Faulty Spill Switches......

[Deleted User]

If I were you, I'd suspect spillage before I condemn the trip switch.

One way to find out if it has been an issue is to place the sensor of a data logger next to the appliances spill switch and see what happens. You'd be amazed at what this equipment does when you're not looking...

ME

John Ruhnke

Faulty Spill Switches......

Has anyone had any problems with the spill switch on the vent damper for gas boilers with auto vent dampers?
I have this commercial project we did last year and three different times on two different boilers the spill switch has tripped.

It is easy to reset, just push the button. But the client is complaining and if this was to happen in Febuary it could cause a freeze up.

Any solutions? Is this a defective part or a design flaw?

John Ruhnke

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Ken D.

Switch

I have seen many switches go bad. They really are a cheaply made item. Does the job have good draft on start up? Jobs with poor draft seem to hasten the demise of the bi-metal switches as well a jobs with bi-metal stack dampers. I believe it is due the switches constantly over heating. Replace it and see if that does the trick. H.T.H.

jim lockard

Spill

Maybe two switches mounted next to or across from each other wired in parallel so that both have to trip to shut the system down. that way you will know if it is a bad switch or another problem (2 defective switches).Best Wishes J.Lockard

Paul Pollets

Wind shear

while I've replaced a few defective spill switches, several jobs had chimneys that created a severe downdraft, because there was no cap on the chimney. The spill switch was simply doing what it was supposed to do. The remedy is to always cap the chimney or install a rotating cap vane that turns to the direction of the wind and stops the shear. These rotating caps are available in stainless steel as well as galv.

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Steamhead (in transit)

Uhhhh, Jim-

that won't work, cause if one switch sticks closed the other one can't shut down the burner. If you have two switches, they must be wired in series.

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Jim Bergmann_2

Required testing for spill switches

This is an excerpt from the Testo combustion guide; you may want to perform the Ventilation air test as outlined in the later part if this commentary. Refernce appendix D of the International Fuel and Gas Code for this information.

If the spill switch is tripped, check for:
1. Chimney or vent blockage.
2. Improper chimney height.
3. Insufficient combustion/ventilation air to provide for proper combustion.
4. Blocked combustion air openings.
5. Air leakage around the return or an open return causing negative space pressure.
6. An attic exhaust fan that is running.
7. A wood burning appliance operating in the house (can create negative pressures).
Perform a ventilation air test as recommended yearly and outlined in the National Fuel Gas Code and International Fuel Gas Code.

Spill Switch Testing (Required Test):
The spill switch is located on the draft hood on older furnaces and on the collection box of some newer furnaces. The spill switch provides protection against a blocked flue by sensing a down draft or back draft condition. The switch location is critical to its operation and it should not be moved or tampered with.
All furnaces must prove draft within 5 minutes of establishing a flame. By ANSI standards, the switch must trip with 10 minutes of continuous spilling.
To test the switch, remove the furnace vent from the flue, block the vent with several clean cotton rags or sheet metal, fire the furnace, and allow the unit to spill into the space. Make sure there is adequate ventilation when performing this test as CO could overcome you if the appliance is not functioning properly. A combustion analyzer if so equipped can be used to monitor the CO in ambient air while performing this test; however, many analyzers are not approved as a personal protective device.
The opening temperature of the switch will vary from manufacturer to manufacturer. The switch should open within 10 minutes of operation. This is the maximum time allowed. Many manufacturers have shorter time requirements. If it doesn’t open within the time frame required by the manufacturer, replace the switch. The most important thing is that the switch opens by the 10-minute time frame required by the standard.

