Aquastat?

[Moose]

I'm installing a wood/coal boiler/radiant heater picture of firebox attached. Now my plan is to use the oil boiler only as a distribution vessel and turn the burner off entirley. I plan to do this by taking the cold water return off the oil boiler and attaching it to the cold water return on the wood boiler. Then taking the hot water output from the wood boiler and attaching it to the cold water return on the oil boiler. Then pretty much leaving the rest of the system alone. The rest of system consists of a DHW heater 2 infloor radiant heat zones and a forced air system with a radiator type heat exchanger. I intend to totally enclose the boiler in it own insulated room and run the cold air return from the forced air system to blow cold air onto the heater and then run the hot air into the forced air system.

So thats the general plan, but I'm not real familiar with aquastats. As I understand they turn the pump on at a set temp and turn the pump off at a set temp. Easy enough.

1. Can an aquastat control more than one pump at the same time. like all four zones as I described above?

2. Can you have an aquastan an a thermostat on the same pump?

3. Is there anything special I need to do to install an aquastat, if I buy an aquastat will it come with everything that I need to install it?

Think that enough for starter, but I have many more question to follow about actual setup and design.

 

[Eric Johnson]

I'm not clear on what you mean by disconnecting the piping on the oil boiler. What I would do is tee into each line and then circulate hot water from the top of the wood boiler into the top of the oil boiler vessel. You can do that with a Taco 007 or some other small circulator.

An aquastat is just a switch, so you wire it up like one. To answer your questions specifically:

1.) One aquastat will control anything that is on that circuit, including more than one pump, zone valves, blowers, etc.
2.) I'm pretty sure you can control a pump with both an aquastat and a thermostat, though if the thermostat is 24 volts, which most are, you might have to work around that.
3.) Most aquastats have probes that go into a brass well that screws into 1/2- or 3/4-inch tapping on the boiler. So you need a compatible well. You can also get surface-mount aquastats that strap onto a pipe, but they need flow to work.

A few more considerations:

Aquastats come in three basic flavors. You've got aquastats that make the connection on temp rise ("make on rise" or "close on rise") and aquastats that break the connection on temp rise ("break on rise" or "open on rise") depending on what you're trying to do. Those are both called SPST switched aquastats. They also make aquastats with "SPDT" switching, which will go either way. Those are the ones I like, because they can be used in either application, and can even be used to do two different things at once, depending on how you wire them up.

Aquastats allow you to set the differential, i.e., the amount that the temp is allowed to rise or fall from the setpoint before doing their thing again. For example, if you have a pump set up to turn on at 140 degrees, you can set the differential to allow the temp to get down to 120 before it kicks off. Or 130. On a Honeywell, it's a little white dial with black numbers on it underneath the terminals.

If you know what you are looking for, you can buy new aquastats on Ebay for a lot less than you will pay retail. Like $20 vs. $70. But make sure you know exactly what you're bidding on, because there are a lot of different kinds of stats, and you could easily wind up with one that doesn't fit your needs. Your best bet is to go to the Honeywell website and look up the part number and read the specs. And you have to watch the auctions, because they come and go.

 

[Moose]

I see what your saying with the tee's on both ends this way I can circulat between just the two boilers.

1. Do you think that I should just leave the pump on at all times or put it on a stat to turn on only when the temp rises to say 100 or so?

2. Why would I want the hot water going into the top of the oil boiler and not the bottom where the colder water would reside?

3. At what temp would you recommend I set the stat to to turn on all the pumps for the 4 zone to keep the system from over heating. I think the oil burner is set for about 175 right now should I try to keep it in that general temp zone, and at what point would the temp be in a dangerous level?

sorry if some of my questions seem elementry, but this is truly uncharted territory for me.

 

[wdc1160]

I plan to do this by taking the cold water return off the oil boiler and attaching it to the cold water return on the wood boiler. Then taking the hot water output from the wood boiler and attaching it to the cold water return on the oil boiler. Then pretty much leaving the rest of the system alone.

I think this is all standard stuff. Almost everyone here probably has a similar setup.
As far as this forced air business you have some explaining to do. Also, I was going to try and answer questions about the stats, but
maybe you should explain more??

Like why aren 't you going to use a hot water to air HX.

Why do you need all these aquastats


One key that Eric points out is

Aquastats come in three basic flavors. You’ve got aquastats that make the connection on temp rise ("make on rise” or “close on rise") and aquastats that break the connection on temp rise ("break on rise” or “open on rise") depending on what you’re trying to do.

