Finished Hydronic Radiant System (finally!)

josephny

Thank you to everyone who helped me through getting my system in place.

I used an IBC SFC-199 (combi) with IBC's prebuilt primary loop manifold, Uponor EP manifold and Aquapex, Grundfus pump, Ecobee thermostat with separate 24v transformer.

Still working on tweaking it -- right now the flow is about 0.3 gpm for each of the 4 loops with the boiler set to 125* F. This is resulting in the temp gauges at the manifold input and output reading ~110* and 95*, respectively.

Here's a pic:

Paul Pollets

Aquapex? For the radiant side?

psb75

He only mentioned Aquapex for his radiant heat manifold set-up!
Should have used Uponor HePex with O2 barrier...

josephny

My mistake: I did use HePex for the radiant heat loops.

Zman

There are some details that need attention before you become a statistic:

• How was it determined that the vent and CA can be reduced? I have never seen a 199 that can run on 2" vent.
  
• Where does the vent go?
  
• Is the PVC vent solid core?
  
• You should not use hard 90's for vent. They should be sweeps.
  
• Did you prime the PVC? Most use purple primer so you don't forget a joint.
  
• Are those Ferncos after the 90's
  
• The PVC needs to be supported and sloped per code and manufacturers instructions, Be sure to provide a strap at the boiler so it won't blow off if you have a preignition.
  
• Can we talk about the wiring? It really should be done in MC. If you are going to use Romex, you need to keep it tight. The wiring to the circ is horrible.
  
• Where does the condensate go?
  
• How was the combustion analysis?
  
• I can't tell what you did with the gas line.
  
• The hydronic piping is OK, more support would be a good idea, I don't like pipes rubbing on each other and the purging must have been a challenge.
  

There may be more, I am on coffee cup #1
I would not sleep in a house with an installation like this.

psb75

That is an odd domestic water system hook-up.

josephny

Zman said:

There are some details that need attention before you become a statistic:

• How was it determined that the vent and CA can be reduced? I have never seen a 199 that can run on 2" vent.
  
• Where does the vent go?
  
• Is the PVC vent solid core?
  
• You should not use hard 90's for vent. They should be sweeps.
  
• Did you prime the PVC? Most use purple primer so you don't forget a joint.
  
• Are those Ferncos after the 90's
  
• The PVC needs to be supported and sloped per code and manufacturers instructions, Be sure to provide a strap at the boiler so it won't blow off if you have a preignition.
  
• Can we talk about the wiring? It really should be done in MC. If you are going to use Romex, you need to keep it tight. The wiring to the circ is horrible.
  
• Where does the condensate go?
  
• How was the combustion analysis?
  
• I can't tell what you did with the gas line.
  
• The hydronic piping is OK, more support would be a good idea, I don't like pipes rubbing on each other and the purging must have been a challenge.
  

There may be more, I am on coffee cup #1
I would not sleep in a house with an installation like this.

Wow, thank you so much for the detailed analysis.

1) The SFC-199 manual specifically states that PVC can be used and reduced to 2", as per the details below. Mine is solid core S40.

2) In the picture you can see the vent going horizontal. It turns up just inches past where you can see it and terminates in open air several feet above that.

3) It's a tough place to work so I used hard 90's and a Fernco. I can replace the fernco if necessary -- is it? Can I keep the hard 90's for such a short vent run?

4) After posting this I corrected the pitch and use a riser clamp on the outside to maintain the pitch.

5) Wiring is horrible. I can use romex if I staple it and keep it straight?

6) Condensate doesn't go anywhere now. I'm having a hard time figuring out how to attach a hose to the SFC. It looks like there's a special (propriatary) connector, but I can't figure it out.

7) I don't understand what is meant by "combustion analysis"

8) What is a good way to support and prevent rubbing of the hepex? Yes, purging was difficult (although it was the first and only system I've purged, so, like everything, it was a learning experience.

Thank you!

Zman

I would try to use 3" if possible. It would also solve your 90 issues as the reducing couple is taking p valuable space. The ferco needs to go, if you change the piping to create room vertically, you will be able to slide the pipe into the boiler.
Unitstrut and clamps work well for supporting pipes.
Can you use the condensate hose that came with the boiler and pipe it to a neutralizer? Your old drain pipes will thank you. (section 1-17)
Combustion analysis is a good idea and is described in section 3 of the manual.

Ironman

What kind of emitters do you have? A radiant wooden floor?
Notice that you’re taken the 1.25” loop and reduced it to 3/4” feeding just one manifold. A 3/4” line can carry 40k btus at a 20* delta T; 20k btus at a10* delta T - which is what a radiant floor should be designed for. That’s the reason that I asked what type of emitters you have.
In either scenario, a 200k btu boiler is gonna short cycle itself to death unless a buffer tank is installed to lengthen the cycle run time.

Zman

Ironman said:

What kind of emitters do you have? A radiant wooden floor?
Notice that you’re taken the 1.25” loop and reduced it to 3/4” feeding just one manifold. A 3/4” line can carry 40k btus at a 20* delta T; 20k btus at a10* delta T - which is what a radiant floor should be designed for. That’s the reason that I asked what type of emitters you have.
In either scenario, a 200k btu boiler is gonna short cycle itself to death unless a buffer tank is installed to lengthen the cycle run time.

Good point. It was brought up in an earlier thread. I think the desire to have a combi unit for hot water once again made the heating system a compromise.

josephny

The IBC modulates down to 23k.

