Pick up loads

Craig Drabenstadt

I reading the BTUH ratings of a boiler, I=B=R rating allows for the piping loss and pickup loads. Can anyone explain was exactly is the pick up loads. I understand the piping loss.

Mark Eatherton1

Pick up loads...

are typically associated with solid fuel boilers, like coal and wood. You load the pickup with fuel, take it to your house and unload it...;-)Thats a pickup load... Thats also a load of crap:-)

The pickup load is the mass of the system being taken from room temperature (whatever that happens to be) to its full production temperature. It includes pipes, the boiler mass and the radiators mass. It is typical dialed in at 50% above the normal load factors. In my personal experience, it is also overkill in most situations. I think it was factored in for houses being built and started in the dead of winter... Once the house is heated, and the flywheel mass of hte home is charged, it is excess capacity to say the least. Driving a tack with a sledge hammer gets the job done quickly, but is it really a wise use of energy??

I prefer using a tack hammer to drive railroad spikes. At least I know none of the energy I'm imparting to the tack hammer is going to waste...

In the days gone by, days of plentiful cheap fuel, it probably made sense. But with todays intelligent equipment, it wastes money IMHO.

Anyone else care to chime in on this archaic sizing methodology?

ME

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don_52

good topic for discussion

Mark,

Your comment;

"Once the house is heated, and the flywheel mass of the home is charged, it is excess capacity to say the least."

This is exactly what is stated in the documentation
on running a "hot water loop off a steamer".

from Dan's Q & A on steam;

Q: How come?
A: Because you're playing with the boiler's pick-up factor. The pick-up load usually represents about a third of the net load, depending, of course, on how the installer sized the steam boiler. One-third of 120,000 Btu/hr is 40,000 Btu/hr. That's equal to 4 gpm, about what you can expect to flow through a 3/4" copper line.

Q: What is the purpose of the pick-up load?
A: The pick-up load gives you the "extra" capacity the boiler needs to heat the pipes as the steam heads out toward the radiators.

Q: Is the pick-up load always available to me?
A: No, it becomes available to your hot water zone only after the steam pipes have heated up.

Q: How about if I'm not making steam?
A: If you're not making steam, the pick-up load (and the rest of the boiler load) is obviously available to your hot water zone.

Q: So the pick-up load sets the limit on what I can do with this zone?
A: Yes.

This along with the "flywheel effect" of the structure,
(which could start another thread).I have observed this in steam heated 3 course, brick, plaster/lath stuctures, although problematic in the shoulder months.
( thinking similar to a radiant slab? )

Some folks have briefly commented on this subject as it
applies to hot water as well, i.e. "net is good enough",
do I need 1.15 etc.

I for one would like to hear any observations or comments.

regards, don

don_52

good topic for discussion

Mark,

Your comment;

"Once the house is heated, and the flywheel mass of the home is charged, it is excess capacity to say the least."

This is exactly what is stated in the documentation
on running a "hot water loop off a steamer".

from Dan's Q & A on steam;

Q: How come?
A: Because you're playing with the boiler's pick-up factor. The pick-up load usually represents about a third of the net load, depending, of course, on how the installer sized the steam boiler. One-third of 120,000 Btu/hr is 40,000 Btu/hr. That's equal to 4 gpm, about what you can expect to flow through a 3/4" copper line.

Q: What is the purpose of the pick-up load?
A: The pick-up load gives you the "extra" capacity the boiler needs to heat the pipes as the steam heads out toward the radiators.

Q: Is the pick-up load always available to me?
A: No, it becomes available to your hot water zone only after the steam pipes have heated up.

Q: How about if I'm not making steam?
A: If you're not making steam, the pick-up load (and the rest of the boiler load) is obviously available to your hot water zone.

Q: So the pick-up load sets the limit on what I can do with this zone?
A: Yes.

This along with the "flywheel effect" of the structure
(which could start another thread).I have observed this in steam heated 3 course, brick, plaster/lath structures, although problematic in the shoulder months.
( thinking similar to a radiant slab? )

Some folks have briefly commented on this subject as it
applies to hot water as well, i.e. "net is good enough",
do I need 1.15 etc.