All of this has to do with differences in water temp. I don't know why you would work these into individual zones or to control the the circs or pumps.

 

[Eric Johnson]

Those are perfectly good questions, Moose. All of us have wondered about them at one time or another.

You want to maintain a certain temp range in your wood boiler for better efficiency, since a cooler boiler doesn't burn the fuel as well. Therefore, you'd want an aquastat to shut the circulator off below a certain temp, say 150 or 160. On startup it will cycle on and off until the boiler gets up to temp, and then run continuously through the end of the burn cycle. You'd mount that stat on a well in the boiler, if possible, for the most accurate readings. You could wire the circulator to run all the time, but you'll have a more responsive system if you control it.

If you pipe the hot water from the wood boiler into the top of the oil boiler vessel, then the hottest water is immediately available to the zones. When you're trying to heat your house, you really don't care what the temp at the bottom of the boiler is, since you draw your water from the top. Makes sense when you think about it but most people, including me, tend to automatically assume that you should pump the hottest water into the return, in order to heat the whole boiler up evenly. But as I said, why?

A typical overheat trigger temp would be 200 degrees. You'll probably have the best results from your system if the boiler water temps are in the 180-190 degree range. But with an aquastat, you can play around with it and see what works best.

 

[Moose]

Ok lets start with the pumps and stats. I want to use one circ pump to feed the oil boiler to ensure thet the oil boiler temp is kept up to temp. As of now all of the zones currently draw off of the oil boiler and I don't see any reason to change this at this point. So rather than just keep the circ pump between the two running all of the time I thought I could control it with a stat to turn it on only when it needed to run. As far as the other stat I was thinking I could hook it up to the other heating zones to turn the pumps on when system started to over heat to keep it from doing so this way even if the zones wern't going to call for more heat I would force the heat there just to dump it in the event of an overheating situation.

The forced air side of the system has a radiator that is attached to the boiler and a large fan forces air across the radiator to transfer heat from the water to the air. its pretty straigt forward I'm just going to reroute the cold air return to run across the fire box to utilize the radiant heat from the wood boiler to move the hot air upstairs. Hope I'm explaining this alright please ask for more specifics if I'm not explaining my self clearly.

 

[wdc1160]

Eric, if it were one stat he was asking about I could see it.
but it seems were dealing with the zones as well?

 

[Eric Johnson]

I understand what he's saying. He needs an aquastat to run the circulator to get heat into the oil boiler pressure vessel, and he wants another one to turn on his zone pumps in case the boiler starts to overheat. They would both be "make on rise" versions, just set to different set points, i.e., 160 and 200, or something close to that.

The boiler shouldn't overheat, BTW, if it's working properly. Most wood boilers just shut off the air supply when they hit the setpoint (say, 190) and that pretty much stops the heat from climbing. You get into overheating problems when a pump fails, for example, and the boiler can't dissipate any heat. So it's a good idea to do what you are suggesting, but it's not going to help you in a power outage. It's a good idea to have a gravity heat dump for those occasions.

 

[Moose]

Eric, if it were one stat he was asking about I could see it.
but it seems were dealing with the zones as well?

Lets break it down into two sides on side it going to be the circulation bewteen the two boilers with a stat to controll it. I want to use a pump rather than gravity. I want to put a stat on this side to keep the pump from running continuously.

The other side has four pumps for four different zones

zone 1: radiant floor heat 1st floor
zone 2: radiant floor heat 2nd floor
zone 3: DHW
zone 4: radiator for for forced air system.

I want to put the stat in for this side to use all four zones as a dump zone to keep from overheating. May not use the DHW as a dump zone. I don't want to controll the water with the fire and danpering the fire. I would rather try to find a what kind of fire I need to substain the system with out danmpering and use the dump zones as a safty if I over fire. I maybe way off base but like I said before this Is all new to me. I've always had your standard wood stoves.

 

[Moose]

I'm looking into power outage options and I plan to have the boiler danmper down if the pumps fail to do their job, but I would much rather have a slightly warmer house than have a smoldering fire if at all possible.

 

[Moose]

Pic is upside down hovent gotten arround to fixing it yet.....

