How to plumb a Harman vf3000 Boiler

Sorry Coalbrokdale I didn't mean to jump in on your thread. I miss read the diagram as a radiant floor setup and thinking that each of your zone controls was a circulater pump.

Wouldn't he already have a thermal break installed in his setup?




<-- on the learning bandwagon.

Hey no problem...

I'll try to take a few more pic's tonight that show more detail of the current system setup. The circle with the triangle in the middle is the circulator pump, and the five rectangles represent the individual zone valves which are hooked to the individual thermostats

I'm certainly not a plumber by any means here. My first experience with plumbing was last fall when me and the wife hooked a new three zone radiant floor heating system with a Bock oil fired hot water tank into our new house. It had electric heat and an old wood stove with a metal chimney that was no good that we had to throw out, so that's why we went with the radiant flooring. But since the price of oil has gone through the roof and I realized how we need a lot more insulation in the attic I started looking for something cheaper to use to heat our house.


In the diagram is the flow of the water backwards? Wouldn't the pump be pushing the water to your individual zone valves rather then pulling the water through them?

In the diagram is the flow of the water backwards? Wouldn't the pump be pushing the water to your individual zone valves rather then pulling the water through them?[/quote]

No, the symbol I used for the pump may be a little confusing, the point the triangle on the pump has nothing to do with it's direction, it's intended to represent rotating impeller in the pump. The water flow comes down from the zone valves to the 1st Tee connection, if the vertical valve is closed it would route water to the left through the horizontal valve which is open in this case. Water flows through the coal boiler and back to the next tee connection, hits the vertical valve, and is pulled into the pump and pushed through the gas boiler and back to the house.

Here I edited it....

Ok I got ya. I wasn't looking at the triangle but at the flow of the water. I not knowing any better would think that the pump would push the water towards each zone switch rather then pull it from them. On my system water flows towards the zones and the water is then pushed through each zone from it's own pump. Sorry for the confusion, but thank you for taken the time to straighten it out for me.

Since the beginning of forced circulated hydronic heat, the pumps have been on the return side. It is better for the pump to be on the supply side. There's a whole book written on the subject called "pumping away" by Dan Holohan. Check it out at http://www.heatinghelp.com Lots of good information on the website as well.

Coalbrokdale wrote:Ok so the Valve prevents thermal loss through conduction? I'll wait to see you drawing

It also prevents circulation in the wrong direction. You get to pay a lot for these babies, you really want them to make themselves useful. If it only did one thing, you would feel like you had another teenager around.

OK, I'm probably all wet here, let me know where I screw up.

The new plumbing you put in should be the next size up as shown in bold. You will also want the next size up circulator. It can go on either side of the boiler but inside the checks. Wire the coal boiler so when powered it always has a call for heat. Set the aquastat on the coal about 10* higher than the gas burner. When you start your coal boiler, once the water meets the minimum temperature setting, the circulator will start. It will circulate a much larger volume of water than your gas boiler has so you will have a larger amount of heat stored. This mass of water will circulate between the two boilers continuously and keep your gas burner from firing. While unfired, your stack damper prevents heat loss up the chimney. You're domestic water is heated. When your coal fire dies, the temperature drops to the low setting and the circulator stops. The flow/check valves shut and you operate as before on the gas. When closed, the checks prevent you from heating the coal boiler and drafting a heat loss up the chimney.

I recommend that you do install isolation valves too for servicing. They should go close to the TEE on the coal side and the F/C valves inside of them. The coal boiler should have its own air bladder and air scoop

So do you guys think this will work? Or will the gas boiler lose temperature with long heat calls?

I'd set the gas boiler's aquastat [the gas burner temp] at least 20-30* cooler than the coal boiler's temp. It takes quite awhile for the coal fire to ramp up and recover from all the cold water returning from the baseboards/radiators.

I'm a bit extreem with mine, I uses separate thermostats for the gas boiler's burner and the circulators for the hot water. If the coal boiler fails, and the house temp drops to the setting of the gas burner thermostat, the house will maintain 55*, the circulators will be running full time, but that's a minor concern.

I WANT to know that the coal boiler has failed, since it's out in it's own building. If I had my coal boiler in my basement, then I would [I would hope] be able to tell if had failed. But in a nice new house with tight doors and floors, I might not know if the boiler shut down. So I'd probably have a similar setup: [cooler house temp on propane boiler].

Greg L

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LsFarm wrote:I'd set the gas boiler's aquastat [the gas burner temp] at least 20-30* cooler than the coal boiler's temp. It takes quite awhile for the coal fire to ramp up and recover from all the cold water returning from the baseboards/radiators.

So you really think it will work? I figured the gas boiler would slowly lose heat if there was a steady demand for very long periods.

I believe the key is to have a much bigger circulator on the coal, at least 50% and better would be twice as big as the zone pump. You also need to make sure you plumb large in the coal loop, even if you need to pull reducers from the boiler. By getting the bigger mass of the two boilers hot and spinning, the return temperature has less of an impact. I would think a graph of the boilers operating temperature over time would be flatter.

Yes/no?

coaledsweat wrote:OK, I'm probably all wet here, let me know where I screw up.

