PurePro?

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joe beagle

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Hello,
I am about to pull the trigger on a new boiler. I have settled on a company that appears to have a good track record and professional field rep. Wasn't the lowest price, but seems more dependable than both the highest and lowest bidders.
There are currently two options: A Peerless MI-03 series and a PurePro AG3N.
I'm leaning toward the Peerless because they seem to be more mainstream (more guys who can work on them and more parts availability.)
Anyone have any insights into PurePro?
And, is my reasoning sound?

Thanks,
Gary
 

Dana

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No insights into the PurePro- looks good enough in the short-sheet spec. Stainless burners might be easier to keep clean, but it's just another barely-legal-efficiency cast iron boiler like the Peerless MI. If there is more Peerless support in your area and it's not a large difference in cost, that's reason enough to go with Peerless.

But before pulling that trigger, get down to the basics- let's be sure a 3-plate/58-59KBTU/hr boiler is the most appropriate size:

What is your design heat load (either by Manual-J calculation, or fuel use analysis- preferably both)?

Number of zones, and amount/type of radiation (per zone)?

Are you planning to heat your potable domestic hot water with the boiler?
 

joe beagle

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No insights into the PurePro- looks good enough in the short-sheet spec. Stainless burners might be easier to keep clean, but it's just another barely-legal-efficiency cast iron boiler like the Peerless MI. If there is more Peerless support in your area and it's not a large difference in cost, that's reason enough to go with Peerless.

But before pulling that trigger, get down to the basics- let's be sure a 3-plate/58-59KBTU/hr boiler is the most appropriate size:

What is your design heat load (either by Manual-J calculation, or fuel use analysis- preferably both)?

Number of zones, and amount/type of radiation (per zone)?

Are you planning to heat your potable domestic hot water with the boiler?

Dana,

My heat load calculation came out to 40,000 using the calculator at www.loadcalc.net. I have two zones with a total of 64 linear feet of baseboard enclosed in metal radiator type cabinets below the windows.
I now have an electric water heater, which I will eventually replace with either a indirect unit off the boiler or a solar system.

For what it's worth, I have had five estimates and most of them chose the 50,000 the 60,000 unit, but I don't think any of them ran specific numbers through a program.

It is a pretty small 1950s house, 1,140 square feet, and about average in terms of insulation. I hope to use the money saved from the oil to gas conversion to beef up the insulation.

Thanks for you input. This is a great site.
 

Dana

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40K load even @ 0f for an 1140' house would be on the very-high side of a house that had insulation in the walls, and glass in the windows. Most would be about 30K @ 0F before improvements.

Don't count on the pros for precision on the heat load, unless they give you a printed out Manual-J and all of the details of the inputs check out. Most online heat load calculators have drastically high air infiltration default numbers too.

If you have a "K-factor" stamped on a mid to late winter oil fill-up, or some oil bills with exact dates & amounts we could narrow in on that by quite a bit. A ZIP code can help find the nearest weatherstation for more precise weather data. It can be even further refined by knowing the thermostat settings (including overnight set-backs, if any.)

How many feet of convector per zone, and how deep / tall are the fins on those convectors, and how tall are the cabinets?

At typical 26" tall convector with 4" square fins is good for ~1500 BTU/hr per foot @ 190F AWT (200 F output on the boiler, 180F back), or about 1250 BTU/hr per foot @ 170F AWT (180F out, 160F back.) With 64' total and a 58K-out boiler you're looking at ~900 BTU/hr per foot, which balances at about 150F AWT, which is fine- the boiler would run a continuous burn during a call for heat without running into destructive condensing temps. But...

With only one zone calling for heat, even it's split 32'-32', that's 1800 BTU/foot. The boiler can't run hot enough for only 32' of convector to dump that 58K of heat into the zone, so the boiler will cycle on/off during calls for heat. It probably won't short-cycle itself into super-low efficiency, but you'll lose some, and it's less than ideal, and to keep cycle counts down & efficiency up, a heat-purging boiler control would be a good idea.

If your heat load is as low as it likely is, there are smaller boilers that would run more efficiently and effectively without cycling on single-zone calls.

Without more info on the actual convector size (and amount of convector on the smallest zone), or the and fuel use it's hard to pick a boiler. A 58K boiler would be fine running that radiation as a single zone, but it's almost certainly oversized for any one zone, and 3x oversized for the the whole-house load level you'll likely be hitting if you get serious about upgrading the insulation & air sealing. You'll probably be able to get the place to 20K @ 0F without breaking the bank if you're judicious about it.

If you're going to go with a 3-plate/60K-ish boilers, the 3-plate Burnhams come with smart controls and are tolerant of low return water temps and wouldn't short cycle. But there are probably smaller/better choices out there for both your current and future loads.
 

joe beagle

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Dana,

Thank you for your reply.
You have given me a lot to think about, so I am going back to square one, redoing my heat-loss calculation, calculating my actual BTU/HDD number and then reconsidering my boiler options.
In the meantime, like a lot of amateurs, I am finding it hard to envision just what is going on with a heating system, even though it seems pretty simple.
So I've been wondering if BTU requirements are somewhat like space heaters: If I put four 10,000 BTU propane heaters in my house, would that be similar to having a 40,000 BTU boiler in the basement?
If so, I can easily see how 40,000 BTUs would be too much. Most of the time, we could probably get by with two. So, 20,000 to 30,000 BTUs would be much closer to what I actually need.
Or maybe my analogy doesn't work at all.
In any case, I am pretty confident that when I get done with the number crunching I'll be a lot closer to your lower numbers and will be saving a good chunk of money because of it.
So, thanks once again.
Gary
 

Dana

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With the boiler in the basement there will be some distribution losses to the basement, but having four 10,000 BTU/hr space heaters is otherwise pretty similar to having a 40,000 BTU/hr boiler in the basement. (With the distribution losses it might be closer to having a 45,000 BTU/hr boiler in the basement.)

When using fuel-use against heating degree-days to calculate the load distribution losses are already factored in. A K-factor stamped on a mid to late winter fill-up or some oil bills with the fill-up dates & quantities would be a good starting point.
 
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