Either way there's something here, steam or hot water.
( technique, technology or something lost to history )

I for one would like to hear any observations or comments.

regards, don

don_52

good topic for discussion

Mark,

Your comment;

"Once the house is heated, and the flywheel mass of the home is charged, it is excess capacity to say the least."

This is exactly what is stated in the documentation
on running a "hot water loop off a steamer".

from Dan's Q & A on steam;

Q: How come?
A: Because you're playing with the boiler's pick-up factor. The pick-up load usually represents about a third of the net load, depending, of course, on how the installer sized the steam boiler. One-third of 120,000 Btu/hr is 40,000 Btu/hr. That's equal to 4 gpm, about what you can expect to flow through a 3/4" copper line.

Q: What is the purpose of the pick-up load?
A: The pick-up load gives you the "extra" capacity the boiler needs to heat the pipes as the steam heads out toward the radiators.

Q: Is the pick-up load always available to me?
A: No, it becomes available to your hot water zone only after the steam pipes have heated up.

Q: How about if I'm not making steam?
A: If you're not making steam, the pick-up load (and the rest of the boiler load) is obviously available to your hot water zone.

Q: So the pick-up load sets the limit on what I can do with this zone?
A: Yes.

This along with the "flywheel effect" of the structure
(which could start another thread).I have observed this in steam heated 3 course, brick, plaster/lath structures, although problematic in the shoulder months.
( thinking similar to a radiant slab? )

Some folks have briefly commented on this subject as it
applies to hot water as well, i.e. "net is good enough",
"do I need 1.15 pickup" etc.

Either way there's something here, steam or hot water.
( technique, technology or something lost to history? )

I for one would like to hear any observations or comments.

regards, don

don_52

good topic for discussion

Mark,

Your comment;

"Once the house is heated, and the flywheel mass of the home is charged, it is excess capacity to say the least."

This is exactly what is stated in the documentation
on running a "hot water loop off a steamer".

from Dan's Q & A on steam;

Q: How come?
A: Because you're playing with the boiler's pick-up factor. The pick-up load usually represents about a third of the net load, depending, of course, on how the installer sized the steam boiler. One-third of 120,000 Btu/hr is 40,000 Btu/hr. That's equal to 4 gpm, about what you can expect to flow through a 3/4" copper line.

Q: What is the purpose of the pick-up load?
A: The pick-up load gives you the "extra" capacity the boiler needs to heat the pipes as the steam heads out toward the radiators.

Q: Is the pick-up load always available to me?
A: No, it becomes available to your hot water zone only after the steam pipes have heated up.

Q: How about if I'm not making steam?
A: If you're not making steam, the pick-up load (and the rest of the boiler load) is obviously available to your hot water zone.

Q: So the pick-up load sets the limit on what I can do with this zone?
A: Yes.

This along with the "flywheel effect" of the structure
(which could start another thread).I have observed this in steam heated 3 course, brick, plaster/lath structures, although problematic in the shoulder months.
( thinking similar to a radiant slab? )

So there it is...

Some folks have briefly commented on this subject as it
applies to hot water as well, i.e. "net is good enough",
"do I need 1.15 pickup" etc.

If this is true for steam, it makes sense that it
must be more or less true for hot water as well?

Either way there's something here, steam or hot water.
( technique, technology, dependence on building fabric
or something lost to history? )

I for one would like to hear any observations or comments.

regards, don

Boilerpro_3

Hi, Don et el

I have ditched using pick up factors for sizing boilers, especially hot water. I size boiler output to heat loss, and then if we are dealing with setbacks, add additional capacity, typically about 20% for deep setbacks...like down to 45 in churches all week. Of course, with tightly built structures with deep setbacks, more btu may be needed.
If you recover temps too fast, you get the cold 70 effect....70F air and very low radiant temp. Honeywell limits the speed of recovery in thier Chronotherms, I believe probably just for this reason. This is probably why they work so well for setback on steam systems and converted water....recovery is paced carefully so as the not overheat when setpoint is reached.

Boilerpro