Boiler not providing enough heat.

[AnthonyW]

Any time a zone shuts off, the water in the pipe to the zone will cool. I doubt it would make it to 60-65 degrees, but it will be a lot less than 150. Oil furnaces only run their circulator pump on demand. The OWB pipings I have seen have always had one loop open and the pump runs all the time. Though none of them were in series with another furnace.

The layout I'm picturing of stumper's piping is:
1) Out of OWB
2) To Supply Manifold.
3) Stop (deadhead) until a zone valve opens
4) Through zone
5) Back to Return Manifold
6) Through Oil furnace jacket
7) Through OWB jacket
8 ) back to #1

The circulator pump may or may not run all the time. If there is no loop for it to run through when no zone is calling for heat, then it doesn't matter anyway as there is no where for the water to flow when all the zones are closed. If this is the case, then I refer to my earlier post. There's just too much water in the loop that is cold and the OWB is being swamped due to too much water (volume not flow rate) being cold. The interesting part here is that slowing the flow through the OWB may actually help by allowing the water to heat more. But without being able to see the temperatures of the incoming and outgoing water it will be difficult to find the sweet spot.

[stumper]

My system is pretty straight forward.

OWB to oil boiler through 70 feet of 1 inch thermo pex, pump runs all the time.  Through the oil boiler back to the OWB.  This heats the oil boiler, and the water within it.

The heat to the house and DHW is provided through the oil boiler, into the 5 zones through the zone back to the oil boiler.  These zones only run on demand.

If for some reason the temp in the oil boiler drops below the aqua stat set point and a zone calls for heat the oil boiler kicks on.

[beenthere]

Doesn't sound like a system that will work well.
But if you get it to work for you, then that is what counts.

[AnthonyW]

My system is pretty straight forward.

OWB to oil boiler through 70 feet of 1 inch thermo pex, pump runs all the time.  Through the oil boiler back to the OWB.  This heats the oil boiler, and the water within it.

The heat to the house and DHW is provided through the oil boiler, into the 5 zones through the zone back to the oil boiler.  These zones only run on demand.

If for some reason the temp in the oil boiler drops below the aqua stat set point and a zone calls for heat the oil boiler kicks on.

All of the oil furnaces I have seen have three connections. (1) Cold water make up in [pretty much irrelevant to this conversation], (2) Out to Zones, (3) Return from zones. To simplify your system, there are 6 connections to make. OWB out and return, Oil Furnace out and return, zones out and return.

The first two connections you describe I can follow: OWB out to oil furnace return; and oil furnace out to OWB return. How are the zones tied in to this loop? I interpret it that the zones are T'd into either side of the furnace. Therefore the flow would be on each side:
(1) OWB out connection to Oil Furnace return and zones return on one side
(2) OWB return to oil furnace outlet and zones inlet on the other side



stumper, once we can confirm these connections, I may have another idea for a possible problem.

[stumper]

The following link shows how I have mine hooked up.

http://www.centralboiler.com/Tech/C210.pdf

The only difference is I do not have the a side arm on the DHW and I do not have a the in line themostatic valve.

[doctorb]

Thanks, Stumper.  Pic is worth 1000 words.

I never considered this part of the equation but....

Is the volume of oil burner water jackets standardized at all?  If the water jacket volume is relatively small, then the percentage of water returning to the oil burner (cool) could be pretty high.  Is there a way to increase the size of the water jacket in the oil burner?  By storing more BTU's in the system at that point you might be able to prevent the drop in oil burner water temp that led to the furnace kicking on.

[AnthonyW]

The following link shows how I have mine hooked up.

http://www.centralboiler.com/Tech/C210.pdf

The only difference is I do not have the a side arm on the DHW and I do not have a the in line themostatic valve.

The side arm on the DHW is a water-water heat exchanger. How are you using the OWB water to heat the DHW?

[stumper]

DHW is a zone off the oil boiler.

[Holmes]

 I believe that you are not getting enough "mix" in your oil boiler. The outside boiler water enters the rear section of the house boiler and leaves the rear section of it and not flowing thru the other sections.  boilers are put together in sections with push nipples about 2 to 4" diameter between each section 1 high 1 low.  The water is not flowing thru each section.  Your idea of putting the return water into the outside boiler return is good except when the owb is not running.

