Steam Boiler Not Firing

Unknown

could definitetly be a problem especially if it is not 18 gauge or greater. The 18 gauge can go 30 feet maximum, any thing beyond that go to 16 or 14 gauge wire. Is this a TS86 thermostat being used or comparable designated powerpile thermostat?

You need to have someone take some millivolt readings.

An Open Circuit reading with the pilot lit and the generator disconnected from the valve must be 540 millivolts or higher, the higher the better.

The next two readings will need to be charted out with a millivolt chart which I can send you by e-mail.

Reconnect the generator wires back on to the PP terminals on the valve, place the meter across the PP terminals this reading will vary depending on the open circuit.

A second reading with the controls jumped out at the gas valve and then chart out these two readings based on where they fall on the chart as to whether the problem is the valve coil or external controls.

It is also a good idea to clean the pilot and while you are at it replace the generator.

What is the make and number of the gas valve?

I would also get hold of the gas company and have them change the meter and check gas pressures to the equipment.Poor gas pressure can cause low millivolt output from the pilot.

You really need a pro to do most of this.

I have an excellent manual on Powerpile available to your heating contractor if they want to purchase it and all this is covered in the manual.

JohnG_3

Weil-McLain EG-40

I have a WM EG-40 steam boiler with a standing pilot light and a 750 mV powerpile, i.e. there is no external source of electricity anywhere in the system. This season it has developed an intermittent problem wherein it does not always fire when the thermostat calls for heat. Sometimes it takes 1/2, 1, 1 1/2 hours or even longer before the burner ignites. There have been some changes in the system since last season:

* We added a hydronic boiler to heat an addition. As part of this change we subtracted some radiation from the steam system.

* We added a gas cooktop. The total demand of the steam boiler, hydronic boiler, hot water heater, gas dryer, and cooktop is greater than it was before and also exceeds the rating of the gas meter.

* The thermostat cable was lengthened, most likely adding to its resistance and voltage drop.

* I turned the pilot light off for the summer to save gas and because we were having work done.

I have three ideas as to what is causing the problem:

* There is enough additional resistance and voltage drop in the longer thermostat line that there is not enough voltage left to open the main gas valve to fire the boiler.

* The powerpile is not generating as much voltage as it used to, due to normal degradation of its performance over time.

* The pilot light is not generating enough heat to fully drive the powerpile and so the powerpile is not generating its rated output.

Anyone have any theories as to what is going wrong, and/or suggestions as to how I can make a definitive diagnosis?

Steamhead (in transit)

Sounds

like the powerpile might be going bad. You need a suitable meter to test it. Time to call a pro, who can also get you a replacement if needed.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Unknown

Voltage drop

My guess would be that by extending the thermostat wires you added enough additional resistance to limit the current available to the valve. When you start out with only 750 millivolts, you dont have an awful lot of voltage to spare.

Did you extend the wire by splicing on another piece or did you run a whole new cable? If you spliced, how good are the connections? Is the new wire heavy enough gauge to minimize the voltage drop?

If you jump the thermostat connection terminals at the boiler location does the gas valve open? Do you have a DVM or multimeter to check the actual voltage at the gas valve coil when the thermostat is calling for heat?

ttekushan_3

Less likely than

what others have said here is a "none of the above" possibility. I mention it only because I remember long ago I had a head scratcher similar to this where it was actually a pressuretrol set to its minimum cut-in and it didn't always want to return to its proper position. It was hair trigger at that low pressure setting and a little schmutz in the pig tail would prevent it from resetting for awhile.

If piping changes were made, contamination of the boiler water can create enough turbulence to deposit said schmutz into low circulation areas like a pigtail.

Just a thought. BTW, "schmutz" is a legit technical term. You can look it up. ;-)

-Terry

JohnG_3

Yes,

I'm definitely using a pro and not doing this solo. I'm helping my heating contractor to pinpoint the problem, partly because it's intermittent and he has not been able to duplicate it when he's on site.

JohnG_3

Excellent questions.

Did you extend the wire by splicing on another piece or did you run a whole new cable?

My electrician spliced on a new section of 18 gauge thermostat wire. The pre-existing wire appears to be lamp cord of standard or one size heavier than standard gauge.

If you spliced, how good are the connections?

He used wire nuts. When I saw these I thought I had found the problem so I soldered the connections instead. Unfortunately, this resulted in no improvement.

Is the new wire heavy enough gauge to minimize the voltage drop?

Very possibly not. Since the new section of cable has five conductors and I only need two, I can double up the conductors to reduce the effective gauge size from 18 to 15 (doubling the cross-sectional area reduces the wire gauge by three steps). This will also halve the per-foot resistance of the new section of cable.

