The Project Has Begun: Harman Mark III Heating Coil Install

If the line goes directly from your stove coil to the tank, yes. It will keep the pressure from going all over the place from cold to hot, plus you could install an air scoop & vent to get all the air out.

If it's in parallel with another boiler that already has one (like my setup), no.

I'm about to do the same thing to my Harman stove ( only one 21T size coil ) do I need to use type "L" copper pipe ?? it will add over $ 100. more to the job.

Is "L" the one with the blue ink on the pipe? I remember seeing blue & red -- red being thinner for better heat transfer in hydronic baseboards.

I used red out in my barn for an air supply from my compressor. It constantly has 110 psi in it -- and has for the last 3 years ( the guy @ Home Depot kept trying to sell me the blue, more expensive stuff, saying it will explode! ). Your boiler will never see 30 psi ( or the pressure relief will blow off excess ) so I would say your safe. I think burst pressure of the red is over 300 psi.

TYpe L is for hydronic heat sytems which use essentially no oxygenated water. Type L is for potable or domestic hot water which is an oxygenrich environment. Type K is for chloride based refrigeration applications. If you are using it in fresh ater to heat your domest you have to go with the type L or you will have pin holes all over the place in only a couple of years.

Hey Smitty

Now that it is getting cooler out how well are those coils working?

Sorry franknbaum -- I didn't see your post...

... but, now that the real cold weather is here, I have a pretty good handle on what these coils can & can't do.

Over the last few days, it has not been above freezing. We've had lows down to 15* & highs of 24*, & some high winds thrown in to boot. What I've found is that the coils do an excellent job of heating my two zones (one zone is the top floor, where our bedroom is, & the other is our TV room with drafty windows & unheated crawl space underneath -- it has cathedral ceilings & was added on to the house within the last 20 yrs or so), but it does need help from the oil burner occasionally. I have the thermostats set @ 70* & the rooms will maintain about 68* on the coldest nights. Boiler temp seems to stay around 155*-165* with the zones running. The oil burner will kick on after you load up the stove with coal, or the indirect boiler gets a call for hot water. I turned the aquastats hi limit down from 190* to 170* with a 20* differential, & lowered the low limit from 160* to 140* with a 10* diff. This minimizes burner run time -- it will only run during a high load period.

2 weeks ago, they were forcasting temps that following weekend to be up to 65*, so I let the stove go out & turned the 2 zones down to 65* to save oil. In just 4 days (before that warm weekend) of temps in the upper 20's at night to mid 40's during day, I burned through a solid 1/8th of a tank of oil!!

During these last 4 super-cold & windy days, I can't even tell if the oil gauge has moved at all -- that's how much of a difference the coal makes using the coils. AND the thermostats are set 5* HIGHER to boot! My house never got below 66* during a 15* morning, which never happened with the Mark I unless it was in the mid 30's outside. It would have been in the upper 50's to low 60's inside (with the bedroom at 54* & the TV room @ 52*) if I still had the coil-less Mark I !

I lit the stove last Sunday, & I've gone through 12, 50# bags already! The Mark III is a hungry bastard! I'm wondering if I'll run out of coal before the season is over -- at this rate I'll need 7.5 tons!!

We had some warmer weather when I first lit the stove ( I think that Monday it got up in the mid 40's ), & when I got home from work , I went to check the boiler temp, seeing that no zones had called for heat in a while. The digital temp on the aquastat was reading 263*!! CORE MELTDOWN!! That was the highest I've ever seen --- & it probably got even higher when I was at work!

So to sum up, these coils have made the rest of the house warm with very little help from the oil burner. It's much nicer to be at home now! I used to use the burner for the TV room & when the upstairs got unbearably cold ( close to upper 40's! ) & of course for DHW, so with the run time it's seeing now, I'll still be using less oil.

smiity I give you a A+ for your effort, one problem I do not see a heat exchanger for your DHW, a real health issue, as without a heat exchanger you are drinking boiler water. another issue to deal with is boiler systems are never considered potible water systems, so fittings are soldered with 60/40 lead based solder, a very serious health concern.take this bit of advise from a pro, install a heat exchanger and a backflow preventer on your boiler supply to prevent mixing boiler water and your potible water.

I appreciate your concern & tips.

My DHW is in an indirect-fired boiler -- the boiler water circulates thru a coil inside the unit, completely separate from the well water inside.