Dump Zone Options LL 110K Boiler

Looking for opinions on how to deal with dumping excess heat on "no/low load" days. I was curious if it makes sense to install radiant under-floor heat and use that as the dump zone.

~John

Can you turn down your aquastat to 140-160? How about a small zone in the basement or garage or somewhere?

Radiant in floor heat usually is pex tubing and it doesn't like real hot water, there needs to be a tempering valve. I like having a large enough zone to dump the heat fast, as long as it doesn't sweat you out of the house. I have 2 different zones that I can use, each on their own aquastat, I just change the temp on the aquastat to dump in the garage in summer, house in the winter. Works for me, others may say it's not necessary if you have a big enough expansion tank ( I do )

AquaStat is set at 165-170 right now. I suppose I could try that, but The boiler pushes 250 when idle on warm days. Idle feed is at minimum 2 minutes on / 9 minutes off.

I have my idle set at 1min on, 7 minutes off. Thereabouts.

That seems to keep the idle on mine from tripping the dump zone for quite a few hours.

This seems to be the finickiest part of this machine, an issue I'm hoping is resolved once the temperature drops a bit more (boiler running more than it is now). As it stands for me, I am dumping the heat into the house which works fine because it keeps the house at ~70f on days where the outside temp is between 55-65 deg f. I don't get much solar gain, so having the boiler put a little heat into the house every few hours keeps it comfortable.

johnniecuse wrote:AquaStat is set at 165-170 right now. I suppose I could try that, but The boiler pushes 250 when idle on warm days. Idle feed is at minimum 2 minutes on / 9 minutes off.

I hope that is not the temps set on a triple aquastat High and Low, they should be 20 degrees apart.

FireMan -

No the high limit is set somewhere between 165 & 170.

Have you tried reducing your timer cycle to keep the boiler temperature a little lower?

In my hand-fired days I used a large cast-iron radiator in the basement for a dump zone. It was simple to hook up and worked very well. You can probably find used radiators on craigslist or at a local salvage yard.

johnniecuse wrote:FireMan -

No the high limit is set somewhere between 165 & 170.

Got ya, is their a 2nd high limit that stops the stoker from running on the timer, or could you back down on the timer cycles ?

I could probably back down the timer cycles but, given my lack of experience with coal, I'm not sure how long I can go before the fire goes out.

johnniecuse wrote:I could probably back down the timer cycles but, given my lack of experience with coal, I'm not sure how long I can go before the fire goes out.

You get pretty good at re-starting the boiler, after a while.

That will depend on your dump temp; Radiant tubing generally does not like water hotter than 160 degrees. For those low load days, though, you could do that if you turn down the control temp for the dump zone (just remember to turn it back up when it gets colder). Other than that you could dump into multiple zones ( if you have them).
Bobcat

bobcat10_4 wrote:That will depend on your dump temp; Radiant tubing generally does not like water hotter than 160 degrees. For those low load days, though, you could do that if you turn down the control temp for the dump zone (just remember to turn it back up when it gets colder). Other than that you could dump into multiple zones ( if you have them).
Bobcat

The tubing I've used is good for 180f at 80psi, I believe.

How would PEX not work in this application?