Presentation for NSPS Consideration:

Oversizing Hydronic Heaters:

1. Oversizing Outdoor Hydronic Heaters (OHH) for residential use immediately invalidates the 

EPA’s stamp of approval of cleaner technology, yet consumers more often than not purchase 

oversized units for the following reasons:

a. Larger firebox which increases time between loadings. 

b. To heat additional out-building such as garages and pole barns. 

c. To prepare for future out-buildings.

d. To heat pools, Jacuzzis, melting ice on drive ways etc.

e. Dealers convince buyers to purchase larger units. 

f. Consumers believe their units are not oversized based on the EPAs whitetag. 

Examples as to why oversized units create nuisance conditions: 

a) Most operators of OHH dislike getting up late into the night to reload fuel. By purchasing an 

oversized unit, the firebox is larger and the unit stays in Category 1 mode for long periods 

thereby preserving the fuel and increasing the time between loadings. 

b) Purchasing a larger OHH to simultaneously heat a home and outbuildings may operate more 

efficiently when both are calling for heat, but during those instances when the owner does 

not occupy the outbuilding(s) the second zone may be turned off to save fuel creating an 

oversized condition for the home. 

c) Many home owners purchase oversized units based on the possibility of constructing 

additional out-buildings in the future. During the time the building(s) are on the wish list 

the oversized unit creates nuisance conditions for neighbors.

d) Pools, Jacuzzis, driveway heating etc., are all temporary with respect to being part of the 

heating load. When an OHH is purchased to accommodate these conveniences, along with 

heating a home, an oversized condition exits when there is no longer a requirement to 

provide heat to the secondary needs. 

Cycling Technology:

Cycling technology employed in Outdoor Hydronic Heaters (OHH) is an inefficient method of 

regulating heat demand of a building. Compared to other heating systems such as natural gas, 

hydronic heaters employing cycling technology do not simply turn off when there is no longer a 
call for heat. Instead, they idle in Category 1 mode, setting the conditions for heavy smoke and 

pollution during the next call for heat cycle. Oversized units exacerbate this condition. 

Research:

The significance of oversizing and its effect on efficiency and emissions is not a recent subject. 

NESCAUM and NYSERDA warned the EPA about the dangers associated with improper sizing in 

past reports. In the following passage NYSERDA not only outlines the hazards of oversizing but 

also implies that the current testing methodology is lacking when considering climates (design 

day) not represented in the test procedures. 

“As the units are increasingly oversized, the amount of time spent in the lower loads increases 

and performance at these loads is typically lowest. As efficiency decreases, PM emissions 

increase greatly, often in an exponential manner below 25% load. The Syracuse model shows 

that for a reasonably harsh climate, the average output of a White Tag unit provides a sizing 

factor of three, which yields about 90% of the operation at a load of 25% or less. It is also 

important to consider that these units are installed nationwide where milder winters such as in 

the South could yield sizing factors much larger than three, hence pushing the hydronic heater 

into even lower load operation. As the heater’s nominal output increases beyond the design day heat 

load, the time spent operating at lower loads increases. The average output of the White Tag units when 

using the load side data is 175 kBtu/hr. This leads to significant oversizing ranging from 2.7—8.8 times the 

design load depending on the climate. (Review of EPA Method 28 OWHH Test Results, NYSERDA, 

Page 11 -13)”

Conclusion:

It goes without saying that government testing programs do not rely strictly on science to arrive 

at final testing protocols. But the issue here is not a few miles per gallon from what the sticker 

reads on a new car, it represents significant nuisance conditions that drives people from their 

homes and harms health. After receiving complaints for years from states’ and citizens’ affected 

by hydronic heaters, the EPA must not squander this opportunity to finally get it right. Human 

health should not be a negotiable. NSPS should require that certification testing be based on 

three climates – very cold, cold, and mild winters. If the manufacturer elects to sell its product in 

any of the three climates then testing should be adapted to represent that climate. Based on 

the EPA sponsored NYSERDA report, the average whitetag unit tested is already oversized by a 

factor of three if sold in a cold climate. This simply does not pass the common sense test when 

considering the requirements of the Clean Air Act and is one of the main reasons Phase II 

models continue to create nuisance conditions. Simply stated, cycling technology in its present 

form cannot operate safely even with a whitetag attached. 

Because there have been countless Phase II oversized units sold many families are now enduing 

a living hell with very unattractive options to remedy the created health hazard. State DEQ’s and 
local government who bought into the voluntary program now have their hands tied because 

Phase II units have been touted as safe and 90 percent cleaner yet most of the models bearing 

the whitetag earned the label as a result of the technology driving the test instead of the test 

driving technology. We ask that this significant flaw in testing be remedied to ensure that sizing 

factors are accounted for based on the projected climate the model will be sold while also 

considering how out-buildings and other secondary variables affect initial load calculations. We 

also ask that strong enforceable language be added to NSPS not allowing oversized units to be 

sold in any climate where the “design day” variable is exceeded to a point where a health hazard 

could be created. Finally, we ask for strong mandatorily enforceable nuisance protections to 

counter the damage already inflicted on families as a result of flawed testing during the 

voluntary program and that this program be immediately discontinued. 

Proposed Language for NSPS:

The EPA cannot guarantee that a certified Outdoor Hydronic Heater will not create a nuisance 

condition if the unit installed is oversized. Additionally, outbuilding or other secondary 

structures included in the initial residential load calculation (Manual J) can also cause nuisance

smoke and odor if these secondary loads are switched off by either low temperature settings or 

the zone is made inoperable when the HH is operational. State and local authorities should also

consider not allowing oversized installations of Hydronic Heaters for anticipated out-buildings or 

secondary uses until the additional heat loads are operational and analyzed by certified 

personnel. 

Manufacturers: 

Hydronic Heater Manufactures are always quick to point out that it’s not their product that 

creates nuisance conditions but how the unit is operated. The aforementioned suggestions will 

assist in proper operation. 

Thank you for the opportunity,

Roger Soldano