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Joined on November 14, 2009

Last Post on April 7, 2014

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@ April 7, 2014 6:18 AM in how should I prepare the system for summer?

In the summer, that's true, but in the winter hot water from a tankless coil is almost free. Between 10/15/2013 and 3/31/2014 my boiler ran 16 DHW cycles averaging 13.7 MBH each.

In the swing season and summer, our DHW is on a setback schedule. Weekdays it's only active for a couple of hours in the morning and evening. From cold start to shutoff takes about 4 minutes. There's also a flow switch in the DHW line for demand hot water during setback periods. It's not instant DHW like a dedicated tankless, but we're willing to live with waiting a few minutes for the fuel it saves.

I'll experiment with flooding and normal water levels in the boiler after the heating season, and post a report comparing time and fuel usage.

Tankless coil

@ April 6, 2014 1:32 PM in how should I prepare the system for summer?

Can you do this (flood the boiler) if you have a tankless coil that's used during the summer?

Not gold or metallic but

@ March 30, 2014 3:29 PM in radiator paint

during a 2011 remodel we painted four radiators and exposed risers black with Duplicolor engine enamel. Pretty sure we used primer too. After three heating seasons none show any discoloration or paint separation.

Vaporstats and vacuum

@ March 22, 2014 4:57 PM in Vaporstat sticking / biasing after vacuum

When I had a vaporstat on my 1-pipe system, it was adjusted for 3 oz cut-out and -0.3 cut-in. There's a bit of wiggle room in the specs, but probably not for the amount of vacuum you're looking for.

Prior to the rectangular form factor we know today, Honeywell did make a "Type C" Vaporstat with a split-unit range of -10" vacuum to +6 psi (see photo).


@ March 10, 2014 10:01 PM in Boiler efficiency cycling vs continuous run

This thread makes me wish I took more thermodynamics, but even then I don't think it would cover this topic.

I'm a firm advocate against short-cycling, and my first venture into boiler control was to eliminate it on my own system. If you've cut out on pressure (assuming a well-tuned steam system, of course), then make the boiler pause long enough for the latent heat to do its job. Short cycling, in this case, is wasteful.

ChrisJ didn't say "short-cycling" though, so that brings up an entirely different question.

I think what is often left out when discussing steam system efficiency is the time it takes to preheat the pipes before steam gets to the rads. It's left out because in most systems there's no way to tell the difference between preheating and actual heating (when steam is being delivered to the radiators). But the relationship between the preheat time and the heating time is far more indicative of the true efficiency of the system than the boiler rating alone. A 100% efficient boiler is 0% efficient until it's putting steam into radiators. Just ask any "spousal unit".

Example: It takes 10 minutes to preheat the piping, followed by 30 minutes of steam to the radiators. In this case, 25% of the 40 minute overall cycle is "lost". If the boiler is rated 80% efficient, then the true overall efficiency relative to the fuel input is 60% (75% of 80%)

There's a balance point, and it depends on the characteristics of each individual system, where the ratio of preheat time to heating cycle time is lowest. My own experience suggests a preheat to heating cycle ratio of 12.5% to 20% at design temperature, with an outdoor reset system. In swing season, overall efficiency plummets because there's much more time between cycles, with a corresponding increase in preheat times and decrease in heating cycle times.

However you have your system set up, it really comes down to two factors, one objective and the other subjective. How much does it cost ($/btu/degree day/sq ft) and what's the perceived comfort level in the home.

Midco LNB-250 modulating burner firing pics

@ March 9, 2014 10:40 AM in Midco LNB-250 modulating burner firing pics

The Midco guys asked me to take some pictures of the LNB-250 burner from low to high fire. Thought I'd share them here too

Wiring Diagram

@ March 9, 2014 7:55 AM in Thermostats (Honeywell and EcoBee)

Here's a generic wiring diagram. You'll need to adapt it to your particular ignition control. For instance the Honeywell R7184 has a 24 VAC connection so you don't need a separate transformer.

Help or Hurt?

@ March 8, 2014 7:49 AM in For all you steam heads out there

It's hard to tell from the video if they were trying to help the homeowner or screw them over.

Time Delay Relay

@ March 7, 2014 1:42 PM in Thermostats (Honeywell and EcoBee)

Assuming you'll be switching 24 vac through pressure switch, use a Schneider Electric model TDR-SOXP-24. Mouser and Allied Electronics carry them.


@ March 1, 2014 8:17 AM in Pickup factor. Help me understand

There's something useful in every steam heating related publication from the University of Illinois Engineering Experiment Station. Their in-depth studies of the effects of radiator enclosures are particularly fascinating.

I wonder when the last time a scientific study was conducted on anything related to steam heating.

Test subject

@ February 16, 2014 8:15 AM in Kickstart THIS!

That's great, ChrisJ, thanks. I'll put you on the list of potential beta testers.

Hot Water

@ February 16, 2014 7:18 AM in Kickstart THIS!

It could, but there's a much wider selection of ODR systems out there for hot water, so it's probably not worthwhile to try to compete in that market space.