If you jump the thermostat connection terminals at the boiler location does the gas valve open?

Yes! I tried this this morning and the boiler fired right away. I think this implicates the thermostat wire, but it is still possible to have a marginal wire AND and a marginal powerpile. I need to measure the powerpile output.

Do you have a DVM or multimeter to check the actual voltage at the gas valve coil when the thermostat is calling for heat?

Yes, and I will use Tim McElwain's procedure to measure the powerpile output as well as the voltage across the gas valve.

JohnG_3

I thought

about the pressuretrol, but don't currently suspect it because nothing about it has changed recently, whereas I did lengthen my thermostat cable and douse my pilot light for several months last summer.

Actually, I suspect the opposite problem with the pressuretrol: that it is stuck on. There is no evidence of the system cycling on pressure, despite the pressuretrol settings being normal (I don't have them in front of me right now). But this is a separate problem. Neverthless, I will check the voltage drop across the pressuretrol terminals.

scrook_2

If T-stat wire's...

4 or 5 conductor 18 AWG vs. 2 conductor, than you could tie pairs of wires together at both ends, two 18 AWG in parallel are equiv. of one 15 AWG (if odd sizes were available) in lieu of pulling a new 16 or 14 AWG pair.

16AWG can go about 1.5X the distance of 18 AWG (~45 ft), 14 AWG about 2.5X (~75 ft). Paired 18 AWG should be good fo r~ 60 ft -- all using Tim's 30ft max for regular 18 AWG T-stat wire.

JohnG_3

The thermostat is a Honeywell VisionPRO 8000 set for steam. The specifications say it is compatible with 750 mV steam systems.

As I noted above, the added wire is 18 gauge but I can easily reduce it to 15. I will try this tonight. The total run length is easily over 30 feet, probably 40 or even 50 feet. The 18 gauge section is probably 20 or 25 feet, with the old "lamp cord" section accounting for the other 20 or 25 feet.

The gas valve is a Weil McLain. There is a number 1399073 marked prominently on the valve on the manufacturer's label, but I could not find this number on the WM web site and I don't know if this is the model number or some other number.

I will call the gas company about upgrading the meter and checking pressures.

If you could e-mail me the millivolt chart I will give it to my heating contractor. I will also give him your measurement procedure. Thanks.

JohnG_3

Bingo

If T-stat wire's 4 or 5 conductor 18 AWG vs. 2 conductor, than you could tie pairs of wires together at both ends, two 18 AWG in parallel are equiv. of one 15 AWG (if odd sizes were available) in lieu of pulling a new 16 or 14 AWG pair.

Thanks, great idea. I lucked out on this, as the new cable is indeed "18-5" - 5 conductors of 18 gauge wire. I'm trying this next.

Unknown

The contractor

does not need to be there when the problem occurs. If he knows how to take a set of readings he will find the problem whether it is running of not. Powerpile systems are somewhat complicated by the fact that jumping out controls and having the system come on is not necessarily an indication that the control jumped out is bad. All switches should have a millivolt drop of 10 MV's or less.

I strongly suggest a new run of wire all the way from the thermostat to the valve.

Weil McLain does not make gas valves, there must be a control name like Honeywell, Robertshaw, White Rodgers and perhaps a number like VS-820.

Has this system ben running with the new thermostat?

I will e-mail the millivot chart.

Unknown

John I tried to send

you the chart and the procedure but it was not received on your end sorry as I am going in for surgery tomorrow I am off the Wall for the next few days. I tried just no luck.

JohnG_3

Powerpile systems are somewhat complicated by the fact that jumping out controls and having the system come on is not necessarily an indication that the control jumped out is bad.

Agreed. What is needed is a sufficient overall performance margin such that any one component can have a problem and the overall system still works. In my case I'm pretty sure my thermostat cable has a problem, but that doesn't mean that the powerpile does not also have a problem, and that it is both problems combined that are causing the lack of heat.

All switches should have a millivolt drop of 10 MV's or less.

I just measured the voltage drop across the thermostat wires at the boiler. I's 80 mV. Quite bad.

I strongly suggest a new run of wire all the way from the thermostat to the valve.

I'd like to avoid doing this but it might be the only good solution. I ought to be able to reduce the run length and use very heavy wire like 14 gauge.

Weil McLain does not make gas valves, there must be a control name like Honeywell, Robertshaw, White Rodgers and perhaps a number like VS-820.

Yes, it's a VS820A1252. I think this is Honeywell, but I can't find it on the Honeywell web site. I found one reference to it:

http://www.patriot-supply.com/products/showitem.cfm/70370

VLV GAS VS820A1252 1/2X1/2 MV

Has this system ben running with the new thermostat?

Yes, no problems here.