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Outside design temperature has little to do with the extreme mean--it is why they call it extreme--and everything to do with percentage of time. There is a standard for sizing all space heating...

Which is why we usually use manufacturers with a deeper commitment to condensing technology i.e. a bigger selection of boilers to choose from.

For small loads we use smallest (lowest output at...

25 years--probably 30--of guaranteed low performance or 15 years of stellar performance if sized, installed and maintained properly. One with with an open chimney and the other eliminating the...

Dana has it right. Though we often see 50% reductions when replacing non-condensing boilers with properly sized and installed condensing boilers with cast iron radiators. When converting steam to hot...

I am an advocate for indirect water heaters but for the tight budget a conversion burner and conventional storage water heater like half of the country.

Sizing the tank to the largest tub is first grade math, though it has been a while...

100% laminar flow and stratification of the flow stream, not likely.

Extruded plates under a finished...

Had the boiler serviced by a professional lately?

Fill valve on?

Pressure relief valve tested or replaced in the last 5 years?

Expansion tank full?

We design and install all kinds of hydronic systems here in Minneapolis and use Lochinvar Knight boilers to drive panel radiators in new construction and renovation. As far as flow rates are...

Primary/Secondary piping on boilers was originally designed to keep conventional boilers hot so they did not suffer sustained stack condensation. Just the opposite of the goal we seek in condensing...

"It takes some real convincing with some people that their heat loads are as low as they really are"


Amen brother

There are all kinds of ways to get hurt when you DIY a residential boiler. Lets start with 200°F water in a boiler bumping off high limit when the circulator fails. Turn off the power and fuel...

"even if you replaced it with a 2-3 plate 50-60KBTU/hr cast-iron thing rather than a high efficiency modulating boiler.

BLASPHEMER !

You don't need Warmboard for a retrofit like yours. I would look for a good deal on European style wall-hung panel radiator properly sized to low temperature applications and controlled for optimum...

First, the Knight condensing boiler is too "big" for the load. It is, like so many, bumping off the bottom.

You may slow down the system pump, but if the boiler pump runs faster your problem may...

Most condensing boilers will provide for priority domestic hot water (DHW) changing set point (boiler water temperature) to 180°F or so. This will satisfy nearly any indirect water heater (driven by...

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Two kinds of efficiency are of concern for boilers. The first is combustion efficiency. If the condensing boiler is properly sized, tuned and loaded, it will achieve 86% combustion efficiency...

Who installed the system?

Most must rely on temperature differential and pipe size to fix the flow. Some ModCons can be adjusted for gross output. The problem often lies in minimum unfortunately....

Thanks Dana.

We are a Bradford White certified contractor and naturally work on many CombiCor water heaters as about half the houses here in Eden Prairie use one to heat the basement and...

We prefer more flow to the system. If the boiler, or the pump serving same, is grossly over-sized, the net results are hard to correct.

This is crazy. First, a proper room-by-room Manual 'J' 8 is, by no stretch of the imagination, WAG. To suggest otherwise is insulting. If the a "heating tech" suggests otherwise, he is too ignorant,...

In a residential, single boiler hydronic heating system, the circulator serving the boiler is consider "primary" and the circulator or circulators serving the distribution system "terminals" are...

Stretching the differential (Dana likes 'hysteresis') will effect comfort more than system efficiency. We don't do it. Many of the ModCon boiler manufacturers, in their mania to sell boilers to...

When we have to install a low-efficiency boiler or are called out to trouble-shoot a radiant floor connected to one, we start with a motorized three-way with outdoor reset and boiler protection...

Just to be clear. Your problems arose from the recommendations of a misinformed "radiant floor designer". I have no problem with Tekmar as I have been using them for about 20 years now. The problem I...

Hold on. I can't watch anymore.

First, the Alpine boiler will suffer a 40° delta T (not for beginners) so slow the pump down as Dana suggests.
Second, by limiting the max operating temperature...