Controls questions, please help

[dogwood]

I am still struggling to understand what controls, relays, aquastat etc. I will need to obtain to operate the zones in my yet to be installed system. I have only two zones. One zone is for the W/A hx, the other is for the DHW flat plate hx. They will be parallel plumbed according to BioHeat plumbing diagram PT3, http://www.woodboilers.com/uploads/public/PressureTank(PT3).pdf (Please copy and paste the whole link into the address bar as the last three letters didn't highlight).

This is what I am designing for and what I need to do:

I have a two position 24 volt motorized ball valve, substituting fot zone valve ZV1 in the PT3 diagram, that needs to be operated by a single pole double throw switch. When open it allows the heated water from my Solo Innova to go to the W/A hx above the existing forced hot air furnace, and/or the DHW flat plate hx. When closed all heated water goes to 1000 gallons of storage.

1. When the temperature in the house falls or rises, a thermostat needs to turn on or off the circ pump for the w/a hx, and at the same time open or close the motorized ball valve.

2. When the 40 gallon DHW tank calls for heat, the the aquastat located near the bottom of that tank needs to turn on two 120 volt circ pumps servicing either side of the DHW flat plate, as well as open that same 24 volt motorized ball valve. When the DHW is up to temp the aquastat control will need to shut off both circs and close the motorized ball valve.

I am not sure how to set all this up. Will I need additional relays? I do have a 24 transformer that came with the boiler. What would be the easiest way to set up the controls and what control devices/relays would be appropriate to use for these two zones?

For DHW use, what do you normally set the differential settings at on adjustable controllers?

Mike

 

[sgschwend]

Well sounds like you are setting up the load side of your hot water heating system. Sometimes there are so many choices it get confusing.

I run two load also. I also want to keep my system a simple as possible. If we assume the boiler will provide hot water on demand with its own controls. Then we are down to controls of moving the water and making sure the water reaches the boiler at an appropriate temperature.

Here is what I did:
Purchased a thermostat that measures the heat in the floor and runs a ciculator pump based on my home heating set point (warm floor, makes a warm house).
I added a circulator pump on the DHW loop that is controller by the boiler's circulator pump circuit, when the boiler is up to temperature then both pumps run, recharing the DHW when the boiler is working.
I have storage, it is great, followed NoFossil's ideas there, it was easy and now I have a lot more flexibility as to when I run a fire, I highly recommend it!

So now let see: I have added two pumps (with internal check valves), one mixing valve, and one thermostat. If you are going to to replace the mixing valve with something else I am all for it, they work but.....

Folks will want you to post a diagram, a good way to receive feedback.

 

[dogwood]

Steve, If you copy and paste the whole link above it should show you exactly my plumbing schematic from BioHeat USA. I called BioHeat today and they suggested I use a Taco SR502, two zone relay. I'll have to look at that closely and see if it can control the two 120v DHW circs as well as the 24v motorized ball valve needing its own SPDT switching.

It seems maybe you need an aquastat with its own control to feed into a relay, which then feeds into the various loads if I am understanding this. Maybe the relay is where the SPST or SPDT business is located, as opposed to in the small controller that is attached to the aquastat when you buy it. Do you think the SR502 should also have the wiring for the other W/A heat exchanger zone run through it also?

I'm trying to understand the workings of, and work out the most basic possible standard electrical control system, since it is all new to me and a bit confusing. When I read the threads about the NoFossil controls or Arduinos or Tekmars I wonder if I'm on the wrong planet. Even thermostats can be daunting mechanisms anymore. Thanks for helping. Any other clarification or feedback by anyone would be appreciated. Thanks and Merry Christmas Eve.

Mike

 

[ohbie1]

Did you get the backup control box with your tarm? If not, then you need a 24vac transformer to power some relays. Let's take the house heat first. TT from living quarters completes 24v circuit to circulator pump relay AND zone valve control head. So this means the TT will activate the circulator and open the zone valve at the same time. Make sense?

 

[ohbie1]

Next DHW: The DHW tank aquastat works like the TT; it will make or break the circuit. You need another relay which will operate the pumps on the DHWHX (How come 2 pumps??). So the circuit goes..... aquastat completes the circuit from the 24v transformer to the pump(s) relay AND also to the ball valve (once again).

Aquastat calls for heat, closes 24v circuit, turns on pumps, and opens ball valve. Make sense?

I assume you know and therefore I did not mention that the pumps are attached to the 120v side of the relays. The relays are activated by 24v but control 120v (the circulators).

