How does a boiler react to having too much radiation?

Brent H.

While doing a heat loss for a new boiler, I found that like most houses I am overradiated. This made me start to wonder how a boiler reacts when there is more baseboard than a boiler can drive. In other words, if a boiler is sized properly for the heat loss but there is 50% extra basboard, what happens on the coldest day of the year? Wouldn't the boiler eventually see a return water temperature that is too low? Please help educate me. Thanks.

kcopp

Not a problem...

All it means is that the zone shuts down faster... not a bad thing. If you are over radiated(not sure you can really do that) that means you can do  a lower operating temp.

Brent H.

Return Temp.

Wouldn't the boiler water temperature drop since it wouldn't be able to keep up with the amout of heat used by the baseboard?

Jean-David Beyer

It depends.

It depends on your boiler. For example, with a mod-con boiler, the colder the return water the better, unless it starts to freeze. With a cast iron boiler, you do not want to go too low because you do not want condensation in them that tends to cause them to rust out and cause a chiminey to disintegrate.



If you have baseboard that is "too big" and a mod-con, you can run it at lower temperatures and get more condensation (which a mod-con is designed to do) and higher efficiency. I deliberately put "too much" baseboard in my baseboard zone so I could use  lower temperatures (110F to 135F depending on outside temperature). I have 14 feet in a room that would need 5 to 6 feet if the water in there were 180F.

Brent H.

Tradional Oil Boiler

I'm asking this in reference to a traditional oil fired boiler.... in my case it will be a Buderus.

kcopp

from your....

other post information  , you will not have that problem. Unless you have A LOT of finn tube. And I mean A LOT. Your system is not that complex and your house not that big.

bill_105

I think this is why ...

God gave us primary-secondary piping.boiler bypass and system bypass.

meplumber

Don't overthink this.

The Buderus casting is capable of return water temps to 104 deg F. Dont read too much into this.



The radiation is only going to recover what the house loses. For example, if you set your t-stat at 70 and it is 20 deg outside, the house is going to lose heat at a predetermined rate according to the heat loss of the structure (insulation, windows, exposure, etc...).



The amount of radiation only comes in to play with the rate that the house recovers. With finned tube baseboard, the output is rated at 580 btu/linear foot at 180 F. The zone would just reach setpoint faster with more fin tube than less.



As kcopp stated, you would have to have a huge amount of baseboard for you to see any significant drop in return water temperature at standard design flow rates.



The bigger picture is that if you are that over radiated, it is an excellent opportunity to install the 2107 control on that boiler and take advantage of outdoor reset. By lowering your water temperatures, you could save significantly on fuel.