Combustion analyzer

Unknown

for the water heater control can be adjusted by removing the cap on the pilot on off knob on Robertshaw controls. White rodgers water heaters have different ways of adjusting. On the SmartValve water heater control the regulator is also adjustable.

Dan C.

Combustion

I put in three Bradford white water heaters today and I tested all of them. I just to Jim Davis's class a couple of weeks ago. All three of them were about the saem. THe CO was at around 30ppm and the O2 was 4.2 or 4.3%. In the class they said the o2 should be between 6 and 9 %. Is it ok to have a reading that low?

Unknown

Are they FVIR

water heaters? If so what was your stack temperature? The FVIR water heaters have a low O2 on them with a very high stack temp. Did Jim go over connecting your millivolt meter to the themocouple while the units are firing and see what happens to millivolts? In some cases a result is pilot outage if not set correctly. Also what was your gas pressure at the valve as I am sure Jim covered checking gas pressure. I have had several cases recently with real erratic gas pressures from some total regulation gas controls/thermostats on water heaters. Also do not vent those water heaters with any fan assited equipment as the pilot on the water heater will not stay lit or you will have the thermodisc (fusible link) attached to the pilot melt. I am sure Jim covered all of this I am just trying to answer your concern.

Mitch_6

Adjusting co for water heatrs

If I remember correct (i could be wrong) water heater gas valves do not adjust like boiler of furnace ones. Jim taught us to adjust gas pressure buy combustion readings not to use a manometer except to check that there was enough supply available before the valve.

As to pressure after the valve we were to use our analizer
(the tool that comes in many colors and does everything) He stressed that we may need more than (3.5 wc nat) pressure after the valve for proper combustion (this most likley to do with the waggle (s.p.) number and such.

For our adjustment on a water heater since we could not control gas pressure we could remove the vent hood and install a draft regulator therefore adjusting air to correct for poor combustion.

That is how I remember it I am sure Jim will correct me if I am wrong.

BTW anything we can do about gas ranges I do not think I have tested one yet that runs below 50ppm.

Mitch S.

Mitch_6

Wh gas valve.

Digging myself deeper the Water heater gas valve can be checked for the 3.5 w.c. nat but is not adjustable such as the gas range although you can adjust air shutters on them (with in my limited case no luck).

Mitch S.

Timco

Last week I moved a WH for a cust, and when I re-fired it, the condensate cooled the flame 'till I had huge O2 #'s and over 1000 PPM CO, (stack around 200) but after heating fully(stack 308) my O2 droped to 6.4% and I ended up with only 3PPM air free CO. Depends on the delta t and draft. If you had low excess air, or higher stack temp, it would account for less O2.

T

Unknown

It is not a good

idea to adjust anything without checking the pressure at the same time. Also keep in mind that water heaters are a total regulated appliance. That means when you are adjusting the regulator you are also adjusting the pilot gas pressure. This is not the case on heating valves as the pilot is not regulated only the mian burner gas. It is also a problem on FVIR water heaters to have the pilot over gassed.

What is a waggle (s.p.) number?

Setting up gas ranges for lower CO is covered in my manual on Gas Ranges, if you e-mail me I can make it availble to you through my catalog.

Unknown

When you fire a just filled

water heater you get much different readings than you would on one that is cycling on and off on temperature as the water is not all cold but somewhat tempered and it is easier to get the delta T up. Water Heaters will test different in cold weather than in warm weather due to different inlet water temps. Keep in mind that entire center flue is surrounded by cold water. Water heaters on a total cold start will condense for 20 minutes sometimes. In fact that is the A.O. Smith recommended procedure for determining a leaker. Anything dripping for longer than 20 minutes can be considered a leaker. It also depends a lot on the ambient air temperature in the room the water heater is located in.

Mitch_6

Waggle S.P.

s p was that i did not know if I was spelling Waggle correctly or i think it was the wobble number in any event I meant the actual btu value of the gas being delivered.

Since the pilot pressure is adjusted at the same time as the main burner I believe that is why Jim wanted to do the adjustment by air flow to correct the fuel gas.

As to pressure adjustment he toughed go by the analizer not the manometer and that we may be using pressures like 4" w.c. or more for proper combustion.

We were warned in class he thinks outside the norm.

I hope range adjustment will be covered in class this February.

Mitch S.

rob

Tim, please clarify

> water heaters? If so what was your stack

> temperature? The FVIR water heaters have a low O2

> on them with a very high stack temp. Did Jim go

> over connecting your millivolt meter to the

> themocouple while the units are firing and see

> what happens to millivolts? In some cases a

> result is pilot outage if not set correctly. Also

> what was your gas pressure at the valve as I am

> sure Jim covered checking gas pressure. I have

> had several cases recently with real erratic gas

> pressures from some total regulation gas

> controls/thermostats on water heaters. Also do

> not vent those water heaters with any fan assited

> equipment as the pilot on the water heater will

> not stay lit or you will have the thermodisc

> (fusible link) attached to the pilot melt. I am

> sure Jim covered all of this I am just trying to

> answer your concern.

rob

Timmie, please clarify....

Did I understand you to say that the new FVIR water heaters cannot common vent with fan-assisted Cat I furnaces?
How come?

Jim Davis

Water heaters as a rule come to the field with the lowest O2 readings of all appliances. The normal O2 for most appliances is 6%-9% but that is not to say they can't run lower. I have seen some that run between 3% and 4%, but that is not the norm. Lower is better if everything is totally controlled which includes combustion air and venting, unfortunately that is not the case unless you prescribe to my recommendations. Water heaters do not normally have adjustable regulators in residential models so they are not adjustable. The reason water heaters cause more poisonings is because they start at such low O2 and don't have much margin for error. FVIR water heater have to be one of the worst designs in the last few years. Allowing an appliance to have a 500 to 600 degree flue temperature right out of the box in ridiculous! They are allowed to be vented with induced draft appliances at this time but that will change. Because of the over heat switches in the bottom of them, induced draft furnaces are causing them to open when the furnace is in post-purge because they blow directly down the water heater fleu at this time.

Dan C.

stack temp

stack temp was 550. Yes they are FVIR.

Mitch_6

Jim Vs Tim

Can I get this clear, Residential gas water heaters cannot be adjusted on the gas side only by draft regulator and added combustion air (fan in can) if there is an adjustment it is main burner and pilot together making the adjustment more complicated to keep the pilot satisfied.

Gas pressure on other appliances boilers furnaces can be operated at higher than the 3.5 wc nat as adjusted by a digital analizer for proper combuston.

Is this correct.

Mitch S.

Jim Davis

Other than changing orifice sizes the gas on residential water heaters in non adjustable. Commercial are much different. Because water heaters can run with such low O2 right out of the box controlling draft becomes more critical. As far as other equipment with gas pressure adjustments, draft still needs to be controlled before raising gas pressures over 3.5"

Mitch_6

Thanks for the clarification

Mitch S.