how do you install a lockout relay?
- Thread starter zappy
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peter d
Senior Member
- Location
- New England
zappy said:
What kind of fan? An attic ventilation fan or a whole house fan? I can see the problem here with the fan sucking flue gas out of the furnace. Is the furnace sealed combustion (ie condensing)?
You could wire it so that when the T-stat calls for heat, you can wire it to a 24 v coil on a relay that opens the circuit on the fan.
Last edited:
stickboy1375
Senior Member
- Location
- Litchfield, CT
WHy on earth would someone turn a attic fan on with the heat running? Gotta love protecting the stupid... :roll:
peter d
Senior Member
- Location
- New England
stickboy1375 said:
I was wondering that myself, but I wanted to try to help anyway.
mdshunk
Senior Member
- Location
- Right here.
If the thermostat is set properly on the attic fan, the lockout relay will be unnecessary. It won't run in the winter anyhow.
If you ask me, it's unnecessary in any event. The attic fan does not draw air from the house. It sucks in one gable vent (or soffit vent) and blows it out. Whoever suggested a lockout relay has just enough education to be dangerous. After all, we don't put lockout relays on the bath fans and range hood exhaust fans. Double retarded.
If you ask me, it's unnecessary in any event. The attic fan does not draw air from the house. It sucks in one gable vent (or soffit vent) and blows it out. Whoever suggested a lockout relay has just enough education to be dangerous. After all, we don't put lockout relays on the bath fans and range hood exhaust fans. Double retarded.
Thanks peter.
Thanks peter.
Its a attic vent fan.It comes with a thermostat so at a certain temp.it kicks on.I dont know if its sealed combustion if it is then can the fan be on at the same time?Is condensing have like a drip pan or something to drain water?I saw something like that.
Thanks peter.
Its a attic vent fan.It comes with a thermostat so at a certain temp.it kicks on.I dont know if its sealed combustion if it is then can the fan be on at the same time?Is condensing have like a drip pan or something to drain water?I saw something like that.
BackInTheHabit
Senior Member
- Location
- Lexington, Kentucky
zappy said:
Who suggested the recommendation of a lockout relay?
mdshunk
Senior Member
- Location
- Right here.
The manufacturer probably put that instruction in the event that you installed an asmospheric burner in an attic space. Not necessary for a basement or crawl space furnace. The lockout relay is pretty simple, if you're stil interested in putting one in. There's a Honeywell part that costs 12 dollars that would be perfect for that. Reply if you insist on putting one in, and I'll lay it out for you.zappy said:
peter d
Senior Member
- Location
- New England
zappy said:
If it's sealed combustion it will have 2" or 3" PVC pipe (rather than a steel chimney) for intake air and exhaust. It does not have a drip pan to collect the condensate, but it does have a small trap and a 3/4" outlet connected to a PVC drain pipe.
Dang marc is there anything you don't know??
Dang marc is there anything you don't know??
Maybe i can talk them back out of it:grin: Yes please marc can you guide me through it?You da man!Thank you.
Dang marc is there anything you don't know??
It also said there may be times in the spring or fall when it may get hot enough in the attic to kick on the attic fan, and cold enough in the house to turn on the furnace.Well i was going to put a switch and then i brought this to the attention of the customer so now they want the lockout relaymdshunk said:
Maybe i can talk them back out of it:grin: Yes please marc can you guide me through it?You da man!Thank you.petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
stickboy1375 said:
my attic fan is wired off a thermostat set to come on at some high temperature. i don't know there is any interlock with the furnace. the thermostat on the fan effectively prevents it from running when the furnace might come on.
it also has another thermostat that shuts it off if it gets too hot - on the theory that it would be a bad idea for the fan to run during a fire.
i did not install it, but I think the HVAC guy that did said it all came with the fan.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Marc, where did you find this?mdshunk said:
mdshunk
Senior Member
- Location
- Right here.
I read... a lot! It was in a book I was reading at the time.LarryFine said:
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Okay, let me rephrase: who wrote it?
electricalperson
Senior Member
- Location
- massachusetts
if the fan cant turn on without the heater being on wont a regular normally open single pole relay work?
quogueelectric
Senior Member
- Location
- new york
There are a couple of different issues here. First of all what type of attic fan are we talking about.
Is it a whole house fan which will place a huge fan in the ceiling of the top floor of a house and suck all of the warm air out of the dwelling space and force it into the attic also displacing all of the hot air trapped in the attic with warm house air.
This fan will cause positive pressurization in the attic.
A gable vent is usually a much smaller sized fan placed in front of a gable vent usually thermostatically controlled.
This fan will create a negative pressurization which is what I think the problem is.
Most gas burning appliances that I have installed require at least 1/2 inches of mercury pressurization for combustion air. I have rarely seen these installed correctly.
I am not sure if a residential gas fired furnace requires pos pressurization for combustion air on such a small scale yet I do realize that neg pressurization could become extremely dangerous if durring the purge cycle the gas valve opened and the purge didnt happen for whatever reason the gas would be sucked into the living space and as Rattus likes to say KABLOOEY.
There is a simple and practical solution to split the feed between the two to a Summer / Winter switch which you could use a 3 way switch feed the point screw and come back to the fan on the summer side and come back to the furnace on the winter side. Just locate the switch in a practical location not to be confused with the emergency shut down switch. I sometimes install a summer /winter switch for an attic fan just to be able to cut a hole if I need a feed in the attic from the basement. Easy access for a dversa bit up and down.
Is it a whole house fan which will place a huge fan in the ceiling of the top floor of a house and suck all of the warm air out of the dwelling space and force it into the attic also displacing all of the hot air trapped in the attic with warm house air.
This fan will cause positive pressurization in the attic.
A gable vent is usually a much smaller sized fan placed in front of a gable vent usually thermostatically controlled.
This fan will create a negative pressurization which is what I think the problem is.
Most gas burning appliances that I have installed require at least 1/2 inches of mercury pressurization for combustion air. I have rarely seen these installed correctly.
I am not sure if a residential gas fired furnace requires pos pressurization for combustion air on such a small scale yet I do realize that neg pressurization could become extremely dangerous if durring the purge cycle the gas valve opened and the purge didnt happen for whatever reason the gas would be sucked into the living space and as Rattus likes to say KABLOOEY.
There is a simple and practical solution to split the feed between the two to a Summer / Winter switch which you could use a 3 way switch feed the point screw and come back to the fan on the summer side and come back to the furnace on the winter side. Just locate the switch in a practical location not to be confused with the emergency shut down switch. I sometimes install a summer /winter switch for an attic fan just to be able to cut a hole if I need a feed in the attic from the basement. Easy access for a dversa bit up and down.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I believe the opposite is the goal: no fan with the furnace operating. A 24v relay with an NC contact in series with the fan's power would do it.electricalperson said:
If the purpose is to prevent interference with proper flue operation, the relay should be energized when the gas valve is, rather than the blower.
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