Mod-Con Boiler and system questions???

hot_rod

Hatterasguy said:

njtommy said:

What if there's no room for a buffer tank in the same room as the tankless boiler? Can you hide it somewhere else?

How far away can your buffer tank be if you two piped it?

Once you have the need for a buffer tank.............and you will with just about every mod-con unless you got it perfectly matched to the heatloss and it has a decent turndown ratio..............you have killed all prospects of a system that is cost-effective.

Abandon that entire strategy and find a mod-con that can modulate sufficiently low enough to avoid the need for a tank. OR, get a modcon with mass (HTP Pioneer as an example),

What about the folks looking to improve an existing system. Starting over with an entirely new boiler may not make sense.

And others that are brand sensitive.

The guys, and gals, here that do it for a living need, and like options.

Brewbeer

I just finished having installing a mod-con with a buffer at my house. Is my system not cost effective?

Gordy

Depends, if you could have did it with out a buffer would your ROI been better. Those (buffers) are the polishing cloths referenced. And extra circs.

Brewbeer

In my case the heat loss was low 32K on design day. Three zones. Concerned about short cycling with fin tube baseboard, hoping the buffer prevents it.

Same number of circs as if it were piped P/S.

Gordy

what if you had a boiler that could accomodate that design loss. Even if it were over sized at its max input. What if that boilers min modulation could cover your low load zones with out buffering at less than design day?

Paul48

Once you have the need for a buffer tank.............and you will with just about every mod-con unless you got it perfectly matched to the heatloss and it has a decent turndown ratio..............you have killed all prospects of a system that is cost-effective.

Abandon that entire strategy and find a mod-con that can modulate sufficiently low enough to avoid the need for a tank. OR, get a modcon with mass (HTP Pioneer as an example),

THANK YOU!!!!!!
Buffer tanks are a ridiculous addition to a system. Trench over to your neighbors house and heat part of their house, so you can say, my system runs efficiently.

Brewbeer

Paul48 said:

Buffer tanks are a ridiculous addition to a system.

That statement doesn't make me feel good about including one on my just installed system.

Paul48 said:

Trench over to your neighbors house and heat part of their house,

Now that sounds MUCH more expensive than a buffer tank.

Rich_49

Lipstick & Paint , make it what it aint .

NYplumber

"Once you have the need for a buffer tank.............and you will with just about every mod-con unless you got it perfectly matched to the heatloss and it has a decent turndown ratio..............you have killed all prospects of a system that is cost-effective.

Abandon that entire strategy and find a mod-con that can modulate sufficiently low enough to avoid the need for a tank. OR, get a modcon with mass (HTP Pioneer as an example),"


Some short cycling is allowed in extreme shoulder season. For one to get a boiler that can modulate all the way down from design day is akin to having a school bus that shriks to a smart car for your visit to LA or NYC. Also recall that high turn down ratio means little condensing due to higher excess air. And high excess air means lower efficiency.

This is where a boiler like the Viessmann CU3A comes into play and where the other manufacturers should aim their sights. Control os key too but thats a separate chapter.

Rich_49

Just the right amount of air when using HTP UFT boiler . Real nice venturi and perfect blend at 10:1

Gordy

The UFT has some interesting aspects.

The HX volume is 3gals same size for four different size boilers. Really manufacturing genius same size HX different size burners. Cost saver.

The wh knight has. 2.5 for 55 and 85 sizes and 3.5 for 110 and 155 sizes similar inputs not quite.

hot_rod

Gordy said:

The UFT has some interesting aspects.

The HX volume is 3gals same size for four different size boilers. Really manufacturing genius same size HX different size burners. Cost saver.

The wh knight has. 2.5 for 55 and 85 sizes and 3.5 for 110 and 155 sizes similar inputs not quite.

It is an interesting product. I like the low pressure drop HX design.

The video on their website claims a 5-1 turndown, but that was recorded at last years AHR, sounds like that has changed?

It mentions a specialized mixer to increase turndown to 10- 1 in another video on the site. Is it a true 10 step turndown? Or how does that mixer work?

It also mentions it has a primary secondary piping inside with it's own circ pump. Does that pump modulate like some of the Viessmanns? Sounds a little like how the GV worked with pump and piping inside. Any thoughts on how that will works with a variable system pump?

The manual shows direct or P/S piping. With P/S you would need 2 additional pumps. The manual is not clear if, or when P/S is required.

njtommy

@ Hatterasguy

I should of said fixing someone else's problematic install.



And yes looking at the price of a buffer tank and price of a anther boiler with either mass equal just about the same price. Some times I wish I put one of the tank style HTP boilers in my own home. Thanks to our buddy Rich.

Or really said screw NG and went with a wood burning boiler

Gordy

hot rod said:

Gordy said:

The UFT has some interesting aspects.

The HX volume is 3gals same size for four different size boilers. Really manufacturing genius same size HX different size burners. Cost saver.

The wh knight has. 2.5 for 55 and 85 sizes and 3.5 for 110 and 155 sizes similar inputs not quite.

