Burnham MPO-IQ versus Buderus G125BE Oil Boilers

[danboston]

Dana:

Great. I really appreciate your help.

So, if I decide to add solar hot water, I should stick with the Alpine 80 and a 30-gallon buffer tank. Under the solar scenario, for the IDHW tank I would need an 80-gall IDHW heater with two coils.

If I decide NOT to go with solar hot water, then the 55-gal HTP Versa sounds like a better option than the Alpine 80 with a 30-gall buffer. It would essentially be one unit, versus three; easier installation; roughly equivalent efficiencies, etc.

For the Versa-Hydro, would not a 10:1 turn-down ration on the space heating module result in an output of 13.5 to 135 K btus/hr? The Main Combustion System has a turn-down ratio of 5:1.

However, if I did want to go with Solar Hot Water, I do see on the HTP web-site that they offer an 80-gallon Phoenix Solar Hot Water tank (with 2 coils) that apparently can be used in conjunction with the Versa-Hydro.

[Dana]

If going solar price out a Versa Hydro Solar solution before commiting to an Alpine 80 + solar solution. The Versa Solar is a fully integrated single tank system, with very little difference between the 80 gallon Versa and an 80 gallon Versa Solar, beyond the extra coil for the solar loop and some extra controls. With 80 gallons of buffe it would guarantees even longer minimum burns in space-heating mode.

Even if you never install the solar end it's efficiency would be as-good. It's a matter of the up-front costs of an 80 gallon Versa Hydro Solar with an as-yet unimplemented solar loop relative to the proposed non-solar solutions up front. An 80 gallon solar tank by itself is a pricey piece of hardware, and adding that to an Alpine-80 + buffer solution would mak for a more expensive total package.

Not to mention, with either a solar or standard version of the Versa most of the system-integration is pre-engineered, whereas with the Alpine 80 you're at the mercy of the system desginers/installers, and the quality of the design & commissioning a full-custom system will vary. It's pretty hard to screw up with a pre-packaged pre-engineered system.

[danboston]

Dana:

I called HTP and they gave me more information about the Versa-Hydro. They offer three different-sized Hot Water Storage units (50-, 80-, 119-gal), but they all have the same burner. The Main Combustion Unit modulates from 26 - 130 K btus/hr, whereas, the Space Heating component modulates from 13 - 130 K btus/hr. Apparently they use a variable speed pump to convey hot water from the hot water storage tank to the heating elements and that is how they achieve the wide modulating range for the space heating. But to compare apples to apples, the Alpine has a lower modulating range (16 - 73 btu/s/hr) than the Versa-Hydro (26 - 130 K btus/hr) for the main burner. The smallest Versa-Hydro Solar unit comes with a minimum 80-gal dual-coil tank. As you said, an 80-gallon tank will provide plenty of mass and it will never short cycle. It is all one unit - no need for a separate buffer tank or separate IDHW tank. We also have the option of connecting solar hot water now or at a later date.

It does not appear that the Versa-Hydro tank or heat exchanger is made of stainless steel. Apparently, the heat exchanger is a 90/10 cupronickel alloy. Not sure if a cupronickel alloy heat exchanger is reliable?? The lack of a stainless steel tank and cupronickel heat exchanger makes me hesitate....

The Warranty on the Versa-Hydro is as follows:

Residential Use Warranty (1 year – Parts, 12 years – Tank)
COVERAGE
A. HTP warrants that it will repair or replace, at its option, any defective Versa-Hydro™ Combined Hydronic Appliance or malfunctioning component thereof that is found to have failed due to manufacturer’s defect during the first year after installation.
B. 1. Residential Use - During the second through seventh year after the date of installation, HTP will repair or replace, at its option, any defective Versa-Hydro™ found to have failed due to leaking heat exchanger, tank, or brazed plate exchanger.
C. Residential Use ONLY - During the eighth through twelfth year after the date of installation, HTP will repair or replace, at its option, any defective Versa-Hydro™ found to have failed due to leaking heat exchanger, tank, or brazed plate exchanger, at a cost to the purchaser equal to the following percentages of the manufacturer’s list price in effect at the date of replacement.
Year of Claim:
8 & 9 (25% to be paid by purchaser)
10 & 11 (50% to be paid by purchaser)
12 (75% to be paid by purchaser)

