Old and discontinued Mizer Johnson Control M35BA-1 Damper control replacement

ddcha

Hi everyone,

I have a 20 year old damper for my furnace and the motor seems to be worn out. not strong enough to open and close the damper. If I give it some help, it can finish the rotation, but seems weak. I need to replace the damper control but this is no longer manufactured. I know that there is an M35BE-1 replacement, but even that is discontinued. Is there a replacement plug and play piece I can use to replace the damper control unit? Please advise.

HVACNUT

Can you post pics of the damper, damper motor, and zone board?

The motor is not strong enough?
Is it power close/power open, or power close/spring open?

How difficult would it be to replace the whole damper, complete with new motor?
It might be easier.

When ordering a zone damper, the motor mounts on the first dimension.
24 x 18. Motor on the 24
18 x 24. Motor on the 18

ddcha

Thanks for your response. So when a cycle starts, the motor turns the gears but not strong enough to turn the damper. I tried to free up the damper a bit to make it turn open/close more easily. It turns clockwise. That didn’t work unfortunately. Here are some pics.

ddcha

One more with damper control taken off

SuperTech

Field controls makes a flue damper that should work as a replacement. What model aquastat do you have?

ddcha

Aquastat L8148E

ddcha

Damper motor picture

SuperTech

The field controls damper should be able to plug right into that aquastat.

HVACNUT

Sorry.🙄
I thought we were talking about zone dampers. I thought I Googled it.

Is it locked closed right now?
Can you manually open it?
Is there a manual lock open switch on it somewhere so it can be used for now?

Agree with @SuperTech .The Molex plug should be typical.

ddcha

Thank you both. I screwed off the damper control and left the damper in open position. This way, the control will cycle and the furnace will fire. Can you tell me which field control product to purchase? I looked at this Field Control GVD Motor Assembly: https://www.supplyhouse.com/Field-Controls-70009800-GVD-Vent-Damper-Motor-Assembly-Metal-Base

However, from the pictures, the back side doesn't seem to match because the part that connects to the damper is not centered.

ddcha

Off center like this:

ddcha

Sorry. Like this

HVACNUT

Just order the whole GVD-?
The number designates the flue pipe size.
15 minute swap.
Don't set any screws that will interfere with the damper.

ddcha

Dumb question but how do I measure the size? Im assuming I need the diameter

Steamhead

ddcha said:

Dumb question but how do I measure the size? Im assuming I need the diameter

Just use a tape measure- hold one end parallel with one side of the smoke pipe and see where the other end measures out to.

HVACNUT

Or a flat ruler.
It also might be stamped on the piping. Ex. 6 in, 26 gauge.

You can get a string and do the whole pi x r2 thing too.

ddcha

Thanks. Wish me luck.

ddcha

I used the string and calculate 7.32inches. 23 inch diameter divided by 3.14 = 7.32. What now.

ddcha

Remeasured. 7.12 diameter by my calc. Close enough.

HVACNUT

7" diameter

GVD-7
Easy Peezy

ddcha

Ordered the GVD-7 and the harness kit. Thanks for all your help folks. Stay tuned.

ddcha

So I installed the GVD-7 with the harness kit. I thought it was going to work. When I plugged it in, the damper moved to the close position (evidence that I'm getting power right?). The problem I have now is that it won't open when I raise the thermostat. Please help.

HVACNUT

Was the system working right up until you replaced the damper? Besides the reason it needed to be replaced.

No obstruction? The damper is able to pivot freely?

Do you have an electrical meter?

ddcha

No obstruction. It was working fine before. I just left it open temporarily until I could get this replacement. The harness is tight and all connections appear correct.

ddcha

I took off the new damper and put the old one back on. Left the damper in open position and took the control off the damper so that the motor “thinks” it is opening and closing the damper. It’s running again. Not sure if it’s a compatibility issue with my aquastat.

ddcha

One more thing I did not mention before is that I have Two furnaces. When I have the old damper controls installed, both furnaces run when the system calls for heat. When I installed the new Field Controls on the one furnace on the left, only the right side would function. Is it because I need the same brand on both sides? Please help.

ddcha

Here is a picture

ddcha

Bump please

ddcha

no one?

pecmsg

Please tell me the Safety switch is still hooked up! If that damper begins to close will the boiler shut down?

ddcha

Thanks for the concern. No it isn't hooked up, but I made sure it doesn't close back up.

waltzKon

ddcha, I have the same Vent Damper on the SlantFin boiler. A FieldControls Vent Damper didn't work on replacement. A little research reveals the connection plug wiring are not the same. Currently, I just jumper the wires between burner and rollout switch to fire up the boiler, but water temperature high limit control will not work. So it is a temporary fix until I find a better solution or buy the right Vent Damper. It is an expensive part and not easy to find.

