Lochinvar Fire Tube

MikeJ

Biding a in floor heat for a garage, Question is- going to use a WHN055 with 4 -1/2" 300' loops. With the lower pressure drop going with the fire tube boiler. Does anyone see problems with not doing P/S piping and just going through the boiler.
According to the pressure drop chart do not see any issues. I have always done P/S piping on all my past installs just looking to be a little more competitive, but still doing it right.
http://screencast.com/t/7cV4Ifo2w

SWEI

Yes, direct-piped works fabulously on these. One pump, less work, and tidy piping.

Now if we just had some small 0-10V controllable ECM circulators to go with...

MikeJ

Thanks SWEI , put bid in tomorrow.

SWEI

If you can forego the ECM circ for awhile (I have been assured by two manufacturers they are coming -- in the next couple of years) I would suggest a properly sized generic PSC circ (think 003, 005, 006) paired with one of these.

SWEI

I've used them to run boiler pumps on ganged 399k mod/cons. These were MCBA-based TT's, so we handled the staging externally. We just paralleled the boiler 0-10V inputs with the Nimbus inputs and set the DIP switches so the pumps roughly tracked the boiler firing rates. No need for the claimed 300:1 range of a VVF there since the boilers have a 3.6:1turndown.

We use them regularly for single and two speed control of small circs. The ability to have off/low/high control on a single 0-10V output saves controller real estate and allows us to choose the speeds for low and high that best match the system dynamics -- and even make seasonal changes.

SWEI

Always. External controls is a big part of where we make our money.

Steve Minnich

Kurt's wicked smaht!

ced48

One of the smartest things I did on my system was to go with direct piping, I could not be happier.

Gordy

Stephen Minnich said:

Kurt's wicked smaht!

He is isn't he!

hot_rod

I think 2016 is the year that we will finally see small, 120V PWM circ pumps.
This little 50W should fit nicely in many residential applications.
In addition to modulating it's speed it will give data back to the control.

Gordy

Words like think, could, should,might,maybe,and probably do not excite me.......,or an ankle grabbing price factor.

Leave it to an intelligent individual to come up with a work around to an on going problem with off the shelf technology, and all of the sudden people get it.

EricAune

I've been direct-piping these firetube boilers with low-load/low head systems for years. I have no less than a dozen systems just like the one you're designing in operation, some TT boilers, more of the Knights. Other areas where this works extremely well are low temp panel rad systems and baseboard.

The Knight control and variable speed circ can be a wonderful marriage. Ramp delay programming is one of my favorite features of the Lochinvar control. Off the shelf, a VR1816 works great as a boiler/system circ with a two-pipe panel rad system. I've got two systems running in their 6th month as such. Not a single problem yet.

ced48

In my case, I am running water from 110 degrees low to 125 degrees high, thru 70 feet of slant/fin baseboard to heat a small home, 900 square feet, located in the north east. I am using the Taco 1816 circulator. Delta T varies from maybe 14, 50 percent fire, my maximum, down to 6 at 20 percent fire. The boiler runs for nice long cycles, sometimes 3 hours, or longer. Using high priced propane, my cost for heat and hot water, indirect, from October to date has been about $300. So I know my delta T
numbers are not text book good, but who cares? I have a boiler that is at least twice as big as I need, but the flexibility of these little fire tube boilers has let me improvise, and come up with a decent operating system.

Run the lowest temp water you can, and let here run. The end results are a comfortable home, and low bills.

ced48

Can you explain what benefit, or benefits, can be gained by achieving these goals? They seem to be out of reach, in my case, if I want to keep flow fast enough to keep air entrapped in the circulated water.

Steve Minnich

Isn't/wasn't the 20* delta T just an arbitrary "Americanized" number to make the math easier?

Steve Minnich

Do the mod con manufacturers certify the AFUE at a 20*Delta at only high fire? Or is at every step of the turndown?

Rich_49

https://www.youtube.com/watch?v=6mNECDHgDrg&index=10&list=PLuuV0ELkYb5VE0I4evUZ30b5U78CRlRdg

Steve Minnich

Hey Rich - I've watched that video a couple times before. Is the answer to my last question in there?

Gordy

The chart giving efficiencies at different modulation rates, and water temps Stephen.

Steve Minnich

Got it.

njtommy

I guess we are talking about the big industry lie agian with primary second dairy piping. What I'm really waiting to see if the manufacturers are going to start pulling away from primary secondary piping or are we going to see more 0-10vdc primary pumps.

Gordy

There will always be a place for p/s piping in certain situations.

Gordy

The premise of p/s piping is to be able to control the flow rates on both sides with out conflict. . With the system side being higher than the boiler side. Most notably larger radiant systems.

ced48

Hatterasguy said:

ced48 said:

Can you explain what benefit, or benefits, can be gained by achieving these goals? They seem to be out of reach, in my case, if I want to keep flow fast enough to keep air entrapped in the circulated water.

