How to plumb a Harman vf3000 Boiler

Ok I made some changes to the design, I added three additional isolation valves and moved the pump to "push away"..
This will allow me to isolate the coal boiler form the gas boiler or allow it pass through both.

What I don't understand is how the Bell & Gossett Flow Control Valves work to automate the switch over process. How do these work? Are they just a check valve to prevent back flow?

Yes CoalKirk My two boiler system is also in series with solid fuel boiler heating the legacy boiler and there is not reason to worry about the oil or gas boiler when it is not allowed to fire or it cold starts only occasionally, or as we have our heating challenged moments - or the doctor will not release us from the emergency room to fill the hopper.....

A primary secondary loop pumping is the best (IMO) - one or the other boiler and any zone can be valved out for service- there is no thermal loss at either appliance - the loop itself can be the thermal mixing mass- solar storage can be added - a 500-1000 gallon thermal mass storage tank can be incorporated to level the demands on the boiler from the load. mass storage also allows you only need to fire the coal boiler once a week in summer for domestic hot water production - but then some boilers will not like that - and I don't want to complicate what can be a simple installation.

So primary/secondary loop pumping a very flexible design. But as I note above, large temp swings to the coal boiler are still possible with coaledsweats design. All I suggest is adding a thermal balance bypass (thermal mechanical or manual), so the coal boiler always sees 140 return water or more.

That could be more easily done by placing the coal boiler supply next to and down stream or the coal boiler return - in the current load return - on close spaced tees with a dedicated aqua stat controlled circulator. Its as simple as moving one pipe on the design, and the home owner only has to break open the return to the oil boiler leaving a nipple at least 18 inches to the oil boiler from the close spaced tees, making it function as an independent primary (hybrid) loop.

I remembered now (I think) what he wanted to do. I recall he wanted to pull the pressure relief valve and I thought it might not be to code so I told him to just plumb it manual. I'm going to guess it was something like this.
The pump is installers choice, and you may want a adjustable spring check in the coal loop for resistance when its off.

AaaHemm - let me venture to guess the threadlets on the saftey and the drain are only ---3/4 NPT max???

You will need a pump that will produce ??? 16GPM per minute MINIMUM at unacceptable head pressures to move enough energy out of the coal boiler - and that may not be enough to stop short cycling much less the drama of pumping with a hi draw pump like that and the wash issues in the vessels.

If you place the coal boiler on two close tees on the return leg of the legacy boiler a small taco three speed cartridge pump would be very economical to operate.

Sting wrote:AaaHemm - let me venture to guess the threadlets on the saftey and the drain are only ---3/4 NPT max???

You will need a pump that will produce ??? 16GPM per minute MINIMUM at unacceptable head pressures to move enough energy out of the coal boiler - and that may not be enough to stop short cycling much less the drama of pumping with a hi draw pump like that and the wash issues in the vessels.

If you place the coal boiler on two close tees on the return leg of the legacy boiler a small taco three speed cartridge pump would be very economical to operate.

What are you talking about? Why would you need 16 GPM? What head pressure for energy? Wash? Which one is the legacy? Why would a three speed pump be more economical?

Most boilers get reducer bushings when plumbed. My oil boiler has a 3/4" PRV and it goes into a 1 1/4" bushing in the boiler. That said, I think a 3/4" would be sufficient. The pump should be the same size as the other circulator.

Use the first drawing as I believe that is the correct one.
With no call for heat, the heated water from the coal boiler will flow into the top of the gas boiler and out the bottom, back to the coal boiler in a loop. On a call for heat, the zone valve opens and water flows from the coal boiler into the top of the gas boiler and out the other outlet at the top to the house. Since the water in the lower crossover pipe is already moving into the coal boiler, it will continue to do so when the thermostat opens the zone and its controlled pump starts.

