Oil Boiler/Condensation/Summer Indirect

kf_2

the dewpoint of oil is rather low, 117 degrees at a 10.5% CO2. Most burners won't achieve that high of a CO2 so the dewpoint is usually even lower. So while condensation may not be a problem, what is a problem is that the burner is firing into a relatively cold casting. This causes impingement and sooting. As the tips of the flame come in contact with the colder iron they start to turn black and create soot on the casting. You would be surprised to see how a thumb nails thickness of soot can decrease a boilers efficiency.


kf

bruce pirger

Consider the oil boiler that supplies hot water for the indirect all summer. Hot water is require in the AM in late PM...all day the hot water has no demand...and the tank has little loss...so there's no demand. In the meantime, during these 12 hours or so, the boiler cools on its own accord (no need to fire).

So when it fires again to produce hot water, the boiler temp is down to say 80-90 degrees.

This happens effectively twice a day...all summer.

Is this bad for the boiler? Is this effectively a "cold start" everytime from a condensation viewpoint? Would it be better to fire the boiler to keep it warm when there is no call for heat from a condensation/boiler longevity viewpoint?

John@Reliable_2

Service alot of systems setup just like yours with no problems

including mine. If at service(cleaning)time you find "mud" on heat exchanger when I would install a diffrent aquastat, but most likely you won't find anything because those two times a day will maintain temp above room temp.John@Reliable

kevin

good question

i have heard from some oil burner service guys that they don't like cold start on oil boilers for this reason. They have seen some cases where boilers get plugged.What they say is to put the boiler at a min. temp. to always maintain.I am not a burner guy so this is second hand advice. kpc

Bill NTSG

Warm start

I prefer "warm start" 120-125° but if you do not shut your unit off completely the normal hot water production should keep you out of trouble. The worst case I see is when there is a tankless coil and the boiler is "off" and the 50° water goes through the coil on the way to a water heater. Cold start boilers that are not used for hot water production run a close second. In your situation you should be ok. Like the other post said , unless you notice a problem at tune up time , don't worry about it

Bob Bona_4

you

have a good set up. The boiler runs just enough to keep it dry and warm. The seals and flue passageways are happy they never see condensation since it cycles enough.

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bruce pirger

Thanks guys. I have a Buderus G115/21 supplying my 55000 BTU/HR radiant load...and also firing the MS53 Megastor. I don't need to worry about short cycling, and with the 53 gallon indirect, I don't think I'll run out of hot water with any "reasonable" drain.

But I do notice that the boiler cools off quite a bit between firings during extended times. I believe the tekmar controls (363) have the ability to maintain the boiler supply at a minimum temperature...but not sure if this is needed.

I'll wait a year (brand new install) and see how it looks.

Thanks to all!

David Sutton_2

on demand...

i have seen alot of these and install alot of them myself, the running times for water demand in most casees is enuff, if its a larger boiler i will put on a 8124L to maintain a setting of 120 degrees, the big thing i see with these is that when it dose sit for that long.. the frist thing it dose is cool the inderect down before it heats it up, i now put in a 6006 to keep the circ from running till the boiler heats up then it lets the circ come on and heat up the inderect. i set this at 120 also. now when it calls the boiler comes on heats up and then we start making hot water...david