They are out of reach for most people in most cases. Most don't really care much about it. The boiler runs fine and they are comfortable.

Condensing in a mod-con happens in a big way once the RWT gets below 125F. There is a slope to that curve and they do condense somewhat at 135F but not well. They do fantastically well at 110F.

So, if the DT is only 5 instead of 20, the mod-con is giving a fraction of the efficiency that it would otherwise provide at the higher DT. It's the big secret from the boiler manufacturers and their miserable P/S piping. Of course, if you have radiation that allows 130F on the design day, the entire discussion is moot and you can use any flow rate that you please.

But, for those who are stuck with fin tube, every degree counts.

I will tell you that it is a frustrating exercise to get an 8K mod-con to perform with a DT pump. Operating at the very bottom of the flow and power curves is difficult.

I am about 75% finished with the UFT-80 and the VT2218 and it has been a challenge but I will get a DT of 11 at 7000 BTUH net piped direct. At anything above 12500 net, I will get the 20 DT.

Try that with any other mod-con out there with P/S piping.

I was under the impression that return water temperature was the major factor in predicting condensing. With a boiler running at 10,000 btu's, or so, the issue of condensing becomes far less important, as there is very little condensate produced at these low fire rates, regardless.

hot_rod

Gordy said:

The premise of p/s piping is to be able to control the flow rates on both sides with out conflict. . With the system side being higher than the boiler side. Most notably larger radiant systems.

Taking PS a step further with some sort of hydraulic separator device will add air, dirt, magnetic removal in addition to properly dimensioned PS. So one device can do 4 or more functions.

No lie involved in PS and it will always have a part in hydronic piping, properly applied, of course

Interesting how our boilers have evolved from high mass, high water content to low mass, low water content, and now back to higher water content

What could be next, thicker walled boilers to extend life expectation

Gordy

HX robustness has its penalties. Thicker walls delay heat transfer. So water content must be used. At least that is usable btus to the system.

I agree on the hydraulic seperators a multi tool if you will.

jonny88

Love hydraulic seperators if only they were available.NY by the way and I am done with trying the Sep 4 no one will stock it any one had luck with Spirotherm which is available.

Robert O'Brien

jonny88 said:

Love hydraulic seperators if only they were available.NY by the way and I am done with trying the Sep 4 no one will stock it any one had luck with Spirotherm which is available.

Make your own!

njtommy

Yes primary and secondary piping will always be around. If we are pushing for efficiency and low return water temps with higher delta T's we must control the primary pump speed or do away with the primary pump depending on application or design of the system.

We design systems for design days. As we are all well aware we don't hit enough design days in a heating system. So now we also are designing systems to work effectively and efficiently for our average winter temps. So system flow rates and firing rates are going to change so why shouldn't our primary flow rates change too.

jonny88

@Robert O'Brien in the process of doing it.

hot_rod

njtommy said:

Yes primary and secondary piping will always be around. If we are pushing for efficiency and low return water temps with higher delta T's we must control the primary pump speed or do away with the primary pump depending on application or design of the system.



We design systems for design days. As we are all well aware we don't hit enough design days in a heating system. So now we also are designing systems to work effectively and efficiently for our average winter temps. So system flow rates and firing rates are going to change so why shouldn't our primary flow rates change too.

Agreed, and with that logic why would one want to lock in a fixed delta T on a system if that is just a design day condition

The pumps we have been asking for will arrive, I appreciate Kurts knowledge to design and build a work around, but we need an affordable, out of the box solution for the masses to embrace.
A circ that is driven by the boiler computer makes sense.

SWEI

Using DDC, we have the ability to 'nudge' AWT by lowering ΔT under certain conditions. We've done this once a panel radiator system where emitter capacity was tight and are working this month on a crazy offgrid hydro-air air system that will use this strategy to operate sans chiller if the batteries run low.

Gordy

Hatterasguy said:

hot rod said:

Agreed, and with that logic why would one want to lock in a fixed delta T on a system if that is just a design day condition

A fixed DT is not a design day condition.

It is a parameter that can successfully be utilized throughout the heating season. If you can control it successfully, which is not easy to accomplish on low mass systems, you have the best chance at achieving the claimed efficiency of the boiler for the majority of the heating season.

Of course, if your SWT is 130F on the design day, the entire discussion of maintaining a high DT is moot. The purchased efficiency is present right out of the box.

But, for those not so fortunate and need 150-160F at design, getting and keeping the DT up above 20 goes a long way to improve the efficiency of the system.

The capability of the DT pump to accomplish this is not matched by any of the DP pumps under any circumstances and they will typically overpump the system for the majority of heating season.

I agree with Hatty. With reasonable mass a fixed system delta can easily be maintained through out the heating season. Even with bang bang technology.