what boiler does Constant Circ w/ outdoor reset besides Viessmann?

GW

I'm at a loss how to write up my quotes to Ho's with this new 'reduced AFUE issue,



I've been selling V forever, and always utilize the constant circ mentality. So, as i try to sit here and write quotes for the coming year (with their new 'reduced' AFUE ratings), can i really write Viessmann is the only manufacturer with this feature? I am well aware that the bud2107 can do it too (it always killed me that the GB142 couldn't do this out of the box, actually had a sales guy once that got me in trouble of that subject years ago), yet i am specifically asking about mod/con at this time.



I am well aware that tekmar can make many of these boilers do constant too.



So, what other boilers can do bona fide outdoor rest and contant circ, with indoor feedback? What other boiler manufacturer can drive a modulating mixing valve off of their mod/con boiler's logic? I need to know what I'm talking about, finally. If there are other boilers that do what Viessmann does, i can't type in my quotes what I am intending on typing.



Thanks for any help, Gary

SWEI

Constant circ

is supported on most mod/cons (if the installer has proper understanding of the controls.)



AFAIK Viessmann has the only onboard controls that can manage a mixing valve on a secondary ODR curve.  Lochinvar has an outboard box that will run three of them, but nothing onboard.



I believe the Rinnai indoor remote does feedback, but don't quote me on that (it's also more than 2x the cost of a Vitotrol 200A.)  I'm genuinely curious to know if there are others.

Steve Whitbeck

constant circ

like he said - most mod/con's can do that. The system has to be properly designed and installed or you are going to have hot and cold spots.

Fonzy

Can make any mod/con constant circ.

If you jump the TT and set up your warm weather shut down and heating curve correctly you have a constant circ system. Have the boiler run the primary and system pump and you're good to go.

SWEI

Right, but

where's the indoor feedback?  I know that with enough care, I can design a system that doesn't need one, but what about retrofits, never mind clueless architects -- or clueless owners?

Jean-David Beyer

where's the indoor feedback?

"with enough care, I can design a system that doesn't need one, but what

about retrofits, never mind clueless architects -- or clueless owners?"



I am not clueless, and my indoor feedback is limited to a fancy conventional on-off thermostat. I have set up my system so it comes close to not needing fancier indoor feedback, but it does need the simple-minded one as a "high-limit" on the indoor temperature. There are two reasons for that.



1.) The boiler, while it has outdoor reset, will not modulate down far enough, so it has to shut off at times, especially when it is over 50F outside with only a small zone running.



2.) I have to run the reset curve slightly too warm to cover the case of high winds in cold weather causing more infiltration than usual. Absent those high winds, the temperature will go somewhat too high at times. Yesterday it was pretty cold all day, and last night it went down to 2.7F outside (design temperature is 14F). I had no problem maintaining temperature inside and the thermostat has called for heat continuously ever since midnight. Yesterday it called for heat for 12 hours 33 minutes, but it was satisfied most of the daytime.



Now a proportional indoor feedback, if there were a place to connect it on my boiler, might have helped keep the boiler running, but the fact that it was not (for the downstairs zone) would not have saved much energy. And most of the time, when the thermostat gets satisfied, the boiler will not modulate any further down anyway.



What my world needs is a mod-con that will deliver at least 35,000 BTU/hour maximum and modulate down to about 500 BTU/hour. I am not holding my breath.

GW

A little rustic

We did that maybe 7 or 8 years ago with some systems, with a simple "heat on" and "heat off" switch. It just doesn't compare to a real indoor feed. Too much, not enough, wasted fuel, maybe you have the special touch with settings, I'll stick with indoor feedback with my euro style rad jobs



I'll use a tekmar if the ho wants a good system but doesn't want a smart boiler



Gary

GW

Clueless

I trust the comment wasn't intended to be taken personally. You seem well informed



I tend to agree with you, without indoor feed some fuel will be wasted or some comfort will be sacrificed



Gary