I can tell you more about relays & their specs if you need it.

 

[dogwood]

Frank, you asked why two pumps on the DHW. One supplies water from the boiler or storage to one side of the flat plate hx servicing the DHW tank, the other is a low flow circ that circulates the DHW in the tank through the other side of the flat plate. On the DHW circuit the relay has to open or close the 24v ball valve as well as start or stop the two 120v circ pumps. The wiring schematic that came with the (non-spring return) motorized ball valve shows a SPDT switch turning it to either the open or closed position. Do you know of any relay that would provide for both voltages, and have a SPDT switch for the 24v motorized ball valve circuit?

I didn't get a backup control box with my Tarm, but did receive a 24 volt transformer. The thermostat for the house heat will more simply have to turn on a relay to one 120 circ pump, plus that relay must open or close the same 24 volt motorized ball valve with a SPDT switch as above. Do you know of a relay that could do this? There are no zone valves, just the one motorized ball valve I substituted for the zone valve (ZV1) in the Bioheat PT3 plumbing schematic. I was thinking maybe I could use only one SPDT switch for the ball valve somehow for both the house heat and the DHW. Maybe that's impractical, and I should duplicate its function with two separate relays, one for the heat the other for the DHW? What do you think? Am I being at all clear? Thanks for your help.

Mike

 

[sgschwend]

Ok I have looked at the drawing:
In this drawing each load has its own circulator, if I remember correctly you said you had one load, hence one pump, and one thermostat to run it, that is what they are showing as item D.
They are showing a mixing valve that is an improved device (F), pretty much plumbed the same as everyone else.
As far as I can tell the other three aqua-stats are shown, E is not necessary B is inside of the boiler, A is used to run the mixing valve.
The last device is a safety power outage energy dump device, that is commonly done two. A member posted he had one that used a 40 gallon hot water tank.
Note the air bleed, buy the small ones and use more than one.
The ZV-1 is not necessary because the load's head will cause the hot water to go to storage unless the circulator is on then it will take the hot water.


The other stuff that is not there and you will probably need is a way to bleed the load. That is at the suction side of the load a valve to drain, needs to have good flow too not just a small bleeder like they are showing. Also your pumps should be placed on the suction side of the load, purchase with check valve and you can eliminate those parts too.


From there drawing we still return to: 2 circulators, 1 thermostat, a mixing/circulator/aquastat valve. Just like I said before. There is also the heat dump zone, nothing wrong with that, the key part is a normally open zone valve, locate the dump above the boiler so the hot water will move on its own.

 

[dogwood]

Steve, appreciate you looking at the PT3 diagram. Item D is where I am stuck. They call it a "Circulator Switch Relay-Typical Controller" I have two zones. One for the
DHW, the other for the house heat via a w/a hx in my forced hot air furnace plenum. I am adding an aquastat to the diagram to service the DHW zone. The house thermostat will control the other zone. I should have been more clear on that. If you look at my reply to ohbie one (Frank) just above, maybe I stated my question about relays more clearly. Thanks for your input and appreciate your help.

Mike

 

[ohbie1]

motorized ball valve shows a SPDT switch turning it to either the open or closed position. Do you know of any relay that would provide for both voltages, and have a SPDT switch for the 24v motorized ball valve circuit?

I didn't get a backup control box with my Tarm, but did receive a 24 volt transformer. The thermostat for the house heat will more simply have to turn on a relay to one 120 circ pump, plus that relay must open or close the same 24 volt motorized ball valve with a SPDT switch as above. Do you know of a relay that could do this? There are no zone valves, just the one motorized ball valve I substituted for the zone valve (ZV1) in the Bioheat PT3 plumbing schematic. I was thinking maybe I could use only one SPDT switch for the ball valve somehow for both the house heat and the DHW. Maybe that's impractical, and I should duplicate its function with two separate relays, one for the heat the other for the DHW? What do you think? Am I being at all clear? Thanks for your help.

