Burnham MPO147 or Buderus G115/34 ?

Robert O'Brien

you do heatloss? I believe the 115/34 nets about 120k Btu/hr. That's alot for an 1800 sq/ft house.

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TONY_22

I'm looking at replacing my oil boiler (about 43 years old). I've been reading quit a bit, and have come down to the MPO147 and G115/34. The 2 seem very similar, so much so that I'm having a tough time deciding between them. They both seem to have a lot of positive comments and supporters on this site. So are there any important differences between them that I'm missing?

I also plan on going from a domestic coil to an inderect hot water heater. Alliance or Buderus?

A little info on my system. There's 1 zone of cast iron baseboard that covers about 1000 sq. ft. and 3 zones of radiant that covers about 800 sq. ft.

Thanks,
Rob

Cunner

MPO vs. G115

Rob,
Both are great boilers and are very evenly matched, the one feature that may make a difference in your case is that the MPO has built-in low return water temperature and the Buderus doe not. The G115 Buderus can handle low temps with the addition of the 2107 control. I see you have cast iron baseboard which would make the return temp an issue. I have used both without incident. I would certainly consult your installing contractor and get his opinion.

Rob_36

heat loss?

Yes. It was about 60k. This was without factoring in DHW, so I wasn't sure what this would add. I thought the output of the G115/34 was 104k. I know I shouldn't oversize, but I thought the next step down, G115/28 at 85k seemed to close.
The existing boiler, which has never had to heat the 800 sq.ft. addition, is 123k. After doing a heat loss, I see that this is grossly oversized for the original 1000 sq. ft., but I'm hesitant to drop all the way down to the 85k range.

Rob_36

MPO low temp return

This is handled internally, without mixing valves or injection pumps, correct?
Any other important differences?
Any opinions on the indirect?

Robert O'Brien

That

heat loss of 60K is on a zero degree day,why would you want a boiler 66% bigger than what you need?

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Cunner

Differences

That is correct, the MPO uses internal mixing much like the 215 series Buderus, otherwise they are a very similar product in performance. As for indirects, Burnham, Buderus, Superstore, Triangle Tube are all accepted as good quality, well performing indirects. I tend to use the same manufacturer for both the boiler and indirect, just my preference.

Rob_36

What would I add for an indirect?

Unknown

Nothing

You want to size the boiler strictly to the heatloss of your home . You can always add an oversized indirect which will take longer to recover , but might get you past peak hot water load times .

As an aside , I have a similar size home and heatloss . I have an oil boiler firing .50 gph and a 30 gallon indirect . Not a problem yet heating the home or with hot water ( 5 people ) .

Rob_36

Thanks

> You want to size the boiler strictly to the

> heatloss of your home . You can always add an

> oversized indirect which will take longer to

> recover , but might get you past peak hot water

> load times .

>

> As an aside , I have a similar

> size home and heatloss . I have an oil boiler

> firing .50 gph and a 30 gallon indirect . Not a

> problem yet heating the home or with hot water (

> 5 people ) .

Ejk

if you install the logamatic with the buderus you can prioritize the DHW tank and it will not affect the heat load.

Joe@buderus_2

Boiler size

It is suggested to size the boiler to the heat load and if there is a large hot water demand look at a slightly larger indirect or possibly an indirect with a storage tank. The output of the G115/34 is 120,000 btu's. IBR rating is 104,000. Based on the information provided, the G115/28 with a 40 gallon ST150 will suit the need. The optional Logamatic control(R2107) should work very well with the cast iron radiators. Please consider an outdoor reset control no matter what boiler you choose. It is suggested to consult with a couple of contractors, listen to their idea's, hire the "pro" that knows their stuff.
Out of respect for Glenn Stanton (Burnham Representative) either boiler, the G115 or MPO will provide an efficient heating system. Boiler size, system design and installation are the most important factors. If there are any questions regarding Buderus products please contact us at 1-800-283-3787.

D107

How was the heat loss done?

As a homeowner who has seen many of these posts, I ask if you did this with a particular software program, or manually following a particular guide. It takes alot of detailed measurements to do it right.

The other thing is have you done any sealing and insulation that could significantly reduce your heat loss? I had cellulose blown into my walls and sealed my fireplace flue and may have dropped 10Kbtu from my loss. I mention this because if your loss is 60K now, and you are sizing to loss only, the G115-21 or Burnham MPO 84 (both net output 64K), though very close, might work, especially if you've sealed and insulated. The heat loss calc programs supposedly overstate loss by a good margin and you shouldn't have to go to the next size. Since it feels like a bit of a risk to get that close to the actual loss with your boiler choice, I always hire a pro to do a heat loss to verify my own, no matter how detailed mine was. It took me over three hours to do mine manually. You should also measure your rad btu 'gain' not to figure loss but to see how well it covers the loss. If you have twice the btus in radiation as in loss, you'll be in great shape with outdoor reset and operating at lower supply temperatures. Good luck.

David

ScottMP

Both are Fine boilers

At this point shop the installer and not the Boiler. Find out which boiler the installer is happier with. Find a competent installer and let him decide.

I would use an Indirect other than the Allaince.

Scott


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singh

If it were my house

I would go with the G115/21 or the MPO 84 sizes.
Indirect run off priority. Outdoor reset a must.

Where are you located, what did you use for design temps when calculating heat loss.

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Robert O'Brien

I'm

Paraphrasing Dan but this thread reminds me of his statement that " The urge to oversize is stronger than the sex drive"

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Robert O'Brien

I'm

Paraphrasing Dan but this thread reminds me that his theory that " The urge to oversize is stronger than the sex drive" is not only very funny but absolutely true!

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TONY_22

0 deg. design temp

I used software offered through this site. I'm located in central PA. I've found Burnham to be pretty common here, but not much from Buderus.

As far as controls go, I like the tekmar tn4, although I'm not sure I can justify the cost.

Thanks to all for your input.