Here is the Warranty information on the Burnham Alpine:

ONE YEAR LIMITED WARRANTY ON RESIDENTIAL GRADE BOILERS
AND PARTS / ACCESSORIES SUPPLIED BY U.S. BOILER COMPANY, INC.
U.S. Boiler Company, Inc. warrants to the original owner that its residential grade
water and steam boilers and parts/accessories comply at the time of manufacture with
recognized hydronic industry standards and requirements then in effect and will be
free of defects in material and workmanship under normal usage for a period of one
year from the date of original installation. If any part of a residential grade boiler or
any part or accessory provided by U.S. Boiler Company, Inc. is found to be defective
in material or workmanship during this one year period, U.S. Boiler Company, Inc.
will, at its option, repair or replace the defective part.
HEAT EXCHANGER WARRANTIES
U.S. Boiler Company, Inc. warrants to the original owner that the heat exchanger of its
residential grade boilers will remain free from defects in material and workmanship
under normal usage for time period specified in the chart below of the original owner at
the original place of installation. If a claim is made under this warranty during the “No
Charge” period from the date of original installation, U.S. Boiler Company, Inc. will, at its
option, repair or replace the heat exchanger. If a claim is made under this warranty after
the expiration of the “No Charge” period from the date of original installation, U.S. Boiler
Company, Inc. will, at its option and upon payment of the pro-rated service charge set
forth below, repair or replace the heat exchanger. The service charge applicable to a
heat exchanger warranty claim is based upon the number of years the heat exchanger
has been in service and will be determined as a percentage of the retail price of the heat
exchanger model involved at the time the warranty claim is made as follows:

Year 8 (30% to be paid by purchaser)
Year 9 (40% to be paid by purchaser)
Year 10 (50% to be paid by purchaser)
Year 11 (60% to be paid by purchaser)
Year 12 (70% to be paid by purchaser)

Both of these warranties look pretty similiar.

Although it apparently does not appear in the Warranty description above, I saw in the Alpine brochure that US Boiler offers a free 5-year warranty on all parts and labor for the first 5 years from the date of installation. What are the chances that something will go wrong in the first 5 years with the Alpine?

Thoughts?

[Dana]

Boilers & HW heaters are all pretty reliable for the first 5 years- even the crummy ones, and these aren't crummy ones. Both HTP and Burnham make quality goods that hold up when installed correctly, but a bad install can kill any piece of equipment. HTP also sells some low-end mod-cons (MC series) that DIYers seemed to manage to screw up the installations on, but work pretty well when done right. People have done combis based on their Phoenix condensing hot water heaters for something like a decade(?) without running into reliability issues.

On the heat-exchanger front, as long as you don't have leaks in the heating system or gross materials incompatiblity with sub components, the water side of the heat exchangers will last pretty much forever. Aluminum heat exchangers on boilers-past have had issues on both the fire side & water side, but SFAIK there aren't any generic or widespread issues with cupronickel alloys.

For the sub-flooring, even pressure-treated ply is overkill in a basement that NEVER floods. The XPS is an excellent capillary break against wicking up ground moisture, and at 1.5" it's only semi-permeable to water vapor. The only time you'd need anything other than a standard ply or OSB subfloor over an XPS-on-slab situation, is for flooding events. Structurally it's fully supported by the XPS & slab- it doesn't even need to be as thick as in a joist-mount but IIRC you need at least 1/2" of wood between the room and the foam as an ignition barrier. As long you don't have wood in direct contact with the concrete (pay attention at the edges) and don't put down a vapor-barrier type of flooring such as asphalt tile or vinyl-linoleum it'll have the same moisture content of any other piece of wood in the room. (Hardwood, bamboo, or carpet are all fine.)

