New Steam Boiler - Oversize then Downfire?

john_ospnj · October 2022

Hi Pros,
So I'm looking at a replacement steam boiler for my old 2 story home in north/central NJ - Weil-McLain EG40 or EG45. EDR is calculated at 319.2. All main lines and feeders in basement are well insulated. 5 risers to rads on 2nd floor seem well within the 33% allocation for piping. The contractor says I'm 'right on the bubble and could go either way with the EG40 or EG45' but he is recommending the 45 and then 'throttling it down to around 135 BTU'. He says the EG40 is right-on, but he prefers to have that extra cushion with the larger model to make adjustments.
I've put a call into Weil-McLain, but no response yet, and I've heard that they aren't great with customer service.
Now the old Crown BSI138 was 138 BTU and 354 EDR was a little oversized, because there were 2 other radiators that have been removed from the system at some point. I had to get the main and rad venting balanced just right to avoid short-cycling. And the home got very toasty warm with the Crown. So with a new boiler I fully expected to go a little smaller, not larger...
So what do you think? The contractor didn't explain exactly how he would downfire the EG45, but there seems to be a lot of caution re that on here. It's not a huge home, about 1600 sq ft.
Appreciate any thoughts/guidance.
John

EBEBRATT-Ed · October 2022

I would go with the smaller boiler. Keep in mind the standard boiler rating builds in 33% for piping and pickup. Since you don't have extensive piping and you are well insulated you will be fine

KC_Jones · October 2022

Don't do it, just don't. There is a 33% pick up factor in those boilers to account for piping and such, which in my opinion is way too much already. He is talking about going above that.

The EG-40 is rated for 321, that's more than adequate for what you need. This really shouldn't even be a question and would make me suspicious of the work they will do.

What is also imperative is that the boiler be piped correctly. Make sure they do that, including proper pipe sizes. The EG-40 requires 2 1/2" pipe for the riser and header, make sure they do that. We see plenty of contractors doing work (posted by homeowners) that refuse to use anything over 2", and that is wrong.

john_ospnj · October 2022

Excellent, thank you both for the quick responses. And I absolutely agree, so now I feel good going back and specifying the EG40.
Also - just got a response from WM: 'The boiler really can’t be down fired – the manifold pressure must be 3.5” wc – anything different from that can cause issues.'
So that seals it.
And yes, other than the sizing comment, he seems ok - he is specifying 2 1/2" on riser and header.
Thanks again.

random12345 · October 2022

Are you sure you calculated your EDR correctly? You have a small house, and your EDR sounds high to me. If you want us to double-check your work, go ahead and post up some pictures of your rads, 1 from front and 1 from side for each. Include exact height and thickness of a single radiator section for each, and manufacturer name if available (found around steam supply tapping or embossed on end-most sections). If a convector, measure depth, width and internal enclosure height. If you'd rather not post, that's fine, I will just say that I agree with what has already been posted.

ChrisJ · October 2022

EG-40 and EG-45 are identical boilers except for a few cheap parts like the burner bracket, burner manifold and drafthood.

Buying and EG-45 and reducing it's gas pressure is silly.

Buy the EG-40 and worst case convert it to an EG-45 but it's highly doubtful you'd ever need to do that.

@random12345 My 1600sqft house has 392sqft of radiation and I'm using an EG-40 because the EG-45 was too big in my opinion.

JohnNY · October 2022

At 319, I'd be happy to know I've found the proper replacement at 321. Why make it more complicated than that?

EzzyT · October 2022

I already gave the OP a quote on a replacement and I recommend the Weil McLain EG40 since it is the closest boiler size to the EDR.

KC_Jones · October 2022

EzzyT said:
I already gave the OP a quote on a replacement and I recommend the Weil McLain EG40 since it is the closest boiler size to the EDR.

If EzzyT is able to do the replacement, I highly recommend you hire him. One of the best around for steam, and judging by the other stuff we see around here from NJ, he may be the only one that knows steam.

Considering the one you posted about doesn't even fully grasp the sizing (which isn't hard), I'd be leery about hiring them to do the actual work.

JohnNY · October 2022

@KC_Jones EzzyT is not the only person in New Jersey who knows steam. The northeast of the USA has most of the steam heated homes and buildings in the country and there are many great techs and installers who will have nothing to do with this forum and so you don't know their names, but I assure you, we're out there in the field every day.

That off my chest, Ezzy is an amazing installer. He's also a smart guy who can think through problems outside of typical conditions and challenges. Anyone who hires him is in good hands without question.

New Steam Boiler - Oversize then Downfire?

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