It is an interesting product. I like the low pressure drop HX design.

The video on their website claims a 5-1 turndown, but that was recorded at last years AHR, sounds like that has changed?

It mentions a specialized mixer to increase turndown to 10- 1 in another video on the site. Is it a true 10 step turndown? Or how does that mixer work?

It also mentions it has a primary secondary piping inside with it's own circ pump. Does that pump modulate like some of the Viessmanns? Sounds a little like how the GV worked with pump and piping inside. Any thoughts on how that will works with a variable system pump?

The manual shows direct or P/S piping. With P/S you would need 2 additional pumps. The manual is not clear if, or when P/S is required.

Im sure there will always be situations even this boiler will require P/S piping, but it eliminates more of those scenarios. Marrying into an existing emitter design would be one of those. When start from scratch design is not possible to control all aspects to eliminate P/S.

Gordy

So what is an ultimate design? Seems the manufactures do listen.



The installers wanted low pressure drop HXs they got them.

Built in P/S.

The installers wanted smaller boilers. You got them.

The installers wanted 10:1 we finally got it here in the states. 15:1 if you want to count

Variable speed pumping. Seems to be a little disconnect there. Between the boiler manufactures, and the pump manufactures.
The big V does it.

Boiler, and buffer all in one.

What else.

Eastman

zone sync
indoor feedback
ability to sync primary and secondary flow dynamically when possible

Eastman

One should never have to futz with the ODR curve.

Eastman

Ability to use forecasted weather temperatures to mitigate overheat and underheat scenarios with high mass systems.

Rich_49

Bob , The UFT does not come with any pump . The piping within would allow one to do P/S just by opening the valve inside and adding the circ . It is 10:1 tdr and does readily accept 1 gpm . Using both top and bottom S & R pipes makes doing Ch and DHW really nice also . Have a few heating and doing DHW right now . Will keep everyone posted .

It is my opinion that one should not rely on the manual to tell you when to do P/S , that should be within every designer / installers wheelhouse . At present they do not possess the proper knowledge to make those determinations unfortunately .

Paul48

Check this out............You put the boiler in "learn" mode. It determines the heat loss of the structure it's functioning in, based on sensor inputs as it cycles through optimizing circulator function. The only input from the homeowner would be ...I'd like it a little warmer, or a little cooler.

Paul48

Windows not DOS

Gordy

depends.

Rich_49

Radiant Floor heat with a design Delta of 10* . Thats one . 10000 BTUh would require 2 gpm on the system side and 1 gpm on the boiler side . Guarantee the proper head loss for a specific circ to move 1 gpm through the boiler . Shiny with no odor .

hot_rod

Hatterasguy said:

njtommy said:

@ Hatterasguy



I should of said fixing someone else's problematic install.

Understood.

Sometimes you have to fix it the best way possible. And, a buffer tank might be the only solution other than changing to a smaller boiler.

One of, if not the first hydronic buffer tank the Boiler Buddy was designed and built by HWP the HTP reps and dealers in Wisconsin.
It was built to help "settle down" the Munchkin cycling. They have a relationship with HTP still and share the assembly of the Boiler Buddy.

Interesting videos at the Boiler Buddy sight as to why and how the buffer came about and some cycling examples it was designed to mitigate.

Interesting guy that Jack Daniels, at HWP, and a great name.

Paul48

Thankfully HTP has learned a lot since those early days.

hot_rod

Clever business model, sell the boiler, then a few years later sell the buffer to many of your customers to make them operate efficiently and dependably.

I say skip the 5 gallon mid-mass, it's really only 3.5 gallons more than the Elite.
Go with the 50 or 80 gallon HTP products if you want a nice, unique, solid running, long lasting burner/tank/mass, high water content product.

With the exception of the Viessmann Bi-ferral, one of the all time great boilers, I'll take high water content design over 5 gallons and 200 lbs multi metal boilers.

With tank style HTP products, no pump, P/S, or separator required, sip the energy off it at what ever low flow rate you want, or use a hydraulic mining pump if you wish. I heard my Solar Phoenix kick on twice all day after the sun went down.

4Johnpipe

Wow I missed a lot...

Paul48

Doesn't HTP make tanks for a lot of different manufacturers?

NYplumber

Gordy
"So what is an ultimate design? Seems the manufactures do listen. 



The installers wanted low pressure drop HXs they got them.

Built in P/S. 

The installers wanted smaller boilers. You got them.

The installers wanted 10:1 we finally got it here in the states. 15:1 if you want to count 

Variable speed pumping. Seems to be a little disconnect there. Between the boiler manufactures, and the pump manufactures. 
The big V does it.

Boiler, and buffer all in one.

What else."

Less models and more parts availability. But thats a different discussion. And more non proprietary parts.

SWEI

hot rod said:

Go with the 50 or 80 gallon HTP products if you want a nice, unique, solid running, long lasting burner/tank/mass, high water content product.

I love the design and it's really close, with a few niggling design challenges IMO.

