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Bobcat boiler/Rad/Radiant System mixing valve issues
Hi there! First post but I have been a wallcrawler for quite some time, especially as I was planning out a re-working of my heating system in my 110 y/o home. Very appreciative of the knowledge and sharing that happens on this site!
Brief history: Moved into our old character home 2 1/2 years ago, major fixer-upper needing new electrical, plumbing, heating, etc. Before we moved in a contractor did asbestos remediation (pipe coverings) and installed a new boiler, S/F Bobcat B120, paired with an Amtrol Boilermate DHW tank. The home uses very large original radiators (2 storey + attic den + basement) on the main floor and 2nd floor. The boiler was piped into the original pipe scheme, therefore the whole house was on 1 zone (thermostat on main floor).
Of course because we gutted and insulated/vp'd/drywalled the entire 2nd floor (bedrooms, bathroom) during the winter it became unbearably warm upstairs with the only thermostat being on the main floor.
I decided that when it came time to finish the basement I would re-do the piping and add a bunch of zones to even things out, and I would also take out the low-hanging steel pipes in the basement to add head room.
Well I am now VERY close to completing that goal and just fired up my new heating configuration two days ago (not at all stressful!). Everything seems to be working relatively well as far as the thermostats (6 total now) calling for heat through the Taco 6 zone switching relay and the relay in turn actuating the zone pumps and firing up the boiler (minus some Bobcat ignitor issues which I know are separate and have had for a while).
My problem seems to be that the Honeywell AM102-US-1 mixing valve (see picture) is being bypassed or something, as the zones after it (4 radiant zones) are not getting very hot, max 80F or so. The pipe on the Cold side of the mixing valve gets super warm to the touch, basically as hot as on the Hot side of the valve, and the Mix pipe stays fairly cool. I have the mixing valve maxed to hot right now with no noticeable/measureable change. It basically seems like the hot water from the boiler is going straight through the mixing valve and creating a mini-loop (not seen on the attached picture is that there is another pump for the primary boiler loop), so my two full-temp hot water radiators are working great, but none of my zones after the mixing valve are getting hot enough.
I'm not a pro or engineer but have a lot of experience in the renovation industry and did about 3 months of research into my design/needs/components, so I'm really hoping I didn't miss something major here. I've seen several similar setups where the mixing valve is used like this in pictures online designed and built by professionals (or for sale as a pre-designed board) so I know I'm not really blazing new trails in terms of design.
Sorry for the long-winded post, hopefully there is enough background to get an idea of what my situation is. I will also attach a picture later of the actual setup, but for now here is my drawing I was working from (if the drawing doesn't come up right here in the forum, here's a link to it full-size: http://ilophoto.ca/blog/wp-content/uploads/2012/12/pipescheme.png )
Thanks for any help you can give!
-Grundfos UPS 15-58FRC pumps (including one for primary loop and another for DHW loop)
-1" copper piping (going to 1" pex in joists for rad loops, 1/2" pex for radiant loops)
-Honeywell AM102-US-1 mixing valve
-Temperature and pressure dials at points seen on picture
-Zones 3&4 are in-slab in basement (yes, I poured a new slab in the basement, this has not been a small job!)
-12" spacing between supply and return on primary loop as spec'd by Slant/Fin for the Bobcat and this type of setup
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