boiler piping review

jcriv

I am installing a Harmon PB-105 pellet boiler with 240 gallons of buffer storage. I am a contractor, but not a heating specialist. I have a little knowledge,but I could use some guidance. My goals are to heat from the buffer tanks when possible. Then charge the tanks from the boiler. Finally, heat from the boiler when demand is too great for the tanks.My heat loss calcs are 39000Btu. Boiler output 113900Btu. 240 gallons of water should yeild 79000Btu's @ 40degree delta [180 to 140]. That should give me 2 hours of heat even on the coldest day of the year. I have attached a drawing for reference. It is to scale, so it literally represents what I would be piping. My questions are:



1.Does this look right in general?

2.If you look closely there are two primary circuits running clockwise[boiler], and counter clockwise[buffers]. A third would be the boiler charging the tanks running clockwise.

Will the pull of the circs create the flow as I suspect?

3. I want to use one of the new adjusting pumps such as a grundfos alpha, is it necessary or even wise to use them in all three positions?

4. In the drawing I have a mixing valve at the boiler return. In retrospect I believe a diverter valve at the T above the #3 pump is a better location.

5.Should the boiler pump could be relocated to the return side of the boiler?



 Thanks for any help. I am open to direction on this project. I do have a wife and daughter that will be asking for heat soon, so time is of the essence. I also need help with incidentals, such as piping diameter, purge valves, air eliminators, ect.

jcriv

Re. help

Anyone? I have tried my local supply houses for help. The problem is that there are a ot of people in the trades that learn practical application without knowing why it is the way it is. I need expert advise. I know your out there. That's why I posted here. Don't take offense, that's not my intention. I just want to get this as right as possible. Thanks.

Ironman

Pellet Boiler

You will find that most of the pro's on here are reluctant to give advice on solid fuel burning boilers due to their inherent safety concerns. Is this boiler approved? Specifically, does it have an ASME "H" stamp? If not, I would not recommend installing it within the confines of your house.



Your piping diagram appears over-complicated for what you're proposing, but more info about the boiler is needed. Is it pressurized? Indoor or outdoor? How is it controlled? Are you trying to connect to an existing system with a conventional boiler? A little more info, please.

jcriv

thanks for the help.

The boiler is in the garage. It has an OTL listing report # 135-s-16-6. Standards : CAN/CSA B366.1-M91 and UL391. I have no idea what that means. It is not plumbed to anything else. It is a pressurized system. The boiler does have a high and low limit. It also has an outdoor reset control. The manufacturer recommends a dumps zone in case of power failure. I have made provisions for that.I hope that I have answered your questions correctly. I understand the concern of giving advice. I am really mostly interested with how to get the most efficient way to use the buffers. If I am correct about stratification, I want to charge from the top of the tanks, and pull from the top.

Robert_25

Why so much storage

Why have you included 240 gallons of storage in your design? I can see the benefit with a wood boiler that must be run wide open to achieve a clean burn, but if you can adjust the feed rate of the pellets to have long burn cycles, I don't see much benefit of the storage.



I must confess that I have never installed a pellet boiler, but I have installed a few coal stoker boilers. There are many similarities, and I have never found the need to add storage.

jcriv

buffer sizing

I must confess it was recommended by a dealer. On the wood/pellet boiler forum was told it was too little. The thing about a pellet boiler is while it can turn on and off it"s not quick like a fossil fueled boiler.Short cycling is wasteful. So in winter I don't think the storage will be very necessary. Fall and Spring should be a different story. Make sense?

Robert_25

feed rate

It is my understanding that the feed rate control works by controlling how many seconds per minute the auger can run. Example, if you set it on #1 out of 6 it will run 10 seconds per minute. I'm no pellet expert, but I have a hard time seeing how a boiler with 30 gallons of water in the pressure vessel will short cycle if the output is throttled down to 20-30,000 btu's per hour. Do as you please, but for the cost of the buffer tanks I would be willing to try it as a stand-alone unit and add a tank or two down the road (if needed).



Here is some good info on sizing and piping buffer tanks: http://www.heatinghelp.com/files/posts/7128/BufferTank.pdf

Ironman

I Agree with Robert

I checked the specs and installation manual of your stove and found that it holds 50 gals. of storage itself. I don't see the need for any more buffer. Just pipe it the way the manual shows with the fin-tube as a dump zone in case of a power failure. Please note: If you've got high and low temp zones, the mixing valve piping on page 19 has an error. Otherwise, follow their manual.



What you read on line is dealing with a stove that doesn't have much, or any, internal storage and little or no controlled burn rate. That type of stove needs a lot of buffer to make up for the lag in response as well as for safety.



The only reason that I can see that you may need additional buffer would be if you're trying to cover periods when the stove is not being attended.

jcriv

boiler capacity

The boiler holds 30 gallons, not 50. The uber expensive, Froling P4 pellet boiler holds 33 gallons. They recommend buffer storage for that unit. I would like to believe that I was able to buy a boiler at have the price that was more efficient, but ... Here is the link http://www.woodboilers.com/admin/uploads/public/P4PlumbingSchematics(4).pdf