backup boiler piping into wood boiler system

[mmudd]

Hey guys, I'm adding 500 gallon pressurized storage. Wanted opinions on my pipe plan as it relate to piping up the backup.

Would it be acceptable to tee off boiler supply line to buffer tank for backup boiler. Wood and backup would share return line to storage. I will have lockout control so backup does not fire if wood unit is operational. Suing a loading unit that would prevent flow thu wood boiler if backup operates. Will have wieghted check valve to backup boiler supply line. My reason for doing this is I want to use other port in top of storage tank for my solar system. Only other port on tank is a 1" down about 18 inches from top of tank along side. Felt it would be beneficial to to have solar supply at very top. What do you all think. See my crude sketch

 

[Clarkbug]

Few quick ?s for you on your diagram.

Do you only have one zone valve before the heating zones? Are they all controlled by a single t-stat? Just not sure why you need the zone valve in the equation, thats all.

In regards to your piping setup, when you run your backup boiler, you would be heating your storage. If you have super insulated storage, thats probably not as big of an issue, but I would try to avoid heating up your storage if you can...

 

[mmudd]

Few quick ?s for you on your diagram.

Do you only have one zone valve before the heating zones? Are they all controlled by a single t-stat? Just not sure why you need the zone valve in the equation, thats all.

In regards to your piping setup, when you run your backup boiler, you would be heating your storage. If you have super insulated storage, thats probably not as big of an issue, but I would try to avoid heating up your storage if you can...

I am following the diagram from tarm biomass. The ZV will open when any zone calls for heat. Maybe do not need? I think it is to ensure no flow to zones if not calling for heat so all goes to storage. I have to have backup go thru storage to prevent short cycling. based on my design. I will not be using backup often. In fact it will not be hooked up right away. I have not used anything but wood for over 10 years, but not gettin younger, so want to leave option for backup.

 

[Clarkbug]

What make/model is your boiler that you are worried about short cycling?

I too followed the Tarm diagrams (sorta). Do you know which diagram you were looking at? One of them has an extra ZV in there that is an "oops" from drafting. If you can post the number, we can cross check that and let you know if you need to keep it.

 

[mmudd]

What make/model is your boiler that you are worried about short cycling?

I too followed the Tarm diagrams (sorta). Do you know which diagram you were looking at? One of them has an extra ZV in there that is an "oops" from drafting. If you can post the number, we can cross check that and let you know if you need to keep it.

Don't have the back up yet. I will let you know on the diagram, can't recall off hand. I too was deviating off the diagram somewhat , since I have solar with two coils in it and the back up boiler to include, which was not in the tarm diagram I was using. I was using buffer tank as my hydr separator between various components.

 

[Clarkbug]

Tarm does have some diagrams with the backup boiler in there, just as an FYI. Not sure how much you already have or how much work you want to do, but the "simplest" sticky thats on this site would also probably work pretty well for you as far as another idea for arranging your piping.

http://www.woodboilers.com/images/stories/documents/woodboilerplumbingschematic1211.pdf

Just in case you wanted ALL the various configurations. Thanks again to Tarm for putting this out there on the web for all of everyone to use.

 

[mmudd]

Agreed , a big big thanks to Tarm. They have been very helpful and have also looked at my plan. I will be piping very soon and have wrestled with my plan many nights. I was going with the the tarm pt3, with modifications, using buffer as hyd sep for solar Indirect H20 and backup boiler. I wondered about need for zone valve too, but planned to install. Issue I'm working around is that my storage, backup and solar is about 25 ft away form boiler but load is close to boiler. Trying to keep pipe runs down and keep it simple (ha), with minimum circulators. I thought about pt2, but backup boiler, indirect H2O heater would require considerable more pipe run in my application.

My dilemma is I'm running out of ports in top of storage tank and not in mood to weld new ones in. I have 2 1.25" ports. If I pipe backup direct into top of storage, my solar hi temp coil will enter about18 inches down from top on side of storage, which might be ok. Just thought it best to pipe solar direct into top of storage if possible.

The reason I'm piping backup to storage is the pt 3 diagram does not have circulation to heat zone unless zone is calling for heat. If I bypass storage with back up, as I understand it would not work well for a propane or oil (another decision) to kick on evey time a zone calls for heat. I don't plan to use backup much, and will have the aquastat sensor to turn off backup when top of storage reached x temp. I will be set up to plumb from a valve to back up boiler at future date without draining down existing sytem.

