How to plumb a Harman vf3000 Boiler

If you are going to be on gas/oil all summer, disconnect the flue pipe to the coal boiler and forget it.. all it would do is heat the water in the gas/oil boiler, the circulators and/or zone valves won't operate or open..since ther is no call for heat.

When you shut down the coal boiler for the summer, clean the flue pipe, just cap it, the rest is same 'ol, same 'ol.

When fall or winter comes, hook up the flue, and start the coal fire.

Simple, and it works.

Greg L
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LsFarm wrote:If you are going to be on gas/oil all summer, disconnect the flue pipe to the coal boiler and forget it.. all it would do is heat the water in the gas/oil boiler, the circulators and/or zone valves won't operate or open..since ther is no call for heat.
When you shut down the coal boiler for the summer, clean the flue pipe, just cap it, the rest is same 'ol, same 'ol.
When fall or winter comes, hook up the flue, and start the coal fire.

Simple, and it works.

I'll agree that it is simple, inexpensive and will work.
However, running your domestic water off a boiler with a minimum temp of around 160*+ is scary.
I also think that the heat loss will be high. Even removing the stovepipe. Unless this VF3000 is a very well insulated boiler, you are doubling, maybe even tripling an uninsulated surface area to give off heat to the room. That is why I feel strongly about the lift checks and separate loop. When the coal goes down, it is self isolating. It can always add heat to the system but it will never rob any.
The loop keeps the larger mass more evenly heated reducing cold return shock, good thing with solid fuels, right?
I would think the parts are under $200, thats about a ton of coal for most of us.

I thought you were talking about summer opperation with the gas/oil boiler providing domestic hot water?? why would the water temp be 160*?? Where is the water set now for DHW during the summer?? The water in the boiler does not equate to the DHW temp... the water does not exit a coil at boiler temp, usually 40-50* cooler, because the delta-t* gets too small or low to pass more heat into the coil.

As far as thermal shock, there always has been thermal shock, all the boiler systems have thermal shock when a zone valve opens and/or the circulator starts... I've never seen any problems of thermal shock in any of my homes with hot water heat... I think this is chasing a theory... is there any history of home-size hydronic systems cracking boilers, or having other effects from thermal shock?? IF so I'm unaware of them. Maybe in large industrial size systems, but a home system the water volume is pretty small, the shock minor, and most residential boilers [gas/oil] are made out of cast iron, which would be the most susseptable to thermal shock and cracking.

I just don't see a need for the complication. My system is just as I describe, but the boiler is remote, and the return water goes through a water/water heat exchanger instead of through the boiler itself. Maybe this is comparing apples and oranges, but I don't think so.

Greg L

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This thread is really starting to run! After going back and looking at Sting's original idea, there is a circ pump in the gas boiler that I mssed (oops). Seeing that, it does shed a different light on his "system hookup". My question to Sting,,, so what makes the coal boiler the dominant boiler and keep the gas from firing, a strap on aquastat placed on the supply of the coal boiler? to de energize gas boiler? I see. So why do the tee's need to be spaced 18" apart. Is that supply and return or boiler boiler? Scott

But,,,,,,,,,,,,, You do need to tell me how to make all these zone valves work with your system. Scott

Hey guys I'm going to be using a seperate Gas fired Hot water heater in the summer.

Greg I don't think the Stroh's Brewing company is still around...? The Six pack reward is on the table.. Multiple winners will be concidered!

I never was a fan of Strohs beer.... Maybe we can share a shot or two at the summer get-together...

Actually I'm alergic to beer, wine, live yeast, fresh mushrooms... BUT,, nothing against distilled spirits !!

Greg L

As for the plumbing, I just prefer simple.. doesn't make it more correct, or better, it just fits in my brain better.. I guess that makes me simple-minded..

Greg L

LsFarm wrote: why would the water temp be 160*??

As far as thermal shock,

I just don't see a need for the complication. My system is just as I describe, but the boiler is remote, and the return water goes through a water/water heat exchanger instead of through the boiler itself. Maybe this is comparing apples and oranges, but I don't think so.

