How To Determine/Find "Return Water Temperatures" (Copper Baseboard)

Sorta

Still working on getting a new boiler...now I'm trying to compare Non-Condensing vs Mod-Con boilers. One of the things that really appeals to me that I've learned from reading here (and elsewhere) is that NON-condensing boilers tend to last longer. And also that they are typically less costly to being with.

We have copper pipe baseboard & a lot of it. And I learned here that condensing boilers work best when low return water temperatures of roughly 130F/140F or lower. How do I know what the return water temps are? Is that listed on a new boiler's brochure specifications? Is it something set-in-stone and unchangeable? Etc. Etc.

Thanks for reading and for your insights & advice.

STEVEusaPA

It's a moving target. You can stick a K-type thermocouple on the pipe and take a reading.

hot_rod

If your system runs 180 degrees now, keeps the home warm on the coldest days, you can probably run below 180 on many of the milder days.
The best answer would require a heatload calculation, then measure how many feet of actual finned tube you have.

The mod cons also modulate to the changing loads to keep efficiency up by lessen if the cycles.

Do you plan on being in the home for 30 years?

15-20 years is reasonable for a top brand mod con.

EdTheHeaterMan

How To Determine/Find "Return Water Temperatures" (Copper Baseboard)

It is different on each system and it is different on each given day. You would use a thermometer to determine your systems return water temperature. It is not something that happens because it is written in the specifications sheet anywhere. It happens based on the supply water temperature and the amount of radiator on the loop and the room temperature the radiators are located, any the amount of heat lost in the connected piping like a cold crawlspace or a heated basement.

Mad Dog_2

The guys are right.  If you are over-radiated (wall to wall Baseboard) you may really be able to use a Mod Con and run at much lower (cheaper $$$) temps that a mod cons thrives on...I tell people this...Mod Cons ARE an excellent technology and WILL save you $$$ on fuel, but count on a yearly service that could run $ Several  hundred bucks $...and order a spare parts kit to have when that puppy goes down on a Friday nite in February and you can't get parts for a week or more!  Make sure, YOU are able to service it OR if you can find a guy or company to service it  you have his cell#.  I get calls every 3 or 4 days for service requests on every mod con made....insert name here.. "The guy who put it in doesn't service them!!!"  Atleast with a conventional cast Iron atmospheric boiler, parts are more readily available (err...usually) and the regular Gus the Plumber can fix.  My two cents...Mad Dog  

hot_rod

EdTheHeaterMan said:

How To Determine/Find "Return Water Temperatures" (Copper Baseboard)

It is different on each system and it is different on each given day. You would use a thermometer to determine your systems return water temperature. It is not something that happens because it is written in the specifications sheet anywhere. It happens based on the supply water temperature and the amount of radiator on the loop and the room temperature the radiators are located, any the amount of heat lost in the connected piping like a cold crawlspace or a heated basement.

The delta T can and often does change in an operating system. It could change minute by minute on first start up.
You could say the delta T you read is an indication of the heat being delivered at that point in time. Put the numbers into the universal btu formula to determine the heat being transferred
500 X (f) ( delta T). Easy to use if you have a fixed flow, gpm, circulator.

And the heat needed and being delivered is based on the load at any given time. The load dictates the operating condition of the boiler and heat emitters.

hot_rod

Sorta said:

Still working on getting a new boiler...now I'm trying to compare Non-Condensing vs Mod-Con boilers. One of the things that really appeals to me that I've learned from reading here (and elsewhere) is that NON-condensing boilers tend to last longer. And also that they are typically less costly to being with.

We have copper pipe baseboard & a lot of it. And I learned here that condensing boilers work best when low return water temperatures of roughly 130F/140F or lower. How do I know what the return water temps are? Is that listed on a new boiler's brochure specifications? Is it something set-in-stone and unchangeable? Etc. Etc.

Thanks for reading and for your insights & advice.

We some number crunching you could nail down some better data to answer your question.

This chart shows how fin tube output drops with AWT. It can vary from brand or type of fin tube, this is based on most common size fins.

So calculate the footage of fin that you have, then the output at say 180 awt. The

Then download temperature data for your area, arrange into bins.

Using this example of upstate NY, consider a -5 degree design day condition. Then determine the % of the time you could run at the lower AWT. If you are grossly over radiated, you could get into condensing range for a % of the year.

With outdoor reset dialed in you can get close to constant circulation and near endless run cycles with a modulating boiler, right down to the lowest turndown rate. Tough to do with a single speed boiler🤔

There is no one answer that fits all homes.