@ February 15, 2014 8:16 PM in Kickstart THIS!

The outdoor reset controls currently available for steam are targeted towards commercial and multi-family buildings rather than the residential market. They're a bit pricey for the individual homeowner.

In principle, there's no reason that outdoor reset shouldn't work on smaller systems. And in practice, the outdoor reset control on my residential system has been operating successfully for a couple of years now (even before the Midco burner).

How about

@ February 15, 2014 7:37 PM in Kickstart THIS!

an affordable outdoor reset control for single-family residential steam?

It's coming. Anyone interested?


@ February 14, 2014 3:14 PM in New Thermostat really improved my steam indoor comfort level

your data for a couple of days at 2 CPH and another couple at 1 CPH, see which works best for you. Let us know how it works out.


@ February 14, 2014 2:04 PM in New Thermostat really improved my steam indoor comfort level

Yes, 67 degrees. The sensors read a bit lower because, in addition to being in different rooms, they're mounted 24-36" below the thermostat.

The manual doesn't say you can set function 240 to 2, but it can be done. A number of people here have seen good results going from 1 to 2 CPH.

Not bad

@ February 14, 2014 12:51 PM in New Thermostat really improved my steam indoor comfort level

What do you have the "First stage heat cycle rate" function 240 (aka CPH) set at?

I recently started running my outdoor reset controls off of the same model thermostat instead of individual temperature sensors, just to see how the two compared. The temperature swings aren't quite as tight as running from sensors, but there hasn't been a perceptible change in comfort level. I have function 240 set at 2. Here's a chart from last weekend.

Outdoor reset?

@ February 13, 2014 10:26 PM in Meet The Cozy

Hi Marshall,

Do any of the steam boilers on your test systems use any sort of outdoor reset control like a Tekmar 269 or a Heat-Timer? Overshooting setpoint is a pretty common problem if they're just controlled by a thermostat.

Word of warning

@ February 13, 2014 7:57 PM in Time Delay Switch Inquiry

Don't use a primary safety limit control (the vaporstat) as any part of the time-delay control scheme. Control limits and safety limits must be kept separate. If something happens and your insurer finds out you modified a primary safety limit device they could deny your claim.

Besides, the Dwyer switch is inexpensive enough. Just saw a new 1823-20 on eBay for $15.

Time delay relay

@ February 13, 2014 6:08 PM in Time Delay Switch Inquiry

Hi Clank,

About four years ago I developed a time-delay relay pressure cut-out and installed it on my system. The thinking was that if the boiler cuts out on pressure, then the system is (or should be) filled with steam. And if the system is filled with steam, then the latent heat should be left to do its job, and the burner shouldn't re-fire until then. After some experimenting I found that a 20-minute "off" period worked pretty well on my system.

Here's a link to the thread with more discussion and wiring diagrams. If possible, I recommend you go with the low voltage solution. If your ignition control doesn't provide secondary 24 vac power like the Honeywell R7184, you'll need to use an external 24 vac adapter to power the pressure & relay circuit.

In the original installation I used a vaporstat, but you don't need to go to that expense. Dwyer Instruments makes a low differential pressure switch that works quite well and can usually be found on eBay for a good price. The one I use now is a Model 1823-20 with an adjustable pressure trip point between 3" and 22" w.c. (1.7 to 12.7 ounces). If your system runs at a higher pressure, check the Dwyer catalog here to find a model that fits your pressure range.

Gross, net, tare

@ February 12, 2014 2:39 PM in Kenawee Smokeless Firebox No. 111

Gross weight is the weight of the coal plus the weight of the container (in this case, probably a truck) that the coal is being weighed in.

Tare weight is the empty weight of the container (truck).

Net weight is the amount of coal delivered. Net = Gross - Tare.

On your receipt, the weight of the coal + truck (gross) is 34,200 lbs, the weight of the truck (tare) is 14,100 lbs, and the weight of coal (net) is 34,200 - 14,100 = 20,100 lbs.

Some questions

@ February 10, 2014 8:13 PM in Meet The Cozy

Hi Marshall,

The before and after charts of room temperature regulation are pretty impressive, and I'm sure this thing works as well as is claimed. What I'm not clear on, and Ban touched on earlier, is the impact to the performance of the boiler once a complement of Cozies is installed. I'm sure you guys have a lot more study data than you've published on either Kickstarter or your web site. I'd be interested to know:

1. Did you evaluate the steam systems before the Cozies were installed? Things like near boiler piping, main venting, boiler rating vs EDR of the connected load. Think "WWDD" - What Would Dan Do?
2. Did you/are you monitoring boiler factors such as run time and pressure, both before and after the Cozies were installed in the test buildings?
3. If all the Cozy's on a system are shut off, is the boiler prone to short-cycling?
4. What happens to the boiler firing rate/pattern when a Cozy is installed in in the apartment or dorm room that contains the common building thermostat?
5. How much power does the Cozy draw? Any fuel savings claimed would need to be offset by this.

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