Series or Parallel ??

[scottinkn]

Hello,

I am getting ready to install my redone NY'r WC-120 and I am not sure if I should install in series or not.
I do not have an install manual for my model only a pdf for the WC-130 so I hope it is close enough....

My Utica oil burner also supplies DHW and has 2 zones, each is controlled by a circulator pump on the return side.

I plan to add storage and some solar panels later as money & time are an issue right now....

So, can I install it so the hot water output of the WC goes to the return of the Utica?

Is there a great advantage/disadvantage to doing this? (money, efficiency or otherwise)

Does that mean I only have to install 1 circ between the 2?

If so, will it be easy to add storage later?

Any thoughts and ideas are greatly appreciated!

Scott

 

[Eric Johnson]

Hi Scott. Welcome to the Boiler Room.

The main advantage to piping in parallel is that you can easily isolate either one of the boilers for maintenance, etc., and it tends to be more efficient because you're not losing heat up the stack of the idle boiler, as well as into the boiler room through all the piping and other standby losses. However, a series installation is easier, as you suggest, by simply piping the supply from the wood boiler into the existing oil boiler, and let it distribute the heat like it always has. When starting from scratch, parallel makes the most sense in most cases. When adding to an existing system, sometimes series is the way to go.

My system is piped in series. I dump supply water from the wood boiler into the top of the gas boiler, so that it is immediately available to the system. There's nothing wrong with putting into the return, but I personally don't see the point.

Storage is not going to be complicated or made easier by either approach, I don't think, although it depends on how your system is laid out.

So to sort of answer your question, parallel is more efficient but more expensive to install.

 

[steam man]

I have an install manual WC-120. If I can get it scanned I may be able to send you a copy. Barring that I may be able to fax it. Some people may make an issue of specific installs for specific boilers but I feel that's not necessarily true unless it could be for a warrantee claim of some kind on a new boiler. My dad's WC-120 was piped so its circ went to the return off the oil boiler and out back to the WC-120. I believe the aquastat on the wood boiler just turned on and off as heat was generated. I don't think he inhibited the oil burner if wood heat was available. I would think the oil burner could be stopped by wiring in the NC relay in the wood boiler circ control relay box to the oil burner to stop it if the wood circ comes on. If the wood circ comes on, the oil burner goes off. To me this is the simplest installation.

Without storage, you want to burn hot and kepp it going. It could be tough. You will make creosote if you idle. My dad had his exhaust tubes opened up more to prevent plugging. Made for a higher stack temp but it solved a few problems. For storage, I have a plan to use a pressurized tank as a buffer tank for the wood boiler that the oil boiler could draw heat off from using a differential controller. That should minimize wood boiler cycling.

Mike

 

[Nofossil]

Eric pretty much nailed it.

I'd add that you might consider in your future plans having your DHW provided by an electric or indirect tank so that you aren't keeping the oil boiler hot just to have DHW,

You can set up a sidearm heat exchanger so that the DHW stays hot whenever the wood boiler is running so it won't use electricity during the winter.

 

[scottinkn]

Thanks for your reply Everyone

I am sorta leaning towards series only because I have plenty O wood and not much cash right now.

I did forget to mention I am sort of starting from scratch because to WC has no controls at all...

If I pipe to the top of oil furnace, I will need a circ pump to keep it moving or will it thermosiphon?

And as for storage? Does anyone think that it will it be a nightmare later to add?

(I am waiting for a few people to get back to me on tanks so storage may happen now if the timing is right.)

Also, aside from the tanks, is there much cost to adding storage to a system?

I surely do not want to use ANY more oil, especially when I have all the wood I can use.


Thanks

Scott

P.S. Has anyone ever thought, in a series install, to maybe to put a NC damper on the oil flue tied to a oil cutoff switch to save a little up the stack?

 

[Nofossil]

Thanks for your reply Everyone

I am sorta leaning towards series only because I have plenty O wood and not much cash right now.

I did forget to mention I am sort of starting from scratch because to WC has no controls at all...

If I pipe to the top of oil furnace, I will need a circ pump to keep it moving or will it thermosiphon?

And as for storage? Does anyone think that it will it be a nightmare later to add?

(I am waiting for a few people to get back to me on tanks so storage may happen now if the timing is right.)

Also, aside from the tanks, is there much cost to adding storage to a system?

I surely do not want to use ANY more oil, especially when I have all the wood I can use.


Thanks

Scott

P.S. Has anyone ever thought, in a series install, to maybe to put a NC damper on the oil flue tied to a oil cutoff switch to save a little up the stack?

Depending on how your zones are plumbed, you might need an additional circulator. Usually in series installs the existing oil circ moves water through both boilers. I don't know the details of Eric's setup.

They make powered dampers to reduce stack loss. You need another interlock to guarantee that the oil boiler won't fire if the damper fails to open.

 

[Eric Johnson]

I really don't think adding storage will be affected one way or another by the type of installation you choose. But I admit to not having thought through the issue where parallel is concerned, so there may be something I'm overlooking. Other than the cost of the tanks, you've got to consider expansion capacity (plenty of it if you go with pressurized storage), and all the fittings, controls and other hardware involved. You can make it simple or complex, depending on your budget and ambition.