This will work as described. The hot water coil and aquastat on the gas boiler are continuously washed with the hot water from the coal boiler in either a call or no call situation. You should have plenty of hot water and the gas burner should not fire until the coal fire fails. The cold water return goes directly to the coal boiler as it should in this case.

Am I wrong?

I am sorry - as a newbee I need to remain positive and productive and I have failed.

Please accept my apology - I should not have participated beyond my first post.

No apology needed, you just confused me more than I normally am with the Greek.

Is that a traction engine in your avatar? Can we get a blowup of that?

Gotta agree with Sting on this one. You need to move water from the coal boiler to your gas boiler and back again with a 1 1/4" pipe. I believe you said you have multiple zones, each of which is returing water with a 3/4" pipe. Anything less than the 1 1/4" will not be sufficient.

coalkirk wrote:Gotta agree with Sting on this one. You need to move water from the coal boiler to your gas boiler and back again with a 1 1/4" pipe. I believe you said you have multiple zones, each of which is returing water with a 3/4" pipe. Anything less than the 1 1/4" will not be sufficient.

You are using pipe size to engineer this. The homes heating requirment is satisfied in this case by flow rate. What you describe would be true if each zone had its own circulator. It appears he has one circulator. Let us assume that that circulator is rated at 10 gallons a minute. If one zone calls for heat it will get 10 gallons a minute. If two zones call for heat, each will get about 5 GPM. Four zones calling for heat, about 2 1/2 GPM. If he had eighteen zones......... Well, you get the picture. Obviously he is heating his home with the system in place with a 10(?) GPM pump now.

Now, in a no call situation the water travels in a circulating loop between boilers at a flow rate of 10(?) GPM, maintaing a large volume of hot water. On a call for heat, one to four zones will open and a flow rate of 10(?) GPM will satisfy his heat calls. The cold return runs to the coal boiler as required. If you cant move 10(?) GPM through a 3/4 inch pipe, how is he heating his home now?

You are correct as far as you went but you're leaving water temerature out of the equation. If he's got 4 zones going to town, there needs to be a sufficient volume of hot water coming from the coal boiler via another circulator or his gas boiler water temp will drop to the point where it's not recovering fast enough. A 3/4" line from his coal boiler will not keep with demand. I'm not an engineer and don't even play one on TV so if I'm wrong or missing something here, I know someone will let me know.
Here's a pic of my oil boiler return. The 1 1/4" line to the left is the supply from the coal boiler. Three 3/4" returns with circulators. On the supply side, same thing, a 1 1/4" line back to the coal boiler.

We cannot simply explain pumping and gpm
So I am a good dog - Ill lay by my dish!
I don't wish to annoy folks that I hope will help me in the future

Ill lift my nose for the possible spanking and say =
This is likely the best 80 bucks you will ever spend on your hobby!
http://www.heatinghelp.com/shopcart/pro ... gory=8-191
add this and your a jump ahead
http://www.heatinghelp.com/shopcart/pro ... egory=2-41

Read these and you will understand how and why!

coalkirk wrote:You are correct as far as you went but you're leaving water temperature out of the equation. If he's got 4 zones going to town, there needs to be a sufficient volume of hot water coming from the coal boiler via another circulator or his gas boiler water temp will drop to the point where it's not recovering fast enough. A 3/4" line from his coal boiler will not keep with demand. I'm not an engineer and don't even play one on TV so if I'm wrong or missing something here, I know someone will let me know.