 

[Eric Johnson]

You would need two make-on-rise aquastats, two wells and the usual wiring gear to set it up like that. Presumably the four zone pumps are on the same circuit. I'm not much of an electrician, but I would wire a hot lead through the aquastat and then run wires off the other terminal to each of the pumps. Set the aquastat to 200 and when it hits that temp, the juice will flow to the pumps. The other one also goes into the top of the boiler and the circulating pump is wired through it. I'd set it at 160 with a 20-degree differential and see how it works.

I don't understand your strategy for controlling the fire at all. Does your boiler have a draft induction blower or is it a flapper that opens and closes as the boiler heats up and cools? Or something else? You can exert some control over the fire with a standard stovepipe damper, which I would recommend installing in any event. But there needs to be some automatic way to control the combustion air. Letting it overheat and then trying to dump the excess heat is a very bad idea. If you can't automatically control the boiler, then don't try to operate it.

Why don't you post a pic of the whole thing, instead of just the firebox? I'd like to see what we're talking about, here. As I recall, it's more of a hybrid than a conventional wood-fired boiler. It may require a different piping and operating strategy than what we've been talking about.

 

[Moose]

front with automatic danmpner and side pic

 

[Moose]

back with plumbing

 

[Moose]

Letting it overheat and then trying to dump the excess heat is a very bad idea. If you can't automatically control the boiler, then don't try to operate it.

I guess I'm not intentially trying to overheat it. It is still going to have a way to control the fire. I am going to attempt to to keep it from over heating with the size of fire that make, but honestly I have no Idea how this thing is going to react so I think I just need to get it installed and see what I have.

 

[wdc1160]

Why no HX?

 

[Moose]

Not sure what you mean please enlighten me..

 

[wdc1160]

Moose you have a unique thing your doing.

Forget all about the pipe, aquastats and zones.

Your turning a old oil boiler into a HX = Heat Exchanger.

Water to air HX.

Many folks have made homemade HX's, but I am sure this must be a first right.

Why isn't the boiler just sold, or thrown out to replace it with a store bought / more conventional homemade approach.

I am not judging, I just don't understand how it came to this. It is probably important.

 

[Moose]

Well I guess in my mind I'm not using my oil boiler as a heat exchanger as much as I am trying to us it as a heat distribution center. The boiler works fine and I used it up until last week to heat my DHW until I ran out of fuel. I suppose I could just go buy some more oil at 3+ dollars a gallon but I've never heated with anything other than wood my whole life even when oil was less than 50 cents a gallon. Eric made a good point in another thread that if I were to take out the boiler or take over its chimney then if I ever had to leave the house for any amount of time in the winter I would have no way to heat the house. I don't know who it was, but some one mentioned that either my insurance or my mortgage company might not think to highly of me removing the conventional heat source. and if I ever wanted to sell the house I would be drastically reducing the number of potential buyers by not having a convential heat source. Plus everything is already there installed and in working order all I intend to do is change the way I heat the water. Heat with wood rather than oil. I suppose If I wanted to spend the extra money I could go buy a traditional add on boiler or just go buy a combination wood/oil boiler, but I dont' think that it would be a cost effictive option for me at this time especiall when I got 2 stories if chimney and the boiler for less than It cost me to instal a chimney in my last house. I don't suppose that what I am doing or what I want to do is the best or most efficient but I have to work with what I have. I am definatly open to Ideas I you think there is a better more cost effective or safer way to do it please let me know because as I have stated I am pretty new to the whole heating water thing.

 

[wdc1160]

Well I guess in my mind I’m not using my oil boiler as a heat exchanger as much as I am trying to us it as a heat distribution center.

Aren't you getting the heat from the boiler to heat air through ducting/sealed room
Was it designed orginally to do that?

I know this has to be frustrating. You have got 10 separate issues in one setup.

Eric made a good point in another thread that if I were to take out the boiler or take over its chimney then if I ever had to leave the house for any amount of time in the winter I would have no way to heat the house. I don’t know who it was, but some one mentioned that either my insurance or my mortgage company might not think to highly of me removing the conventional heat source. and if I ever wanted to sell the house I would be drastically reducing the number of potential buyers by not having a convential heat source.

Taking out the orignal boiler would be reality suicide. Not everone is a wood burner. You not gonna changem so don't try by removing their furnce.

I thought you meant that it was broken down, not wanted, or unfixable. So it is in working order, but your not actually going to be using it for anything except shipping heat to various places.