My 200 gallon open storage solar draindown tank will basically serve as an indirect domestic water heater and a heat supply unit to some extent. The 500 gal pressurized storage will be heat bank for solar in summer and I'll be able to send hot water to a 2nd water heater some distance away. I could even operate this tank to be additional storage with the 2 stage controller working the 2 circs if boiler has capacity.

Any thoughts are appreciated. This is a great site with much knowledge ,inspirational too.

Mark

 

[Clarkbug]

Just so you know, my personal setup bypasses storage when I run my oil backup. The controls on the oil (when its enabled, and there is a call from a zone) fire the oil burner until the water gets to 180, then there is a differential. Once the water temp falls down to 160 or so, it fires up again. There is enough volume in the loop in my house that it doesnt short cycle the boiler. It is a "cold start" boiler that doesnt need to be kept hot, and it doesnt seem to have any problems running when I dont load up the wood boiler enough or if I got lazy and overslept.

You can definitely heat the storage with your backup and it will definitely prevent you from short cycling, but you end up having to dump a lot of BTUs into that tank coming from backup that you wouldnt have to otherwise.

What type of heat emitters are you using for your house? That would make a difference as to how low you can let the water temps get, and also how well your solar could help you heat things.

 

[mmudd]

Just so you know, my personal setup bypasses storage when I run my oil backup. The controls on the oil (when its enabled, and there is a call from a zone) fire the oil burner until the water gets to 180, then there is a differential. Once the water temp falls down to 160 or so, it fires up again. There is enough volume in the loop in my house that it doesnt short cycle the boiler. It is a "cold start" boiler that doesnt need to be kept hot, and it doesnt seem to have any problems running when I dont load up the wood boiler enough or if I got lazy and overslept.

You can definitely heat the storage with your backup and it will definitely prevent you from short cycling, but you end up having to dump a lot of BTUs into that tank coming from backup that you wouldnt have to otherwise.

What type of heat emitters are you using for your house? That would make a difference as to how low you can let the water temps get, and also how well your solar could help you heat things.

I'll have fan coil and wall & floor radiant to be added. Getting away from fan coil will be the priority after I get the storage on line

If my backup could operate properly just with water volume in pipes, I could close valve to storage tank and bypass it completely, which is a good reason to Tee into supply and return between boiler and storage rather than pipe backup direct into storage. That would not be automatic however and would eliminate solar as heat source. Iin order to make the system switch from wood to oil with no action on my part, Would I need pipe runs from backup to the manifold that supply the heat zones after the ZV? If I used pex it would be relatively cheap. approx 50' of run.

Which tarm scheme did you go off? What oil boiler do you have? I'm looking for a good used one.

One other question: the schematics call for wieghted checks on each zone. do you think the checks that come in a circulator suffice for this, or should I add spring checks?

Thanks for your help.
Mark

 

[Clarkbug]

Oh man, I had just typed up a nice reply and I closed the window by accident before posting. Doh! Ill give a brief recap.

I may have been premature in saying you would always flow through your storage with the backup, sorry about that. Im going to need to think about that some more....

Im using a modified PT1 diagram for my setup, which still needs some tweaking. My boiler is a New Yorker (came with the house), and works just fine. If I was buying one outright, I would go with a Buderus. Just my thoughts there.

If you have checks on your circulator already, no need to add a separate gravity check.

That diagram does have the extra zone valve that you dont need. You wont get any flow in that leg of your piping as shown unless there is a call from a circ anyway, so no need to bother putting it all in.

Automatic is what you want for backup, not any manual switching. You have the right thought.

How are you intending to control all of this?

 

[mmudd]

Oh man, I had just typed up a nice reply and I closed the window by accident before posting. Doh! Ill give a brief recap.

I may have been premature in saying you would always flow through your storage with the backup, sorry about that. Im going to need to think about that some more....

Im using a modified PT1 diagram for my setup, which still needs some tweaking. My boiler is a New Yorker (came with the house), and works just fine. If I was buying one outright, I would go with a Buderus. Just my thoughts there.

If you have checks on your circulator already, no need to add a separate gravity check.

That diagram does have the extra zone valve that you dont need. You wont get any flow in that leg of your piping as shown unless there is a call from a circ anyway, so no need to bother putting it all in.

Automatic is what you want for backup, not any manual switching. You have the right thought.

How are you intending to control all of this

I have lost a few posts that way too. Good question and one I have grappled with for some time, but here is what I plan .

I think you are right. Some flow may go to storage. I could envision the load not using all the flow coming from backup, so it would send some to storage if only one zone called for heat and storage tank/backup aquastat circuit energized (closed) ?

