Alternatives for HTP Vision 2


Old 12-19-16, 06:18 PM
Thread Starter
Join Date: Dec 2016
Location: USA
Posts: 2
Alternatives for HTP Vision 2

I have been advised by HTP that the main board in a Vision 2 controller is failing. HTP no longer makes or stocks the Vision 2 or its main board (HTP part 7250P-222), and has no suggestions for alternatives from other manufacturers. I am looking for some suggestions regarding alternatives. Sorry for the long post, but I wanted to provide enough detail for the question to make sense.

SYSTEM OVERVIEW: This is a residence where the boiler provides heat to (1) numerous hydronic radiant loops, (2) hot water coils to two air handlers, and (3) a DHW tank. In total, there are 10 different radiant loops/pumps controlled by 7 thermostats (which all run to a series of Nix relays) plus the DHW loop/pump. The boiler is a 1-year-old HTP Pioneer PHR-199-55, and the zone pumps (other than DHW and return) are all Grundfos UPS15-58FC. The pumps (other than DHW and return) are all wired to a series of 3 Nix boxes containing 10 relays (9 of which are in use). The DHW runs straight to the Vision 2.

VISION 2 CONFIGURATION: The Vision 2 thinks there are 3 zones: DHW, radiant and other. Zone 1 is DHW and has priority, so all other pumps will shut off when DHW calls for heat. There is a DHW temp sensor wired to the Vision 2, and the Vision 2 controls the DHW pump. Zone 2 is radiant, and has a temp sensor and mixing valve on the radiant feeding loop (set to 115). Zone 3 is the fan coil feeding loop (no temp sensor or mixing valve on that loop). Whenever zones 1 or 3 are calling for heat, the Vision 2 instructs the Pioneer to heat to 180-degrees. If only zone 2 is calling for heat, the Vision 2 instructs the Pioneer to heat to 115-degrees. If zone 2 and 3 are calling for heat, the Pioneer will heat to 180-degrees and the mixing valve will keep the radiant loop (zone 2) at 115-degrees.

PROBLEM: The problem was that the Pioneer was not heating beyond 115-degrees. HTP diagnosed the problem as the Vision 2 board (the outdoor temp sensor is reading correctly but when connected to the Vision 2 board the boiler constantly modulated to 115). When the sensor is disconnected from the Vision 2, the boiler will kick to 180 if the DHW or fan coils are calling for heat. I could just keep running without the outdoor temp sensor and just lose the efficiency of the outdoor reset curve. However, HTP advised that when one part of the Vision 2 goes bad, other parts are likely to follow. Sounds like an alternative is in order.

ALTERNATIVES: One alternative would be just stop using the Vision 2 and wire everything straight to the Pioneer. The Pioneer has 2 zones, so I would need to add a relay to bridge two of my current zones. Bridging the fan coil and DHW loops makes the most sense, since both get 180-degree water and run without mixing valves, but doing so would mean I lose the DHW override priority. Or I could bridge radiant and fan coils if I wanted to keep the DHW priority, but then I would lose the ability for the boiler to run efficiently at 115-degrees when only the radiant loops were calling for heat (radiant loop would always get 180-degree heat and rely on the mixing valve to get to 115-degrees). In either case, Iím not sure if I would need to replace my current mixing valve with a mechanical valve or if the Pioneer can control that valve.

Does anyone have any suggestions for (1) possible Vision 2 replacements, (2) ways to make everything work without the Vision 2 or a replacement, or (3) places I might find a new/used/refurb Vision 2 main board?
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Old 12-22-16, 02:47 AM
poorplmbr's Avatar
Join Date: Feb 2003
Location: long island ,new york
Posts: 296
Try Jupiter They have many HTP parts in stock.
Old 12-22-16, 05:04 AM
Thread Starter
Join Date: Dec 2016
Location: USA
Posts: 2
Thanks poorplmbr. I already tried Jupiter. They have neither the Vision 2 nor any parts, and don't know anyplace that does.
Old 12-22-16, 06:24 AM
Join Date: Dec 2016
Location: United States
Posts: 35
As a full replacement, I took a look at the Tekmar website, and there are a couple of different products which might meet your need.

I think the Tekmar 422 might be your best bet, but you'll need to do a bit more research to be sure...
It supports a 0-10V modulating boiler, two outdoor reset controlled setpoint temperatures, and a separate DHW override setpoint.
It doesn't seem to have enough connections to operate both of the ODR temperature zones, so you might also need a Tekmar 440 expansion module to get the 2nd setpoint output.

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