The new plumbing you put in should be the next size up as shown in bold. You will also want the next size up circulator. It can go on either side of the boiler but inside the checks. Wire the coal boiler so when powered it always has a call for heat. Set the aquastat on the coal about 10* higher than the gas burner. When you start your coal boiler, once the water meets the minimum temperature setting, the circulator will start. It will circulate a much larger volume of water than your gas boiler has so you will have a larger amount of heat stored. This mass of water will circulate between the two boilers continuously and keep your gas burner from firing. While unfired, your stack damper prevents heat loss up the chimney. You're domestic water is heated. When your coal fire dies, the temperature drops to the low setting and the circulator stops. The flow/check valves shut and you operate as before on the gas. When closed, the checks prevent you from heating the coal boiler and drafting a heat loss up the chimney.

I recommend that you do install isolation valves too for servicing. They should go close to the TEE on the coal side and the F/C valves inside of them. The coal boiler should have its own air bladder and air scoop

So do you guys think this will work? Or will the gas boiler lose temperature with long heat calls?

Here is the rub as I see it!
All the energy of the coal boiler must pass into the gas appliance before it exits to the load

INTURN
all the spent energy of the load also must pass in and out of the gas boiler

IF
a great deal of the load begins to circulate cold water back into the gas applaince and the coal boiler is not heat soaked to give up enough energy ---- there is no way to temper the energy out either to the load or back to the coal boiler and the Gas boiler must fire or both appliances will fall below condensing level. There is no way to balance the energy out for lower circulation temps to level the load on the coal boiler.

Now I don't say my design is perfect but it does elevate this when the gas boiler is off and my pellet boiler is attempting to carry my load alone.

Perfect design is to build a primary loop pumped anytime the load calls for heat. Then heat that primary loop with both boilers (clocked as Greag outlines or with a lead/follow Teckmar control) on separate pumps with supply and returns into this primary loop and supply the load off that primary loop.

Benefit of primary loop pumping - place a small colored light (where YOU can see it) to lamp when the appliance is above circulation temps and pumping energy into the load. There is no more satisfying sight on a cold night - then looking out the window and seeing those pilot lights.

I'm not sure what you said there, but I think you said the same as I, that the gas appliance would lose heat over time with a continuous load (my bad, running the loop faster would reduce the amount of heat the water would pick up). The plumber that did mine wanted to do it in a fashion similar as it would be automatic and heat my domestic water in the oil burner. I wanted it manual as it was a hand fired.

I will try and track him down today. It has been a long time (14 years) and now, IIRC, he wanted to use additional taps on the oil appliance. He said that is the way he would do it and he has been a plumber for about 25 years.

I am not a professional - I am a poor mathematician - and I do not host a TV show - but I learned from a dead guy who learned from another dead guy. I now sometimes help their son (grand son) with wet work ( on the side ) and its funny to listen to him verbally tear apart work as we sit at the diner - done by folks who were or still are in the business for a jillion years --- and they still install so systems do not work as well as they could.

I am in no means saying your friend is wrong and neither is it wrong to circulate like as you detail - but free you mind to several other possibilities that may take more time to install and more pumps to run but will work better and more economically!

Thermal cycling protection for the coal boiler is a good thing!

I know I am the newbee here and please forgive me sticking my words between your chat. Just trying to help - I don't mean to offend. Sorry if I have.

http://www.houseneeds.com/shop/heatingp ... ermain.asp
just add the second boiler to the upper design above ( just as the first boiler is piped do not use the lower design) and you have a great system with boiler protection and fall back second boiler fault tolerance.

My system is plumbed that way. I constantly circulate hot water from the coal boiler through the oil boiler and all zones come off of the oil boiler. The oil boiler is really just a mixing vessel for zone return water and hot from the coal boiler AND a hub for the zones. I don't just have the oil boilers aquastat turned down, I have it disabled electrically so it can't fire. Will you maintain a constant water temperature in the mixing vessel? No, but it doesn't matter. You don't maintain a constant temperture in a gas or oil boiler either. You don't need to be overly concerned about your "primary" or gas boiler being able to come on "if the coal boiler goes out." Unless you travel alot or are very undisciplined in your coal regime, it's not going to go out and you will come to think of your coal boiler very soon as your primary. My coal boilers been out once since the end of October. Totally my fault. Yuengling dark, nuff said.
I've been thinking recently about my oil boiler being used as I described above and I think since I absolutley the don't use it, I'm going to remove the flue pipe to the chimney for next season as it occurred to me I probably lose alot of heat up the oil burner stack. Anyone else done that?

My propane boiler has an electricly controled flue damper, so the flue is closed unless the burner is running.. I'm not losing any of my coal-heat up that chimney.

I'm all for simple.... I like just running the systems in series, like coalkirk's system... you can even use the current circulator on the existing oil or gas boiler. just put the coal boiler in the return line before the oil/gas boiler, set the aquastat on the oil/gas boiler 30* cooler than the coal boiler's and watch it work...

No need to get too 'cosmic' with valves, pumps and controls... unless that is fun for you, for me, simple is better... I deal with way too much 'cosmic computerized widgets' in the airplanes I fly.... I don't want to deal with them in my heating system.

Greg L