The Ventilation Air Test
As more and more homeowners seal and tighten up their homes and in commercial buildings, it is very important to perform a ventilation air test as outlined in the International Fuel and Gas Code. (IFGC)

Section 304 of the IFGC specifies the air requirements necessary for proper combustion, ventilation and dilution of flue gasses for gas utilization equipment installed in buildings. It is not necessary for technicians to understand the design requirements for ventilation air, but all technicians should be able to field test for ample combustion, ventilation and dilution air. Home depressurization can be a major contributor to CO in the home if appliances cannot vent, or burn properly. The ventilation air test is a worst-case test used to determine whether or not enough indoor air and infiltration air is coming into the building for proper ventilation / infiltration under actual operating conditions. Older versions of this test could have put the technician in harms way, so the current method should be referenced and followed.

Natural draft and induced draft gas appliances use air from inside of the building to burn the fuel. If air used during the combustion/ventilation process from inside the building is not replace by outdoor air:

A. There will be insufficient air in the building for proper combustion.
B. There is a very high probability that carbon monoxide (CO) will be generated due to the lack of sufficient air (Oxygen) inside of the building.
C. Poor ventilation/infiltration can cause a negative pressure inside of the building.
D. If the building is under a negative pressure, the chimney will not draft. The higher pressure outdoors will force air down the chimney or flue vent spilling the flue gasses into the building.
E. Vent spillage increases the probability that the flue gasses will contain Carbon Monoxide (CO) due to poor combustion.

RECOMMENDED PROCEDURE FOR SAFETY INSPECTION OF AN EXISTING APPLIANCE INSTALLATION AS OUTLINED IN THE 2003 INTERNATIONAL FUEL GAS CODE TM
Used with permission of copyright holder.

Note: If appliance fails this test, do not proceed until repairs are made.

The following procedure is intended as a guide to aid in determining that an appliance is properly installed and is in a safe condition for continuing use. This procedure is predicated on central furnace and boiler installations, and it should be recognized that generalized procedures cannot anticipate all situations. Accordingly, in some cases, deviation from this procedure is necessary to determine safe operation of the equipment.

(a) This procedure should be performed prior to any attempt at modification of the appliance or of the installation.
(b) If it is determined there is a condition that could result in unsafe operation, the appliance should be shut off and the owner advised of the unsafe condition. The following steps should be followed in making the safety inspection:

1. Conduct a test for gas leakage. (See Section 406.6 IFGC)

2. Visually inspect the venting system for proper size and horizontal pitch and determine there is no blockage or restriction, leakage, corrosion, and other deficiencies that could cause an unsafe condition. (This will require removal of the vent from the chimney in most cases)

3. Shut off all gas to the appliance and shut off any other fuel-gas-burning appliance within the same room. Use the shutoff valve in the supply line to each appliance.

4. Inspect burners and crossovers for blockage and corrosion.

5. Applicable only to furnaces. Inspect the heat exchanger for cracks, openings, or excessive corrosion.

6. Applicable only to boilers. Inspect for evidence of water or combustion product leaks.

7. Insofar as is practical, close all building doors and windows and all doors between the space in which the appliance is located and other spaces of the building. Turn on clothes dryers. Turn on any exhaust fans, such as range hoods and bathroom exhausts, so they will operate at maximum speed. Do not operate a summer exhaust fan. Close fireplace dampers. If, after completing Steps 8 through 13, it is believed sufficient combustion air is not available, refer to Section 304 of this code for guidance.

8. Place the appliance being inspected in operation. Follow the lighting instructions. Adjust the thermostat so appliance will operate continuously.

9. Determine that the pilot(s), where provided, is burning properly and that the main burner ignition is satisfactory by interrupting and reestablishing the electrical supply to the appliance in any convenient manner. If the appliance is equipped with a continuous pilot(s), test the pilot safety device(s) to determine if it is operating properly by extinguishing the pilot(s) when the main burner(s) is off and determining, after 3 minutes, that the main burner gas does not flow upon a call for heat. If the appliance is not provided with a pilot(s), test for proper operation of the ignition system in accordance with the appliance manufacturer’s lighting and operating instructions.

