Boiler recommendations?

nicholas bonham-carter

Note, I am editing this post to reflect changes to the EDR of the radiation.

For my Chapel project I need some recommendations for a wet-based gas boiler, for a stone chapel with a mostly intact Dunham 2-pipe system. The drum shaped trap is still on the return, but the old leaking boiler has been superceeded years ago by a badly installed furnace.

The ground floor has 757 ft of radiators, and 207 KBTU heat loss.

The basement has 162 ft of radiators, and 63 KBTU heat loss.

The total EDR is 919 ft, and the total heat loss is 270 KBTU.

As the Dunham system may have orifices installed (or could be installed), I wonder whether to get a boiler which matches the EDR, but which could be dialed back to the heat loss, if we get all the orifices in place.

How difficult is it to derate a gas burner 33%? Assuming the use of a combustion analyzer, is this a matter of adjustment, or changing of parts?

Another difficulty is the lack of local representation here in Nebraska of all the makes I see mentioned on this site. --NBC

Dave in QCA

A Dunham System

Nicholas,

I am pasting two links here. The first relates to the trials and struggles of getting our old Dunham system to work reasonably well.



The second relates to a boiler replacement. Here is thee system data after installing the new boiler:

Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.

System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.

Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279



http://www.heatinghelp.com/forum-thread/131216/The-Best-Heating-System



http://www.heatinghelp.com/forum-thread/143629/New-Boiler-at-the-Best-Mansion

nicholas bonham-carter

Arithmetical errors

Thanks Dave, I will be refreshing my Dunham knowledge.

I edited my first post about this, and after having got down on my hands and knees in the chapel, I find I have less radiation than I thought, under some marble side benches.

The ground floor has a heat loss of 207 KBTU, but the radiator total is 757 ft.

The basement has a heat loss of 63 KBTU , but only 162 ft

Therefore the total Heat loss is 270 KBTU, served by 919 ft of radiation (221 KBTU) leaving me short by about 50 KBTU .

Either some radiators have been removed, or the building was under-radiated. When built, there were 2 large cremation ovens in the basement, and maybe theses were taking up the slack. Alternatively, in 1913, there were no powered soil defrost ears, enabling graves to be dug in the depths of winter, so maybe not much use for the building at that time.

Alternatively, the supplies and returns have some EDR , which I have not taken into account, but as it is a Dunham system, the pipes are fairly small.

Wet base boilers for that size do not seem to offer any hi-lo-hi burners (gas), so are they easy to derate to the load?

Possibly, the SlantFin heat loss App is overdoing the heat loss.--NBC

vaporvac

SF TR60 or 70?

Hi NBC, I'm glad to finally be able to maybe help YOU with something! I believe either the SF TR60 (933edr) or TR70 (1108edr) is rated for the Riello two-stage gas burner. I think my Tr50s were one size too small to use that so mine is a single-stage Riello G400. The tech support at Riello was very helpful finding the correct burner. Theirs was the quietest of the lot I was considering. I could review all my notes if you decide on the SF. I believe one i looked at (too big) was linkageless which would have had a few advantages. Believe me when i say I talked to all the manufacturers concerning compatibility and multi-stage firing which is what I preferred and haven't yet thrown my research!