EBEBRATT-Ed

@waltzKon

If your jumping safety's to get heat just realize YOU are the safety. Your doing that at your own risk. Don't let the boiler run unless you are constantly their to monitor it

EdTheHeaterMan

What boiler do you have? is there a wiring diagram on the boiler anywhere? With that diagram We can figure out the proper wiring for your field control damper to work.

EdTheHeaterMan

Here is a possible wiring diagram that MAY help you. Post picture of the inside of the L8148E control you have, and the make & model number of YOUR boiler. It looks like a Hydro Therm but I may be wrong



The basic concept (Operational Logic) of an automatic vent damper is to close off a natural draft chimney in order to reduce the down time loss of heat from the boiler and inside the home safely. You don't need Draft Exhaust if there is no flame, because there is no dangerous exhaust when the burner is off.

This must be done Safely by not allowing the burner to operate if the damper is closed. No path for exhaust equals no burner operation.

To accomplish this Safely, the motor mechanism must have 24 V power always. This is to be able to close once the controls and safety devices determine there are no exhaust gases that require venting. The Motor is actually connected to what we call an Actuator. This is the motor and some switches, thermostats, and relays that by design, regulate when the damper may close. In the case of Field Controls and other control manufacturers like United Technologies, and Honeywell, the Molex plug terminal 1 and 4 are the terminals that have constant 24 volts for damper actuator operation. Once it is safe, 24 volts on terminal 1 and 4 will operate the motor until the damper is closed. The internal switches and relays will stop the motor from operating once the damper is in the closed position.

In this closed position the gas valve can not get power to operate the burner as long as the damper is in the closed position.

On a call for heat, IF all the other safety devices are satisfied that it is safe to operate the burner, the #2 terminal on the Molex connector will be energized with 24 volts and the damper motor will start to turn. The motor turns until the damper is in the full open position. Once fully open, the internal relays and switches stop the damper movement and the damper will stay in the full open position. Another set of switches and relays will then energize 24 volts to the #3 terminal on the Molex connector. This then sends power to the gas valve to open and allow the flame to establish. As long as there is a flame or other source of exhaust gasses (or perceived exhaust gasses... by high temperature in the exhaust pipe may be one way to tell) The damper can not close.

Most automatic vent dampers operate on this principle. Some have a spring opening and electric close, but most brands have a damper plate that rotates in the same direction making a 180° revolution every cycle or a 360° revolution every 2 complete burner cycles

Regardless, what ever brand or design of vent damper you have, the safe operation MUST be maintained by proper wiring, and free unobstructed path for the damper plate to open.

All the Professionals on this site fully understand this Sequence of operation (or Operational Logic) for vent dampers. Not all would like to deal with manually wiring of the device and prefer to just "Plug and Play" using a new control on a new damper ... where the now universally accepted "STANDARD DESIGN" makes wiring effortless and fool-proof in most cases.

I hope this helps you with your particular situation. If you feel up the the job, you now have all the information you need. If you are not comfortable with control wiring or do not fully understand the safety and importance of getting this right, then PLEASE GET A PROFESSIONAL that understands how this should work. Where do you find this technician? Go to you local Plumbing and heating or HVAC wholesaler and ask the counter man, "Which one of your customers is good at control wiring?"

They know who they are, because they are the guys that buy lots of controls and never return them because "This darn thing was bad out of the box"

Steamhead

Slant/Fin used some unusual damper wiring hookups. Someone- might be Hydrolevel with their HydroStat- includes an adapter so the S/F damper will hook up to the new control.

Did you replace the cable along with the damper?