Mike

Sure. It looks like you need one DP relay for each system. The DHW circ(s) go on P1 of relay 1, and the ball valve goes on P2 of relay 1. The house circ goes on P1 of relay 2, and the ball valve goes on P2 of relay 2. Relay 1 is activated by the DHW tank aqst, and relay 2 is activated by the TT. Thus the ball valve is energized by either relay, while one relay energizes the DHWHX circs and the other relay energizes the heating circ.
You can use any 24vac actuated DP relay. It's contacts must have enough amp rating to handle one circ and 2 circs for the other relay. So if the circ is rated say at .5 amps, and you have 2 on 1P, that's 1 amp. You then figure double to be safe, so you would need 2 amp contacts. You could use Taco (or similar relays), or buy from surplus (usually a lot cheaper). I'll dig up some surplus websites for you to see how these relays come, and you can Google 24 vac relays or surplus electronics. You will find a bunch of offerings

 

[ohbie1]

http://skycraftsurplus.com/search.aspx?find=24vac+relays

 

[ohbie1]

http://www.grainger.com/Grainger/items/1N185

 

[ohbie1]

http://www.electronicsurplus.com/ccp80000479-dpdt-12amp--24vac-relays-190r-ly2-ua-008009-140624.htm - 75k

 

[sbleiweiss]

First about the plumbing schematic. I don't understand ZV1 is drawn where it is. Shouldn't it be between the boiler and storage so that the house can draw from storage without pushing water through the boiler when the boiler is cold?

To your original question, the two building blocks that I have used are electronic heating controllers (Ranco or Johnson Controls) and Taco SR501 relays. The heating controllers have SPDT relays and can be used to switch 24V or 110V or even 220. I have one on the boiler, and another to check the storage temp. These come in single stage where one control setting controls one relay and dual stage where there are 2 independent set points (and modes) controlling 2 relays.

The various heat demand thermostats / aquastats can generally be wired in parallel to create a single demand signal for the system. These are usually just dry contact single pole (spst) switches.

The zone valve will usually have an end switch which can be helpful in creating a control signal for relays.

The Taco SR501 relay is a very versatile building block. It has 2 output SPDT relays. You could use one for the zone valve and another for the circs. The relay has 24V available that you can use if you don't need a lot of power. It has enough to run a heat controller and probably these motorized ball valves. You can activate it with a 24V control signal or a simple SPST switch from a zone valve end switch or thermostat.

Regards,
Scott B.

 

[dogwood]

Thank you very much Frank for all the links and your careful explanation of how I should lay this circuitry out. I'll look through all your links and study your explanation today.

Scott, I think the Termovar loading unit might prevent water from flowing through the boiler when storage is providing the water for heating. I'm not sure however. I'll have to ask BioHeat. The way you describe the zone valve location is the way I had it in my own plumbing schematic, before I decided to use BioHeat's schematic instead to avoid warranty issues. And thank you very much for that clear explanation of the controls and relays you utilize. I'm beginning to understand this better. It does seem like controls and relays are similar in function. Could you or anyone explain the difference between controls and relays? Are controllers more than an assemblage of relays? I function better when I understand the concepts behind what I am dealing with. I've been looking at the installation guide and submittal sheets for the Taco SR501 and SR502 relays. Your explanation of how the SR501 works is very helpful, right on time, and way better than what I managed to figure out. Thanks so much.

I'll look up Ranco and Johnson controllers too. Any particular models of either you might recommend? Both of you have a Merry Christmas too.

Mike

 

[sgschwend]

Dogw.
A common DHW solution is to have a small circulator pump that moves water through some storage then to the domestic hot water heat and back. The pump does not need an aquastat it would be run by the boiler's aquastat. More of a pre-heat design where the input to the hot water heater is from the storage. This is a simplification of the system design.

There is nothing wrong with the way you have it, it does help control the DHW temperature.

 

[sbleiweiss]

I looked at a number of other Tarm plumbing diagrams to get a feel for the concept for ZV1. It appears to be used to isolate the wood boiler and storage from the radiator loops and a fossil fuel boiler. If you don't have a backup boiler in the system, then ZV1 must be kept open all of the time. if this is your situation, leave it out. I would still want to insure that I was not pumping hot water from storage through a cold boiler, and I don't think that the Termovar will prevent this. I would add a zone valve between the boiler and storage and activate it when the boiler circ is running. Maybe you can control this with careful piping layout, but not sure. There was a thread here that demonstrated that you can gravity feed to storage if piped carefully so that might be an option to further simplify the system by eliminating the automag zone valve.

The electronic heating controllers are simply an electronic version of an aquastat. They control their relay based on a temperature. The SR501 relay class devices are switched based on a remote input such as a thermostat or zone valve closure. That is the basic difference. You can see the various heating controller models here: http://www.rancoetc.com/

They sell both brands I mentioned. I have found the 24V versions to be easier to wire up. Given a choice I like the Johnson better. It seems to be a better quality unit and has an LED to tell you that the relay is energized or not. Both have LCD temperature read-outs and adjustable modes and differentials. The Ranco is easier to program with everything settable from the menu. the Johnson requires you to open it up to move a jumper to select the basic heating / cooling mode. Only Ranco makes a 2 stage version.

