Boiler control for Non-Condensing

Steve D._2

It looks like my contractor is too busy to install a modern boiler in my home this year. My current boiler is a W-M CG5, which is non condensing.

Is there a control setup that can reset based on outside temperature but also prevent my return water from dipping below 140* to prevent condensing?

I do not have P/S piping. Main house is one zone, CI rads, TRV's upstairs. Addition is one loop of baseboard (oversized)on its own circulator. The new zone installer set up the addition to circulate but not fire the boiler upon a heat call. He also neglected to install any flow prevention so I get gravity flow all winter and the room is comfortable by dumb luck.

Comments appreciated,

Steve

Al Letellier_9

outdoor reset

Sure, you can use a reset control. Tekmar controls allow you to set boiler min. temps to prevent condensing.

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Justin Gavin_3

Outdoor Reset

Tekmar 256 will do the trick.

Rely_2

tacoi

take a look at Taco pc701

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Tim_24

Your Boiler

manufacturer offers a reset as well, BCP-3

Enough

Tekmar

I looked at the Tekmar 256 install brochure and there is a sensor for boiler output. Do I need to concern myself with return temp? If so, there is no sensor for that. I assume that the circulators become decoupled from boiler firing during heat calls. Am I correct?

Steve

Enough

Taco PC700

I thought the instruction manual looked familiar. This is on the last page.

Steve

Chuckles_4

> I looked at the Tekmar 256 install brochure and

> there is a sensor for boiler output. Do I need

> to concern myself with return temp? If so, there


Yes, the return temperature needs to be high enough to protect the boiler, you have to set the minimum supply temperature high enough to ensure this. So the Tekmar 256 (or any other) is really not very useful...the range between 180F and (say) 150F is a small one and not worth the effort and expense to automate. If 180F is more than enough to heat your house on a design day, 150F is still too hot 95% of the year.

Try an experiment: manually lower the water temperature to 150F using the aquastat dial somewhere in your boiler. See if you can feel a difference, any improvement in comfort. If you like the change, and are willing to watch it and raise it only when really necessary, try this "manual two-position reset" for a year and then get a condensing boiler next year. Remember that the full capacity of the boiler is very rarely needed, most of it is for those rare design days. If your boiler is oversized as most boilers are, 150F may heat your house for the entire year, even on a design day.

The correct way to do reset with a cast-iron boiler is with some new plumbing: use mixing valves. The boiler will still run at 180F but the valves will inject controlled amounts of the hot water into the loop that goes to the radiators. (Tekmar makes specific models to drive mixing valves.) This won't increase boiler efficiency but it will dramatically increase comfort, assuming you have the typical situation where you can tell when the radiators are on because you feel the radiant heat. You won't have those too-hot radiators after putting in full-range reset using mixing valves, but your house will be evenly and steadily heated.

> is no sensor for that. I assume that the

> circulators become decoupled from boiler firing

> during heat calls. Am I correct?


I am not sure what you mean. Circulators normally run constantly during the entire heat call, but the boiler is turned on and off by the aquastat or reset controller during the heat call so as to maintain the desired water temperature (e.g. 180F). Unless you have a more complicated system.

Bob Sweet

Tekmar

The 256 or 260, the 260 offers domestic hot water priority and indoor sensor capabilities, as an added benefit.

Anthony Menafro

Tekmar

Tekmar 256 will do the trick!
Anthony