upper water temp limit

Dale

If the boiler is controlled by a house thermostat as it is in the states, most places the room temp is what shuts off the boiler, even is the rad temp is 10 degrees above room temp and the heat loss is less than input, which it almost always is, especially in spring and fall, the boiler will cycle off.

Dan m_2

Upper water temp limit

My gas fired GV5 runs a(2 pipe) hot water sytem with cast iron radiators.The piping is new 1 inch copper fully wrapped with insulation. The rooms heat well and the bolier cycles about 3 times a hour with cycles around 4-5 minutes long. The water temp rises rapidly to about 150 deg and then kind of stalls their.The thermostat eventually stops the cycle. My circulator pump (taco 007) is wired to run continously. I guess my question is, Is this in the relm of a normal cycle or shouild the boiler water temp frequently reach the upper setpoint (180 deg) and shut the burner off until the water temp drops to the lower kick in point and continue this process untill the thermostat says so? The boiler seems to heat the house faster than the upper water limit is reached . It has not been that cold lately with lows in the single digits only for a few nights and highs in the 30's( Northern ILL) I have ran the boiler by setting the thermostat to higher temps to force a long cycle and the water temp still refuses to go much over 150.

[Deleted User]

Water temps

Your boiler output rating {btus] is probaly lower than the amount of radiation you have.Your radiators are can run at lower water temperatures and satisfy tstat before boiler hilimit is reached.The only thing to be concerned about is the low return water temps.You do not want combustion gases to condense in boiler or flue.You might need a bypass installed so you can mix hot supply water with lower temp return water to keep boiler temp up.

Arthur

Boiler water temp

Greetings from NZ, That paradise in the south Pacific were it's summer at present,

If the boiler output was lower than the Radiators was putting out the burner would not shut off, How ever at say 150f the boiler output and the rad output might be the same so an equalibian stage might be reached, Boiler out = Rad out.
Things to check are is the burner under firing? or has additional rads been fitted after the boiler was sized? perhaps you could shut down the rads in areas which are not being used, Thermostatic rad valves may help by shutting of when areas are up to temperature so preventing overheating.
What is the temp difference between the flow and the return into the boiler it should be around 20f. Also are the rads balanced ie all rads when operating should also be around 20f difference flow and return. These should be balanced on the footvalve on the rad.

Floyd

The GV5....

has a device or pump internally to protect the boiler from low water temps.
That is why it goes to 150 so quickly.... it is working like it is supposed too....
The reason that it does go on up in temps. is because with the rads you have a
very large volume of water to heat up and it does have time to do that till the t-stat
is satisfied and it shuts the boiler back down.

Sounds like everything there is just Honkey Dory!!!!!

Floyd

Unknown

Boiler cycling

The thermostat is in control of the system. When the T stat is satisfied it shut down the burner.

The fact that the circ pump runs continuously is the reason you do not reach high limit.

Heat is continuously removed from the water therefore the delta "T" is wider than is customary.

Running the pump continuously makes the house more comfotable as temperature swings in the rooms are less than if the pump cycled on or off.

As long as the boier water temperature does not drop below 140 degrees you will be fine.

If you are looking to make the operation more finite you can install a control system that operates off outdoor and indoor sensors. The runs continuously and the burner comes on line via the indoor sensor.

The control system sets the water temperature based on the out door temperature. The spread is from 140 to 180 degrees.

The colder it gets outside the higher the boiler water temperature gets.

This is called out door reset.

This control system is resonably expensive. You have accomplished the same thing by operating the pump continuously, but not quite as good as the outdoor reset.

You are O.K. with what you have.

I always go back to this addage, if it aint broke don't fix it.


jake

Dan m_2

Thanks

Thanks for the help

You guys have a great Christmas
and a Happy Hydronica

Had to say that !

Thanks again
Dan

Arthur

Boiler hi limit

Hi Again,
Good point, Dale and Jacob, You certainly wouldn't want the control by shutting off the pump as you would soon kill the burner alot on hi limit and be a pain needing to be reset a lot of the time.
however must assume it's an old system before thermostatic rad valves were common.

Jeff Jordan

Determine Boiler Temp.

I have a direct vent unit and the house has heater coils within the blowers to heat my home. Don't know if this extra info helps but I added it if it does.

The person who installed my heating system set the boiler temp at 180f. Just wondering if setting it to lets say...160f would save some oil or would it burn more being that the temp is lower and it would cool off quicker?

Please give some feedback.

Thanks.