You suggested running the solid fuel at 40* higher temperature than the gas appliance, I would assume that would be the very least it would have to operate at, probably more. Maybe.

I am not talking about thermal shock, I'm talking about the rate of loss. With the single loop the mass of heated water is reduced in half. The boiler will see a faster drop in temperature due to that fact. Rermember the loop doubles the amount water available at heating temperature to service the demand.

With your single loop the gas boiler does not see heat unless a zone calls for it, a long draw of domestic water will fire the gas burner. There is no doubt in my mind that this will happen. If I spent $3-4000 to heat with coal, I would not be happy if I heard the gas burner running a couple of times a day or even in the course of a week. There is just something unnerving about that.

I don't see the additional loop as complicated. The only difference in the two designs is really one part and the flow pattern. The pump, you are already have one in the system. Do you think it would be more prone to failure? Is it the cost? Any good plumber worth his salt is going to insist on installing the checks between the two boilers in either configuration to stop stanby losses when the coal boiler is out of service. The lift checks are as reliable as the pipe they are installed in. Those parts are about $80. So that should not be any different. What is different is that there is an additional pump. That is $60, maybe $80 dollars. I'm not sure where he lives, but that is probably a 1/4 to 1/2 a ton of coal for most of us. I would think the cost of the pump will be paid back the first year in savings from two things. One, the firing rate will be easier to tune to the load and second, the gas boiler will never fire. It will also reduce the risk of overfiring the coal. I see savings there. The cost of running the pump is insignificant relative to the fuel savings and ease of operation.

There is one more point here. In the event of the zone circulator failing, the coal boiler pump should carry the load. It may have a lag, but I believe it will heat the house reasonably well. The single loop will not. Backup is worth something, yes/no?

It is automatic, no operator interaction. Works when your home sleeping or visiting grandma for two days. No valves to play with, no stack to remove, no electrical connections between the two. Plenty of reserve DHW and the gas/oil never starts unless the coal fails. I think that is pretty simple too.


All that said, send the beer to Greg. I don't drink.

I am just amazed that the guy that flies jet airplanes for a living finds my loop and pump on a heating system complicated.

Cut the boss some slack!

I have watched electricians pull wire for a complicated system after looking at a plan once.
I have watched pilots take off and land and all the voodoo that takes place in between.

And I have had these same folks look at primary secondary loop heating and ask when I took up playing the pipe organ in church!

Its all about what you comfortable with!

Coaledsweat, can you repost your method, I'm still not 100% clear of how it would work. And can you recomend the brand / model of check valves to use?

Greg if you like scotch then we would get along just fine. Maybe this summer on my way up to Traverse City I'll swing by with a bottle of blue!

I think it is because I fly jet aircraft that I like simple.. The plane I fly is just too 'auto-magic'.

OK, I'm confused on where the hot water coil is or isn't, I thought the oil boiler had a coil in it, but wasn't going to be used and the New coal boiler was also going to have a DHW coil..that was going to be used. Now I hear that in the summer the DHW will be from a stand-alone gas heater..Maybe I have this thread confused with a different but similar topic.

If the DHW coil for winter use is in the coal boiler,, then I like my simple system. If the DHW coil is in the oil boiler, then keeping the coil warm is important, and I'll give the nod to Ian's system [coaledsweat] . The cost of the additional parts is not the concern, you are right, about $200 for a pump, a few checks and addtional fittings.. I just get a headache figuring out some of the controls and flow diagrams.. and what will happen when, and how.

I think this photo is worth a double vodka and 800mg of Advil:


This is in my basement,, everything is an after-thought, and an add-on, and I think the plumbers were all drunks. And only three soldered joints in this photo are recent and mine.. the rest was like this when I bought his 'Money Pit'.