[Hilltop366]

 I'm wondering if a problem with running the return to the wood boiler is when there is no call for heat the wood boiler will not circulate to the oil boiler, could put a motorized valve in between the feed and return manifold on heating loop to open when there is no call for heat, or a three way motorized valve to connect heat loop to wood boiler when there is call for heat then when no call for heat returns to normal circulation from wood boiler to oil boiler.

[talldog]

Very interesting discussion. Stumper, I have a similar set up with propane. One question, Do you have circulator pumps inside your oil burner? Not the ones that go to the zones.  I do in mine. I had a problem that I solved by unplugging those pumps when the OWB was operating. It seems that they were fighting against the pump in the OWB. Just remember to plug them back in after spring shutdown.

[stumper]

no pups in the boiler

[tempforce]

if you are using the hot water tank, heat exchanger system.
there is a possibility that inside your oil boiler there is no contact between the fresh water and treated water tubes...
as some boilers feed fresh water direct into the water heater, without a heat exchanger.. and the water to the heating zones is a treated system to prevent corrosion and freezing.
resulting in very little heat transfer to your living areas...
if so, you will need to re-configure the system.
so that the water from the wood boiler is directly connected to the house zone heating system..
connect your wood boiler feed to the oil boiler house feed line.
do the same with the cold return lines...
to resolve back flow issues.
install a check valve on each supply line just before the junction connecting both feed lines to supply the house.
think of a 't' a check valve on each side of the 't' and the flow coming out the bottom...
the oil boiler will not be heated by the wood and the same for the wood boiler won't be heated by the oil...
the house will be heated by either or both boilers. as required...

you can wire in a relay to operate a bypass valve for the wood boiler supply/return, so that the supply and return lines for the wood boiler don't cool and to prevent a dead head.
the relay would open the bypass, when ever it didn't received a signal from any of the zone thermostats...
..
a method of doing this, is by using a primary relay for each zone. the primary relay sends a signal either with power/current or the loss of power/current to a secondary relay that opens a bypass valve... preventing a short between thermostats/zones.

[Hilltop366]

tempforce here is a post with a link that explains how the boilers are hooked up.

The following link shows how I have mine hooked up.

http://www.centralboiler.com/Tech/C210.pdf

The only difference is I do not have the a side arm on the DHW and I do not have a the in line themostatic valve.

[boilerman101]

I don't see any problem with that CB diagram or Stumpers hook-up. Looks pretty straight forward. Also sounds like when Stumper increased his OWF water temp up to 190-195 his house is warm. There is a pump on the OWF running 24/7 so the full water storage capacity of the OWF water is always running through the indoor boiler with no heat loss experienced through a heat exchanger. When indoor pumps fire to feed house, they should be pulling the hot supply from high in the indoor boiler and from the OWF supply feed. Stumper has stated it is only a problem when it gets "real" cold out. Sounds to me like not enough "exchangers" i.e. baseboards/radiators in the house to meet the heavier btu demand days. Therefore increasing the water temperature of the OWF helps to make up for the lack of sufficient exchanger area on those severe cold days when greater btu's are required.

[doctorb]

Boilerman-

If your theory is true - not enough baseboard / radiators to meet the heavier heat demands of cold days, wouldn't the problem be reversed?  That is, the boiler would stay hot - be able to hold temperature in the boiler, but the house would be cold because not enough heat was able to be transferred to the house?  It seems to me that too much heat is being lost for the boiler to maintain temp, and not the opposite.  Now, I know from our years here on the Forum, that you've got a lot more experience in this sort of thing than I do.  So just correct me gently as a Christmas gift and I'll be quiet. :D

[Hilltop366]

I does get confusing with two boilers, if we remember to put "wood" or "oil" in front of "boiler" it would help clarify what is being said.

The way I read it, the problem is not a issue with the amount of heat that stumper is getting at the rads but that the oil burner is coming on when there is plenty of heat left in the wood boiler.

This is during a cold spell when all of the zones are on.

I would guess that once the heating loop return line warms up the oil burner would stop running and the wood boiler will keep up?

[albirk]

Stumper
Try to hook both return lines together so when your indoor pump kicks on most of the cold water from your house will go to the OWB for reheat and not mix in your boiler pot to kick your oil burner on worked for me


good luck