 

[dogwood]

Scott, thanks for taking the time and trouble of looking through those BioHeat plumbing schematics. I will definitely call BioHeat about your thoughts on the ZVI this week. I do not have a backup boiler in the system as you say, and will not be pleased if that ZV1 can be eliminated, as I purchased a pricey motorized ball valve to be the ZV1 on that 1.5 inch pipe run.

I thought the ZV1's function might be to keep any heated water from circulating to and through my two zones, the HX loops (what you called the radiator loops), when they were not calling for heat, and all heated water should be going to storage. I think the ZV1 should function to eliminate any ghost flow or thermo-siphoning from storage too that line too.

If the Termovar Loading Unit will not prevent hot water from storage from being pumped through the boiler when heated water from storage is being supplied to the two zones, maybe I can relocate that motorized ball valve to between the boiler and storage to prevent this prevent this, if it is not need in its current location. Thanks again for your thoughtful input.

Anybody else have a thought on this? Here is the link to the PT3 plumbing schematic again if you'd care to take a look at that ZV1 location. On that diagram I am using the single tank storage variant. Where they show heating zones taking off I have only two, one for a W/A HX supplying the home's heat, and one for a DHW HX. Again, please copy and paste the whole link into your address bar as the last three letters won't highlight: http://www.woodboilers.com/uploads/public/PressureTank(PT3).pdf

 

[Gooserider]

Looking at the manual, It is unclear if the Termovar will prevent flow through the boiler when the boiler is cold - There is an optional "flapper" / back-flow preventer in the bottom cross pipe, that is present in some models, but not in others. Looking at the diagrams, when the unit is running this valve is closed, and the pump pulls the return water up, mixes it with the heated supply water from the top connection according to the mix thermostat position, and then sends it back down and out the other bottom connection to the boiler... At startup, with a totally cold boiler, the thermostat will have the return passage completely closed, and routes the flow 100% supply to return, until things start to warm up, and it opens...

In all the diagrams of the non-running unit they talk about the unit thermosiphoning through that bottom flap after it stops in order to get the last bit of heat out of the boiler. It also opens to allow the system to actively thermosiphon in a dump zone situation. But all the diagrams show that valve, which isn't present in all models - it appears that it can be replaced with a solid piece, which makes the difference between the two units. Without that valve, any flow would have to go through the pump, and it appears possible that the mix thermostat will close to block that passage as the unit cools to go back to the startup position. In addition, the manual does say that the flapper will prevent thermosiphoning in the reverse direction if the tank is hotter than the boiler.

My conclusion is that it looks to me like you wouldn't have a thermosiphon problem in the case of just a hot tank and cold boiler sitting there, as the Termovar would stop that.

What isn't quite clear is what impact any water circulation from pumps would have on the ability of the Termovar to keep flow out of the boiler when the house load pipes were pumping in and out of storage. In the wonderful world of theoretically perfect plumbing, it shouldn't have any effect, as the storage tank is providing hydraulic separation, but reality isn't always the same as theory... It looks to me like there would be a possibility for a small amount of flow unless the plumbing is such that there is a lot less flow resistance going through the storage tank than there was to go through the boiler - in that case I wouldn't expect enough flow to worry about.

Gooserider

 

[dogwood]

Gooserider, thanks for your reply and looking through that manual. I did ask for that backflow flapper from BioHeat and have it separately in the box with my Termovar. Sounds like from what you are saying I should go ahead and put it in at least to prevent errant thermosiphoning. I think I will after consulting with BioHeat, move the ZVI to a position between the boiler and storage as Scott suggested. This location makes more sense to me and will stop any flow through the boiler when heating through storage only. If you wouldn't mind taking a look at the PT3 schematic, (link provided above), do you think moving the ZVI like this might cause any problem with flow going through the pipeline where the ZV1 is supposed to be located, when only the storage is being charged by the boiler? Thanks.

Mike

 

[Gooserider]

I'm not really sure if ZV1 is needed in either position, or if it might be needed in BOTH locations...

Essentially in the position where drawn, it prevents flow through the load circuits when there is no house call for heat, thus ensuring against "ghost flow" and making sure all the boiler output goes to storage.... But it wouldn't prevent flow through the boiler when the house loads are supposed to just be pulling from storage. I don't see anything else in the heating circuits that would prevent this flow, other than their presumably high head load resistance, which should cause most flow to go through storage since that would be the low flow resistance path. Depending on what other plumbing is in those load circuits you might already have enough flow resistance to not need ZV1 there at all... Not sure.

