HVAC advice/boiler alternatives

[dja4260]

I have 750sq ft (3 bedrooms/ 1 bath) on the second floor of my home. The second floor has 16 inches of blow in insulation above rafters, new energy efficient windows, new 1/4 exterior insulation, and vinyl siding. Each room has floor board heat exchangers (34 feet total of finned copper).

We do not currently use this space unless we have company over. This space has been heated to 72 degrees for a total of 5 days during the heating season. The thermostat is usually set on 55 degrees.
First floor has forced air and a pocket door at the top of the stairs keeps the spaces separated.

I'd like to replace the current gas boiler set up that's from 1962.


Knowing all of this, what would be your suggestions?

Thanks for your time!

 

[HerrStig]

One boiler for the entire hose and two zones.

 

[dja4260]

Originally Posted By: HerrStig
One boiler for the entire house and two zones.


I think you missed the part that the first floor has forced air.

I'm interested in using a hot water heater to replace the boiler.

 

[JHZR2]

I'd say you need to do a manual j to determine the requirements and go from there.

The big question is not how you use it, but how it is set up for the future if things change, you sell the home, etc.

Depending upon the comdition of your water heater, I'd look into a modulating condensing boiler with an indirect water heater. I'd suspect that in the winter, the post-water heating circulation would provide enough low quality heat (water below the design point for the radiators) to keep it close to 55, and the rest of the time for such a low temperature it would be way throttled down and in the ultra high efficiency modulating and condensing mode.

It's not a full rigorous calculation, but you can probably determine boiler size based upon design temperature of the finned copper (IIRC 180F), area/length, and how many btu/hr max it can shed. Then you can see how to right size or possibly slightly undersize the boiler, and see if it's rating is sufficient for your water heating duties, if applicable.

I'm a big believer in gas mod/cons and have been very happy with our setup. It is extremely efficient and works great.

 

[Rob_Roy]

I would rip out the ductwork and install fin-tube baseboard on the first floor, then install a new boiler to run the two zones. If for some reason you can't or don't want baseboard radiators on the first floor, you could put a water-to-air heat exchanger in the forced air system and run it like that.

A hot water heater is a poor substitute for a boiler, but can be made to work in some small applications that don't need high water temperature.

An indirect water heater would be a nice compliment to the new boiler.

 

[sleddriver]

Originally Posted By: JHZR2
I'd say you need to do a manual j to determine the requirements and go from there.

+1.

After having done a Man. J on my own house, I highly recommend it. I also worked through a Man. D to design a new duct system. Previous duct-work was too small on both return & supply. I was paying to run a 3 ton heat pump, but only getting about 1.7 tons of cooling out of it. FUBAR.

 

[EA82]

Do U use AC at all?

 

[dja4260]

Originally Posted By: laserred96gt
Do U use AC at all?


Yes, the house has new AC/furnace for the first floor/basement that we use during our short summers.

 

[Thermo1223]

Baring branding or size(Manual J Calculation for that) get a 98% eff gas boiler. PVC exhaust and intake.

Now does the gas boiler supply domestic hot water? If not then access the age of your current water heater and consider getting an indirect hot water tank installed to run off the new boiler. That what it just doesn't sit unused during periods of no heat.

I water heater is a horrible idea and not designed to put out constant heat like a boiler. and not very efficient since you are heating a large volume of water.