First, what size reducing bushing is in his PRV if 3/4" is such a crisis?
One zone or four, the flow rate remains the same. The gas boiler won't lose any heat, the hottest water from the coal boiler goes there first, then to the zone where it loses its heat. If the pipe is 1 1/4" or 3/4" the pump will still move the same 10 gallons of water in a minute. The only change would be the velocity of the water through the pipe, NOT THE BOILER, THE PIPE. The large pipe, the water would move slower. The smaller pipe, the water would move a little faster. It is still 10 GPM leaving the coal boiler. 10 GPM entering the gas boiler. And when a zone calls for heat it is moving at 10 GPM. Exactly what he has now.
The pump he has, whatever its rating is currently heating his house with a gas boiler the size of two vegetable crates. I'll assume it has about 20 gallons of capacity. I don't care if the pipe is 3/4" or 6", the water will only flow at the pumps flow rating. Now he adds a coal boiler with say 25 gallons of capacity. The pump on the coal boiler should be the same size as his circulator. When up to temp, the coal circulator starts......... and runs at his current flow rate in a loop. On a call for heat, his zone circulator starts and draws water from the top of the boiler to the zone. The coal boiler continues to pump heat into the gas boiler. Instead of returning to the coal boiler, now it goes to the zone. The cold return runs into the coal boiler. The rate of flow in the system remains exactly the same as it did, whatever it is. Since the volume of heated water is almost double, the shock from the cold return is reduced considerably.

If the VF3000 can't heat at the flow rates his gas boiler currently runs at, I would think he spent a fortune for nothing.

You are correct about pipe sizes as an engineering practice. However engineers will always use the theoretical scenarios. Steam coils in pairs always have a separate trap because its practice. They work fine with one. The additional cost is carried by the consumer, the profit for the additional parts and labor goes into profit. Still works the same, just costs more money.

Ok guys I got a little lost here... Not sure if we are still discussing my original question or not. Is there a generaly accepted method, and should I add an additional pump and valves and should I push it through the gas boiler..sorry pull it, right "pumping away"..? I will certainly post my pump size and pipe diameters if it is helpful. Wow we've got a "heated" debate going here...:Ha

The only way to understand the difference between moving sufficient GPM [SUCCESSFULLY] is to read the books I have listed. We cannot go into the detail it will take here. I understand your doubt and please don't take offense at my persistence. Read the books and gently learn why. May I add also, if you use a port on the boiler other than the recommended supply and return ports, you could make hot spots by incorrect wash inside the vessel and crack the boiler - such as your diagram using the safety port and the drain port (if mfg dedicated as such) for a second boiler loop. Pumping liquid and moving energy with a liquid are two different things. Moving liquid energy is best done with volume not pressure, and I agree as you note; if you raise pressure you can obtain almost any flow rate. But raising pressure takes a hi watt demand pump - thats electricity you will have to buy for the rest of what ever!!! The small TACO variable speed pumps today run on minimal wattage, and variable GPM can support better transfer efficiency when seasonal demand varies by degree days. Lower gpm rates for lower firing days and Higher for higher days, no pumping when the coal boiler is catching up!

Here is another pressure analogy: You can drink from the water fountain at the library because the water flows over your mouth at some gpm of LOW pressure. BUT if that same gpm is applied to your mouth by a cheep pressure washer at HI pressure it will not be as palatable. Your boiler also does not like hi pressure flow of any rate.

Hope that helps - I tried to keep the Greek out!

Coalbrokdale wrote:Ok guys I got a little lost here... Not sure if we are still discussing my original question or not. Is there a generaly accepted method, and should I add an additional pump and valves and should I push it through the gas boiler..sorry pull it, right "pumping away"..? I will certainly post my pump size and pipe diameters if it is helpful. Wow we've got a "heated" debate going here...:Ha

I can understand why your lost and yes we are discussing your original question.

As far as there being a generally accepted method? I would like to take this opportunity to define that here and now. Once we do that, a talented board member will offer his auto cad skills and we can put the "Plug and Play" coal boilers definition in a library.
It probably would be a good to do that in general with a lot of these general subjects, that would build a better knowledge base for the newbies.

Its not heated yet, I can can tell you are new to coal. You haven't seen anything like anthracite heated.

Please, post your pump's model and rating. Also, I would like a closeup pic of the your boiler pressure relief valve to determine it's size and whether or not it has a reducing bushing. If you are familiar with nominal pipe sizes, just post it's NPT size.