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Author Topic: Question about my new system (is it designed well)  (Read 341 times)

savebigmny

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Question about my new system (is it designed well)
« on: September 12, 2019, 08:56:20 AM »

I'm looking for some opinions about the system at the house I just bought.  I will try to describe it as best I can, correct me on wrong terminology as I am new to OWB but very excited to be using it soon.  The house is a raised ranch about 1800 square feet, built in 2013 .  2x6 walls and good insulation in the attic so the heat loss shouldn't be horrible.

Boiler is a Cadillac 3600, On the back is a Taco 2400-WB pump (new I just bought it because the original pump was missing) It is pushing to the house.

underground is 1" pex that goes about 80' to the house.

Once in the house it is a primary secondary ( I think that is the right terminology) loop with close spaced T's.

First load is the basement floor which has a Grundfos pump 1/25hp (not sure the model) feeding 5 loops in the concrete floor (about 1800 square feet)  There is a mixing valve so the temperature can be adjusted.

Second load is all flow through a plate HX which preheats potable water on it's way into a 40 gallon electric water heater.

Third load is all flow through 16x20 radiator in the furnace duct to heat the main floor (same 1800 square feet)

Fourth load was 3 loops in the garage floor but that has close spaced T's and the same pump like the basement has (I say it WAS the fourth load because all 3 loops leak down air pressure rapidly, I have not yet looked at it with a thermal camera to see where or how many leaks there are.)

From what I have read it would be ideal to have the basement floor loops come off the system after the potable HX and the furnace radiator because they don't need as hot of water anyway.  Is that correct?

Any other thought from people with more experience about what is good or bad about my system?
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mlappin

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Re: Question about my new system (is it designed well)
« Reply #1 on: September 12, 2019, 09:52:29 AM »

You’re correct, DHW (domestic hot water) first, followed by your furnace exchanger then your floor loops.
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savebigmny

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Re: Question about my new system (is it designed well)
« Reply #2 on: September 12, 2019, 10:56:48 AM »

Thanks, I would have to redo piping to switch the order which I will probably do anyway because I don't like droopy pex tubing all over.  How big of an impact do you think it would have?  Worthwhile to switch it up now before heating season starts or leave it until next summer?
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savebigmny

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Re: Question about my new system (is it designed well)
« Reply #3 on: September 12, 2019, 01:08:39 PM »

Another question I thought of.  Some places I see mentioned that an open system is not good going straight to floor loops and should have an isolation HX.  Why or why not?  My boiler fill point is higher than any other point in the system if that matters.
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wreckit87

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Re: Question about my new system (is it designed well)
« Reply #4 on: September 12, 2019, 03:28:02 PM »

I concur that the radiant should be last, in that the temp requirement will be lower. I also concur that the radiant should be separated via a heat exchanger and pressurized. Unfortunately your garage loops have frozen (a byproduct of an open system) and will likely need to be abandoned. Repair is seldom possible without a complete fresh start. The reason atmospheric radiant systems suck, is that the slab is the low point in almost all systems and atmospheric systems WILL take on sediment, scale, oxidation/rust, and other foreign material from the atmosphere which eventually settles in the slab tubing due to low flow velocities and over time plugs up the loops rendering them useless. I see it all the time, and preach hard the importance of closed loop radiant. The "well it works for me" guys are everywhere, but from any standpoint hydronics, they are wrong if they say it's proper.
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Re: Question about my new system (is it designed well)
« Reply #5 on: September 13, 2019, 02:59:36 AM »

I agree with the others- DHW, hot air coil, radiant. You'll see consistent domestic water temps regardless of whether the radiant kicks in or not, and flow rates required on the main loop is less. Which means smaller pump sizing. If it's piped in pex switching it to the correct order wouldn't be all that difficult, but it'll heat the house as it is.
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savebigmny

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Re: Question about my new system (is it designed well)
« Reply #6 on: September 13, 2019, 06:41:47 AM »

Wreckit, thanks for explaining why.  Makes perfect sense that sediment would build up.  So it is ok that the DHW HX and the furnace are in the primary water loop and you would just use a heat exchanger to isolate the floor loop system?  What type of heat exchanger would you recommend?  So what I think you are saying is the floor HX would be last and it would have constant flow through it on the primary loop side and then the secondary side would be pressurized closed loop with probably the same pump I am using now turning on and off based on calling for heat, with the existing mixing valve limiting the temperature going into the floor.

Is the clogging something that can happen in just a season of operation?  I flushed all of the lines until the water was clean by hooking a hose to the manifold and opening one loop at a time just to see how they flowed before I blew them out with air and pressure tested them.  All seemed well so far, heating season is closing in and what I am asking is can I wait until next summer to set that up properly
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Re: Question about my new system (is it designed well)
« Reply #7 on: September 13, 2019, 07:49:12 PM »

Generally, yes you would put all 3 exchangers in series in the primary loop. DHW first, then W2A coil, then the radiant plate before returning to the OWB. I would recommend a 30 plate HX in the 5x12 size with 1" ports. Your existing pump and mixing valve can be reused, you'd basically need to add an air eliminator and expansion tank along with a relief valve. As for the floor loops, odds are slim that there's much of an issue after only a year but when you close the system, I would recommend flushing each loop individually again to be sure it's clean. Domestic pressure will flow at a high enough velocity to suspend any particles and flush them through, while the Grundfos is merely a trickle in comparison so the particles will sink
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savebigmny

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Re: Question about my new system (is it designed well)
« Reply #8 on: September 19, 2019, 01:20:16 PM »

Excellent thank you.  I will collect parts and set it up that way next summer.
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