Real Estate Investor · Audubon, PA · Member since 2009 · 13k+ posts · 8k+ votes
12y
Regarding tankless, the gas line and main must be able to support these; not all lines can supply gas flow needed for tankless.
What kind of efficiency are you looking for? Starts at 80% and goes to 95*%. Then we need to know the venting that this house can support. Direct vent is common for the higher efficiency units; your existing system almost certainly is chimney vented. For direct vent, the unit will need to be located near an exterior wall.
Real Estate Investor · Audubon, PA · Member since 2009 · 13k+ posts · 8k+ votes
12y
Regarding tankless, the gas line and main must be able to support these; not all lines can supply gas flow needed for tankless.
What kind of efficiency are you looking for? Starts at 80% and goes to 95*%. Then we need to know the venting that this house can support. Direct vent is common for the higher efficiency units; your existing system almost certainly is chimney vented. For direct vent, the unit will need to be located near an exterior wall.
Investor · Narragansett, RI · Member since 2013 · 8k+ posts · 4k+ votes
12y
What kind of fuel do you have? I think that will make a difference. Is it to supply heat and hot water?
We have an older oil boiler and switched to electric tankless for the hot water.I really like it as the oil on demand heater did not get water to the second floor tub effectively. We never run out now. When we looked at a local tankless just for the upstairs bathroom it was more cost effective to get a whole house one. There were wiring changes involved to upgrade the electric but we were doing that anyway. Also the electric bill did go up. If I had to replace heating and hot water at the same time I might have done it differently and just purchased a new oil system. I have a newer oil on demand in a five unit and the tenants don't complain about lack of hot water at all-- but maybe they just haven't gotten to it yet. If you have gas I have heard they are better then the electric on demand units.
BiggerPockets Founder · HI · Member since 2008 · 16k+ posts · 5k+ votes
12y
Hey guys -
I've got gas and the venting is to the roof, but the unit is near an exterior wall. So all those issues aside, what else do you guys have to say on this? I appreciate the feedback so far!
Investor · Tampa, FL · Member since 2013 · 2k+ posts · 1k+ votes
12y
Here's our new system (and the one with Spriovents we talked about on the Podcast). Its a Buderus boiler which hangs on the wall as you can see. It operates at 96% efficiency. The boiler also heats the hot water. So the big platinum colored Weil McLain tank to the right is purely hot water storage. The system is set up for multiple zones and automatically adjusts the load based upon demand and exterior temperature to operate at maximum efficiency.
This picture was taken just before completion. Its so quiet you need to check a light on the unit to know its operating. It runs on natural gas. Our next step is to hook it up to the internet to control it from wherever we are. I modeled the install after seeing this set up on YouTube.
We have one that looks similar to the picture posted by @Darren Sager ... though we have a storage tank {which is essentially a giant thermos bottle} before our in-line water heater/boiler because we have installed a solar thermal system in the property.
The sun {pre}heats water for both domestic use and the hydronic heat ... the inline gas-fired heater/boiler is a little smaller than what Darren is using, but it has to contend with less lift since the source water temperature is higher. If the building had radiant heat rather than hydronic baseboard, we would have had the option of heating directly with solar.
We are planning a further alteration to the system to have the return line(s) from the heat fed into the heat exchanger of the solar system - or perhaps a second heat exchanger - to allow recapture of residual heat in the return lines to preheat source water.
I probably over sized our boiler however I did it to ensure we'd never run out of hot water. The way its sized up it can heat water faster than it can be used. The system will shut off other zones and prioritize the heating of water to make sure we never run out. We're also set up for when we finish the basement and add another 800sq ft. of living space down there.
Using a drain coil type heat exchanger (perhaps 2-4 in parallel) is one option we are entertaining. The advantage is they are relatively cheap to construct and install. The downside is they are not as efficient, nor compact, as something like brazed plate or tube-and-shell exchanger. We presently have a "solar boiler" on the solar thermal system.
While this installation has been educational and well on its way to paying for itself, recent advances in photovoltaic system (cost/efficiency) combined with heat-pump hot-water heaters has us at a point where is may be more cost effective to heat domestic hot water in this manner than using solar thermal.
Rental Property Investor · Denver, CO · Member since 2013 · 4k+ posts · 2k+ votes
12y
@Joshua D. I have looked into replacing a gas fired boiler that is probably 100 years old. It is a coal furnace that was converted to gas by inserting a gas burner. It's very inefficient. It's covered in asbestos so it's going to be very expensive to replace. It heats a duplex so I am also looking for a way to split out the gas so each unit gets their own bill from the power company.
At any rate, to answer your question about using a on-demand water heater to supply the water for your heat. This is what I found. The on-demand water heaters are designed to heat the water to about 120 deg F or less. Boiler systems with hot water baseboard heat run at about 180 deg F. The on-demand water heaters will not work for hot water baseboard was my conclusion. To work properly, the baseboard fins require the hotter water temperature (180 deg F). It would be nice if I was wrong because they are lots cheaper than boilers.
I have been told the on-demand heaters work for the radiant floor heat. The down side of this is you have to install the radiant floor heating system (pex pipe snaked under every square inch of living space-lots of labor cost). My duplex has a crawl space under it so that may be the way I go. Either way it's big bucks.
There are both on-demand water heaters for DHW and wall mounted boilers for hydronic baseboard heat systems (they look physically similar, but are usually larger) and a few units which do both.
If you look at @Darren Sager picture above, he is using a boiler - you will see the overflow tank - with a storage tank. It is possible to run a system like this in {almost/near} on-demand mode with minimal to no storage we are effectively doing this because we are using solar to pre-heat the source water for the system (as well as DHW). The amount of storage you should have will really depend on the characteristics of the system (volume, length of runs, etc) and the capacity of your boiler.
Wholesaler · Holiday, FL · Member since 2013 · 571 posts · 221 votes
12y
Before I have to write you a novel - First tell me this -
What kind of heating fixtures do you have now? Cast iron baseboard? Cast iron radiators? Copper tube/aluminum fin baseboard? Wall convection units? Wall fan/coil units? Radiant wall panels?
What fuel doe the present boiler use?
What fuels are presently available in the house?
What fuels are presently available TO the house?
Is the present chimney lined? If so; with stainless steel or with tile?
What are your plans for the house? 5-10-20 years out?
Queensbury, NY · Member since 2013 · 11 posts · 0 votes
12y
For what its worth my family owns an HVAC company, you are better off going with a reliable utica boiler with a cast iron heat exchanger the amount of money you save between 85% efficiency and 97% actually isnt huge mainly because you almost never get the 97% and most people installing the super high efficiencies dont install them correctly to achieve said efficiencies. To go beyond that I do daily service calls on new tankless systems and ive torn out a number of super high efficiency boilers.
Wholesaler · Holiday, FL · Member since 2013 · 571 posts · 221 votes
12y
1956 was a long time ago. Is the boiler original to the house? Or is the house older than that? I ask because the chimney is almost certainly as old as the house. Code will very likely call for a masonry chimney to be re-lined and a metal chimney to be replaced. Both of which will cost a substantial amount of money - which funds, to my way of thinking, would be far better spent on installing high efficiency equipment which can be sidewall vented through PVC pipes - instead of on improving an obsolete chimney.
If it were me I would hang a Navien condensing tankless boiler/water heater on the wall and use that for both purposes. I used to use Tagaki but have since come to prefer Navien. Installing it as close to the gas meter as possible will make the gas line as inexpensive as possible. Check code for the clearance required - I think it's 4' separation - but check the BOC and gas code rather than believing my memory.