modcon boiler

aldefed

Hello,
Is the Lochinvar WHN055 the smallest firetube modcon available (lowest BTU output)?
Thanks,
Al

SWEI

Lochinvar CDN040 is even smaller.

Tom_133

Anyone have any experience with these as in install any? I would prefer the fire tube hx, so the WHN055 if available even with the just under 11K low fire is more appealing than the cadet at 9K and the Giannoni HX. I don't have any real world with the Cadet though.

aldefed

Thanks for the info.
I'm strictly looking at the firetube boilers. My whole house is radiant heat that currently uses a conventional boiler (84000 BTU output) with a Taco Iseries mixing valve with outdoor reset. I've done my heat loss but have also collected real world data over the last 3-4 years. I have a timer that times how long the gas valve is on and I count the number of cycles the boiler turns on. The system side is a constant 3 GPM. The hottest water that has ever gone thru my radiant is 105 degrees with a return of 85 with a burn time of about 8 hours. Recently, the weather has been between 20-30 degrees outside and my supply temps are about 90 degrees with returns of 80 with burns times around 4 hours. I'm also set up for constant circulation and the whole house runs at the same temperature. I have each loop set so I get a 10 degree drop with the outside temp at 30.
The one question I have is I see no reason why I would not plumb this direct thru the boiler. I have no plans to use an indirect as I have a tankless water heater. Thoughts?

Thanks,
Al

SWEI

We'll be commissioning our first CDN040 later this month. I too would prefer a firetube HX, but the combination of the cost (roughly 35% less than a WHN055) and the lower minimum firing rate (originally quoted a 8,500 IIRC) made it the best choice for the project. At a 30˚F or 35˚F ΔT the Giannoni HX has a head loss we can live with.

hot_rod

Don't fear the Giannoni Properly installed, pumped and maintained they are an excellent HX. In that size a small an 80W circ, or even a small ECM is plenty to flow them.

Plenty of welds in a fire tube to design, every one a potential leak, just saying.

SWEI

Off topic, but what kind of small ECM options do we have available here? The Laing/B&G Ecocirc e Vario pumps are my current choice, but they're rather pricey and require external unions to facilitate service.

RobG

If you go with the CDN you MUST pipe primary / secondary.

SWEI

RobG said:

If you go with the CDN you MUST pipe primary / secondary.

It depends, actually -- but in most cases I would agree.

aldefed

I'm currently setup primary/secondary. That was one of the reasons I was steering toward the firetube, because I would not need to do that. It would save one pump and since I'm constant circulation, it would save some electricity.
How come manufacturers don't make smaller boilers than these? No demand?
Just as a side note for other people, I did an on the top subfloor, heavy extruded plate system when I remodeled and added an addition. I should have used warmboard on the addition, but I was originally going to put baseboard in there. There is a floating floor on top of that. The house is all spray foam insulation and is about 2500 sqft.

hot_rod

SWEI said:

Off topic, but what kind of small ECM options do we have available here? The Laing/B&G Ecocirc e Vario pumps are my current choice, but they're rather pricey and require external unions to facilitate service.

Plenty of basic ECM, Alpha, B&G Varios, Wilo, Armstrong, Taco. I'm thinking these to replace an 80W, standard PSC type 15-58, 007, Star 16, NRF, etc.

SWEI

Looking for something smaller than all of those. Running at minimum flow all the time is not a good way to go. The VR1816 does look a little bit better than the rest on its lowest curve.