Burnham series 2 short cycling?

cass72

I just got a brand new burnham series 2 model 204E installed forced hot water. I think it has a short cycling issue. I have been monitoring and it goes through stretches of firing for 3 to 4 minutes then off for 15 - 20 minutes, which I think is normal firing. Then it seems it goes through stretches, mainly when the outside temperature drops, of average 5 minutes off and firing from 1 to 2 minutes, over and over. I noticed during the "normal firing" it would fire for literally 15 seconds a minute or two after the firing cycle, almost like a hiccup right after. All in all when it is "short cycling" it seems to fire about 8 times an hour for 1 to 3 minutes. I have heard that Burnham series 2 boilers are notorious to go on off a lot and it is normal but then every article I read says this is short cycling.
We already had the installers change out the thermostats, so that is not the issue.
We have a 2 zone ranch style house, main floor and finished basement, about a 1000 square feet both thermostats seem to be in ideal locations. On the boiler it will reach 180 degrees on firing and shut off. It seems to fire on its own when it hits around 140 to150 or so.
when it short cycles it seems to fire any temp even almost at 170. The PSI are hovering at 20. Everything else seems in working condition

Maybe this is normal for this type of boiler or maybe there is a defect internally or some kind of setting adjustment the installers can make. I am hoping to have this boiler last the life span of 15 years, but it seems short cycling can reduce that dramatically.

If there is any other information I can provide please let me know.

Thanks!

Jamie Hall

First thing to check is the thermostats. They may be new, but were they set up for hot water? Or did someone leave them in the factory default, which is for hot air and may cause just what you are seeing.

The next thing to check is for adequate circulation in the boiler. If it is shutting off on the aquastat high limit, you may have inadequate primary circulation (in a primary/secondary arrangement) or though the zones.

cass72

Thanks Jamie

regarding circulation, how do I check this? do you mean circulation like in the boiler room or air going out and entering etc..
The thermostats the installer put in Honeywell Home Pro 1000, so I think the factory default is for gas or oil furnaces less than 90% which is what we have.

RonBeck

First thing @ 1000 sq ft, sounds like the boiler is oversized.
The control on the series 2 with factory defaults acts like this. When a heat demand is received the control will fire if the water temp is less than 140, if over 140 it will not fire until the water temp drops below 140f less the 15f differential.
if it is cycling off around 180f, drops 15f and re-fires this is normal as long as the boiler control goes.
This can be caused by flow, air, piping, pipe or boiler sizing, or thermostat cycles per hour menu settings if provided.

JUGHNE

The circulation referred to is the water flowing thru your pump(s).

You do not have a any furnace....you have a boiler...you have to use the hydronic...water...steam..etc.....setting in the tstat. This will give you longer tstat cycles.

cass72

Thanks for all the advice
It seems that one of the thermostats was still at 5 cycles per hour, so I changed it to 3, so now the boiler is going at about 5 or 6 cycles per hour, ranging in between 6 minutes and 15 to 20 minutes; the cycles(or fire on) are 1 to 3 minutes long until it hits 180F. I am guessing this is now about normal? Or is it still short cycling?

Jamie Hall

Still shorter than desirable. Try 1 cycle per hour.

JUGHNE

Post pictures of the boiler and piping, especially show a side view of the pump.

EdTheHeaterMan

Your boiler is making more heat than the house needs, or it is making more heat than the pipes can move. That boiler will produce 77,000 BTUh of usable heat. When you have a Heat Loss calculation of your home done, I believe you will find that the heater is too big.

Think of it like this. on the Design condition (What I used to call the coldest day of the year) if your house needs 40,000 BTUh and you have a Series 2 model 203E the burner will generate 50,000 BTU of heat every hour. Your house will use 40,000 every hour. So the burner can go OFF 12 minutes every hour. There might be 3 minutes OFF and 17 minutes ON for a total of 20 minutes. That will happen 3 times every hour that the outside temperature is at design temperature. Whenever the temperature is above design (like most of the winter) the OFF time will be longer and the ON time will be shorter. So at a 35° outside temperature day the burner might only operate for 30 minutes every hour. Maybe like 7 minutes ON and 7 minutes OFF. At a 50° outdoor temperature the burner may operate 2 minutes on and 5 minutes off.

By having a Series 2 - 204E you are making 45% more heat that you need on the coldest day of the year. Even if the outside temperature went much lower than Design Temperature. In my 50,000 heat loss example, your heater will still cycle off and on at a rate of 4.5 minutes on and 3 minutes off at the very cold Design Temperature. When it is 50° outside your heater will likely only operate for 1 minute on and 6.5 minutes off.

And that is only one possibility. What if the connecting pipes are not big enough to move the 77,000 BTU/h from the boiler to the radiators? That is a whole different set of problems that could cause short cycling.

These numbers are not exact calculations based on your Heat Loss and precise calculations of your home’s insulation and infiltration factors. I don't know them. These numbers are offered as an approximate scenario of what might happen and the reason for it. Since your installing contractor most likely did not have a Heat Loss calculation in order to select the proper boiler size, You have an oversized boiler and will most likely live with it for many years. There will be more parts failure as a result of the short cycling because the more times you turn something on and off the more likely it is likely to fail. Especially Ignitors.

cass72

Thanks, If I were to drop the thermostat cycle to 1, wouldn't that cause the house not to stay heated? anyways it seems like I will have to live with the issue of having an oversized boiler. Too bad there is no way to adjust anything internally to compensate, but at least I know what is causing the issue. Like all of us, I am sure as long as this issue doesn't potentially have any dangerous effects, I hope, I am good with dealing with repairs what not. Too bad the installer did not realize this issue before the work was done. Thank you for all the comments!

JUGHNE

Can you post the pictures??

There is one remote possibility of an issue that can happen by the installers.

What type of heaters do you have?
Cast iron radiators or baseboard heaters.

If the baseboard heaters how about how many feet are there?

marco_7

pics will help; how many zones are there? zoning via zone valves or circs?

cass72

Baseboard and 2 zones. I think I originally got the square footage wrong. Zone 1 and zone 2 are upstairs and downstairs; both floors are 1000 sq ft, so wouldn't that make my square footage 2000 sq ft. sorry for the lack of knowledge. I will post pictures soon.