Combine Viesmann and Wood fired boiler

hr

or switch the circs to ones that have the integeral check valves. What may be happening is that your indirect is acting as a buffer tank to your wood boiler. Depending on how the various pumps are controlled.

Without the flow checks it looks as if the oil fired boiler could heat the HX and possibly the Greenwood either by ghost flow, or worse case the Greenwood circ starts to run and take a larger portion of the oil fired output with it. Essentially turning an unfired wood boiler into a cooling tower!

Ideally the whole package would be piped with a primary secondary allowing a good, and complete seperation between the various generators and emitters.

Also a buffer tank for the wood fired boiler may be needed to prevent over temping.

The addition of either flow checks, zone valves, or 3 way zone valves could make a workable system out of what you currently have piped, to keep all the flows going where intended when intended.

hot rod

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=144&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

J B

Viesmann and Greenwood

I have an oil fired viesmann with all the bells and whistles. I did none of the installation. It did well with my radiant and DHW. This year we installed a Greenwood wood fired hydronic furnace outside, piped to a 20 plate heat exchanger. Once I set the slope back to 1.0, the outside wood boiler kept the Viesman boiler at between 150 and 170 degrees. And the first couple of days, it kept the DHW very similar to the temperature of the boiler. But now . . . seems no matter how hot the boiler is, the DHW keeps dropping until the Viesman fires. Now I realize the oil it will take me to heat the DHW is minimal compared to heating the 6 zones in my 4,000 [] residence, but I do not want to use the oil until summer gets here. Can anyone think of why the DHW used to mimic the boiler, but suddenly doesn't anymore?
Jim

ALH_4

change

Something must have failed or changed in some way. Without knowing all the particulars of your system, or having a piping diagram, it is nearly impossible to tell what is happening. Why was it keeping the DHW tank at the wood boiler temp?

J B

Why it was, I don't know. But I will tell you this. . . it was great!! The DHW was like 1505-162. . .the whole neighborhood could take a shower at my house! So are you saying that the DHW shouldn't be near the boiler temp? The DHW was set at 125 degrees, but was always higher, untill . .like you said, it seems like something quit or something. The only changes in the programming that I have attempted were:

1) Change the slope from 1.5 to 1.0 (I have under-floor Pex; the Viessmann manual seems to indicate the 1.5 was way off) I made this change at my contractor's sugestion, back when the burner was comming on instead of letting the Greenwood do the work

2)After getting moderatly frustrated with the burner coming on to heat my DHW, I dropped the slope to 0.8 and bumped the shift up 2.

J B

Damn! Just reread your reply. The Wood boiler maintains 175-190 degrees. . .the DHW was very close to the Viessman temp, not the wood boiler

ALH_4

control

The heating curve setting should not affect your DHW operation. DHW is a separate setting. Yo do want your heating curve set as low as possible that will still maintain a comfortable temperature in your home.

Whatever senses your tank temperature, whether it is the Vitotronic 200/300 control or an aquastat, should be able to control the temperature of the tank by controlling a separate DHW pump. Something has to be piped so that there is no control of the tank temperature, at least when the wood boiler is firing. If you have digital photos of the boiler piping with some explanation, particularly where the wood boiler connects, it might be possible to diagnose something.

I assume you have a tempering valve on your domestic hot water so you do not have 160 coming out of your faucets. if not, it would be much safer to install one and not worry about anyone getting scalded.

jp_2

high DHW?

why so high? i can see 140F, but anything higher doesn't sound safe?

if the anti scald valve fails to hot during a shower, someone could get badly scalded with 160F water.

sounds like the control is not set up properly.

hr

The piping between all the components

is critical with wood, fuel, and DHW. Typically a P/S is need to keep all components in their controlable range.

Be sure the Viessmann can never heat the Greenwood!

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

J B

Please find attached some pics I took this morning. I recognize the concern about the DHW being in the 160's. . . I don't mind if it stays near 140, but I do mind the fact that, though the Viessman says the boiler temp is in the 160's, and the greenwood is chuggin along at 180, my DHW keeps dropping until the burner in the Viessman comes on. I figure if the inside boiler is 20 degrees hotter than the DHW, it should be able to heat the DHW without firing the burner.

If it isn't obvious yet the only thing I know about heating systems is what little I've gleaned from the Viesman manual. If only the Germans wern't so . . . German! Anyway, speaking of stupid questions. . . without the Greenwood, the Viessman used to run boiler temps at like a MAX of 138 as I recall. Is getting it up to 171 (the highest I recall seeing since we installed the Greenwood and heat exchanger) bad for the Viessman?

J B

I am going to attempt to add some pics. I understand the concern about the DHW being over 140 . . . my issue is that the Vieessmann indicates a boiler temp of say 161, yet the DHW will just keep dropping to my desired set point (currently 125) then the burner comes on. It seems to my homeowner-brain that, if the boiler is that hot, and the DHW has priority, the DHW shouldn't be triggering the burner.

Oh, btw, is having the Viessman up to 160 deg regularly going to be bad for it? My recollection is that, before the Greenwood and heat exchanger, the boiler temp used to max out around 135

J B

Can you see anything?

J B

Couple more pics

jp_2

control problem,

sounds like a control problem. maybe at first there was some crud stuck in a valve or check allowing wood boiler flow to pass through the indirect(more like a ghost flow). then later that crud cleared up and the indirect acted normal.

so, now the indirect needs hot water it calls the boiler to fire, so seems you have a control problem. i suppose maybe the boiler automatically knows it wants 180F for priority DHW.

you need a logic part that tells the boiler the wood boiler can handle it......

Mike Norgan_3

Location of HX

Jp,
I would pipe it up this way, At the bottom of the Vitola where the drain is add another tee and at the top where the safety header is add a tee. Then pipe up the HX to those openings, you will also have to add flow checks I couldn't remember if they were in your pictures. This is the way I piped up a Vitola after the home owner called me because his system wasn't working right. He had the low bidder install the HX on my original install, The home owner bought the outdoor wood boiler a few years after we completed the house. Hope this helps.

Mike Norgan

J B

OK, like do any of you work in upstate NY? Starting to look like I need to learn how the Viessman works. . .I probably should have saven some Deutch Marks and bought something with way less controls, knowing the outside boiler was going to do the heating.

Does anyone know if getting the boiler temp on the Viessman up to 170 deg is going to shorten it's life?

Jim

Looks like I need to go Google terms like 'HX', etc . . .