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Comparison

Raypak Hi Delta SS HD251 vs HD301

Verdict in brief

Both the Raypak Hi Delta SS HD251 and the Raypak Hi Delta SS HD301 belong to the Raypak Hi Delta SS line of non-condensing boilers. Published ratings: Raypak Hi Delta SS HD251 at 250 MBH input, 210 MBH output and 85% efficiency; Raypak Hi Delta SS HD301 at 299 MBH input, 251 MBH output and 85% efficiency. Raypak Hi Delta SS HD301 lists 49 MBH more input than Raypak Hi Delta SS HD251 (299 MBH against 250 MBH). Both list the same published efficiency of 85%. Raypak Hi Delta SS HD301 lists 25 lb more shipping weight than Raypak Hi Delta SS HD251 (250 lb against 225 lb).

Side by side

Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.

Comparison of Raypak Hi Delta SS HD251 and Raypak Hi Delta SS HD301
SpecificationRaypak Hi Delta SS HD251Raypak Hi Delta SS HD301
Input250 MBH299 MBH
Output210 MBH251 MBH
Weight225 lb250 lb
Height (B)14-1/8 in15-3/4 in
Width (A)28-5/16 in31-9/16 in
Venting categoryCategory ICategory I
FuelNatural gas or propaneNatural gas or propane
Thermal efficiency85 %85 %
Flue outlet5 in5 in
Maximum water flow44 GPM44 GPM
Electrical<5 A boiler draw, 120 V class<5 A boiler draw, 120 V class

What actually separates them

Published ratings: the Raypak Hi Delta SS HD251 is rated 250 MBH input, 210 MBH output and 85% efficiency; the Raypak Hi Delta SS HD301 is rated 299 MBH input, 251 MBH output and 85% efficiency. Raypak Hi Delta SS HD301 lists 49 MBH more input than Raypak Hi Delta SS HD251 (299 MBH against 250 MBH). Both list the same published efficiency of 85%.

Raypak Hi Delta SS HD301 lists 25 lb more shipping weight than Raypak Hi Delta SS HD251 (250 lb against 225 lb). The height differs: the Raypak Hi Delta SS HD251 lists 14-1/8 in, while the Raypak Hi Delta SS HD301 lists 15-3/4 in. The width differs: the Raypak Hi Delta SS HD251 lists 28-5/16 in, while the Raypak Hi Delta SS HD301 lists 31-9/16 in.

Both records print the same venting (Category I), fuel (Natural gas or propane), efficiency (85%) and flue outlet (5 in), per the cited sources.

CurrentCanadian status unknown
Input
—
Output (max)
210 MBH
AFUE
—

The Raypak Hi Delta SS HD251 is a compact non-condensing copper finned-tube commercial hydronic boiler rated 250 MBTUH input and 210 MBTUH output at 85% AFUE, with a 5 in flue and a 225 lb shipping weight per submittal 241922.

Natural gasPropaneHeating-only
Specifications, manuals and service
CurrentCanadian status unknown
Input
—
Output (max)
251 MBH
AFUE
—

The Raypak Hi Delta SS HD301 is a compact non-condensing copper finned-tube commercial hydronic boiler rated 299 MBTUH input and 251 MBTUH output at 85% AFUE, with a 5 in flue and a 250 lb shipping weight per submittal 241922.

Natural gasPropaneHeating-only
Specifications, manuals and service

Frequently asked questions

Which of the two has the higher maximum input?

The Raypak Hi Delta SS HD301 lists 299 MBH, against 250 MBH on the Raypak Hi Delta SS HD251, per the cited documentation.

Which model is more efficient?

Both list the same efficiency of 85%.

How much heavier is the Raypak Hi Delta SS HD301?

It ships at 250 lb against 225 lb for the Raypak Hi Delta SS HD251, per the cited sources.

Not sure which one fits your home?

A consultation includes a heat-loss review so the size is right the first time.

On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.

Call 778-909-5731Request a consultation

Related

Sources and verification

Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.

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