Mixed Fuels into One Flue...and a Question

DaveGateway

I say always seperate services for each apartment and let the tenant decide how hot or cold or how much hot water they want to waste. Let them get their own serivces cut off by the utilities for non-payment, etc. Get the extra gas meters and look at some gas combo wall boilers from Monitor or Baxi for each apartment.

PJO_5

Looking at a house...

Wallies,

I am looking at a house that has the following; two of three apartments heated by baseboard with a 30 to 40 year old W/M oil-fired boiler (model number not obtainable, but it's CI with a tankless coil that has been mothballed and a 1.25 gph nozzle). A single large B&G circ (bigger than a 100) feeds the return side of the boiler to a spaghetti of pipes and two zone valves (feed side) provide zoning. No outdoor reset, no setback t-stats...a typical rental building if you may.

The replacement HWH is a 75 gallon NG fired AO Smith...it is only about three or four years old.

The third apartment is heated by electric baseboard, but is located directly behind the boiler room.

The owner pays all heat and hot water, while the tenants pay the electric (which includes heat for the third apartment).

I have done the basics for a heatloss calculation (Slant Fin - based on my memory of room sizes, etc) so it's within about 10% of 115 kbtuh for having heat in all three apartments...not sure of insulation, wall thickness, etc.

First question: The home inspector is meeting me tomorrow...I have learned from The Wall that two different fuel-fired items (oil and gas) into the same flue isn't such a good thing, but is it against code? This is in Brigantine, NJ.

Next question: Besides the issues of efficiency/gas versus oil, etc. I am considering one of two options. Since the boiler is on it's last legs and sits all summer staying cold, I believe it will need replacing pretty soon. The settings on the unit were 190/170 and the tenants say the heat works okay...but this boiler has not not been treated well for a long time. I will get my tech there after the purchase, so I'll have a better idea in January as to it's real condition.

I want to add heat from the boiler to the third apartment no matter what, because my family and friends will use this for weekends at the shore over the winter, and it will only take about 15 to 20 feet of baseboard and a 1/2" line of Pex to do this.


Option #1) Replace the boiler with a direct venting oil-fired unit in the 85% range, and add an indirect in five years when the HWH dies. Primary/secondary piping, an outdoor reset, etc. I pay the heat and HW until the cows come home.


Option #2) Put in three boilers - all gas - probably with three tankless coils or maybe three indirects, and the tenants pay all the bills. I have to get two more gas meters, and break up all the piping, etc. so it won't be easy - or inexpensive. Two boilers about 50-60 kbtuh, and a third smaller one...how small can I go?

Option #3) Put in a condensing gas boiler and ditch the oil. Add everything I can to make it as efficient as possible while I keep paying the heat and hot water. As I rehab the units, I will put in extra baseboard to increase condensing in the boiler.

Oil is not as much of a bargain on this coastal island, so the advantage of 40,000 btuh per gallon (versus gas) or so is dwindled. I have lots of experience with both oil and gas, and usually prefer oil, but in this situation gas may be better - especially if I go with option #3 of course.

I have done basic recon on possibly doing solar hot water, but it's a long shot. There are trees and a flat roof that make this tough...it's a shame because this would make the decision easier.

Wallies, please let me know your opinion...especially in question #1.

Dan, I don't have a contractor within 50 miles of this place. Not sure what I'll do, maybe talk real nice to someone that's over an hour away? :-)

Thanks, PJO

Bob Harper

Interconnection of liquid and gaseous fuels is acceptable as long as certain parameters are met. Sizing, clean out, primary safety controls, etc. See NFPA 211, 54, and 31
HTH

Bob Harper

Interconnection of mixed fuels

Interconnection of liquid and gaseous fuels is acceptable as long as certain parameters are met. Sizing, clean out, primary safety controls, etc. See NFPA 211, 54, and 31

HTH

Constantin

My thoughts...

You have to be the first landlord I've encountered who actually wants to make his tenants happy... (just kidding!)

One way to keep your single boiler and heat all three apartments is to keep track of the pumping and water temperatures beign called for. In Germany, they use either (notoriously unreliable) evaporative systems or electronic ones in apartment buildings to basically make each tenant pay their fair share.

You could do the same by installing a data logger that measures the heat calls in each zone and proportionally charges folks. It could be as simple as plugging the circulation pumps for each zone into one of those electricity meters that allow you to measure energy consumption of appliances. Then, put the oil tank on a automatic fill-up plan and charge folks for the oil in propotion to the "on time" for each pump.

On the other hand, installing a number of T50's not only will lower your admin requirements, it also takes you out of the loop as far as ensuring that a fuel makes it to the house. As far as the tiny apartment, a tankless water heater may be the best option, particularly if the unit isn't going to get used much.

Naturally, you could also install a larger condensing boiler and rehash my "on-time" pump measurement idea. However, that makes you responsible for the gas bill (and $$$ collection). I guess I'd stick with T50's to minimize the oversight requirements...

PJO_5

Update...

Joe, Bob and Constantine,

Thanks for the comments guys. I'll look into that information about the two fuels/flue situation, and the ideas involving the combo boilers are great. The third apartment and the tankless idea are perfect...only trouble will be getting the vent through an 8" block wall :-(

I went through the place yesterday with a very good home inspector. The heat works pretty well, but I found some interesting things:

No insulation on the pipes or under the building (found out when we were in the crawl space). I can't imagine how much money the owner has wasted by not having insulation. Think I'll increase the heatloss calculation until I can spend a lovely weekend under the building :-)

The boiler was last serviced two years ago - I was pleasantly surprised to see that - but no combustion tests were listed. They didn't make any reference to cleaning the boiler, either, but I'm going to call them today if I can.

The HWH is from '93 so I give it five more years tops...

Seeing the piping for the second time, it will be fairly easy to split the heat, but the hot water is another story.

Thanks again gents! Take Care, PJO