First Time Hydronic / Boiler / Indirect WH System Design -- Feedback Wanted!

bryantroll

Looking for input on boiler selection and tube/zones for our staple-up and ceiling radiant. We have gotten a lot of good info from this forum and spent a lot of time reading through the Modern Hydronic Heating textbook to get to this point, but we don’t have any installation experience so hoping we can get a little more guidance before purchasing equipment and moving forward.

We recently did a blower door test on the existing house (before new windows, doors, and thorough air sealing) and got a result of 1.2 air changes per hour. We are hoping to tighten this up some still, but there will also be a fireplace added the chimney will be a liability.

The house is a concrete dome with two separate units -- one unit above grade, and one unit in the basement. The dome is 2" of concrete with 3" of spray foam designed to be R21 above grade. The basement unit will be R5 on the floor and R15 on the walls.

Basement: ceiling radiant tubing
Main Floor: under-floor staple-up radiant tubing
Loft: under-floor and in-wall radiant tubing

Here is the current data for the project:
• Using the Heat Load Estimator and an estimated completed-project ACH of .9, we got a total heat loss of the upstairs unit of 41,000Btu/h and the downstairs unit of 40,700Btu/h, respectively. See below.
• We want to utilize a ~45-gallon Indirect Water Heater with a mixing valve for DHW. We assume another 40,000Btu requirement for this but need to make sure we can support the possibility of 3 showers simultaneously.
• Currently selected Grundfos UPS15-58FC 3-Speed Circulator Pumps but open to other suggestions.





Second, please take a look at our schematic and let us know if we should change anything. We used the Modern Hydronic textbook to calculate tube lengths but couldn’t quite match it due to having to work around the joists.
We are considering breaking off circuits 1, 2, 4, and 9 of the “Main Floor” into their own manifold and want to know if that is advised? It would increase the number of manifolds and pumps but break up the number of circuits into more manageable chunks and allow the bedrooms to set a different temp from the main part of the house.
NOTE: Zones 5-8 on the Main Floor are open to the 2nd floor loft, so the volume is much greater in this area compared to the rest of the house.



Questions:
1) What boiler would you recommend and why (size, features, reliability, price)?

2) Is it ok if the designed supply temp is over 120 F, or will we be designing a less efficient system if it runs at a higher supply temp?

3) Any input on oxygen barrier vs pex-al-pex, and also stamped vs extruded plates? I've seen preferences in all directions here.

4) Where should we start with researching ERVs? The upstairs and downstairs spaces are separate units so I am assuming I will need two ERVs. There is no existing ducting or central air.

5) Any other tips or tricks, or specific component preferences?

Thanks for taking the time to read and respond, and if there's any other info I can provide please let me know!

Hot_water_fan

There’s no reason to add capacity for DHW - that’s what the tank is for. Your boiler will be plenty big as is.

bryantroll

Thank you, I believe the thought for the boiler size at about 120k BTU was to be able to sustain ~6 gpm of water heating capacity to keep up with the possibility of 3 showers running at once, or similar scenario. 

That all depends on the boiler selection though — do you have any suggestions on boiler makes to look at, or what features to look for? 

Hot_water_fan

120k is overkill for heating and you have a tank. Stick to your heat loss, your boiler is plenty big. 

For what it’s worth, 120kbtu cannot do 6 gpm continuously anyway so you’re oversizing and gaining nothing.

Boiler make isn’t that important. Find something installed in large numbers by reputable installers in your area. Any mod con that can turn down to 10k Btu or so will be great. 

hot_rod

Lochinvar is well supported in that area
A 106 input Knight puts you just about at your load. I would not go below a 100K input size.

You size to the largest load , so if you need a lot of dhw the boiler sizes to that

I doubt you ever need 6 gpm. You have the tank dump load and a 110 would get you around 2 gpm continuously

psb75

Yes you had better give thorough consideration to air exchange! Moisture control is critical. HRV or ERV system is necessary. Low ACH number is efficient...but plenty of healthy air is also rather important! Your heating design seems to me overly elaborate. Better to err towards fewer zones--not necessarily less tubing. Cut down on the 'mechanicals'--more things to go wrong. Lower your costs. Improve efficiency.

bryantroll

Thank you for the replies, we are learning a lot.

Couple questions remain…

2) Is it ok if the designed supply temp is over 120 F, or will we be designing a less efficient system if it runs at a higher supply temp?

3) Any input on oxygen barrier vs pex-al-pex, and also stamped vs extruded plates? I've seen preferences in all directions here. 

