Fan in a Can wiring

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GerryB

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woodbridge, ct. USA
The job is a basement finish, and because of the walls going up the inspector wants the boiler to have air flow. I forget if these things are make up air or exhaust, but I know the fan has to come on first or the boiler won't start. I did one a few years ago and it was a nightmare, but mainly because the fan motor was no good from the start. (of course that took a few calls back and forth with tech support to determine.) That particular one took 2 three wire cables if I remember correctly and I guess the t-stat wire. That was one zone, This boiler is 2 zones. My question is any one familiar with these and can give me a heads up what to look for, or a brand name? (the contractor is supplying it and trying to tell me he thinks it just plugs in:roll:) Thanks in advance.
 
1.) 2 zone thermostat

2.) Make up air

I really don't understand why these are yours requirement. I would think these are all the requirements of the HVAC Contractor! And in fact that it's all within the controller of the unit. Just get some power to them!

I could only think of various motor line diagrams where these are placed in series with a motor!

I thought make-up air is usually only on gas forced air systems, or a fire hood exhaust system.
 
I have to agree it should be the HVAC contractor's problem.

Besides that, does this boiler need fan supplied air or just some assured method that it does get combustion air?

If it is a power ventilated combustion system to begin with - usually the blower is part of the unit and has enough capacity to both take in intake as well as expel the exhaust. If it can't move enough air for proper combustion then line sizes or length, or a combination of both are likely the issue.

If it is a natural convection combustion system (and likely an older system if that is the case) all that is necessary is enough opening to allow for sufficient air flow for combustion needs.
 
You guys are right, it should be the hvac guy, but there is none. The boiler is existing. There is a plumber for the half bath who I worked with before who might get involved. I'm surprised the inspector want's it because the boiler is still in a room that's about a third of the basement. The other one I did they completely closed off the boiler the size of a closet. It's an extra but I'll have to fight a little bit with the contractor and now I can't finish the rest of the job in a day like I planned. Actually as I'm writing this I am wondering if my permit and license even covers this. Thanks for your input though.
 
If it's residential, combustion air is typically an open duct or vent that opens into the boiler space, or sometimes the outside air duct can connect directly to the appliance. Code would require x number of sq in of free opening with an additional allowance for grills or screens. A motorized damper would require an end switch, proving switch, that allows the boiler to fire when the damper proves open.

Don't quote me, that's heat, not electrical. All of the work necessary for combustion air is the heating contractor's job, and if they don't have a heating contractor, they need to hire one. It is work necessary to meet code. Liability issue also.

The fan in a can combustion air does not sound like something typical. I may have wired a combustion air fan system with proving limits for boilers that also had a burner fan and draft inducers, but that was for a school. Residential is either an open vent or an open duct directly connected to the appliance.
 
I have to admit I just looked up "Fan in a Can".

Never seen such a beast before, all combustion appliances I have ever seen were either newer with their own combustion blower, or older natural draft style usually had a non powered make up vent if necessary. If powered at all it was just a motorized damper and no blower.
 
All the fan in a cans I have wired were terminated in a relay controller designated for a Viesmann System.


Is the "proving switch" the device that proves the boiler room is getting the make up air it needs before the boiler fires up?
just asking:)
 
The proving switch closes when the fan is running or the damper is open. Fan proving switch on the Fields draft inducer fans are air pressure differential switches, sensing air pressure with a sampling tube both sides of the fan. I would guess the Fields make up air fan is the same.

Had no clue the fan in a can was a Fields unit. Call for heat would power the make up air fan (and a draft inducer if also present). The proving limit switches go in series in the boiler operating control circuit.

Also if the fan powered drafts are not set up properly, they can suck all the heat from the boiler before it has time to transfer heat to the boiler.
 
__dan said:
Also if the fan powered drafts are not set up properly, they can suck all the heat from the boiler before it has time to transfer heat to the boiler.
Click to expand...
I can see that easily happening as you are forcing air through something that was designed for natural convection to move air through it. "All the heat" is kind of extreme, but you definitely are making a lower efficiency appliance even less efficient.
 
kwired said:
I can see that easily happening as you are forcing air through something that was designed for natural convection to move air through it. "All the heat" is kind of extreme, but you definitely are making a lower efficiency appliance even less efficient.
Click to expand...

Yep there are a number of parameters and typical US made boilers control for none of them unless you are maybe looking at a condensing modulating nat gas boiler.

You would want to control for flue gas temp, excess O2 in the flue gas (lambda sensor), variable speed draft inducer, motorized variable combustion air dampers, modulating burner firing rate, boiler return water temp (to maintain the boiler above the condensing temp for non condensing rated boilers).

Then with the right controls you could match firing rate to demand, lower the excess O2 in the flue gas, lower the flue gas temp, raise the boiler return water temp above the condensing temp for non condensing rated boilers ...

Oil burning is an obsolete technology for residential heating. You may be able to find a control package like the above in one of the state of the art European pellet boilers.

Typical boiler would have non of that and you can typically see exiting flue gas temps of 400 to 600 deg F in oil boilers. About the only adjustment they will provide for is the fixed setup drafting, and that varies a lot over the course of the burn and the course of the year.

http://www.weil-mclain.com/en/weil-mclain/pd-wm-97-wall-mount-gas-boiler/

http://www.woodboilers.com/products/pellet-boilers/froling-p4-pellet.html
 
__dan said:
Yep there are a number of parameters and typical US made boilers control for none of them unless you are maybe looking at a condensing modulating nat gas boiler.

You would want to control for flue gas temp, excess O2 in the flue gas (lambda sensor), variable speed draft inducer, motorized variable combustion air dampers, modulating burner firing rate, boiler return water temp (to maintain the boiler above the condensing temp for non condensing rated boilers).

Then with the right controls you could match firing rate to demand, lower the excess O2 in the flue gas, lower the flue gas temp, raise the boiler return water temp above the condensing temp for non condensing rated boilers ...

Oil burning is an obsolete technology for residential heating. You may be able to find a control package like the above in one of the state of the art European pellet boilers.

Typical boiler would have non of that and you can typically see exiting flue gas temps of 400 to 600 deg F in oil boilers. About the only adjustment they will provide for is the fixed setup drafting, and that varies a lot over the course of the burn and the course of the year.

http://www.weil-mclain.com/en/weil-mclain/pd-wm-97-wall-mount-gas-boiler/

http://www.woodboilers.com/products/pellet-boilers/froling-p4-pellet.html
Click to expand...
I hadn't given much thought to an oil burner, I can probably count on my fingers how many residential oil burning heating appliances that I know of that are still in service. I have never connected power to a new one either, they are all older existing units.

I have dealt with waste oil burning heaters - usually in service shops, some farm shops but that is because they are getting essentially free fuel source. They are nasty though. Regular oil burners are messy enough from what little experience I have had with them, but waste oil burners are worse yet.
 
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