Pressure problems-wood boiler tied into hot water baseboard heat

[robertlk]

I have a Temp/coal wood-coal stove. It was built in Adams Mass and the company is out of business. I have tied it into my oil burner but I am having trouble regulating the pressure. I am using wood because I can get it free...Here's what I did:

1. I am using the same 8" chimney to vent the wood stove and oil burner. When the wood stove is on the oil burner hardly runs.

2. The water from the return goes through the circulate pump then into the cold (dip) wood stove.

3. The hot water goes out of the wood boiler then into the oil boiler.

4. The hot water travels to the upstairs baseboard through the zone valve which is always open.

5. I just put in a manual switch to that I turn on to run the circulate pump when the boiler pressure hits 20psi.

The theory is that as the water warms it will travel from the wood boiler through the oil boiler through the open zone valve and heat the upstairs of the house. It is working except for the pressure problem.

I have been to several plumbing supply houses in the area and they are unable to help, Any Ideas?

Robert

 

[BenW]

What kind of pressure problem are you having? Does it blow off the relief valve? What pressure is the system at when cold? Hot? Do you have an automatic water fill valve? Do you have an air elimination device "air scoop" and air vents? Do you have any pictures of the system you could post? Just needed more info to try and understand your system.

 

[LeonMSPT]

Might be wrong, because I am only the son of a master oil burner technician who is now retired. But.... unless I am mistaken, the "pressure" in a hot water hydronic heating system is simply the "head pressure". In other words, the result of the height of the water column at its maximum, the top loop in the system. Should never be steam in the system, which is what would cause "pressure changes" in the water. Water doesn't expand or contract appreciably with temperature changes, unless you transition it to steam or ice.

1. I'd want to make a decision about whether or not a circulator between my oil boiler and wood/coal boiler based on the temperature of the boiler in question.
2. The contractor who is doing my wood/coal boiler did a common supply and return. He left a "T" with a valve at each when he put in the new heating system. The wood boiler "supplies" hot water to the system at the supply, and water returns to it through the return which is T-d off the return of the oil boiler. If there is a demand, it's satisfied from the wood boiler. No demand? The water from the wood boiler circulates through the oil boiler from supply to return, maintaining the temperature between 160 and 200 degrees. If the oil boiler should drop below 150 degrees, it will start and supply enough heat to bring itself up to 180 degrees or the demand is satisfied.
3. I can isolate the wood boiler loop by closing the gate valve in the supply side of the loop. If I need to drain the wood boiler from some reason, I can close the valve in the return and do so without disturbing the oil boiler's water level.
4. The circulator is set up on an aquastat to start at 160 degrees in the wood boiler.
5. High limit is going to be set at 190 degrees.
6. Overheat zone is set at 200 degrees, and activates a circulator and Modine heater in the basement area where the wood boiler is located. Also a garage area, has been "sanitized" of all flammable liquids like gasoline and coleman fuel... lighter fluids.... no need for fires thanks.

Everybody can't do everything the same way, and sometimes a particular way works better in a specific situation...

 

[robertlk]

Thanks for your replies....The system does have an expansion tank and it is working. Today, the constant pressure is 15 psi. The cold pressure is also around 12-15 psi.

I only have one aqua-stat and it is on the oil boiler. The wood has no controls at all.

The pressure was building to 30 psi and blowing the safety valve, flooding my wash room.

The system has a cold fill.

I have been advised leave a zone valve open and sweat in a water temperature switch that at say 190 will close a circuit and send current to the circulator reducing the water temp. This will prevent the water from turning to steam and blowing the safety valve.
Does this make sense?

 

[LeonMSPT]

Should be a well for an aquastat in the water jacket of the wood boiler for that. Absolutely, set that baby at 160 degrees or so, and watch it go.

Be sure you've got an overheat zone connected too... largest zone in the house. When the boiler gets to 200 degrees, it should start the circulator and blow off the excess heat, preventing steam formation and overheating. Not good for heating system to be constantly sucking in fresh water, or overheating for that matter.

Let us all know how it works out.

 

[LeonMSPT]

Lots of plumbing and oil burner shops don't really want to deal with do it yourself jobs. Dangerous, in that if it goes wrong, you get hurt or damage your property, they're afraid you're going to sic your lawyer on them.

Read posts here, and examine drawings of piping schemes well. Take what looks like will work for you and use it. It helps to have friend or relative in the trade.... or some experience, no matter that you were an unappreciative teenager when you got it.

 

[LeonMSPT]

No idea what the weather is like in New Jersey right now. But we're "between times" right now here in Maine. Even if my wood boiler was hooked up, I might be hesitant to use it unless it was less than 30 degrees out. Much easier to fire the insert in the living room fireplace and avoid over pressure because of lack of load on the wood boiler.

Wood and coal fires don't just go out when there is no load. So, they keep making heat even when nothing is calling for it. In a no load situation, I don't see how it is going to get rid of the standby heat without storage... so it's going to overheat in mild weather.

 

[robertlk]

Thanks for your help. Sorry I couldn't respond sooner. I was told to get a "percentage timer" from an electrical supply store. It works like this....A 30 minute timer set at 10% will close the electrical circuit for three minutes every 30 minutes. The shortest setting is 5%. So if set at 5% the circulator will run for 1.5 minutes every 30 minutes. This sounds simple. No time of day to set and no sequencing. Now if I could find an electrical supply store that had one.....

By the way....In Sussex NJ the High temp today was 22 degrees. What't the temp in Maine????

 

[LeonMSPT]

Mid 20's today, supposed to have some bitter weather coming in tomorrow evening. Mid teens tomorrow night and single digits Monday.