Harman Magnum Stoker - Hot Water Coil Hookup for Hot Water?

I may be confused, (actually I usually am!) but I think there are some misconceptions about the Amtrol heat exchanger unit and how it is hooked to the boiler. Yanche was explaining how the controls should work, with one minor modification (the capability to run the circulator continuously) that should stay as it is. One word of caution, if you allow the Harman to produce hot water without limit you will have to install a tempering valve to protect your family

The attached sketch is out of the Amtrol manual (available at: http://www.amtrol.com/boilermate.htm ) and includes my suggested hook up based on three assumptions:
1. you are only running the boiler to heat water and in the event that the house is not warm enough.
2.our suggestions for air circulation in the other thread are going to cause the boiler to run even less than before
3. the control scheme for the circulator on the Amtrol will modified to run all the time as long as the Harman is fired up (perhaps a manual override switch)

A side benefit for keeping the water flowing through the coil all year will be a nice dry and non corroded stove during the summer months.

Also beatle, you said your expansion tank was 43 gallons, I think you might have expansion tank and your domestic supply tank in the Amtrol confused (see the drawing for it's probably current location on the boiler loop). You may have to increase the size on the boiler to account for the Harman, but I tend to think you won't have to.

Just my two sense based on my planning for installation of an Amtrol with my coal boiler. As I said before, nothing like a good science project to stir up the thought process!

Thanks guys!

matthaus, you're right, I was confusing the expansion tank for the Domestic tank. THANKS!

OK, so I added a few more pieces to my current hookup so you can see more of the pieces that are in my system.

I left out drain and shutoff valves, but I can add them later when we get to that point.

I will add a tempering valve to the household hot water in a future rev.

It looks like I need to have a direct path to the expansion tank, which my current setup doesn't have b/c of a flow check valve on 1 side and the circulator pump on the other side. [see attached pic]

matthaus,

I may have missed something (not hard for me to do!), but the only part of your diagram I don't understand is how does the water flow through the Harman? It looks like the circulator pump will be pulling from both the Harman and the Boiler?? And likewise the return from the Amtrol will return to both the Harman and the boiler?

How do I guarantee I will be pulling water from/to the Harman?

Also, I like the idea of wiring the circulator pump to the Harman so it only runs when the Harman is active, but don't I have to worry about the stove still being hot when the stove shuts down and the water can still flash to steam?

You guys are AWESOME! Keep up the brainstorming!!!

Thanks,
Jeremy

As the water is heated in the coil it will naturally expand and seek the path of least resistance (if you plumb it correctly that should be through the Amtrol HX). If my assumptions about your set up are correct (and you know what they say about assumptions!) the water will flow out as it expands and the return water will take it's place. The check valves assure that water doesn't go where it shouldn't and the purge valves assure that there is no air trapped in the coil. You can use the valve on the boiler return loop to help force the water through the coil as well (just as long as you don't close it completely).

One weakness of hooking the Harman up in series (as shown on your concept) is that boiler water will run at full tilt through the coil and may not effectively transfer the heat. Obviously some temperature measurement gauges on supply and return of the Harman will make sure we have a true science project.

I would put a delay timer in the interlock circuit so that water flows at least 10 minutes after the Harman shuts down. This will provide a means of making sure it all works, especially if you can adjust the timer based on some real water temp readings.

As in any endeavor there are infinite ways to skin this cat, just have to keep the objective in mind.

Hi guys,

What kind of delay timer are you talking about and where can I buy one?

Which control schematic are you using? Need to do a little planning based on your current control schematic, easiest way is probably to figure out which Honeywell you are using.

An alternative is to provide a manual override switch (would connect the terminals on the thermostat) to force the circualtor on when using the Harman, this would make you the timer. Probably the cheapest solution.

matt,

ok you've lost me this time. These controls are on my oil boiler? Or are these controls actually in my Amtrol Domestic Tank?

I was thinking. Wouldn't it be better for the circulator pump to run always on?

Reasoning: Stoker went out and wife/baby need hot water.
Downside: with water continually circulating with stoker out, boiler runs more.

Hopefully we never get to this case, but it will guarantee hot water.

Which leads me to another thought. Should I wire thr circulator pump to be on a lever type switch? One side of the switch will be my "Harman Circuit" (always on? ect), the other side of the switch will put the pump back to the original "Boiler Mode".

Reasoning: When we go away and the stoker gets shutdown the pump will only run when the Amtrol tank calls for it?

Thanks,
Jeremy

Yanche,

You mentioned that the Harman needs a direct path to the expansion tank.