I'm using uponor Quik Track under plywood subfloor (which is under wood flooring), with rock wool insulation below the tracks, and each loop is about 250'.

hot_rod

The pump manufacturers like to see the junction box on top, removing the 4 allen bolts allows you to rotate the motor. Most radiant manifolds can be mounted on their side, Caleffi has inverted versions to clean up that pex spaghetti

Tom_133

Not sure what size that pump is but if you are using quicktraks at 250' I hope its large. I thought quicktrak only used 5/16", meaning a lot of head!

Zman

Tom_133 said:

Not sure what size that pump is but if you are using quicktraks at 250' I hope its large. I thought quicktrak only used 5/16", meaning a lot of head!

The picture shows 1/2" tubing. I think he meant joist track.

josephny

Hot_rod: Going there today (hopefully) to redo the wiring and put the terminal block on top side of pump and (hopefully) swap out the Ferncos with PVC couplers.

Tom_133: I'm using 1/2" HePex with a Grudfos UPS15-58FC.

Thank you everyone!

Ironman

josephny said:

The IBC modulates down to 23k. I'm using uponor Quik Track under plywood subfloor (which is under wood flooring), with rock wool insulation below the tracks, and each loop is about 250'.

Modulation is designed to accommodate the firing rate to the actual load as the outdoor temperature changes, not to compensate for over-sizing. This is the major issue with most combi’s. In order to have enough horsepower to meet the average domestic load, the boiler is way over-sized for space heating.

If at your design temp (coldest night of the season), you only need 20k btus, then the boiler is over-sized at any warmer outdoor temp and will short cycle.

A buffer tank is the simple and economical solution. It’s a lot less $$ than replacing the boiler because it died young from short cycling.

josephny

Ironman said:

josephny said:

The IBC modulates down to 23k.

I'm using uponor Quik Track under plywood subfloor (which is under wood flooring), with rock wool insulation below the tracks, and each loop is about 250'.

Modulation is designed to accommodate the firing rate to the actual load as the outdoor temperature changes, not to compensate for over-sizing. This is the major issue with most combi’s. In order to have enough horsepower to meet the average domestic load, the boiler is way over-sized for space heating.

If at your design temp (coldest night of the season), you only need 20k btus, then the boiler is over-sized at any warmer outdoor temp and will short cycle.

A buffer tank is the simple and economical solution. It’s a lot less $$ than replacing the boiler because it died young from short cycling.


Thank you for the explanation.

Is it accurate to say that a combi boiler is designed to accommodate what would otherwise be short-cycling because it is intended to be used to provide hot water, which can easily be a 1 or 2 minute firing session?

Can you recommend an economical buffer tank for my system/config?

Tom_133

Zman said:

Tom_133 said:

Not sure what size that pump is but if you are using quicktraks at 250' I hope its large. I thought quicktrak only used 5/16", meaning a lot of head!

The picture shows 1/2" tubing. I think he meant joist track.

Oh good! I have seen that done before!

Ironman

josephny said:

josephny said:

The IBC modulates down to 23k. I'm using uponor Quik Track under plywood subfloor (which is under wood flooring), with rock wool insulation below the tracks, and each loop is about 250'.

Modulation is designed to accommodate the firing rate to the actual load as the outdoor temperature changes, not to compensate for over-sizing. This is the major issue with most combi’s. In order to have enough horsepower to meet the average domestic load, the boiler is way over-sized for space heating.

If at your design temp (coldest night of the season), you only need 20k btus, then the boiler is over-sized at any warmer outdoor temp and will short cycle.

A buffer tank is the simple and economical solution. It’s a lot less $$ than replacing the boiler because it died young from short cycling.

Thank you for the explanation. Is it accurate to say that a combi boiler is designed to accommodate what would otherwise be short-cycling because it is intended to be used to provide hot water, which can easily be a 1 or 2 minute firing session? Can you recommend an economical buffer tank for my system/config?

HTP has a nice 20 gallon SS one. Or, you can  use a small electric water heater. The object is to add mass to the system to create longer run times.

Though some domestic cycles can be short, they’re only a small percentage of the total in a normal household.

Some combi’s come with an internal indirect tank to address this issue, but a heating boiler + an indirect is usually the better choice though higher in initial cost.

Ironman

What’s the square footage of your house?

Was a Manual J (or similar) heat loss calculation done? If so, what was the total calculated heat loss?

With four 250’ loops being fed by a 3/4” line, 20k btus is about the best output you can expect from the floor, depending upon floor coverings.

mattmia2

Most boilers also have a maximum firing rate setting for DH to keep it from firing at max rate for 3 minutes and getting the DH loop up to temp and shutting down as well as settings for the on/off differential and short cycle times to help keep them from short cycling where they DH load is much less than their max firing rate.

josephny

Ironman said:

What’s the square footage of your house?

Was a Manual J (or similar) heat loss calculation done? If so, what was the total calculated heat loss?

With four 250’ loops being fed by a 3/4” line, 20k btus is about the best output you can expect from the floor, depending upon floor coverings.

It's complicated.

The house is 3 stories with electric wall panel heaters in each room.

First floor is about 1000 sq ft above the basement with another 450 sq ft not above the basement.

Second floor is about 1200 sq ft.

Third floor is about 1000 sq ft.

I installed the radiant system to supplement the electric heat. Well, more accurately, to become the primary heat for the first floor, leaving the electric in place as a supplemental heat source but also because the first floor extends past the borders of the basement (100 year old house that was added on to several times.

Loops are probably closer to 275' each.

Does that make sense?

Thanks!