Low draft on oil fueled water heater

[LI-NY Tech]

I have a Bradford White Model CF-32-6 oil fueled water heater.  It's exhaust feeds into the same exhaust as the oil burner and they both exit through the chimney (see attached photo).  When both the oil burner (Weil McLain Model # P-460-W) and the water heater are running there is exhaust gas escaping from the damper(?...red arrow on attached photo) where I believe air is supposed to be pulled in to aid in exhaust draft.  When only one or the other is running there doesn't seem to be a problem.  I don't know much about heating so I have no idea if my setup is correct (just bought the house in October).  HVAC guy says there should be no exhaust escaping this from damper, his proposed solution is to install a device that would prohibit the water heater from running when the burner is running.

 

The chimney is not blocked.  The heater and oil burner work fine otherwise.  Any ideas?  "low draft, bent 'baffels'" is written on the water heater, so I assume someone looked at it once before, but didn't solve the problem. Any ideas?

 

Edited January 3, 2014 by LI-NY Tech

[Budget Appliance Repair]

Probably neither one is totally drafting correctly by itself but OK to get by until you fire the second unit at the same time.

 

I don't believe venting into a brick chimney is up to code if there isn't a liner installed.   All of the water heater install info I've every seen cautions against venting into a brick chimney without it being upgraded to a liner system.

 

I see it all the time in old house and has usually worked with no problems but with two into the same vent pipe then into the chimney I could see it causing problems when both are on at the same time.

 

Here's the installation manual for your water heater:

http://s3.pexsupply.com/product_files/CF-32-6-Install.pdf

 

What it says about venting, (Doesn't say not to vent into a chimney):

 

VENTING
The connection from the water heater vent to the stack must be made as direct as
possible and of the same diameter as the vent outlet. The recommended slope of
any horizontal breaching is at least 1/2" rise per linear foot. A certified draft
regulator (barometric damper) shall be installed in the venting with a location at
least 18” downstream from the water heater. This water heater is designed for use
with type “L” venting.

 

CAUTION
The stack must extend at least (3) feet above the highest point of the
roof to insure proper venting. The stack should be provided with a
weather cap of approved design.

Note: Provisions shall be made to prevent contact of the vent pipe with
combustible materials in accordance with all codes and regulations.

 

A separate vent and barometric damper for each appliance is strongly
recommended, consult the National Fire Protection Standard For Oil Burning
Equipment NFPA No. 31 (latest edition) or CSA B139 (latest edition), for vent
sizing and installation information.
 

WARNING
Draft reading in the stack should be -.02” W.C. to -.05” W.C. High draft
may be caused by over firing, or too much excess air. If there is back
draft caused by down draft, DO NOT operate the burner until this
situation is corrected. Back pressure (back draft or down draft) may
also be caused by the chimney termination being lower in elevation
than surrounding objects, such as buildings, hills, trees, rooftops, etc.
Back pressure may also be caused by an exhaust fan in the building.

Edited January 3, 2014 by Budget Appliance Repair

[LI-NY Tech]

The chimney is on a flat section of the roof, the peak of the rest of the roof is about the same height if not slightly higher.  Should I go with the HVAC guys suggestion of installing the device which only allows one at a time to operate?

[Budget Appliance Repair]

That would probably be the easiest and cheapest way to solve the problem as long as you know for sure each is venting/drafting OK on its own.

 

Hard to actually see how the vent from the furnace connects into the same vent for the water heater from your picture, (appears to be a straight up pipe "T"-ing into water heater vent, but not really sure from picture).

 

Does the furnace have a draft inducer motor also, (I know the water heater is power vented)? 

 

I would assume the furnace would also and when it comes on depending on how the transition from the furnace vent enters the water heater vent pipe you are probably creating back pressure or turbulence when the two vent streams interact causing flue gas to be pushed out the damper, which I would assume is the (barometric damper) that shall be installed in the venting with a location at least 18” downstream from the water heater, that is mention in the installation instructions, (it doesn't appears as it is 18" downstream as called for).

Edited January 4, 2014 by Budget Appliance Repair

[LI-NY Tech]

The water heater seems to have been added on haphazardly at some point. I'm considering just replacing it with an electric one since the chimney probably isn't meant for both the furnace and the heater. Not to mention the oil it uses it crazy expensive. I have a small house, one bathroom, just my wife and I and my year and half old son. Do you think a tankless electric heater could do the job?

[Budget Appliance Repair]

Never worked on or have had a tankless, but from the little I've read about them they would most likely be fine for you but you really wouldn't want to vent into that same shared chimney and they usually require a fairly large gas line so you might start running up a pretty hefty bill installing one depending on your setup.

[LI-NY Tech]

I don't have gas here, just oil.  So I was thinking of switching it to electric to a) save on oil, and eliminate this venting problem.

[Budget Appliance Repair]

Duh!! I totally missed the point where you said ELECTRIC.

 

Do they make a tankless electric water heater?   Seems like it would take quite the large heating element to instantly heat water with electric heating elements.

[telefunkenu47]

I think I would check and clean the squirrel cages on both burners, remove years of buildup from the inside of the blade cups and air slots on the burners.Sometimes the burner guys fail to do this over time,adding a little more air each year over time. Once you have done that, try down firing both the water heater and the furnace, IE cut the firing rate bach and test for smoke. The water heater for example doesn't need a .75 gph nozzle if its just you and wifey. Cut it back to .5gph x 80a. Do the same on the furnace if you can get away with it, at least one nozzle size.  Then see what happens. Again, dont adjust the air shutters by eye. Use a smoke tester for the final adjustments. This isnt the end all soloution, but it may alleviate the symptoms.  Get back to us if it helps. Can you post a pic of the chimney and the burner air shutters?

[LI-NY Tech]

Budget:  They do make tankless electric heaters but it looks like they require more amperage than my puny antique electrical service provides for the whole house.

 

telefunkenu47:  What is a squirrel cage?  I can probably downsize the water heater but the furnace struggles to keep the house warm on very cold days (fortunately I have a fireplace).  I don't have a smoke tester, can you recommend a decent one?  Pics are attached below?

 

Edited January 13, 2014 by Samurai Appliance Repair Man
Removed attachments because they didn't make it thru the migration. Please re-attach!

[telefunkenu47]

After looking at your pix I will advise you to replace this setup with a new boiler and indirect water heater. A 4 section Pensotti with a 36 gallon superstor tank goes in around here for around 6500 dollars. The setup you have is loaded with code violations and is outdated. It simply wont work. Just bite the bullet and spend the sheckles. This is simple caveman stuff. Even the neanderthal knew not to let the fire go out. If he did, his wife and kids died, and his dna didnt go any further.  Pm me if you like Ill be glad to talk to you. 

[LI-NY Tech]

It's old for sure, but barring single digit temps it gets the job done. I need about another year out of it before I can replace it so I'd like to solve this exhaust problem with the water heater until then.

[LI-NY Tech]

What is the device that would prohibit both units from running at the same time called?

[LI-NY Tech]

Do you know what the device that would prohibit both units from running at the same time called?