HTP Verso-Hydro and Tekmar Controls

woodshed · July 2015

Hi all-

Please let me lay out the scenario:

Currently radiant heat and DHW is provided by a HTP Voyager with Tekmar 369 zone controls, Tekmar 362 reset mixing control with a variable speed injection pump and Tekmar RTU's. The Voyager and Tekmar controls are 15 years old.
The heat load is 35,000 btu's, 5.5 feet of head and 3.6 gpm. The Voyager is supplying Wirsbo (Uponor) 5/16 quick trak floor tube panels, the second floor joists have blown in fiberglass insulation and the first floor joists have closed cell spray foam insulation. The basement is not heated. All zones (12) use RTU's and valve actuators. Most of the rooms are carpet and pad which raises the rValue and requires 160* supply to the furthest rooms on a -5* design day. The homeowner claims there is one room, NW corner, 2nd floor, furthest from the Voyager that is 'slightly' cool and can feel a temperature drop walking down the hallway, not uncomfortable. When this install was done 15 years ago, there wasn't a thin pad for radiant floor heat available and the homeowner's wanted carpet/pad because that's what they were used to. The Voyager was set at a 170* supply temperature and the system worked fine. The supply temperatures range between 130*-160* on a -5* design day.

So, now the Voyager needs to be replaced and I'm suggesting a HTP 130,000, 55 gallon Verso-Hydro.

I would like to keep the Tekmar 369 reset control because of the characterized heating curve (indoor temperature feedback and able to specify type of terminal unit) instead of using a reset ratio.

1. Would using the Tekmar 369 reset control without boiler sensing and also using the Versa-Hydro outdoor reset ratio work together or would they conflict with each other, assuming I used the same parameters for each? As I stated earlier, the injection piping and controls are already in place;
2. Currently the system pump is a fixed speed pump which I was going to replace with a Taco Delta P pump;
3. If the Versa-Hydro used it's own outdoor reset separate from the Tekmar control, would I be able to lower the supply temperature from the Versa-Hydro to get the return temperature lower for condensing?

I realize all of the Tekmar are discontinued but at this time they are working and I haven't had to replace any of these controls since they were installed; yes, the homeowner is on borrowed time.

Thanx for taking the time to read my post and your help/suggestions is much appreciated.

Rick

Rich_49 · July 2015

What is their domestic hot water usage like ? Do they need lots of hot water ? Versa is alot of unit to employ for such a small heat load in both power and price .
You would not be able to get higher than 160* space heating water with Versa , the tank will stack and shutdown on top tank sensor safety , have seen it numerous times . Quite the PITA . HTP clearly states an expected top space heating temp of 160* . In either case you require hotter primary water to mix down through an injection loop .
There are ideas that come to mind . I will look for your response .

SWEI · July 2015

woodshed said:
Most of the rooms are carpet and pad which raises the rValue and requires 160* supply to the furthest rooms on a -5* design day.

Given how nice the rest of the install is, I would start with the floor coverings. Really.

woodshed · July 2015

Rich said:
What is their domestic hot water usage like ? Do they need lots of hot water ?
There are ideas that come to mind . I will look for your response .

Rich -
Currently there are two adults and no children. There are 2.5 bathrooms: 3 toilets, 4 bath faucets, 1 shower with multiple shower heads, 1 tub/shower with multiple spray heads. The tub is a whirlpool/soaking tub (fiberglass all-in-one unit) but they don't use the whirlpool or the bathtubs, only the showers, 1 kitchen faucet, 1 laundry faucet, 1 washer hookup, 2 dish-drawers and 1 slop sink.
They do not consume a lot of hot water and the Voyager has not been a problem supplying hot water. Please note: this is a 4 bedroom home so in about 10 years they might be selling and more than likely the new buyer will be a family with kids so hot water demand would be higher.

I went to the house this morning and grabbed some info from the Tekmar 362 mixing control:
Design indoor temperature is set to 68*
Design supply water temperature is 130* at 0*
Maximum supply temperature is 140*
Highest recorded temperature at the mixing sensor was 167*
Setpoint for the Voyager was 160* with a 20* delta T

The homeowners claim the Voyager kept up with the load and only noticed a slight decrease in temperature in one office (bedroom) that is the furthest from the Voyager (2nd floor, NW corner). At no time did they claim they were uncomfortable regardless the outdoor temperature.

So based on the above numbers it appears the Verso-Hydro should work as a replacement for the Voyager.

Please let me know if your thoughts or alternatives.

Thanx, Rick

woodshed · July 2015

SWEI said:

woodshed said:
Most of the rooms are carpet and pad which raises the rValue and requires 160* supply to the furthest rooms on a -5* design day.
Given how nice the rest of the install is, I would start with the floor coverings. Really.

SWEI -

The homeowner indicated they would consider replacing the carpet/pad in the two upstairs bedrooms furthest from the Voyager with laminate flooring in the "near" future; they weren't specific on a date, I imagine they want to save funds after the boiler replacement.

Rick

Rich_49 · July 2015

If those are the temps and that was the reset ratio you should be ok with the occasional excursion into the higher temps . At least with Versa you always condense while making hot water and most of the time your return water temp will be low enough to allow for higher efficiency operation during space heating calls .

HTP Verso-Hydro and Tekmar Controls

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