Question about a new boiler.

tim smith

It may be a good idea to check sizing of the different zones. If your cast is well oversized but your fin tube not. This may force you to run a higher temp than ideal to get output of fin tube zone. Still workeable but it may then give you a possible reason to change radiation on the fin tube side to keep lower operating temps, if $$ feasible. Just a thought.

Randy Bultmann

Mod Con boilers

Hello everyone, I've been reading this forum for several years, and in the process of replacing my boiler. The old one is a standard cast iron boiler about 40 years old. I was interested in a new mod/con. I had 2 contractors that deal with the Lochinvor Knight and 1 with the Triangle Tube Prestige. I have 124K btu heat loss. I have both cast iron and fin tube radiation. The 2 contractors that deal with the Knight both bid and acted like there was absolutely no problem with the install. The other just called me and said there was absolutley no way he would ever put in a mod/con in my type of system.

So now I'm wondering if it is the right thing to do? I really am impressed with the mod cons and the way they can modulate. But I also don't want to put something in and be disapointed. Please help........

Dan C.

Why?

Did he explain why he would never do it?

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Robert O'Brien

Some

people mistakenly feel a condensing boiler won't work well with a high temp system.Attached is some interesting reading regarding condensing boilers and baseboard systems

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Randy Bultmann

Yes, he said that all the literature that he has read says a mod/con will not work efficiently with high heat temps, i.e. fin tube / cast iron. That they will only work with radiant floor or low temp systems to actually be able to condense. So that is why he said he would never put a mod/con on a system that would need a 180d water temp.

S.S.R.

mod-con

there is no problem with installing a mod-con boiler in this application. these boilers are ran off of outdoor reset so this means that with the proper D.T. of 25-30 deg. these boilers will work perfect. they will only make 180 on the very coldest day of the year the rest of the time it will modulate to only what it needs. so if you have a 30 deg. D.T. and it only needs 165 to heat then you will be condensating. hope this helps

Brad White_190

Limited if not silly thinking

Just because a system might (might also being an operative word here) need 180F water, that is only on a design day and those occur only 1% of the annual hours or less, depending on how the system was sized.

To declare that a single operating point is the only thing the system is capable of is denying reality and all potential.

Sure, your car speedometer says 120 MPH but no where does it say you should always drive it that fast. In fact, there are a number of very good reasons not to, ranging from caskets to handcuffs.

Many systems, especially those in older homes with original radiation and which have been improved by insulation, air sealing and new windows, often have 50% to 100% excess radiation. You might be able to demonstrate that the system will work starting at 150 or 140F water, or less, on the coldest day.

From there, using outdoor reset (ODR), savings can increase.

The essential principle in all of this is ODR- you retain your highest temperatures for the worst weather but run 90% of your winter hours at lower temperatures and 80% or more of the hours well inside the condensing zone where return water temperatures promote highest efficiency. Controlling the water temperature thusly and aggressively is the key.


Also the boiler must be capable of putting out the highest temperature you need. Some but not all are limited by their European design to 167 degrees. Not a hardship in most cases- I would tend to think your radiation will exceed your heat loss if you have improved your envelope at all.

My $0.02

Brad

Randy Bultmann

Thanks guys for your input. I thought a mod/con would be a good choice, just for the reasons you mentioned above. But when this guy told me he would never install one with cast and fin tube radiation, it made me start wondering.

Bruce Stevens_2

Cast anmd Fin

""But when this guy told me he would never install one with cast and fin tube radiation, it made me start wondering.""

Or did he mean with cast or fin tube radiation because if you have both on one zone that can be a problem of it's own, same system different zones ok but same zone a no no due to different heat transfer rates.

AlHeating

Mod/cons with baseboards

There's ABSOLUTELY no problem to use a mod/con boiler with this kind of system.

The only small issue will be, as the other guy says, to find the good settings to set the indoor/outdoor and satisfy both zones (cast iron and tubes).

The Knight boiler is all indicated with the 'easy to control' factory supplied indoor/outdoor. We installed a LOT of them in colder climates (hotter water temperature) and we've seen good savings even in "mixed systems". (about 30% compare to the older gas boiler)

Randy Bultmann

The cast and fin tube are zoned separately.

Mark Eatherton

No difference in operating the boiler, but...

There are a lot of misdirected hydronic purist roaming about the face of the earth. What they don't understand is the physics of the whole shebang. Even during its worst operating conditions, the boiler will reduce the energy consumption of a given structure by 20 to 30%. And THAT is not something to ignore.

