HTP Pioneer setup

DavesHouse

Hi Everyone,

I had a different post a while back to figure out what boiler was best for my panel radiator system, I ended up going with the HTP pioneer based on simplicity, installation cost, and low maintenance. I am getting ready to have the system installed and had a couple questions about the best way to set this up. Right now I have an electric heat pump water heater because we didnt have a gas line in the house when we bought it. the water heater works fine, but 2 showers back to back can sometimes be a bit much for it, and I just added 2 new bathrooms in an addition we are building.

If I set the pioneer up just for heating it will run 140 supply at design conditions and use the onboard outdoor reset control. This should be pretty efficient. If I replace the heat pump water heater eventually with a conventional gas water heater i'd have 2 gas appliances running at the same time.

If I set the pioneer up to run an indirect tank, I'd have to store at 180 and have a outdoor reset mixing valve for the radiators. It will never condense, and be less efficient than the first setup. But, if I store at 180 and mix down, I'll be using less water.

Does anybody here use a similar setup to either of these? I'm wondering how much difference in efficiency i would see. I know I would never condense with the system storing at 180, but If i'm mixing and using less of the hot water that may make up for some of the decreased efficiency.

Maybe i'm overthinking this, but I dont want to do anything with the installation that i'll need to have changed down the road. I know there are other setups that might be a better fit (boiler with separate buffer and indirect tank) but the difference in installation, material and maintenance costs led me to where I am now.

Thansk

SuperJ

From the manual.



Congrats on a great choice in boilers. Would be my top pick if I had to replace my older Polaris (but it still runs fine).
Had a quick look at the manual and it looks like you should wire the indirect temperature sensor and pump control directly to the pioneer. You definitely don't have to run at 180F 24/7. With the indirect sensor you sense the DHW tank temperature directly (no aquastat needed), and you can set a reasonable DHW setpoint (say 130-150f), the pioneer will control the pump and burner as necessary to achieve the indirect setpoint. It likely won't have to go to 180f to do so. I think parameter 19 lets you set the heating water temperature target when running in DHW priority mode. There is a post purge setting for the indirect pump, this should allow you to dissipate some of the hotter water at the end of the cycle. There is a setting to limit the modulation when heating an indirect tank (to match the output of the indirect coil). You will get hot water pretty quickly at the top of the tank despite the mass due to thermal stratification. The bottom of the pioneer could still be quite cool with the top at indirect temperatures.

Since you have panel rads you probably don't need a tempering valve, but if you had infloor you would want a mixing valve between the tank and heating pump.

I have panel rads on my Polaris Tank (similar configuration to the Pioneer but no modulation). I'm amazed how much stratification I get, it condenses at lot even at high temps since the cold return stays at the bottom and the heated water rises to the top.

TLDR: use the built in Pioneer controls and it will work fine with an indirect tank.

DavesHouse

Thanks for the help. I guess the way i've been thinking about it is if i use the onboard outdoor reset and run an indirect, and if it is the spring or fall and my supply temperature is only 100 degrees, would the unit be able to keep up with DHW demand? I dont know how warm the tank would need to get to satisfy the DHW demand, but it would take about 22 minutes to heat from 100 to 180. If i had a 50 gallon or so indirect stored at 140 with a mixing valve down to 120 i'd probably have a fair amount of time to run the tank down.

I know the radiators wont care about getting a warmer supply temperature, and the thermostatic valves should prevent any over heating, so it may just use less of the warmer water in the tank after it ramps up to satisfy the indirect tank a couple times a day.

SuperJ

I think the pioneer has more than one sensor (hi and low tank sensors and possible a DHW tank temp sensor), it appears that it will start the DHW pump when the temperature in the top of the tank is above the (DHW setpoint minus the offset). It shouldn't take too long for some hot water to build up in the top of the tank even if the bottom is cold. You don't have to run the DHW priority at 180f either.

If you have enough capacity, delta p pump, and trvs on your panel rads, you may just want to leave the heating pump on during a DHW call, even at the higher temperatures. Since you're not interrupting space heating for a DHW call you could tune your DHW recovery down a bit.

Another option would be to limit your OAT reset to a min of about 140F supply (with properly balanced TRV'd panel rads your rwt should be way lower for lots of condensing still). Then just run a flat plate with a pump started off a flow switch. You should be able to get a 10degF approach temp on your DHW. @hot rod has down something like this.

Rich_49

SuperJ said:

I think the pioneer has more than one sensor (hi and low tank sensors and possible a DHW tank temp sensor), it appears that it will start the DHW pump when the temperature in the top of the tank is above the (DHW setpoint minus the offset). It shouldn't take too long for some hot water to build up in the top of the tank even if the bottom is cold. You don't have to run the DHW priority at 180f either.

If you have enough capacity, delta p pump, and trvs on your panel rads, you may just want to leave the heating pump on during a DHW call, even at the higher temperatures. Since you're not interrupting space heating for a DHW call you could tune your DHW recovery down a bit.

Another option would be to limit your OAT reset to a min of about 140F supply (with properly balanced TRV'd panel rads your rwt should be way lower for lots of condensing still). Then just run a flat plate with a pump started off a flow switch. You should be able to get a 10degF approach temp on your DHW. @hot rod has down something like this.

HTP actually made that unit , it was called Versa Flame . Unfortunately not enough folks realized the usefulness of such a product and it is no longer produced .

A 30 plate would give you all the 120* DHW you need at 140 - 150* . Use a mixing valve also , high volume type Caleffi or Taco to avoid possible scald issues

DavesHouse

Thanks Rich. I remember you mentioning this when I was asking about my heating system setup. I do like the thought of the FPHX and basically making a better tankless heater. I've looked at a few calculators, but i'm not sure how accurate the assumptions are but it shows I might not have enough GPM or would need a bigger boiler (I have the pioneer 100k). There must be something that works though since HTP made the same unit.

For those who do this sort of thing, would you recommend a FPHX for hot water over an indirect tank? I can get a pretty good deal on the indirect tank plus a tax credit, so it might be the cheaper option up front, but i'd rather set up the system for payback in the long run.

hot_rod

Seems 120- 130,000 is the small end for combo units making DHW with plate HX

On rule of thumb is 50k for 1 gpm dhw

The actual boiler output at the operating condition is the number to use when calculating hx performance

Pre-heating water to the hx helps performance numbers

Rich_49

hot rod said:

Seems 120- 130,000 is the small end for combo units making DHW with plate HX



On rule of thumb is 50k for 1 gpm dhw



The actual boiler output at the operating condition is the number to use when calculating hx performance



Pre-heating water to the hx helps performance numbers

Most combi units do not have the benefit of 55 or more gallons of mass either Bob . Rules of thumb suck too . This document would disprove the 50K per 1 gpm theory also .

http://www.htproducts.com/literature/HTP-Versa-Flame.pdf .