Greg L

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LsFarm wrote:OK, I'm confused on where the hot water coil is or isn't, I thought the oil boiler had a coil in it, but wasn't going to be used and the New coal boiler was also going to have a DHW coil..that was going to be used. Now I hear that in the summer the DHW will be from a stand-alone gas heater..Maybe I have this thread confused with a different but similar top.

That's one of the problems with the thread, it has morphed over time. I think the original idea was to have the hot water off the gas burner as it is at present and add a coal boiler that works automatically. That would reduce the cost and time of the install and simplify the process. That was the only basis of my design. If the DHW from somewhere else, it could change things significantly. We really need to clarify what he wants to do at this point.

Coalbrokdale, are you are sticking to the original plan? Or have you decided to change things around? I have an E-mail in to the PE about some questions I have. His input has caused me to question a few things that are not really a big deal, I just want to clarify things. I found it odd that the plumber and the PE are so far apart on this stuff, I need to know why. The plumber has many solid fuel appliance installs, the PE has none (he seems lost with the concept ). I will try to get a clearer drawing and description of operation together and repost it. That should send this thread into the record books!

I'm looking at the best solution since I think I need to replumb most of the cooper in order to move the gas boiler and position the coal boiler in place. So basically this is the setup: Harman VF3000 with DHW coil, Gas 50 gallon hotwater heater, Burhman 164 btu gas boiler (no DHW coil). I don't plan on using the hot water heater in the winter unless there is some advantage to it, such as routing the VF3K's DHW coil water through it... I would like to have the VF3000 as the primary boiler with the gas as a standby in case the coal fire goes out. If it the works out to be cheeper I would consider the use of the VF3K in the summer for only DHW but I don't think that would be the case.

Coalbrokdale wrote:I'm looking at the best solution since I think I need to replumb most of the cooper in order to move the gas boiler and position the coal boiler in place. So basically this is the setup: Harman VF3000 with DHW coil, Gas 50 gallon hotwater heater, Burhman 164 btu gas boiler (no DHW coil). I don't plan on using the hot water heater in the winter unless there is some advantage to it, such as routing the VF3K's DHW coil water through it... I would like to have the VF3000 as the primary boiler with the gas as a standby in case the coal fire goes out. If it the works out to be cheeper I would consider the use of the VF3K in the summer for only DHW but I don't think that would be the case.

I figure after a week of this, I ought to be able to pick up a VF3000 cheap.

Why the gas water heater? A Boilermate will cost next to nothing compared to another appliance. Just pull one more zone to feed it and you can have the same 50 or even 80 gallons stored. And again, it will run from either the gas or coal which ever is fired, summer or winter. You can scrap the two DHW coils and buy a case or two.

Using a zone to heat your water will give you a more evenly heated water. It also, absolutely prevents the system from delivering scalding hot water which is a possibility when using solid fuel appliances to heat DHW..

There is no one "best" solution

All our "enhanced" wet systems are a series of trade-off's unless we are willing to design from scratch.

These "trade-offs" may be viewed clearly in the picture that Greg has shared. The lowest bidder will only open a system enough to get his equipment in and functioning as fast as possible. Time is money. Unless you willing to clear the boiler room and THEN begin a major project like this - there is no best. Simply 'functional'

I am new here but would enjoy helping if I may!
How far do you wish to go to achieve "best" and help me to understand what you feel is "best"!
Are you looking for quick - with least piping and less functionality and operation economy because fuel is cheep
that would be boilers in series and reuse as much as possible, some manual things to swap, twist, or tweek during the season to keep things on line and some work (as the season cools and warms) to make the boilers play together as you wish.
- or
Most fault tolerant, less human interaction, best economy in all seasons? That would be a correctly sized Primary/Secondary loop design with boilers in parallel, piping your zones with thermal traps, insulated pipes and automatic controls.

For some excellent reading on P/S check out Dan Holohans books “Pumping Away’ and “Primary Secondary Made Easy” at heatinghelp.com. Also John Sigenthaler has quite few articles available at http://www.pmmag.com on primary secondary design and applications.

From here I think Ill just PM my thoughts so I don't appear argumentative!