Help sizing new gas boiler

LInewbie

Hi, I'm planning on having a local contractor on Long Island replace our very old oil burner with a gas system (Buderus GC124) and a 53 Gal indirect water heater. Never having done this before, I took a stab at the Slant Fin Hydronic Explorer and came up with a heat loss of 81,600 BTU's. That included the mostly below grade unfinished basement, but not the unfinished attic (storage only).



We live in a 2000 sq ft frame colonial built in 1923, which has double pane windows and 1/2 inch insulation under vinyl siding. Is the GC 124/4 with a DOE output of 87,000 btu's big enough, or should I go with the GC 124/5 that puts out 112,000? Thanks for your help.

Robert O'Brien

Fudge

There is plenty of fudge in the software and over 40BTU per sq/ft is a lot,I'd go with the 87K with no concerns. We're on LI also,the new model GC124 is eligible for the Nat Grid rebate. You are going to need a chimney liner if you have a masonry chimney

LInewbie

Thanks

Thanks very much. Yes, the contractor included the cost of a stainless steel chimney liner, and let me know about the rebate.

Jim Pompetti

Sizing

Highest eff.possible

Lowest water to heat .

Smallest boiler than will cover heat load.

Thats how to save the most.

gennady

new boiler

why not 90+% efficiency boiler?

Robert O'Brien

Gennady

Were you at Viessmann in Warwick last July with Wales-Darby?

gennady

viessmann

Yes  i was there.

Robert O'Brien

Thought

I recognized the name!

LInewbie

why not 90+ eff boiler

Thanks everyone. Considered a mod/con boiler, but the only way to vent it would have been through the front wall of the house. Also saw a lot of posts about poor water quality damaging the heat exchangers. Wanted to go with something with long term reliability, even though the efficiency is lower.



One other question. Is the Buderus GC124 worth the price premium over the Burnham Series II of the same size? I know that the Buderus has a higher efficiency and qualifies for the Nat. Grid rebate.

gennady

venting

many high efficiency boiler have a vent kits installed in chimney and allowing for venting trough the existing chimney, and  no ss lining required. as per water quality, your heating system circulates same water, being treated with water conditioner like sentinel x100, it becomes completely harmless. Don't fall for 50 year old technology.

Robert O'Brien

GC124 vs Series 2 ?

The Series 2 is not eligible for the rebate,the Burnham ES2 is eligible and is available through Nat Grid so that would be a fair comparison,only you can decide if it's worth the difference. A condensing boiler can be vented using the existing chimney as a chase for the plastic vent

ColoradoDave

Boiler Venting

We recently used PP pipe (the brand was Centrotherm Innoflue) to vent a Laars Neotherm.  M&G Duravent is another PP pipe, we haven't used it yet though.

I must say, it went together great and only cost about twice what PVC pipe cost.  The ease of installation more than offset the slightly additional cost.

We are currently bidding an installation that will require running through an existing chimney being used as a direct chase for the existing boiler.  Centro-therm has a flexible vent that can be dropped down the chimney and directly tied to the boiler.  I'd recommend that as an option for putting in a mod-con with higher efficiency.

The Centrotherm is ULC S636 approved.  http://www.centrotherm.us.com/products/flex/

ColoradoDave

Boiler Venting

Fast fingers this morning, submitted post twice!!

Robert O'Brien

Dave

I agree,PP is great. Can't tie the flex directly to boiler,have to transition to hard pipe at the base of chimney

gennady

Wanted to go with something with long term reliability

If you need something with long term reliability, why not consider wooden stove? Just kidding. It is 2012 today.

LInewbie

53 Gal indirect hwh

Is the 87,000 btu large enough for a 53 gal hwh? We have two full baths and I want to make sure that there's enough water for both showers to be used at the same time (about 4gpm total). The indirect would be set at 140 or 160 and wired for priority.

Alan (California Radiant) Forbes

DHW

Just make sure you install a tempering valve at the outlet of the water heater - 140F or 160F is too hot to go to the fixtures.



The smaller boiler with the indirect will be fine, especially at the higher water temperature.

LInewbie

Thanks!

Yes, definitely will have a tempering valve. Thanks