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Power Vent Runs Needlessly

Hi.

New system, Smith Cast Iron boiler, Beckett buner. No chimney, so we used a Tjernuld (sp?) power vent. Taco control system, 4 zones.

Anyway, anytime a zone calls for heat, the power vent runs. This occurs even if the boiler has enough hot water and doesn't need to run. This is concerning me since the power vent runs almost all the time, and it pulls heat from the basement if it runs and the boiler isn't running. We have a Honeywell Aquastat, I think 8148A.

Is there a way to change this so the power vent only runs when the boiler needs to run? Do I just need a different aquastat, or is it the controller on the burner that needs to flip a relay?

I'd appreciate any help.

Thanks.

Comments

  • Power Venters

    should only be running when there is call to bring the burner on. They do, however, have a post-purge cycle that operate the venter after the burner cycle has been completed. This would normally be about 3 minutes. If your venter is continuously running regardless of whether the burner is running or not, then there may be a wiring error causing it to do so. The other possibility is that the post-purge cycle is excessively long. Hope this helps.

    Glenn Stanton
    Burnham Hydronics
  • john_24
    john_24 Member Posts: 23
    power vent

    I would check the wiring. with some of the new pre/post purge controls you can get bleed by voltage that will turn the power vent on without the burner. If you wire it to power from b1 on the aquastat instead of from the output on the cad cell this may help.
    John
  • John@Reliable_5
    John@Reliable_5 Member Posts: 76
    As Glenn said and,

    that boiler is a good one but very tight and hard to clean.
    When ever I install one I always over do the post&pre purge cycles, why? on pre I want plenty of draft before start up and post I want to get rid of any left over combustion by-products. Most boilers get "dirty" at start-up and shut-down so anything you can do to avoid it will make that boiler happy,the cost of electric will be small compared to the boiler getting soot on heat exchanger which will cause eff to go down. P.S. did you call back installer? they should be able to explain or fix it. Hope this helps John@Reliable
  • todd s
    todd s Member Posts: 212
    powerventer

    If you are using a powerventer you should add outdoor combustion air. These things move alot of air and in new construction theres usually not enough of it.
  • sootmonkey
    sootmonkey Member Posts: 158
    hey

    Ditto what Glen said AND what Todd said.
  • JackFre
    JackFre Member Posts: 225
    Tjernlund

    I'm the Tjernlund rep in New England. As previously stated your pv should not run unless ther is a call for heat. Perhaps try wiring thru the a=stat. If you have continued difficulty give Tjern. a call at 800 255-4208. The Tjern unit will give both pre and post purge operation.
  • Richard D._2
    Richard D._2 Member Posts: 156
    Fan problem

    As all said check your wiring ,Do you have a Carlin Cad cell relay on the burner?If so it is a self checking controll and runs about 32.4 volts on the off cycle..May be a problem..I am not sure off the top of my head if it is the TJ. venter or fields has a 24v -120vac timer ..the voltage trickle keeps the fan running..It bit me in the butt once!Cann;t remember which one..If it is the Carlin controll you need a isolation relay or use a Honeywell..Wiring diagramis os controll paper work... Hope this helps now or later...Richard
  • John@Reliable_5
    John@Reliable_5 Member Posts: 76
    I think some missed the problem, or lack of a problem!

    It's a cold start boiler, has an 8148 aquastat which will run the burner on a call for heat until either hi limit or the call for heat stops. Then powervent will run until postpurge stops, this could seem like it's always running.But it really could be doing what it should. John@Reliable
  • Mark Wolff
    Mark Wolff Member Posts: 256
    Tjerlund Side Shot's

    > should only be running when there is call to

    > bring the burner on. They do, however, have a

    > post-purge cycle that operate the venter after

    > the burner cycle has been completed. This would

    > normally be about 3 minutes. If your venter is

    > continuously running regardless of whether the

    > burner is running or not, then there may be a

    > wiring error causing it to do so. The other

    > possibility is that the post-purge cycle is

    > excessively long. Hope this helps.

    >

    > Glenn

    > Stanton Burnham Hydronics



    I just hooked one up two days ago with the same primary control. The sideshot requires L1 and L2 (hot and neutral) continuous power, And the B1 lead power, and the orange off the primary control and the black off the burner motor pigtail. The challenge I run into is that some of the install manuals don't cover all major primary control color code wiring diagrams. It can be a pain making sure the right wires are connected.

    It sounds like you have some wiring mixed up. Call Tjerlund or check their website for the wiring diagram for your specific primary control (it's not an aquastat) and
  • Mark Wolff
    Mark Wolff Member Posts: 256
    Tjerlund Side Shot's

    I just hooked one up two days ago with the same primary control. The sideshot requires L1 and L2 (hot and neutral) continuous power, And the B1 lead power, and the orange off the primary control and the black off the burner motor pigtail. The challenge I run into is that some of the install manuals don't cover all major primary control color code wiring diagrams. It can be a pain making sure the right wires are connected.

    It sounds like you have some wiring mixed up. Call Tjerlund or check their website for the wiring diagram for your specific primary control verify your wiring. An hour of wire tracing will clear the problem up for you.
This discussion has been closed.