Moving ZV1 to between the boiler and storage inputs would certainly block flow through the boiler when drawing from storage, but the Termovar looks like it should be doing that anyway plus, once again, the low resistance flow path is through storage... Assuming the Termovar does block unwanted flows, then ZV1 would be redundant in the boiler-storage loop...

If I had to put bets, I'd say the case is slightly stronger for needing ZV1 in the drawn position, but I think I'd be sorely tempted to put the system together without it in either location to see how things worked, while trying to design so as to make it easy to add it in later if it turns out to be needed...

Gooserider

 

[dogwood]

Thanks for taking a look at the ZV1 positioning Gooserider. I appreciate your input on locating that valve. I'll consult with one of BioHeat's techs and tell them what your and Scott's thoughts on this and see what say. It'll be interesting too, what they have to say about whether or not the Termovar can stop any unwanted flow. I'll post their answer tomorrow. Then I'll get back to figuring out the electronics, which should be my last hurdle prior to installation. Thanks again.

Mike

 

[sbleiweiss]

Mike,
Good luck with your system build. In your situation you only have two loads. one is a water to water HX and pushing a little hot water through that due to ghost flow will not cause much heat loss since the circ on the DHW side won't be running. Pushing hot water through the fan coil Hx will result in some convection carrying heat into your ducts. It won't matter in the cool months, but you certainly would not want it in the summer. If it is just a seasonal thing, then a ball valve (which you may already have in a pump flange) would be all you need.
I would suggest that you sit down and list out all of the "modes" that the system will be run in as well as how you plan to fire the system. You might find that you want to adjust the topology or control of the system to best suit how you plan to use it. Here is an example of some things I found out along the way...

The boiler I have (wood gun) holds 80 gallons of water and the boiler itself is 2000 lbs of concrete and steel. It is a big thermal mass and poorly insulated. For that reason when the boiler finishes firing, I continue to draw heat from it until it is cold, then switch over to drawing from storage.

The boiler low temp shut-down is pretty useless with storage. The boiler temp will be artificially held up by the storage water preventing it from shutting itself down. For that reason I use a solar controller to charge the storage (through a zone valve) and I use an electric timer to shut the boiler down before it uses up all of the wood.

Decide if you want to prioritize heating to the loads and not storage when the system is just starting up. This works into how often you fire the boiler and how cool you plan to let the storage get. If you need 150 degree water to get decent heat and the storage temp is at 120, you might need to wait a long time for things to warm up.

Once you map out all these scenarios, the topology you choose might be a little different. I was greatly helped by visiting Nofossil's site where I could see how he manages the system as well as some great topology simplification ideas.
Regards,
Scott B.

 

[dogwood]

Thanks for your advice Scott. I will be prioritizing heat to the loads rather than storage. I was thinking of letting storage cool to the 140-150 range before refiring. I'll have to see how much usable heat I get through th W/A hx at the lower temps to guide when to refire.

Mike

 

[dogwood]

Gooserider and Scott, I just got off the phone with Chris from BioHeat. He said the Termovar will prevent any ghost flow from cycling through the cold boiler when heat is coming through storage. This is w/o the backflow flapper in place as well. He also indicated the ZVI in it's designed position is likewise utilized to keep any ghost flow from circulating through the zones when only storage is being charged. Scott was right however in that ZV1's primary designed function was for use with a backup boiler as in their other plumbing schematics. Thanks for both your help and Happy New Year to you.

Mike

 

[JayDogg]

I have a tarm solo 40, buderus oil backup, 65 gal indirect dhw and am in the process of hooking up a 500 gallon propane tank for storage. I called BIOheat to see what I needed for materials and the told me I would need to follow the PT1 drawing and that I would need the ZV1, the termovar loading unit and the BLT controller. Have any of you used anything besides the BLT controller? They wanted 400 bucks for it and that seems to be a bit pricey? Are there any other controllers that I could use that wouldnt be difficult to connect and are cheaper? Right now my tarm goes through the buderus before it goes to any heating zones. I am going to be following drawing PT1 to change the system so that the water from the tarm goes to the zones first, then storage, and eliminates keeping the buderus up to temp for no reason. Any input would be greatly appreciated before I go and spend the 400 bucks for the BLT.