Radiant boiler installation

raemac

I am converting from gas steam to radiant under floor (heat only) system in an old victorian 1920's home. I removed all the steam piping and rads. I am doing thermofin c plates with foil and insulation in the bays and I figured a total heat loss of 110k btu for structure for 2 floors. I have 3 floors but can only get under floors for first and second floor.

I dont need much heat on third floor (bedrooms) and was thinking of doing radiant with wall hanging european style rads by droping pex down steam pipe holes. If not, then electric space heaters. Radiant baseboard could be option as well but seems very cumbersome.

I am at the point where i am hiring a plumber to install a new viessman vitodens 110w boiler, piping, and uponor manifolds. He has done a few radiant systems over the years but not a viessman. The plumber gave specs to local supply house (supply house guy is designing system) and came back with supply list for system. At first they wanted to do combi unit with dhw option for 3rd floor baseboard. This would involve mixing valve and more mechanical.

My thought was heat only with separate zones for first and second floor with space avail for zone for third floor and basement in future if needed. This would keep the piping very simple with just primary/secondary loop, closely spaced tees, low temp only and simple schematic.

Questions:

1. Which system would work best - low temp radiant only or adding mixing valve for high temp baseboard?
2. Is plumber experience ok if never installed specific brand boiler?
3. 3rd floor option - which to use?
4. Low loss header - part of supply list.
5. Primary/ secondary ok?
6. Boiler choice ok?

Thanks
Mac

Gordy

I assume you did a room by room heat loss. So what water temps are going to supply the radiant portion of the system? Third floor loads? You may not need much heat, but maybe next owner will do it right while doing it.

You can oversize emitters to get water temps lower.

Use the low loss header viessmanns.

The boiler you install is only as good as the persons ability to correctly install, and set it up. With that being said a persons ability to install, and setup a boiler usually plays into their familiarity with a certain brand(s). Viessmann are top notch equipment.

raemac

Thanks for reply Gordy,
yes, i did room by room heat loss. I will add third floor to calculation. Would that add to boiler size?
Water temps at 120 going out.

Still not sure best way to heat third floor. Baseboard or wall heaters or other options?

Gordy

Panel rads.

Yes the boiler is sized to the total heat loss. We're there any envelope upgrades?

hot_rod

Juggle heat emitter types and sizes to get the entire job at one temperature if you can. You should be able to run all that at 120- 130° max.

Another option for a hydrosep, this is a true 4 in 1 device, easily serviced. A lot of Viessmann installers use this Sep4.

jonny88

Gordy I love your info on oversizing emitters to get lower temps.
Worked out beautiful on a job I did with panel rads.
Their are so many boilers to choose from and you will get a different opinion on every one from each installer.Pick a guy who knows his boiler has support and get pics.More about install than boiler these days.

Gordy

Question for the OP. It sounds as though you have already installed the under floor portion of the radiant ?

Most emitters will have output charts at various water temps. Use the charts to properly size the emitter of choice to get you in the radiant supply temp realm.

Save the money on the foil. It does little if anything for rvalue. Even less for reflective properties once crumpled, and dusty.........myth.

Mark Eatherton

What Gordy said. Save the aluminum for more important and worthy things, like containing beer. Or making extruded heat transmission plates. No insulation air gap wanted or required. Keep conductivity as your sole primary heat transfer mode. Avoid convection until it hits the floor. I LOVE my radiant walls...

ME

RobG

Screw fiberglass batts and just use bubble-foil!

RobG

RobG said:

Screw fiberglass batts and just use bubble-foil!

Just kidding!

SWEI

I'm really not a fan of fiberglass batts, but for this application they really are the least expensive option that actually works. Kraft-faced R-13 is amazingly affordable.

njtommy

Here is some low temp baseboard for you.

http://smithsenvironmental.com/products/he2-heating-edge-baseboard/

SWEI

And here is some more
http://www.mysoncomfort.com/static_files/int/media/downloads/Myson-Radiator-Brochure-2015-06-05_Contractor-Series.pdf

raemac

Thanks guys,
They want to use closely spaced tee's instead of low loss header.
I checked viessman mechanical manual and they strongly recommend LLH if flow is higher than 14gpm or on low end. I will be about 8gpm. Any thoughts?

Rich_49

Tell him to use the LLH or a quality sep like Hot Rod posted above or hit the road .

Gordy

Most people can't get away from closely spaced tees. When they look at the cost of LLH they compare it to two tees, and forget about the labor, and everything else a LLH can offer...simplicity,space saving, multi functional, and labor costs.