[Dana]

Ultimately, the quality of the system depends more on the quality of the system-design and how well it's implemented. Going with something that both installer & manufacturer back up with local support is more important than any warranty clauses. What this thread has given you is the basic education by which you can disuss the pros/cons of different approaches with the contractor better than the average homeowner/buyer would, and also gives you a handle on their competence or lack thereof. At the very least you're more likely to end up paying too much for something 4-5x oversized guaranteed to short-cycle itself into an early grave, expiring 10 minutes after the warranty does. Most residential boiler installations in MA are oversized relative even for the heat-load calculation software numbers, which are as a rule oversized to begin with. Modulating burners can mask some oversizing issues, but getting it right-sized (or adequately buffered) for the loads is always a better way to go.

[danboston]

Dana:

Great. Your knowledge of boiler systems and the ability to convey that information is unbelievable and you have been of immense help. I really do appreciate it!

I will price out the HTP Versa-Hydro Solar. Looks like a great system and hopefully dummy-proof installation.

P.S., What about the 2x4 plates that need to be installed near the base of the interior foundation wall for the new framed wall? Those really cannot be "floated"? I plan to use pressure-treated 2x4s for the foundation wall plates that would be nailed into the concrete using a concrete nail gun. I should put a moisture barrier down between the concrete and the PT-2x4 plate? Are there any other options or steps I missed?

For the partition walls in the basement, I was planning to use 2x3's and float them on top of the 1/2"-plywood (which overlies the 1.5" XPS foam boards). They would be glued and nailed to the plywood - however, am not sure that would be sturdy enough. Should I nail them to floor like the 2x4's (I would have to rip PT-2x4s down to 2x3s but that is easy enough).

Finally, I wanted to use OSB sheets to float over the insulation since they come with a tongue and groove system - that way, I would not have the edges potentially buckling up/down where they butt up against each other. Home Depot has some T&G OSB product made by Home Advantage. The Advantech OSB boards are nice but are about 40% more expensive than "Home Advantage" boards.

[Dana]

The studwalls aren't load-bearing, so putting the bottom plate above the XPS tapconned into the slab or just nailed/screwed to the subfloor is just fine.

T & G OSB is fine. It just has to meet a minimum fire rating (typically a 15 minute barrier per ASTM E 119 test ) to be used as the ignition barrier for the foam, unless you're putting down a wood, ceramic, or other substantial flooring that would add to the fire-rating of the floor assembly. IIRC most 7/16" & 1/2" goods and all 5/8" or thicker OSB out there meets spec on their own. The Home Advantage t &g subfloor goods are nearly 3/4" thick (and probably overkill, since it doesn't have to span between joists, and is 100% supported by the XPS + slab), so the fire-rating would be a non-issue.

[danboston]

The HTP Versa is also an appropriate solution, and will run as efficiently as the Alpine 80 if usng fin-tube as the heat emitters. With radiant floors and/or panel radiatorsit's possible for a good designer to squeak 3-4% more efficiency out of an Alpine 80, since you could then run the heating zones at temps much lower than domestic hot water for high combustion efficiency. The Versa is inherently self-buffered, and making the system design & implementation comparatively simpler- you'd have to work at it to really screw it up (but I'm sure there are installers up to the task. :-) ) Unlike Trianco or Bradford-White combis, the Versa is fully modulating & condensing, with a 5/1 turndown ratio to (same as the Alpine 80's high/low ratio)- they're not really in the same class. Even though the smaller-burner Versa only cranks down to ~25K of outuput compared to ~15K for the Alpine 80, the 55 gallons of water in the smallest Versa is more than 2x the minimum buffer we were talking for the Alpine-80 solution with 10F of hysteresis, for less than 2x the min-mod burner output. There's literally no way to short-cycle it, and it'll average better than 90% efficiency at your anticipated fuel-use derived heat load using your given lengths of baseboard, since you won't need to it up above typical DHW storage temps- it'll ALWAYS be firing in condensing mode.

