Mod-con used for a multi-temp system

MikeyB

The company I work for uses a lot of IBC Boilers. http://www.ibcboiler.com

IBC Boilers have conrols built into the boiler that allow you to control 3 seperate heating loads (4 pumps - 1 primary, and 3 secondary pumps).

You pipe this boiler in a primary-secondary fashion (recommended by IBC) with a primary pump which moves heat out of the boiler in the primary loop, and you have your 3 secondary loops (supply/returns) coming off of the primary loop pumping for your Indirect Tank, Your Hot WAter baseboards, and your radiant floors. In fact I have done a house that had the exact set up you describe only with a few less zones of radiant.

The digital display for this boiler allows you to program all the temps for your heating loads, as well as it has an outdoor reset sensor which will allow the boiler to modulate it's heating temp and load depending on the outdoor temperature. This boiler has a 316 Stainless Steel Ti Heat Excahnger which is equivocal to the material Viessmann Uses for their heat exchanger on their Vitodens models.

It's a pretty good package for what you get out of the box, short of buying other boilers where you often need external/third party controls to control 3 seperate temp loads.

Andruid_2

Mod-con boiler for a multi-temp system

I am going to install a mod-con boiler with a stainless steel heat exchanger, but haven't chosen one yet. There is an indirect tank which will need priority, one high temp zone with fin-tube baseboards, and 7 zones of radiant floor heat. I don't want to set the supply temperature high for the fin-tubes and lose the efficiencies of low-temp supply water. I don't think I can use the priority output for the indirect tank to heat my fin-tubes. Is there a stainless mod-con that can output high or low temp water to the house heating depending on what the system needs at the time?

nathan_8

???

A couple questions is the home new construction or a old home that is having the heating system updated?

The difference of running the system at say 180 or 110 is only a few percent on most mod-con boilers and if you are running your home with the outdoor reset then your boiler will only be running at the high temp a very short amount of the heating system.

Now don't get me wrong I do agree that the lower water temp you can run your system at the better. And I've never seen or installed a IBC boiler but I have heard good things about them. But what I would look at is whats available in your area and what you can get parts for as well. And if that means choosing a boiler that only has the two set-point temps then go that route and look to save money in other areas like ECM pumps, insulation, window upgrades, etc. Because the last thing you want is in the middle of winter your boiler to quit and not be able to find parts or someone who can work on it. I have a friend who was building a home and ordered a boiler off the Internet from an outfit back east. the boiler isn't sold in the state and know one carries parts for it up here but his reasoning was "it was cheap". how cheap do you think that boiler will be when it breaks down in the middle of winter on the weekend or a holiday and he has to wait on parts from back east.

Plus you may find as I did that your home doesn't need as high of temp water as you think for the baseboard zone. my home is 30 years old 2x4 construction with residential sun-temp baseboard through out and at my design temp of -30 the baseboard only needs 165 degree water to keep the home a comfortable 70degrees so with a 20 degree delta T my return water temp is 145 and that is at -30 so every day it is around 10 degrees warmer then that the boiler is condensating and operating at greater and greater efficiency. In Fact when it gets near 40 outside my baseboard only requires 110 degree water. That is the beauty of outdoor reset you can dial in your system for optimum efficiency based on the outside temp.

I know I didn't recommend a three temp mod-con boiler with a stainless heat exchanger as I have no experience with one but I hope what I did share was of some help to you.

Uni R_2

"The difference of running the system at say 180 or 110 is only a few percent on most mod-con boilers"

LMAO

Nathan_6

it's about 7 to 8 %

The difference is about 7 to 8% depending on boiler manufacture. As the boilers published DOE AFUE rating is tested at 140 degree supply water and 120 return water.

Don't get me wrong I'm all for low temp high efficiency systems but if he is unable to find a boiler sold and serviced in his area that has the three temp capability then don't sweat it and install a two temp mod con boiler and mix down for the radiant zones. Or spend the money for a Tekmar boiler control, and an additional set-point controller.

But lets say you have a 1200 a year gas bill the difference between running @ 180 versus 110 would be $96. Which does add up over time but back to my original point if you cannot get service or parts for a particular boiler in your area is the $96 in savings worth it when you do have a problem??? That is the question each individual has to answer for themselves.