Pellet boiler piping

[Bruski]

Hi,
I am new to this forum. I bought an old split level house in Kelowna BC and we are remodeling it. I am putting in a 130k BTU pellet boiler to run as secondary heat for the heat pumps. I want to run 6 kick space heaters, a coil in the main air handler, and 2 fan coils for the garage and shop. Could you have a look at the design of my primary/secondary idea to see if this will work. Any help would be greatly appreciated.
Regards, Bruski

 

[Deering]

Two scenarios that might be challenging from my perspective:

1. If your boiler buddy is fully heated and your boiler is off, then a call for heat comes from, say your fan coil heaters. How do they draw heat out of the boiler buddy without having to pull it through your pellet boiler? Ideally the pellet boiler would be on an isolated circuit so water only flows through it when it's actively burning.

2. When the boiler is running, hot water is leaving the boiler and feeding into the distribution emitters. Their cold return water then goes into the top of the boiler buddy. What you want to strive for is maintaining heat stratification in your buffer tank - hot on top, cold on the bottom - it allows for more efficient use of the available BTUs in that tank. By dumping that cold return water in the top of your tank you destroy that stratification in the tank. Ideally you would return the cold water to the bottom of the tank.

I would use the tank as a hydraulic separator between your boiler and your secondary loops. Think of it as the middleman. The boiler buddy should have 4 taps, two top, two bottom. The boiler supply goes into one of the top taps and the zone supplies go out the other top tap. The zone returns go in one of the bottom taps, and the boiler return in the other. This keeps the cold water low and the hot water high. It also allows the zones to pull hot water from the tank without immediately firing off the boiler. An aquastat in the control well of the tank tells the boiler when its heat is becoming depleted and tells it to fire up and recharge the tank.

Lots of subtle permutations on this, but that's the basic config. Take a look at the tank sketch on Boiler Buddy's home page to see the general concept: http://www.boilerbuddy.com/ Look at some of the pics in their photo gallery - they show it very nicely.

 

[Bruski]

Two scenarios that might be challenging from my perspective:

1. If your boiler buddy is fully heated and your boiler is off, then a call for heat comes from, say your fan coil heaters. How do they draw heat out of the boiler buddy without having to pull it through your pellet boiler? Ideally the pellet boiler would be on an isolated circuit so water only flows through it when it's actively burning.

2. When the boiler is running, hot water is leaving the boiler and feeding into the distribution emitters. Their cold return water then goes into the top of the boiler buddy. What you want to strive for is maintaining heat stratification in your buffer tank - hot on top, cold on the bottom - it allows for more efficient use of the available BTUs in that tank. By dumping that cold return water in the top of your tank you destroy that stratification in the tank. Ideally you would return the cold water to the bottom of the tank.

I would use the tank as a hydraulic separator between your boiler and your secondary loops. Think of it as the middleman. The boiler buddy should have 4 taps, two top, two bottom. The boiler supply goes into one of the top taps and the zone supplies go out the other top tap. The zone returns go in one of the bottom taps, and the boiler return in the other. This keeps the cold water low and the hot water high. It also allows the zones to pull hot water from the tank without immediately firing off the boiler. An aquastat in the control well of the tank tells the boiler when its heat is becoming depleted and tells it to fire up and recharge the tank.

Lots of subtle permutations on this, but that's the basic config. Take a look at the tank sketch on Boiler Buddy's home page to see the general concept: http://www.boilerbuddy.com/ Look at some of the pics in their photo gallery - they show it very nicely.

Hi Deering thanks for the advice. I have revised the diagram please let me know if this is better. I also have a couple of questions if anyone can help me with.
1) Do I need more that the one air separator that is on the top of the boiler buddy (Spirovent Jr.)
2) I want to run a loop to a coil in the garage. It will need to have glycol in it for when it is not on in the winter. I am thinking I could run it from a plate heat exchanger.
Can I hook the non antifreeze side of the heat exchanger into the zone taps? Will I need a pump on both sides of the exchanger or will the boiler side have enough flow it it is just plumbed in.
3) should the primary loop pump always be on or only when the boiler is firing?
Thanks again for any comments.
Bruski

 

[Deering]

Hi Bruski,

Here are my answers, but keep in mind there are some folks here with a lot more experience and brains than me, so my advice is worth what you're paying for it...

I like your schematic. Much better.

1. Vent: Unless you have some long runs that are at a much higher elevation than your boiler, the Buddy should do it for you. That's a great way to pull air from your system because the water velocity slows way down and allows the entrained bubbles to float out.

2. Garage: I'd treat the heat xchanger just like another zone. With a zone pump from the Buddy through it, and another pump on the glycol side. Tho reasons: a) You want to be able to pull heat out of the Buddy w/o the boiler running. b) If the boiler's off, its pump shouldn't be running (for several reasons), so the pump you'd be relying on is not reliable. Zone pumps are relatively cheap...

3. Lots of discussion on that one here. Depending on your boiler, it may want to control its own circulator for its own purposes. Check in with your boiler supplier o how the pump should be wired. The primary thing to be aware of is that the boiler needs to be protected from cold return water (typically <130F) causing the flue gases to condense in the combustion chamber or on the heat exchanger. This will cause corrosion and lots of other undesirable results. There are a variety of ways to protect against this. First, consult with your boiler supplier, then search through the forum archives on boiler protection - lots of great info in there.

You're on the right track. Looking good and asking the right questions.