Cycle Rates

Rodney Summers

Thanks for the reply. I should have added that yes my boiler is oversized . Rad and pipe load = 230sq ft approx 54000 ibr. Boiler ibr =404 sq ft 94000 ibr. Gas Bills are high considering semi attached house 1500 sq ft and very little heat loss(new windows etc.) Can a pro adjust the gas pressure valve and reduce my fuel burn?Is this the only possible solution?I heard of downfiring,sounds drastic and against boiler specs.Or am I stuck with oversized boiler that will always burn too much gas for too small of a load?Thanks

Rodney Summers

Steam head help with Cycle Rates

I need to know if this is normal. Peerless boiler set at .5 lbs in 1 1/2 out. When it calls for heat boiler runs for some time approx 10mins. rads get hot. Then it continues to make multiple cycles of 1 1/2 min ON 1min OFF until stat is satisfied.Is this short cycling? Is the boiler supposed to run constantly until the stat reaches temp? One pipe system- plenty of main vents- rads all heat properly but how may cycles should there be before stat reaches temp. Stat is honeywell 3600 program digital. PLEASE HELP

t. tekushan

cycles

It certainly seems to me that the boiler controls are doing exactly what they're supposed to do.

The boiler may in fact be a bit over sized for the amount of radiator EDR you have. You say the radiators get hot in 10 minutes. Thats pretty fast. If they are fully heated (saturated) and the vents are snapped closed, the boiler will quickly build pressure to the cut-off point (cut-in pressure plus differential). The cycle on off times make sense here.
Now, if this is a change in some way from past performance, and nothing in the system has been changed (including pressurtrol settings) you should have a professional look at the gas valve pressure regulator. Some friends of mine rented a place with hot water heat with a WM cast iron boiler and the flame was roaring! I said, "Ehem. Have that checked out because of the potential for carbon monoxide and outrageous gas bills." I got their attention by pointing out that the former might make the latter irrelevant.

On the other hand, you might check out the Library here and measure your radiators (be sure to use the correct charts for the style radiator you have) and compare that to the I=B=R rating of your boiler. If the boiler is way over what you've measured, then that is the issue.

t. tekushan

judgement call

To some extent you're stuck. I have always liked the performance of a boiler thats about 15% oversized. But this is way too much! Yes you can downfire, and it may be advisable. But you can't go too far down for a bunch of reasons. 1) Carbon Monoxide rises quickly as you underfire in the absence of any other changes; to minimize this, downsize the orifices and leave the manifold pressure alone. 2) the flue and passageways will be too large, increasing the proportion of draft loss, negating some of what you have done. 3) A vigorous boil will decline towards a simmer since you still have the same amount of iron and water. I guess you can block off one orifice instead. But I'm not sure this deals effectively deals with the problem.
So go down a little, maybe up to 20% I don't know how much it will really save...