Why is it advantagous to use this boiler and sealed room as a "heat distribution center" <- (In indiana this is a police station)

 

[Moose]

Well I guess in my mind I’m not using my oil boiler as a heat exchanger as much as I am trying to us it as a heat distribution center.

Aren't you getting the heat from the boiler to heat air through ducting/sealed room
Was it designed orginally to do that?)

I do have a heat exchanger where the hot boiler water is circulated through a radiator looks like what you would find in an air conditioner or car with a fan that blows air from the cold air return across the radiator wich picks up heat from the radiator and the air is then pushed into the house... I don't know if boilers were ever really designed to do this but the unit with the radiator in is was. it looks just like a furnace with no heating eliment other than the radiator that is heated by the boiler on the other side of the room. I'll take pics tomorrow maybe this will help.

Why is it advantagous to use this boiler and sealed room as a "heat distribution center" <- (In indiana this is a police station))

I'm not sure what your asking here I guess I'm falling back on if it ain't broke dont' fix it. the thing works I just want to use another fuel to heat it. If your refering to the sealed room I was talking about ealier I was going to enclose the wood boiler because not all of the heat is going to be transfered to the water and at least half of the btu's will be radiant. by enclosing the wood boiler I am going to attempt to get the most warm air as I can upstairs and out of the basement before the cold stone walls have a chance to absorb the heat.

 

[Eric Johnson]

How is the air to the wood burner controlled?

BTW, I don't think you're doing anything very exotic or unusual. It seems logical to me. I'm just confused about the nature of the beast you're going to be using. It sounds like this is more of a wood stove with some water piping, in the sense that the air controls are set manually, like a stove. So in that case, you really wouldn't be able to control it like a conventional boiler, and perhaps your heat dump idea makes sense. Or maybe there's some relatively easy modification that would make it work better.

The nice thing about projects like these is that much of your work goes into piping and controls that can easily be adapted to another boiler, if you decide to upgrade in the future, which you would probably want to consider doing anyway. There are plenty of good used wood boilers around for pretty cheap if you want to do the heavy lifting. I picked up my previous boiler, which kept us warm for 4 seasons, on Ebay for less than $300. I put another $3,000 into the piping, etc. Made it a lot easier to upgrade to the gasifier.

"Heat distribution center." I like that, Bill. Around here it's called Dunkin Donuts.

What EKO model are you getting?

 

[Bartman]

Hey guys, just saw this post.
Moose, it sounds like you are trying to install what I have here, except for the water/air heat exchanger. My system has 5 zones, 1 DHW, 2 radiant, 2 hydronic baseboard. Personally I feel that you should keep the oil burner in place, it's not hurting anything to keep it there. I am a fan of redundancy, only for the simple fact, if something can go wrong, it probably will. What will happen if for some reason the wood boiler goes down, you're screwed, or you're running on wood and it's cold out and all of a sudden you have to get to the hospital (hypothetical), the wood goes out, you have no heat. With the oil burner, wood goes out burner kicks in, you're covered. After reading the posts I drew a quick sketch of my plumbing of the 2 boilers, I also took some pictures to maybe help in illustrating how I did it. My system uses 3 aquastats, 1 triple action, 2 spst. On the wood boiler, the aquastat on the left controls the combustion air blower, opens @ 165F, the aquastat on the right is the overheat aquastat and closes to energize the 4 pole overheat relay to overide all 4 heating zone thermostats, that closes @ 190F. My oil boiler has control of the system, but wood boiler has priority, unless outside temps dip below 20F, then both burners have priority. Currently I'm looking into changing the way the system works a bit to make the boiler really idle, then really burn.

Right now I'm having a little trouble reducing the pixel size of my drawing, so bear with me.

 

[Moose]

Eric, you are correct in saying that what I have is a wood stove with coils in it and it has no induction fan. I just use the term boiler lightly for simplicity sake. as far as induction air as far as I know there is a bi-metalic coil in the door which helps control the induction air automatically. I will install a dampner in the black pipe and control that manually as well. I would love nothing more than to get a nice gasification boiler but having two mortgages right now has that on hold. So this is what I have right now and I feel pretty confident that I will be able to heat my house better that what I am doing now. I will post some pictures of the current set up with the oil boiler and the water/air heat exchangers and I think this will clarify some things.

 

[Bartman]

Here's the schematic, pardon the lousy drawing. When running in non-wood mode, valves 1 & 3 are closed, valve 2 open. In wood mode, valves 1 & 3 open, valve 2 closed.