Also, there’s an unused Weil-McLain Aqua-Plus 45 Pewter Indirect Water Heater for sale for $750 I’m thinking of picking up. 

I am on hard well water — does it matter if I go with a stainless or composite indirect water heater tank? 

Do I also need a water softener to protect equipment?

Hot_water_fan

2) Is it ok if the designed supply temp is over 120 F, or will we be designing a less efficient system if it runs at a higher supply temp?

How much above 120F? You want return temps around 120 (or lower) for best efficiency. But as design temp is only for a smidgen of hours a year, a design supply temp of 140F still means you're condensing most of the time.

hot_rod

Its the return temperature to the boiler that drives condensing. Even if you need to run 130 at some condition, with a 10- 15 delta you are still in condensing mode.

The only way to get lower SWT requirements, is lower the load of the space or tighter tube spacing. But two tubes per joist bay with plates is about the best you can do, works out to about 8-9" oc spacing.

I would tube the rooms as you show, you could always combine zones at the manifold by combining actuators if you feel it is too micro-zoned. Only one chance to get the tubing done correctly.

bryantroll

We have been busy -- would love any feedback you have before install is finalized. I will attach some photos of a mock up of the main boiler room wall.

One question: is a bypass to the makeup water line necessary for initial fill, or can I just fill through the makeup water line? It seemed unnecessary and is currently omitted, but could be added if it is in fact necessary.

The system has 4 zones: basement, main floor, main/loft bedrooms, and indirect water heater.
The basement and main floor manifolds will be mounted on one wall, the main/loft bedroom manifold will be on a separate wall.

This will be a ceiling radiant in the basement, underfloor radiant on the main level, and combo of floor and wall radiant in the loft, using the space available.

I plan to install everything onto a sanded/painted 3/4" plywood wall, with blocking behind the boiler.

The pex will come off the manifolds and run through a slot in the wall to keep things tidy and also get it into a cavity leading toward the ceiling.

How does this setup look? Any feedback or suggestions?

pump 1 to loft manifold on other wall
pump 2 to indirect HWH
pump 3 to main floor manifold
pump 4 to basement manifold








mock up / test on a scrap piece of wood of running tubing through slot in the wall




couple snippets of tubing installed under floor -- roughly 2500' installed so far across 9 loops and have 7 more loops to do in total. Labor intensive, especially in a round house where routing stays interesting!

hot_rod

Here is the suggested piping for close tees. It is good to have some piping distance before and after the tee assembly.

Why so many fittings below the tees? One ell, or an ell and a 45 to offset.

bryantroll

Thank you.

We are managing an elevation difference between the supply and return and the only way we saw to get that exact was with two 45s to get the right offset. A 90 and 45 didn’t get us there.

As for the distances before and after the closely spaced tees, is the diagram you posted a different configuration than I have? Mine has the main loop entering the side and the secondary at top and bottom in line. I want to make sure it’s being installed correctly but not sure what minimum distances are required on my configuration.

Do I need to make sure I have 8” off the bottom of the tee? So move it up to allow for a longer straight length off the bottom?

If you have a suggestion on how to reconfigure I’m all ears!

hot_rod

8 pipe diameters before the tees and after

So if you use 2” pipe or tube have at least 8” before and after the set of tees

For best results

bryantroll

Ok thank you. I am using 1" pipe.

In my setup photographed above, I think I need to relocate the closely spaced tees to allow for 8" (8D) on the inlet side, and I already have far more than 4" (4D) on the outlet side of the tees. This is the in-line side of the tees. Is this correct?

For the inlet and outlet on the left side of the tees where the boiler and the pump is, is there any minimum length to be aware of?

bryantroll

Is this change correct?
Is there a min length for the other two ports of the closely spaced tees?

Lengthened a couple pipes around closely spaced tees.

Alan (California Radiant) Forbes

One question: is a bypass to the makeup water line necessary for initial fill, or can I just fill through the makeup water line? It seemed unnecessary and is currently omitted, but could be added if it is in fact necessary.

The bypass is to make purging easier. Don't put it in and you will learn the hard way that something so simple will make a big difference.

If you're using plates under a hardwood floor, do not exceed 120F water temperature.

bryantroll

https://forum.heatinghelp.com/discussion/comment/1799954#Comment_1799954

thank you Alan.

The bypass should be an unrestricted flow and could probably do 20gpm if the pump could maintain 60psi through the 3/4 pipe, but my well pump can only maintain 5-6 gpm based on my testing.

With this in mind I didn’t see how the bypass would restrict my max potential flow — or am I missing something?

bryantroll

Added a makeup water bypass and starting to get things mounted on the wall to verify placement.