For the wood and fossil fuel units I have taco 6 zone circulator control. I will have a couple more zones coming off one of the 3 loads & backup as shown

I need to finalize my plan. I am looking at changing my diagram for the solar tank also, which has two coils and two circs, Both the solar zones and the backup boiler will pipe out of supply and return pipes between boiler load Tee and storage. As I understand it, This type of diagram requires reversing flow in lines between Tee to loads and storage tank. If call for heat to zones was minimal, boiler may supply load and some to storage simultaneously. If no call for heat, flow all goes to storage.

I plan to install a swing check just after boiler but before loads Tee in, to prevent any backflow thru loading unit/wood boiler when no fire. This pipe set up may cause loading of storage with backup boiler, but it will be well insulated, once top of storage tank reaches setpoint, aquastat will turn off the backup, and zones will draw off storage, so excess btu's pumped to storage will not all be lost..

For solar, the200 gal stainless drain down tank has sensor bulb well, I have 2 stage ranco 120v controller with high and low diff controls that will control min tank temp for dhw and supply hi temp load circs if solar tank is hot. The ranco control is not connected to the taco control, so if solar tank is hot, it will pump to storage or zones if calling for heat and if solar tank needs heat, it will pump from supply line between load tee and storage.

Final diagram I'm leaning too is PT3, with solar cirs and back up boiler piped between load Tee and storage tank in supply and return fashion . I have lots of distance between this connection, unlike the diagram. Real driver in decision is distance between my boiler /loads and storage/ solar. Don't want more pipe runs. I don't envision not using storage, Guess I could install a crossover between supply and return lines just before lines enter storage or in event of isolating the storage turn off solar circs. The solar control is independent from other controls. I don't think the solar circs should run if loop is not made thru storage. The backup will be tied to the taco control and will only fire on a call for heat if storage is cold.

Man, it is hard to explain this stuff in writing! Hopefully I'm not sounding like Mr. Haney from green acres ! and this plan will work ok.

You don't think that zone valve is required just ahead of load? It would help without it to lower hea. requirements. Any suggestion/ advice is appreciated
Mark

 

[mmudd]

On second thought, I am going to stick with original plan in regards to the 2 solar coil hook ups. Since the controller for solar is independent of the taco control for the rest of the system, I think it is best the solar coils be piped directly to storage in order to ensure hydraulic separation from rest of the system The back up will be piped into the supply and return lines just before the storage. The back up and wood systems will never be running at the same. This cannot be said for the solar system, This will help keep peace between the various circs and controls. Today was a good solar day. 180 degree tank temp, and it shut off early.

 

[Clarkbug]

You bring up one other item about your solar... If all of the water is shared, and you have a hot storage tank from the wood boiler, you wouldnt want to run your solar, since it would be pushing hot water through your panels. But it sounds like you ranco controller wont let that happen anyway.

You will need to add some other controls other than the Taco zone controller so that your system knows to use storage or fire the backup. You can do it via aquastats and relays or buy an off the shelf controller, or even go full custom. NoFossil (a member who had frequented this site, not sure how much he can check it any more) used to offer fully customized solutions, which would even interface with your solar setup. Not sure if he still does that or what the cost is.

You are right, the backup will provide heat to the loads and some flow through the storage if it needs it.

I guess the zone valve could come into play since your wood boiler will be a distance from your storage. I dont see that you would need it, but hydronic experts here may know better.

 

[mmudd]

You bring up one other item about your solar... If all of the water is shared, and you have a hot storage tank from the wood boiler, you wouldnt want to run your solar, since it would be pushing hot water through your panels. But it sounds like you ranco controller wont let that happen anyway.

You will need to add some other controls other than the Taco zone controller so that your system knows to use storage or fire the backup. You can do it via aquastats and relays or buy an off the shelf controller, or even go full custom. NoFossil (a member who had frequented this site, not sure how much he can check it any more) used to offer fully customized solutions, which would even interface with your solar setup. Not sure if he still does that or what the cost is.

You are right, the backup will provide heat to the loads and some flow through the storage if it needs it.

I guess the zone valve could come into play since your wood boiler will be a distance from your storage. I dont see that you would need it, but hydronic experts here may know better.

 

[mmudd]

I planned to basically use the solar tank as indirect water heater in winter. Using solar as additional storage might not work out. If solar tank needs heat, boiler could supply. Set low range diff at 10 degrees kick on at 120 off at 130. etc. Then have high range kick on at 170 and off at 150 or whatever works as supply to storage. I thought the backup could run off the taco controller, but I obviously will need to do whatever it takes to get it working whe that time comes. I have to get the wood unit piped up. Thanks for your thoughts
Mark