My series setup is pretty simple. I have a system pump that pumps hot water from the supply of my wood boiler into the top of my oil boiler anytime the aquastat on the wood side kicks the pump on. All my zone pumps, relays, thermostats, etc. work just like they do when the gas boiler is running. BTW, I shut my gas boiler off at the beginning of the heating season and plug up the chimney. The house doesn't care where the hot water originates--it just pumps it into the radiators when there's a call for heat and enough hot water in the gas boiler vessel to get the job done.

You can get a lot fancier, but simple is a good place to start.

 

[scottinkn]

NoFossil,

I am not sure what you mean by depending on how the zones are plumbed?
Is it that I currently have 2 circ pumps on the return side of oil burner? (1 for each zone)
Or is there something else I need to know?

Thanks

Scott

 

[Nofossil]

NoFossil,

I am not sure what you mean by depending on how the zones are plumbed?
Is it that I currently have 2 circ pumps on the return side of oil burner? (1 for each zone)
Or is there something else I need to know?

Thanks

Scott

Yes - some systems use zone valves instead of circulators.

If you just insert your wood boiler between the circs and the oil boiler it should work fine. You might want to also plumb in a bypass with a shutoff valve so that you can bypass the wood boiler when heating with oil.

 

[scottinkn]

So when you say insert between the circs and burner you mean.....

The outlet of wood boiler to inlet of oil furnace? it will circ between the two naturally? I am not quite sure....

If anyone needs to see my existing install I can take pics or draw if necessary....

 

[Nofossil]

If you can post a plumbing diagram that would be good. I'm hoping someone with a series installation will chime in with details - I've never done one.

There are a bunch of ways to do this, and I'm not the expert. I think simplest is outlet of wood to inlet of oil, through loads and circulator(s), back to inlet of wood. Simple, uses existing circulators. Could have problems with flow rates being too low, but unlikely. Means you always have to heat both boilers. In this scheme you can have a bypass around the wood so that you don't have to heat it when you're burning oil.

 

[Eric Johnson]

It's really about as simple as you can get: The supply from the wood boiler is plumbed into the oil boiler, either through the top or at the return. The return back to the wood boiler draws off the bottom return of the oil boiler. An aquastat on the wood side turns on a circulator at the setpoint temp, say 150, so that hot water is always being pumped away from the wood boiler and into the oil unit. Everything else works just like it does when the oil boiler is running, i.e., the zones and stats don't know where the hot water is coming from and they don't care. If you have a domestic hot water coil in your oil boiler, then use it for DHW. If not, you can put a sidearm or other HX somewhere in the piping between the wood an oil boilers.

That's about it. As I said, you can get pretty fancy, but if you set it up as described above, you'll be able to heat your house.

I think too many people hang up on the notion that the oil or gas boiler has to be operational at all times so that it can pick up the slack if the wood fire goes out. You can do that, but it does complicate things. In my experience, if you're serious about heating with wood, you don't need a backup for most of the heating season. Simply decommission the fossil fuel unit at the beginning of the heating season and fire it back up either when you go on vacation, or in the Spring. JMO.

 

[muncybob]

Don't mean to hijack the thread, but if the oil boiler has a coil for DHW is it still feasable and cost effective to use a sidearm and/or tank such as the Superstor?

 

[Eric Johnson]

It's certainly feasible. Why you wouldn't want to use the existing coil is another question, although you save a circulator if you go with a sidearm, since it works off a combination of the primary pump plus gravity. With the coil, you'd need to pump potable water through the coil and into a storage vessel, which in most cases means you'd need a bronze pump. And they're not cheap.

You could get away without a second pump if you treated the coil like a tankless water heater (which it arguably is), but then you're pretty limited in how much hot water you're going to get. Great for a small demand--not acceptable if there's womenfolk involved, IME.

 

[scottinkn]

Thanks everyone!

Well now it is time for me to get to work.....

I have an install plan for now to get me by.
Only thing left is to fix front cover leak (won't hold 60 psi)
And begin installation.
Wish me luck!

Scott

 

[muncybob]

It's certainly feasible. Why you wouldn't want to use the existing coil is another question, although you save a circulator if you go with a sidearm, since it works off a combination of the primary pump plus gravity. With the coil, you'd need to pump potable water through the coil and into a storage vessel, which in most cases means you'd need a bronze pump. And they're not cheap.

You could get away without a second pump if you treated the coil like a tankless water heater (which it arguably is), but then you're pretty limited in how much hot water you're going to get. Great for a small demand--not acceptable if there's womenfolk involved, IME.

I've been told not to go with an indirect tank for dhw since my oil boiler w/coil is not a cold start boiler.....not sure what that really means. I plan to keep the oil boiler as not only back up but maybe also dhw in non heating months. So, when I install my wood boiler and indirect storage tank(or possibly electric water heater) should I look at bypassing the oil coil? I can't get it thru my thick skull why I would not want to keep the oil coil. How much is the average cost of the bronze pump you mention? The storage tanks ain't cheap either! But, seems to me an indirect tank or even a good water heater would have less heat loss than my old oil boiler?