JohnNY

I have never installed a buffer tank, but the Ergomax piping diagram has had me thinking about it. The website is terribly amateur but I think this is an interesting concept and product. Run everything through the tank and pull your DHW out with it. http://www.ergomax.com/E-Info.htm
One drawback of course is that pesky question keeps coming up: "When am I condensing?"
And the answer seems to be "practically never", especially if we're storing hotter water and using a mixing valve to temper it like NYC Code requires.

Paul48

The versa hydro and versa flame are more like what you were considering Hat.

Chester

njtommy said:

The problem is with baseboard is that it can only pick up so much heat and that's it. Your not forcing air acrossed it. Once those fins get hot your delta just drops off and your no longer running a 20 delta t. Is more like 5. Especially on mild days.



Does anyone make a ECM pump that goes down to 2 gpm?

My Grundfos Alpha sits at about 2 gal/minute when it's feeding my smaller zone. My larger zone requires 5.

Gordy

Chester said:

njtommy said:

The problem is with baseboard is that it can only pick up so much heat and that's it. Your not forcing air acrossed it. Once those fins get hot your delta just drops off and your no longer running a 20 delta t. Is more like 5. Especially on mild days.



Does anyone make a ECM pump that goes down to 2 gpm?

My Grundfos Alpha sits at about 2 gal/minute when it's feeding my smaller zone. My larger zone requires 5.

This is where delta t pumping shines. VT 2218 so long as the curves work for you.

You don't always need the 2 or 6 gpm. The argument is how low you can go.

Chester

This is a really interesting thread even though it gets pretty technical. From non-pro, homeowner's perspective I'll just add that I'm in the process of dialing in my new boiler and am very surprised how low I can go. Installer left things pretty much at default settings and I've been tweaking it slowly but surely. Last night was the first time we dipped into the low 20's this winter. I tried the strategy of dropping my curve down (126F design day supply temp) and setting the thermostat high (72F). This morning it was 22F outside and the boiler was keeping the house at a very comfortable 68F with 106F supply. It's condensing like crazy. (Do I really care what my Delta T is if I have low return temps and long run times?)

This is a 1400 sq/ft cape built in 1940 with cast iron radiators. I calculated my EDR at 560 (90,000 Btu/hr @ 180F). House is fairly tight and well-insulated with a heat loss of somewhat less than 30,000 Btu/hr at +5F. I have a 57,000 Btu/hr Bosch that modulates down to around 12,000. The charts I've seen suggest I have enough radiation to satisfy my design day at 130F.

I'm lucky to have a house that was designed for hot water and has lots of high-mass radiation, and I was obviously wise to invest in some envelope upgrades. I'm also lucky because the availability of various rebates made the modcon decision a no-brainer.

My mantra to other homeowners and less experienced pros is: 1. do the heat loss; 2. calculate the EDR and adjust as necessary; 3. don't oversize the boiler; 4. consider envelope upgrades as well as properly designed and installed heat; 5. don't be afraid to adjust the ODR curve aggressively; and 6. sit in front of the boiler with a couple beers and watch the condensate go drip, drip, drip....

hot_rod

Hatterasguy said:

Paul48 said:

The versa hydro and versa flame are more like what you were considering Hat.

I really wanted to use Hydro. Perfect machine. Unfortunately, the 160°F limitation was the killer. Flame really can't make decent hot water. So, I was going to make a "high performance Flame".

The UFT will do much better.

Time will tell on that statement

I make DHW with my HTP Phoenix, all the way down to a 120 operating temperature, enough for a shower flow anyways.

Paul48

I really wanted to use Hydro. Perfect machine. Unfortunately, the 160°F limitation was the killer. Flame really can't make decent hot water. So, I was going to make a "high performance Flame

There's no getting around the fact that these are for low temp applications. If you want 160* off a FPHX, what's the temp of the DHW in that tank? They show the Phoenix feeding an air handler, but I don't see a separate HX.

SWEI

This is the problem with the single tank combi. If you have an efficient emitter system, the DHW temp requirements will drive the heating temps up above what is needed the majority of the season. It gets worse when you add solar to the picture: raise the tank temp at night and you limit your morning collector efficiency.

Solar thermal and DHW work somewhat magically together given the low EWT and 365 day demand. Pairing solar thermal preheat with the right tankless can be a great fit.

Throw in space heating and system optimization becomes a much more complex challenge. When the tank temp falls below the calculated ODR setpoint, the tank suddenly switches from a source to a sink, which requires changes to water flow in order to (a) minimize fuel usage and (b) deliver the coolest water possible to the collectors the next morning. It's not rocket science, but it does require some real skill on the part of both designers and installers.

Gordy

The spirit of the discussions is overall system efficiency, there are many micro, and macro efficiencies in a system that all come together to produce the big picture. Boiler,pumping,heat transfer,emitter,envelope to name a few. What efficiencies can take a hit to make others shine . System cost to achieve that goal, and create an exceptable ROI while providing ultimate comfort at cheap operating costs.

Brewbeer

Along the lines of efficiency, I'd like echo one of Chester's comments a few posts up:

"Do I really care what my [boiler] Delta T is if I have low return temps and long run times?"