Does this schematic solve that problem? I put a check valve in a direct line from the Harman to the expansion tank.

I've also, put a single 3 way ball valve in the new schematic w. a few check valves. Makes the switch from "Harman" to "Boiler" dummy proof

All,

Please feel free to comment and chime in.

Matt,

For now, I'm going to stick with the method that Greg and I talked about b/c I'm not smart enough to see all the science behind your method. But please feel free to object/comment on my current design

Thanks,
Jeremy

The boiler controls (probably one of the Honeywell aquastats in the drawing I posted) the circulator pump by causing it to run when the temp in the tank goes below the set point on the T-stat. It works in conjunction with the temp sensor on the boiler to fire it up when needed. You need to leave this circuit intact to allow for proper operation when the circumstances dictate extra heat needed from the boiler.

One little nit on the schematic you drew, need to make sure you understand which way the check valves will be facing. Once you fix the direction the flow checks are facing I can see if it flows (no pun intended).

woops, Here's an updated pic with the check valve showing the correct orientation.

Hi guys,

I have a question about wiring the existing circulator pump.

How can I leave the pump wired up as it is today to the Amtrol tank, which can turn on the circulator pump & boiler when needed and also wire up the circulator pump to an aquastat that is near the Stoker, so when it gets up to temp the circulator pump will run continuously?

This way, if the stove goes out, the boiler can kick on with the circulator pump and run as usual.

The way I visualize it, if either the Amtrol or the aquastat control turn on the pump, the entire line will be energized. Maybe I don't care, but I'm not sure.

Thanks,
Jeremy

I forgot to comment on your drawing with the check valve orientation corrected, looks good!

On the question of circulator tie in, after thinking about it maybe a parallel thermal switch hooked into the Amtrol Tstat circuit would be easiest (refer to the schematic in one of my previous posts). That way when the circulator will run automatically when the water in the Harman coil is up to a predetermined temp (I would say a set point of 150*F would be good). Also by doing it that way all the other controls would work. The only exception is that the boiler will fire if the water in the loop is below the aquastat set point. You could change this setting for winter operation to make sure the boiler does not run except when needed to supply hydronic heat when the stove can't keep up.

Not sure if I explained this sufficiently, will try and find time to make you a sketch. I do need to know which aquastat your boiler has installed so I can figure out how the controls to the Amtrol are wired.

You just may get this science project up and running yet!

Thanks for looking over the drawing for me.

Ok, I will check on the aquastat for you.

I'm gonna ask a question, but if it's better left aswered when you find out what type of aquastat I have just tell me to simmer down

So by wiring a parallel thermo switch and making sure the existing thermo switch is set low enough, the pump & boiler will still turn on in the case that the stove goes out and the water temp drops?

Likewise, if the stove keeps up with the hot water demands, the circulator pump will kick on when the new aquastat set at 150F trips?

Thanks!!!!

ok, so I now understand (mostly) how my boiler & Amtrol tank are wired.

There is a honeywell control on the boiler. The Amtrol tank is wired to the honeywell as a separate zone.

I tested this by jumping the zone wire from the Amtrol to the Honeywell to 120V and the boiler fired up, SWEET!

I dun learned me sumtin twoday!

I'll explain what I saw and I'll try to post a pic as well.

Now there is a HOT 120V that runs into the Amtrol tank.

This feeds into the Thermostat (which activates a 2 output relay), and into 1 side of each of the 2 relays (all one unit).

relay 1: goes to the boiler (to kick it on)
relay 2: goes to the circulator pump

It looks like all I would need to do is hook up a second aquastat/relay in parallel to relay 2.

The attached pic is the control inside the Amtrol Tank. The words Black and Red in the diagram are attached to hot (120V).

See attached pic

Yes you saw what I was figuring would work, the way to try it out is to find the part you plan to use and then simulate what would happen when you hooked it up and make sure it works OK.

Then you would simply adjust the control you select (might be able to find an inexpensive one on ebay) to operate at the temp you want (yeah right, simply! )

And the science project rolls on.

AWESOME! Thanks coach

Quick question. It seems that all aquastats turn off when they get to hot and ON when they get to cold.

That's the exact opposite that I want.

Do they make what I want?

Man I wish this was digital logic, I could just throw an inverter in the circuit and all my problems would be solved

EDIT Sorry for the ignorance. Looks like a Low Limit or High Limit aquastat will do what I want.

This was taken from a Honeywell Spec.

L4008B—makes a control circuit on a rise in water temperature. It is normally used as a circulator controller to prevent circulator operation until boiler water temperature is at or above the control setting.