Radiant

[Deleted User]

Is there a difference between a boiler that is used to heat hot water baseboard and a boiler used only for radiant heat?

Unknown

There are differences in terms of what boilers may be ideal. For instance if you radiant temps are low, a condensing boiler might be a very good option, whereas it's not so good for baseboard with its higher water temps.

However, any standard boiler can be used for either. We do highly recommend outdoor reset at least!

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[Deleted User]

Thanks Rob.
Was looking at some of these posts and saw some talk of the Munchkin, Viessmann, etc & wasnt sure why someone would choose thee over a more "conventional" boiler like the Burnham, Pierless, WM, etc.

Dale

Rads

IMHO you are wasting your money going to a condensing boiler if all you are heating is bb or rads that need 180 degree water. If you plan to use the boiler for domestic hot water this is another wrinkle as the condensings like the munchkin work well there. A compromise if you want side wall venting is something like a WM gold. If it was my money and I needed 180 degree water and no domestic I would just buy a correctly sized little cast iron like a Dunkirk. The outdoor reset is always a good idea and will save you some cash.

[Deleted User]

Not Domestic or BB

The application is for radiant heat only. No domestic & no baseboard radiation.

Constantin

Some further opinions...

Some boilers can handle low return water temps, some can't. Condensing boilers love low return water temperatures and thrive in applications like in-floor radiant heat, snowmelting, etc. The lower the return water temperature, the more efficienct a condensing boiler becomes. Examples of such boilers include the HTP Munchkin, the Monitor MZ or FCX, the NTI Trinity, the Viessmann Vitola, the WeilMcLain Ultra, etc.

Most cast-iron boilers on the other hand cannot take low return water temperatures because the low return water temps cause the insides of the boilers to rot out due to condensate formation. The Viessmann Vitola and Burnham Opus, etc. are exceptions to this rule. Otherwise, one adapts the boiler with a 4-way valve or injection pumping to ensure that the water going through the boiler always stays above the dew point of the combustion gases inside it.

A standard rule of thumb is that the boiler water inside a cast-iron boiler needs to be maintained at 140°F or higher to prevent condensation. Naturally, this leads to higher standby losses than with a boiler that has a lower internal water temperature.

Where I disagree with some of the above posts is that there is no reason one cannot run a condensing boiler with base board. After all, the shoulder seasons predominate our heating climates, base board is cheap (so install extra), etc. In fact, there are plenty installers today who design their base board such that the return temp of the water coursing through it never drops below 140°F, even on a design day.

Thus, I doubt that the return temps will be above 140°F for most of the year. And for the 2-10% of the heating season where return temps from BB systems do exceed 140°F, thermal efficiency will drop from 90+% to 88% with a condensing boiler, while minimum-efficiency cast-iron boilers will only give you 80% year-round. Those savings will add up in a hurry.

Plus, you can use the condensing boiler to heat your domestic water very efficienctly by using an indirect hot water heater. Using a standard cast-iron boiler under those conditions is usually inefficient because of standby losses and because a lot of boiler mass has to be heated first before the water inside a cast-iron system gets to benefit from the heat inside the boiler.

Thus, IMHO, if gas is your fuel of choice and you're not using steam heat, anything but a condensing boiler is a waste of money in the long term. However, the actual equipment choice should be dictated by the installer (what is he/she familiar with/good at) and the maintenance personnel in your area (same issues as with installers).

Lastly, before embarking on getting the best heater for your system, take some time and understand better all the energy options before you. For example, you may discover that it's more efficient to insulate and weatherize your house before installing a new boiler since it'll allow you to install a smaller boiler, etc. I also second the call for outdoor reset control, regardless of what boiler will be installed.

[Deleted User]

Great info..

> Some boilers can handle low return water temps,

> some can't. Condensing boilers love low return

> water temperatures and thrive in applications

> like in-floor radiant heat, snowmelting, etc. The

> lower the return water temperature, the more

> efficienct a condensing boiler becomes. Examples

> of such boilers include the HTP Munchkin, the

> Monitor MZ or FCX, the NTI Trinity, the Viessmann

> Vitola, the WeilMcLain Ultra, etc.

>

> Most

> cast-iron boilers on the other hand cannot take

> low return water temperatures because the low

> return water temps cause the insides of the

> boilers to rot out due to condensate formation.

> The Viessmann Vitola and Burnham Opus, etc. are

> exceptions to this rule. Otherwise, one adapts

> the boiler with a 4-way valve or injection

> pumping to ensure that the water going through

> the boiler always stays above the dew point of

> the combustion gases inside it.

>

> A standard

> rule of thumb is that the boiler water inside a

> cast-iron boiler needs to be maintained at

> 140°F or higher to prevent condensation.

> Naturally, this leads to higher standby losses

> than with a boiler that has a lower internal

> water temperature.

>

> Where I disagree with some

> of the above posts is that there is no reason one

> cannot run a condensing boiler with base board.

> After all, the shoulder seasons predominate our

> heating climates, base board is cheap (so install

> extra), etc. In fact, there are plenty installers

> today who design their base board such that the

> return temp of the water coursing through it

> never drops below 140°F, even on a design

> day.

>

> Thus, I doubt that the return temps will

> be above 140°F for most of the year. And for

> the 2-10% of the heating season where return

> temps from BB systems do exceed 140°F,

> thermal efficiency will drop from 90+% to 88%

> with a condensing boiler, while

> minimum-efficiency cast-iron boilers will only

> give you 80% year-round. Those savings will add

> up in a hurry.

>

> Plus, you can use the

> condensing boiler to heat your domestic water

> very efficienctly by using an indirect hot water

> heater. Using a standard cast-iron boiler under

> those conditions is usually inefficient because

> of standby losses and because a lot of boiler

> mass has to be heated first before the water

> inside a cast-iron system gets to benefit from

> the heat inside the boiler.

>

> Thus, IMHO, if gas

> is your fuel of choice and you're not using steam

> heat, anything but a condensing boiler is a waste

> of money in the long term. However, the actual

> equipment choice should be dictated by the

> installer (what is he/she familiar with/good at)

> and the maintenance personnel in your area (same

> issues as with installers).

>

> Lastly, before

> embarking on getting the best heater for your

> system, take some time and understand better all

> the energy options before you. For example, you

> may discover that it's more efficient to insulate

> and weatherize your house before installing a new

> boiler since it'll allow you to install a smaller

> boiler, etc. I also second the call for outdoor

> reset control, regardless of what boiler will be

> installed.

[Deleted User]

Great info...

You mentioned that if gas is my fuel of choice, anything but a condensing boiler is a waste of money in the long term.
Well Oil is an easier and more practical application here. Should I still be looking at condensing? thanks!!

jerry scharf_2

condensing oil

Fred,

The problem as it has been explained to me is that the quality of the oil that is delivered is the US extremely variable and sometimes very poor. A batch of oil with lots of crap in it can really trash out the condensing oil boiler. There are more consensing oil systems in Europe, but the quality of the oil is better there. Modulating is much harder with oil as well.

Monitor does make the FCX, so they must have figured a way around these problems. Perhaps someone on the wall with direct experience with these can fill us in.

jerry