Now, with that said, what your BODY will notice is the MRT (Mean Radiant Temperature) differential. In other words, you are walking around your house with a thermometer in hand, reading air temps. You walk from the room with the cast iron in it, which was reading 70 degrees F into a room with hot water baseboard emmiters in it, and the room air temp is still 70 degrees F, but your BODY is saying "This room is not as COMFY as the last room...But you've probably already experienced that phenomena, and know how to compensate (more clothing in the BBR room) for that condition.

That is the difference. Operating efficiencies diferentials are nil. As for equipment choices, I like both, but the Lochy has a much more user friendly H.I.D. (Human Interface Device). The TT is extremely limited as to what parameters can be accessed and adjusted.

I say go for it and don't look back, but also don't forget to service the appliance. This ain't your grandpa's boiler any more.

ME? I'm basking in the warmth of radiant glass windows at my mountain home, looking THROUGH the heater at a full, beautiful lake behind them :-)

ME

Randy Bultmann

Mark Eatherton

Mr. Eatherton, and I say that with utmost respect, as I stated earlier, I have read this board for several years and it has helped me keep the old boiler running. I value your opinion greatly, as with the others that have posted earlier.

I remember specifically your instructions on how to remedy a water logged steel expansion tank. I followed your instructions and the old girl still had a couple of years in her, but now she's on the down hill side.

Radiant windows???? Is that true??? Wish I had that view!!!!

Charlie from wmass

only one reason for concern with modcons here

Some mod cons do not like to be attached to iron loaded systems. buderus requires care to be taken when attached to systems with cast iron radiators as direct flow from them through the boiler can lead to clogging of the water passages. I am not familiar with the triangle units or the knight units. But the contractor may have had issues with build up in other installs. JUst a thought.

John Ketterman

Actually the guy who wouldn't install a mod-con did have a point. I suspect he said it because he had never installed any mod-cons and didn't know them and didn't want to admit it, but still, he had a point.

It is true that, with reset, you won't be running at 180F all the time. But efficiency is not determined by the number of days when you are condensing vs not condensing; it is determined by the number of degree-days. To say the same thing differently, most of your heating costs are spent during the coldest days, and during this time you may not be condensing.

Of course, you'll still have a more efficient boiler than the one you're replacing. On the other hand, it will be a more complicated boiler that probably won't last as long.

It is true that some homes have excess radiation and so can run condensing even on the coldest days. But I suspect that if you have some rooms with fin-tube, your home is not one of those. People put in excess radiation in the old days when giant cast-iron radiators were required to heat rooms even though windows were left open or at least had no storms (energy was cheap, cast iron was cheap). But I suspect that few people have more fin-tube than necessary.

Contractors give advice based at least partly on their own interest. In some cases, they make more money from mindlessly doing lots of quick change-outs, and so they recommend simple cheap boilers with high markup. Other contractors see more profit in installing expensive overly fancy boilers, or at least they find these jobs more interesting. No one here can tell you which one is a better deal for you; no one can accurately predict how much you'll save in your particular situation.

But outdoor reset will certainly result in increased comfort compared to bang-bang heating. That can be guaranteed.

Bob Gagnon plumbing and heating

You Could Easily add

More baseboard where you have baseboard already, and your system would run more efficiently at lower temperatures.

Thanks, Bob Gagnon

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[Deleted User]

RGB...

Yes, it is true. These guys have figured out a way to induce voltage into relatively clear glas (low e coating) and cause the window to heat up. It can be used with DC power, hence I will be tying (eventually) mine into solar PV system with battery storage and keep my cabins nice and comfy for FREE for most of the summer. I don't use them during the winter, so am realy not too worried about that then.

More information can be seen at www.rgiglass.com

We hope to be in a position of mass production within the next two years.

Glad I could help.

ME

Big Will

The free heat loss software

From Slant finn really helps for this. You can see how much BTU you will get based on the linear feet of base board regardless of type. If you play with the numbers you can get a real idea of how often you will need to run the boiler at non-condensing temps. Just get your hands on the weather history for your area. I have run into only one home were there was not enough base board to keep it inside condensing temps enough to make it worth the cost of the boiler. Like the guys keep saying you will find that most homes are over sized both in the emitters and the boiler. This is really in you favor. Being the home owner the fun part is playing with the reset curve to find the lowest running temps you can get away with. I use the Knight all the time its a great boiler. Its summer you have time play with the load calc software and you will find out for yourself. No question is the best question.

Plumb Bob

Sure, but baseboard is limited by the perimeter of the room and often further limited by doors, built-in furniture, etc. In most cases it is very hard to over-radiate using baseboard.

Plus you are now asking the OP to spend more money than he presumably planned to spend.