 3 levels here and the t-stat is in the hall of the 2nd floor.

All doors are closed at night so the stat is isolated from most of the heat.

There is one radiator in the hall about twenty feet away but we have nearly 18 feet ceilings.

I just got a set back t-stat hoping it will help by raising the temp starting at 5 am.

I figured that the old timers knew there was no need for a t-stat, just windows.

I am getting ready to get thermostatic controls for ea. radiator, that should do the trick.



input welcome and asked for.

J.P.

Dinosaur Whisperer

t-stat

I have the pressure set at 12oz. w/ a diff of 4oz.

There are 3 levels here and the t-stat is in the hall of the 2nd floor.

All doors are closed at night so the stat is isolated from most of the heat.

There is one radiator in the hall about twenty feet away but we have nearly 18 feet ceilings.

I just got a set back t-stat hoping it will help by raising the temp starting at 5 am.

I figured that the old timers knew there was no need for a t-stat, just windows.

I am getting ready to get thermostatic controls for ea. radiator, that should do the trick.



input welcome and asked for.

Dinosaur Whisperer

right

the rooms get too warm and the hall, being closed off from the rooms, does not sense the right temp.

One of my predecessors removed a few of the radiators believing they were plugged since they would not heat and installed the t-stat.

For the last 20 yrs. they have had an operating pressure of 0 psi.

First thing I did was remove the Pressuretrol and install a vaporstat control, an oz. gauge,

replace the traps, replace the air-vents (all of which were original), clean the F&T's, and level all the radiators to slope toward return.



I am now considering installing thermostatic control valves at the radiators.

input please.

Dinosaur Whisperer

pressure

I might add that the gas pressure was set too low and the mixture and manifold pressures were mis adjusted as well.

I had a burner co. come and adjust both. I marked the damper positions after they were set, in case they get molested again in the future.

I have achieved a record high pressure of 8oz. after all my labors.

I was pleased with myself since true heat had not been achieved for 20 yrs.



I am finished bragging now.



Really now, should not thermostatic control valves remedy my over heating now???

J.P.

nicholas bonham-carter

courthouse overheating

why not move the thermostat to the coldest top floor corner room in the building, and set it for a couple of degrees cooler than the norm [64 deg]. the call for heat will come earlier, but be satisfied before the judges roast!

are all the radiators getting steam at the same time? remember that you cannot over-vent, and if this is an orifice system, the supplies could be vented as well to speed up the steam.

what about installing some ceiling fans for those high ceilings?

thermostatic valves would solve some problems, but they should be only installed after the system has been properly vented/maintained. good on you for the vaporstat, and low pressure gauge--you're almost there!--nbc

Dinosaur Whisperer

move the t-stat

I am very frustrated and here's why.

The top floor-where the court room is-has two split systems that service all but two offices, the judges chambers and emergency preparedness.

These two rooms are heated by steam.

The two levels below are all steam.

It has been 3 days since the setback t-stat and thing are much better.

It has not been very cold however.

I have it set to come on at 4am and run up to 74f and drop back to 68f at 6:30-5:00 then 60f from 5pm - 4am.

I still would like to hear about thermostatic controls for the radiators.

I may be wrong but believe that if I can maintain my 6-14oz. steam pressure then the thermostatic valves can be set for each area and life will be a little better for my sore ears.

Need input please!!!

Unknown

Heat Controls

Hi- Realistically with a two pipe system it should be possible to regulate the amount of steam which heats each room by closing opening the valves on each individual radiator. However since you are working with lawyers /judges most of which are "technically challenged" I can understand where you might want to automate this function so I've attached some links to info on TRVs.  Keep in mind TRVs will ONLY prevent overheating.

Here are links to info on Danfoss TRVs



http://na.heating.danfoss.com/PCMPDF/RA%202000%20Datasheet_5_05_08.pdf



http://na.heating.danfoss.com/PCMPDF/013R9356_VI51T622_standard.pdf



http://na.heating.danfoss.com/Content/161A8B0F-A195-42B2-9487-7EE4083398CF_MNU17456446_SIT209.html





As was mentioned before you might want to look into an overall heating control for your building such as one from Heattimer

http://www.heat-timer.com/En/Application.aspx?AppId=0

or by Tekmar  http://www.tekmarcontrols.com/index.html

These controls use multiple sensors to detect the temperature throughout the building and have outdoor reset control.  I'd contact the companies and have them send out a rep to explain the operation and advantages of their individual systems to you. On a large system thes controls can make a big savings in operating costs plus give you a well balanced comfortable heating system.

- Rod