Hello/introduction and draft question

[nmerrill]

Hello folks,
New member here, hailing from The Champlain Valley of Vermont.
I'm just completing the install of a Harmon PB105 boiler plumbed primary/secondary to 2 radiant floor zones, one baseboard zone, an indirect DHW tank (smart 50), and eventually the hot tub and shop.
So far I've had the Harmon fired up a few times connected only to the DHW tank to check things out, and chase leaks in the primary loop.
Ooohh that was fun! I love leaks!

Anyway, to my first question I came here for!
I have tested the draft on the install. I have approx. 13ft of rise in my Simpson PVP vent. I measured a high draft of 0.80 I.W.C.
The problem I have is that I can't get the low draft into the spec range that Harmon indicates in the manual.
With the adjustment pot turned all the way down, I still measure a low draft of 0.70 I.W.C.
The specs indicate that low draft should be between 0.25 and 0.35, with a max of 0.55.
Anyone have any experience with this issue?

Also, I need to "vent" about the performance of the Simpson PVP vent pipe... it leaks!! "No silicone required" my A***

Ok.

Thanks!
Nat

 

[Eric Johnson]

A belated welcome to the Boiler Room, Nat. I'll be in Essex Jct. for our show May 9-10 at the Champlain Valley Exposition (Northeastern Forest Products Equipment Expo).

I can't answer your draft question, but we have members here who do know what they're talking about on that, and I expect they'll be able to help you out.

 

[nmerrill]

Thanks Eric.
I spoke with my dealer, who called Harmon and got back to me. Harmon apparently does not think that a low draft that strong will be a problem.
Why bother measuring it then, and putting an "acceptable" maximum in the manual?
I'm still trying to determine what would be the root cause.
I have not installed the outside air hose yet, and the intake flap door opens easily, and fully under operation.
So, is the voltage supplied to the exhaust fan out of standard factory specs? Who would know without a service manual/ info from Harmon?
My primary concern over having a low draft that strong, is that this boiler has a long "cool down/ shut down" fan cycle. When the boiler reaches temp, and shuts the fire down, I have noticed that the fire may be long gone, but the blower runs for at least another half hour, or more.
It's not the electricity that I'm concerned about primarily, but the blower drawing potentially sub zero air into the heat exchangers (firebox) for 45 minutes after shut down!
My Dealer said the time is controlled by the ESP. I suspect that is correct, but the program must be looking for really cold exhaust temps before stopping the blower!
There must be a better way to control that fan cycle. I suspect that residual vent heat, and inherent draft would pull out any lingering smolder smoke just fine, without the fan at all. Maybe not.
Anyway, any folks here who have any experience with the PB105 controls?
Thanks for listening!


Nat

P.S. about to take the plunge to full pellet heat, hooking the PB105 to the heat system tomorrow for the first time. Unfortunately, the way things are configured, that means dropping the oil burner completely from the system. Just in time, since my oil tank is well below 1/4...
Wish me luck!

 

[Eric Johnson]

The fan running long after the fire has gone out is a fairly common problem with many wood-fired boilers. Some people get around it by running their blower connection through a timer which can be reset every time you load the stove. You have to know how long to set it for, which takes some observation and experience with different weather/heat load conditions, but seems to work well for those who do it that way. Or, there may be a way to set your controller to better serve your needs. I've found operating manuals in this business to be generally pretty lacking in useful information, so don't feel like you're being singled out.

 

[MikePelletier]

I just installed my PB105 in parallel with my oil furnace last week. It's been too warm to
try it for more than just getting the water up to temperature. I was unable to put my hands
on a manometer to measure the IWC on low. I have one on order and I expect it in a day
or so. I'll let you know what I can adjust it to once I've completed the exercise. I'm venting
into a 35-foot chimney but there's a barometric damper at its base. We'll see.

Thanks,

Mike Pelletier