Dana:

When you say the Versa-Hydro will ALWAYS be firing in condensing mode, does that ssume that the return water needs to be 110 F or lower? Or is it the Delta-T needs to be at a certain threshold value? I had a contractor tell me that it is the delta-T, not the actual return water temperature that determines whether the boiler will enter into and stay in condensing mode. Also, as an FYI, the highest output T that the Versa-Hydro Solar unit (PHE130-80S) can generate is 160 F.

[jadnashua]

A burner condenses when it's exhaust gasses are cool enough. To get that, the return water must be cool enough to drop those temperatures down. This is a function of the design of the heat exchanger, the exhaust path, the burn rate, and the return water temp...the return water temp must be low enough. Once it gets too hot, it can't condense. Now, if your supply temp was 130, the return would be low enough, but it is still a function of the return water temp.

[Dana]

Depending on the exact mix of combusion air & fuel the dew point of natural gas exhaust in a mod-con is between 120-125F. The heat exchangers are thin & refractory for the lowest possible delta-T from the fire side to the water side, but in practical terms it won't be condensing much at all with return water temps much above 120F. If the contractor believes otherwise, he's saying the laws of physics are violable, and his statements on all matters technical need to be treated with great skepticicm.

The 160F high-temp limit on the Versa isn't a problem- with 145' of fin tube that would deliver ~60KBTU/hr for a sub-40K load. At 140F you'd be looking at ~45KBTU/hr out of the same fin tube, and with flows low enough for a 20-25F delta-T you'd be in the 88-90% range. At 130F the 145' of fin tube would deliver ~30-35K, bringing the return water temps down to ~110F, at which point your efficiency would hit the 92-93% range. Getting better than 92-93% is unlikely with any fin-tube system (of any length) because the abilty to get heat into the room with boiler water under 120F/return under 100F gets very limited and hard to model or design for, but with panel radiator or radiant floor/ceiling it's possible by carefully tweaking outdoor-reset control schemes. The Versa uses an outdoor reset curve for the heating system (which has to be programmed- the setup instructions are on page 60.), but since you'd probably never want the heating system output to go under ~120F (the fin-tube emittance modeling issue- it's not linear like the curve is) and your design-day heat load would likely never need more than 135F even at -5F outdoors, yours will be a very flat curve. But it's tweakable- and you SHOULD tweak it to as low a temp that still allows all zones to keep up as the outdoor temps fall. (It'll probably do OK at the default settings, but you can probably get another 2-3% percent out of it with some adjustments that costs you nothing but your tweaking & observation time.)

[danboston]

Dana:

With Federal Tax Credits, State and local utility rebates, the HTP Versa-Hydro Solar system is by far the best deal. It's like getting the solar hot water system for free! I have posted a new Thread under "Water Heaters - Solar and Geothermal" pertaining to inquiries about Solar Evacuated Tube Panels...

[Dana]

Thanks for the feedback!

I've not seen a Versa Solar installation in person- post pics (or pm me) of the installation details as it comes together, if that's the route you end up taking!

[Shelly Brawn]

Dan,

Did you have any luck installing the Versa Solar Hydro system? I want to install one in my home, but I haven't been able to find anyone to take me seriously. I'm not a licenced plumber, and my town won't let me do it myself. I live off Rt 3, north of Boston.

[danboston]

Shelly:

Yes I did have the HTP Versa Hydro Solar system installed. The contractor was great and is local. I had a hard time finding someone who would do it. He is relatively young and new to the business and is not tainted with oversizing boilers like most of the old school guys are. Send me an email to dfolan@yahoo.com and I will give you his contact information.

Tx, Dan