Solar integrated with a condensing boiler

Jack Pieterman/Practical Plumbing

Can anyone help me with a design? I have been asked to design a system , the center of which is a NTI, Trinity T-200 condensing boiler. This boiler will be suppling the heat source for a fancoil unit, rafiant in-floor in the basement and two ares of staple up radiant syste. (Each approx. 300 sq. ft.) Also we will be supplying heat for an Amtrol BoilerMate WH-7L. This is no problem. The client wants to integrate solar collecters into this system. The solar system supplier is using a 60 gal. electric water heater into which he puts a heat exchanger into the drain port (much the same as with ground source heating of domestic hot water). He informs me that I am to route my cold supply for my domestic hot water through his 60 gallon storage tank before it goes to the WH-7. All fine and dandy, but I would like to be able to use this solar heated water for the rest of my heat load without using too many heat exchangers. (which at low temp are not very efficient. Has anyone done anything like this and willing to share their expertese?
Practical Jack

Jack Pieterman/Practical Plumbing

Integrating solar with radiant heating

Can anyone help me with a design? I have been asked to design a system , the center of which is an NTI, Trinity T-200 condensing boiler. This boiler will be suppling the heat source for a fancoil unit, radiant in-floor in the basement and two areas of staple-up radiant heat. (Each approx. 300 sq. ft.) Also we will be supplying heat for an Amtrol BoilerMate WH-7L, indirect water heater. This is no problem. The client wants to integrate solar collecters into this system. The solar system supplier is using a 60 gal. electric water heater into which he puts a heat exchanger into the drain port (much the same as with ground source heating of domestic hot water). He informs me that I am to route my cold supply for my domestic hot water through his 60 gallon storage tank before it goes to the WH-7. All fine and dandy, but I would like to be able to use this solar heated water for the rest of my heat load without using too many heat exchangers. (which at low temp are not very efficient. Has anyone done anything like this and willing to share their expertese?
Practical Jack

Ron Huber

Is this an American Solar Network system?

Boaz

Primary Loop Design

The system you are describing is a typical system for us, as we specialize in solar heating.

We design such solar heating systems with integrated boilers with a primary loop design. You have the choice of filling the boiler, Amtrol HEX, primary loop, floors, and solar collectors with glycol, or filling only the solar collector loop with glycol and using a heat exchanger to transfer heat to the primary loop. Secondary loops connect to the primary loop for boiler, Amtrol HEX, floors, fan coils, etc. You probably need additional storage to deliver solar heat to the staple-up radiant tubing, while mass radiant floors can act as their own storage media. For cxontrols, we mostly use simple single and dual stage setpoint controls, and differentials for some applications.

We can provide a piping and wiring diagram if you would like after some phone or email consultation to get us up to speed on project details.

Boaz Soifer
Cedar Mountain Solar

Boaz

No electric tank needed

By the way, the Amtrol is all you need for domestic hot water; since both solar and boiler are tied to the primary loop, and the primary loop is tied to the Amtrol, the electric tank is redundant - your condensing boiler is all the backup you need.

Dale Pickard

Don't do it..

Hey there practical Jack,

1. It's harder than you think, as you say "witout too many heat exchangers".

2. More important, if the solar installer is providing a 60 gallon solar storage tank, then the collector array should be no larger than 120 ft sq. to get good solar dhw performance.

Such a solar system will supply heat to a small domestic hot water load, but no more. If you want more heat, especially in the winter, you will need more solar collectors.

Keep it simple stupid. Solar water heaters are great, simple and cost effective solar applications that save more energy and carbon than many people realize. Leave it that way. One can screw up a nice simple solar water heater by trying to make it do more than it can. Nothing magic in solar.

Dale

Steve Paul

Solar with indirect

I have been running my Amtrol 40 Gal. indirect water heater with my State, 3 panel,120 gallon storage tank as a pre-heater for the domestic hot water. The elements in the tank were never connected, strictly for storage. The result is that whatever solar gain is achieved is used to pre-heat the cold water supply to the indirect Amtrol. Some times in the warmer months my boiler will go on just once or twice a day for only a few minutes. My gas consumtion was drastically reduced when I installed this set-up. I can't quanitify the exact savings, but I am sure it amounts to at least 30-40%.

Unknown

It's also probably not even worth tying it into the radiant unless the radiant was designed for low temperatures. Staple up, fancoil... not likely.

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Ron Huber

Dale is right

And, is this an American Solar Network system? I have one of these systems on my house installed in 1991 as part of a State Gov. council on energy study. I can tell you the pro's and con's of this system.

David Woycio

solar system

Depends on where your job is located to determine heat gain. My company is in Denver where we get over 300 sunny days per year. If you're back east you may be half of that. We like Super Stor's Ultra tank. A little pricy but they're made of stainless steel and have a built in heat exchanger. Double walled if code dictates. Makes plumbing easy a and neat. I agree with most of the other posts that if you only have 65 gallons of storage that interfacing the solar thermal system with the heating system doesn't make much sense economically.

A bigger collector array and a larger storage tank works better for systems such as these. Do your heat loss calc. if you go this route. Money may be better spent in extra insulation and weather stripping.

Mike T., Swampeast MO

Practical Jack -- I Feel Your Pain

Am trying to do something similar but with very low temperature requirements, small load and still am told that it's impractical. (Does though require a dual HX coil tank.)

"Need storage."

"What are you going to do with all that heat when not being used by the space heating?"

I say that "all that heat" is based on supplying the space heating in very favorable conditions for collecting solar, but it seems I'm trying to break some kind of "rule"...

David Woycio

how big?

How big is house? solar? storage? heating system? Do a heat loss calc. and talk in BTU's then you can figure solar advantage. Check the solar collector for it's btu rating.

Mike T., Swampeast MO

Check currently active post titled "Solar Integration" for the numbers.

David Woycio

?

All I see is a 65 gallon tank. What about the rest?