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Analyzing and deciding between bids - Propane combi boiler in Vermont
Kate111
Member Posts: 1
in Gas Heating
We currently have a 30 yr old propane boiler with 4 zones. One zone is for indirect DHW for which we have a storage tank. This system has worked well for us. We got bids from 2 local outfits - one our propane dealer who also sells, installs, services boilers, the other is our HVAC / plumber. Reputation-wise, we are comfortable with either. Propane dealer recommends going tankless for DHW, and installing a Rinnai combi boiler. HVAC guy recommends keeping our indirect DHW storage tank and installing a NTI FTV combi boiler, using one zone for DHW as we have now. Our water quality is excellent except for being somewhat acidic. We have a water quality system installed to bring the pH back to neutral. Major differences between the quotes - the Rinnai has slightly better warranty (12 yrs, not 10) on heat exchanger, one recommends installing new high-efficiency circulating pumps and one doesn't. Would appreciate some expert thoughts and opinions. Thanks in advance. Kate
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Comments
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The NTI FTV isn’t a combi unit it’s just a boiler which would work great with your indirect tank.
Be sure that the boiler is plumbed primary/secondary piping schematic which is shown in the manual.
The high efficient circulators will pay for themselves relatively in a year or two. Most likely for the heating side of the system you could can get away with a single circulator and zone valves.0 -
Do you have a tank style indirect? Is it 30 years old also?
How many people in your household?
Combis can work well for small families.
A heat load calc is a good first step.Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
A year or two? Maybe if you're paying 2 dollars per kWh.... At 50 watts of savings, with the circ running 24/7, and a rate of $.10/kWh is $3.60/mo saved. Call it a 6 month heating season, and be more realistic with run time, we're talking less than $10 a year. By the time the payback is reached, you're about due for a new circ again.EzzyT said:
The high efficient circulators will pay for themselves relatively in a year or two.0 -
He is not looking at the big picture. The savings on electricity is only a portion of the circulator's cost of ownership. By using one circ and zone valves, you can get better comfort control with the proper pump setting.GroundUp said:
A year or two? Maybe if you're paying 2 dollars per kWh.... At 50 watts of savings, with the circ running 24/7, and a rate of $.10/kWh is $3.60/mo saved. Call it a 6 month heating season, and be more realistic with run time, we're talking less than $10 a year. By the time the payback is reached, you're about due for a new circ again.EzzyT said:
The high efficient circulators will pay for themselves relatively in a year or two.
This will reduce the gas bill a little too. Not big savings, but every penny helps.
On the other hand. I like to keep things simple. old school pumps are also just fine.
That said, I like the indirect tank over the tankless for the same reason. Too much junk inside a small box with the ModCon boilers, add a tankless water heater to the box and you are asking for a no heat or no hot water service call in the next 5 years that may be a several day affair.
Just my experience with Combi systems. Parts are not always on the shelf at the supplier.Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics0 -
To clarify the zone valve idea. The DHW tank should have a pump, the Boiler should have a pump, and the system should have a pump Three pumps total. the system pump will operate whenever any zone valve is open on a call for heat from that zone. The ECM pump will work well for the system circulator.
That configuration is in the install instructions.Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics1 -
You said the propane dealer recommended an on-demand for the DHW and a combi boiler? You don’t need a combi (heating & DHW) if you get a tankless. If you get a tankless, your boiler will be heating only.
Both suggestions sound fine. The benefit with an on-demand with a separate boiler is that they are independent. If one busts, the other one can make life bearable until the other one gets fixed. Also, with an on-demand, you’ll never run out of hot water.
I’d ask for references; even go visit one of their installations. It should look clean and neat with all the pipes insulated.8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0
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