Yea, leaking, rotted returns is a very common thing. I'd estimate that we repair a dozen or so every year. Not as common on the supply piping but it does happen, especially at the radiator valve which are another source of problems because packings wear out and valves freeze in position. Then you get into radiator and main vents that haven't been changed in 50 years, radiator and main traps that quit working properly sometime in the 50's. Steam is wonderful when everything is in new condition and functioning properly but its expensive to maintain. A quick tell, is when you see the pressure-troll cranked up to 5 lbs or so trying to compensate for other problems. Most residential steam was designed to run at around 1/2lb steam.
Last edited by gennady; 08-30-2013 at 07:35 PM. Reason: Grammar, English is not my native language
Last edited by gennady; 08-30-2013 at 07:51 PM.
"The higher the water temperature delivered to the radiation, the higher the heat load. Yes, the heat load since temperature differential between indoor air and outdoor air during design conditions is but one factor of heat loss 200°F radiators next to double hung window from the horse-and-buggy days will drive more heat out of the building than the same radiator at 100°F operating on ODR."
Yes, a hotter radiator next to a high-U section of exterior (like a window) does in fact increase the heat loss of the building, in exactly the manner he states- you can't cheat the raw physics. Raising the convecting column of air next the window several 10s of degrees relative to what it would be with a low-temp system creates a higher net heat load, even at the same average room temperature.
Similarly you somehow mis-read Viesmann's promotion of P/S plumbing at a mandate for the same, which it clearly is not. It explicitly spells out "When to use a low loss header:", leaving implicit the conditions under which is it not needed. A suggestion is not a mandate- designers who can do the math know the difference. If the design flow requirements of both the system & the boiler are in the same range there is no requirement (or any real reason) for hydraulic separation.
When making the argument, please try to parse the words of Viessmann or BadgerBoilerMN a bit more carefully, lest it stop making sense.
where in my post
"these are clear guidelines for LLH
also make a note that in viessmann opinion primary secondary arrangement does promote condensing in condensing boilers, quite different from your statement."
you see words viessmann mandates?
Also see all benefits listed. Why not do it right?
And on all jobs conditions of flow in the system within parameters of boiler flow? Hard to believe. P/S guaranties trouble free performance of system and boiler. When I design systems, I do not go pennies and dimes, system must be done right, no corners cut. Eliminating P/S makes no sense whatsoever.
I do not buy into argument that 2nd pump consumes more electricity or can break. There 2 ways of doing job, right or whatever.
Last edited by gennady; 09-03-2013 at 09:03 PM.
Around 20 large is possible with the right crew and we have the right crew. It's the labor that usually gets you.
Nobody was making blanket statements that direct pumping is suitable "on all jobs" either, only some.
Yet again, you bark up an empty tree, mis-stating or misconstruing the statements of others rather than parsing the actual sentences.
Quote Originally Posted by BadgerBoilerMN
QUOTE: Viessmann does not mandate P/S and one of the reasons they are one of our favorites on steam and gravity conversions. They do like to sell hydrolic separators, something trade magazines and those who write for them are sensitive to.
There is no logical argument for doubling electrical operated costs and the chance of a nuisance no-heat by adding a redundant circulator to any single zone hydronic system. The only thing this will accomplish, beyond the obvious wasted labor, material and operating cost, is to inevitably raise the return water temperature to the boiler. This is not progress where condensing boilers are concerned. END OF QUOTE
MY RESPONSE: something quite different is indicated in viessmann document. And this difference is that P/S does promote condensing in condensing boilers
and this is what i wrote in my post:
These are clear guidelines for LLH
also make a note that in viessmann opinion primary secondary arrangement does promote condensing in condensing boilers, quite different from your statement.
Again, the difference is that BadgerBoilerMN stated primary secondary is not progress where condensing boilers are concerned, and viessmann statement is that primary secondary does promote condensing in condensing boilers. you see, this is the difference
MY RESPONSE: P/S does promote condensing in condensing boilers according viessmann manual
Also if you read viessmann list of benefits, you see there are benefits in P/S, and this is quite different from the statement:
QUOTE: There is no logical argument for doubling electrical operated costs and the chance of a nuisance no-heat by adding a redundant circulator to any single zone hydronic system. END OF QUOTE
it is not just redundant pump and doubling electrical costs.
please read list of benefits.
Also Dan Hologan wrote a book, named " primary secondary pumping made easy", addressing all these benefits, you can see picture of its cover few posts earlier, read it, you might like it.
Simply put, if the flow through the system and the boiler are adequate to both no advantage can be gained by applying P/S piping either for hydraulic separation or flow control. The design has it's applications, mostly commercial, multi-boiler and multi-temperature applications but a steam or gravity conversion most certainly is not one of them.
"Promoting" a practice is a very very distant cry from "mandating". When the math proves that it's not necessary, it's simply not necessary. Presuming that P/S is the only way to "do it right" is for folks who can't or won't do the math (which is apparently the vast majority of boiler installers.)
Since P/S piping can limit the damage from a host of design errors from the folks who can't/don't do math it's in the manufacturer's interest to promote the practice, but that doesn't mean it's always the right thing to do.
So, if you using TRVs, do you use p/s or you still using direct pumping ? Also buderus , Weil McLain and slant fin are great brand names and I feel good you some how place me in that group in regards of single minded average plumber I am.
So still do you use TRVs with direct pumped boiler ?
Two words " VFD pumps"
Here is why you should/must be using a LLH with a Vitodens 200. There is no TT on the boiler. The boiler logic utilizes a down stream/LLH sensor to maintain the proper supply side water temperature the system needs based on the set ODR curve. Second, Viessmann boiler pumps are sized for 40 degree rises meaning your boiler or primary side flow rate is much lower then the system side flow rate. As an example the max flow rate for a B2HA35, 19,000-125,000 is 6.2gpm. If the system side has a need for higher flow rate you must pri/sec or use a LLH. Now can you direct pipe it. Yes you can but you will now loose some of the control logic and features in the control.
For a direct piped system you would have to utilize the 143 plug, ie, external demand. Now you've just made a smart boiler dumb and have to tell it what to do. Generally the 143 plug is used when your either doing snowmelt or maybe a pool HX were you want a fixed set point.
The biggest issue with condensing boilers is the boiler pump selection. We select fixed speed pumps based off the traditional 20 degree rise that promotes high boiler side flow rates that the system side cannot take away and you end up with elevated boiler return water temps and short cycling condensing boilers. You can never oversize a condensing boiler on the high end output because the boiler will never get there unless it sees the design delta-t but it sure can be oversized in the low end and that fixed speed pump is always the culprit.
The additional benefits of air, dirt separation and protecting the HX from system debris and the utilization of the system side or LLH sensor is why Viessmann strongly recommends the LLH over pri/sec.
What happens to your fixed speed boiler pump when piped direct? Either one or two things. You over pump the zones or you beat the living day lights out of the pump because if your not splurging on a couple of tees you sure the heck aren't buying a pressure differential bypass.
Last edited by LamdaPro200; 09-05-2013 at 05:17 PM.
"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."