Honeywell outdoor reset with cast iron oil fired boiler

SuperTech

Hey everyone. I'm hoping someone can help me out with a project I'm working on at my house. I have a Peerless WBV oil fired cast iron boiler and the Honeywell L7224U digital aquastat and the W8375S1008 outdoor reset module. I live in NY and want to save oil this winter. I'm currently using an Intellicon HW but I've heard outdoor reset provides greater savings and comfort.
My problem is that I'm not familiar with using these controls. I have a little experience with Tekmar but the company I've been working for doesn't do any outdoor reset controls. I have an old setup, split loop with cast iron baseboards. Would I need to pipe in a bypass? What are the optimum settings for the control? Am I better off staying with the Intellicon? What is the best location to mount the outdoor sensor?

njtommy

Personally I like the Taco out door reset controls. Either the stand alone or the PC-700 that attaches to the expandable relay/zone panels.

The out side air sensor always goes on the North side of the building if you can. If not find a spot where the sun will not effect it.

SuperTech

I figured it should be on the north side, Honeywell says it can be mounted in any location but that didn't seem right.

Misery of the controls? I enjoy stuff like this. If it works for me it will work for my customers.

I might try the 150 degree experiment. I read on another forum that you can operate an oil fired cast iron boiler with 120 degree return water. I know currently with the Intellicon my burner shuts off often at 150 and runs the pump, no evidence of thermal shock after 6 years.

SuperTech

Thanks Hatterasguy. The last combustion test I did a month ago I was running at 30% excess air. I'm really want to learn as much as possible about these controls since they are the way of the future. Unfortunately I have to try them out on my old cast iron boiler and baseboards.

So at 30% excess air how low can my return water get before thermal shock is an issue? There's a lot contradictory information on this subject online, what works for you guys?

SuperTech

Yes you are right. Condensation is a major concern. My head is spinning after all the reading I've done tonight on the subject.
I definitely don't want to wreck my Peerless after all the work I've put into it.
Anyone have any thoughts on outdoor reset versus the Intellicon/heat manager for my setup?
By the way I am running a single zone, no zoning on the boiler yet but it might be an idea in the future to separate the first floor and basement.

SuperTech

I was looking into the Taco and the different Tekmar controls. I went with the Honeywell because I have the L7224U aquastat and all I needed was the outdoor sensor.
Any advantage of one over the other?
I always thought the Intellicon only shut the burner off earlier and ran the circulator longer based on supply temperature. Of course the manufacturer claims it's just as good as an OD reset.

Solid_Fuel_Man

Once you've looked into it, you will see that all the Taco controls are rebranded Tekmar. I do like to reset all boiler installs. With cast iron baseboards, you really should play with SWT and find your low limit. As Hatt said, keep the RWT above 130 to be well above the calculated 117.

In my experience with most cast iron emitters, ODR works very well. By doing this, you will get much longer circulator on times, which will make a call for heat much less noticeable.

Taylor

SuperTech

Thanks Taylor. I believe my questions have been answered.

SuperTech

One more question I've been wondering about. I will definitely monitor return water temperature, but I've read that adding a bypass is a must. Is this true? Shouldn't RWT dictate wether or not I need to install a bypass?

Paul48

That aquastat incorporates circulator control with the lo-limit. If you set your lo-limit high enough, you won't have any problems with flue gases condensing, and a bypass isn't necessary.

SuperTech

Thanks again guys. I definitely know where to proceed from here. I'm looking forward to setting this up and saving oil! And of course what I learn from experimenting on my own boiler will definitely help me provide greater efficiency for my customers.

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