10. Visually determine that the main burner gas is burning properly (i.e., no floating, lifting, or flashback). Adjust the primary air shutter(s) as required. If the appliance is equipped with high and low flame controlling or flame modulation, check for proper main burner operation at low flame.

11. Test for spillage at the draft hood relief opening after 5 minutes of main burner operation. Use a flame of a match or candle or smoke.

12. Turn on all other fuel-gas-burning appliances within the same room so they will operate at their full inputs. Follow lighting instructions for each appliance.

13. Repeat Steps 10 and 11 on the appliance being inspected.

14. Return doors, windows, exhaust fans, fireplace dampers, and any other fuel-gas-burning appliance to their previous conditions of use.

15. Applicable only to furnaces. Check both the limit control and the fan control for proper operation. Limit control operation can be checked by blocking the circulating air inlet or temporarily disconnecting the electrical supply to the blower motor and determining that the limit control acts to shut off the main burner gas.

16. Applicable only to boilers. Determine that the water pumps are in operating condition. Test low water cutoffs, automatic feed controls, pressure and temperature limit controls, and relief valves in accordance with the manufacturer’s recommendations to determine that they are in operating condition.


***If conditions can be changed to temporarily correct the condition like removing the door from the adjoining space, cracking a window in the basement, or locking out another appliance that is not deemed critical for heating the structure, the heating appliance can be left in operation provided the corrections to the combustion / ventilation system are incorporated prior to returning to normal conditions. Any changes made should be noted on the work order and signed off on by the customer before any changes are made. Any appliance left in operation must not show any signs of combustion / ventilation problems.

This test should be performed on all furnaces, boiler, hot water tank, or other fuel burning appliance inspections or installations including the installation of woodstoves or other fossil fuel appliances.

Steamhead (in transit)

Jim, we didn't know Testo published this guide

how can we get a copy?

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Jim Bergmann_2

Combustion Guide

I can e-mail a PDF, where do you want me to send it. It is currently being printed so a hard copy is not available at this time. I would be glad to send you the PDF and you can print it. FYI I am a new hire for Testo (a little over a year now) I am an instructor by trade for Testo and Cuyahoga Valley Career Center in Brecksville Ohio. I also write for several trade publications, Goggle may name and HVAC and you can see some of them that were posted online.
I specialize in commissioning systems, Gas Furnace, Boilers, A/C, Heat pumps and combustion testing.

If I can ever be of any help let me know.

Thanks

Jim

Steamhead (in transit)

Thanks, Jim

please e-mail to allsteamedup@verizon.net . Our company uses Testo analyzers- Gordon has two 325M units and I have two 325-1 units. We like them.

And since I haven't seen you on the Wall till very recently- welcome!

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[Deleted User]

Sign me up too!

And thanks for contributing Jim!

mark.eatherton@advancedhydronics.com

Look forward to meeting you some time.

As Frank said, welcome to the Wall.

You're a welcome addition.

ME

Unknown

Me too!

I would also be interested in a copy of the guide if you don't mind Jim. Thanks.

gstanton@burnham.com

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

S Ebels

Nuisance spill switches

I've run into a few of them that locked out for no reason. What I found was that when the boiler shut down after a nice long burn, the heat coming off the castings would build up in the draft hood and cause the switch to trip. In all the instances, the problem disappeared after I drilled a small "relief" hole in the flue damper. The holes wound up at about 5/8"-3/4". This allows a very small amount of air flow up the chimney but that little bit of air flow is enough to keep the temp from building up high enough to pop the spill switch.

Note: All of these were on boilers with the draft hood integral to the boiler, not one that fits up on the stack. Three of them were on Buderus G-124 series gas boilers. All these boilers were spark or direct ignition of some sort, no standing pilots and that's what tipped me off. The standing p[ilot models have the "relief" hole in the damper to allow flue gas from the pilot to vent into the chimney.

Obviously, ALL the other things mentioned above should be checked out first.