New user requesting help with radiant plans.

Magnus042

Hello everyone,
I need some (a lot) of help planning my new radiant heating system. I'm in climate zone 5 with an old steam boiler (natural gas) and cast iron radiators currently. I've decided to yank it out and change over to radiant via Uponor joist plates between the floor joists. I'll outline all the information I have available:

-subfloor is 3/4" covered with 3/4" hardwood flooring throughout the house with the exception of the kitchen and bathroom, which are both tiled.

-The joist tracks are 1/2" O2 barrier pex installed 8" O.C. and will have 2 layers of R-15 rockwool insulation underneath for a total of R-30. All pipes are overhead and travel down to the utility room.

-I've created 6 loops total of pex runs, each is less than 300 feet.

-The second floor is 1 bedroom and I ran 1/2" pex to accommodate a panel radiator.

-Domestic hot water is taken care of via an electric heat pump water heater.

-Heat load was calculated using this method:
https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new

- my numbers are as follows after using January temp and fuel data:
28,875 BTU/hr (with a 65°F balance point assumption)
35,265 BTU/hr (with a 60°F balance point assumption)
my 99% outside design temperature is 15°

My plan is to use use two Uponor stainless manifolds one for 4 loops and the 1 panel radiator, and the other for the two tiled loops for a lower water temp.

I've had 3 HVAC contractors out to give estimates and they have all recommended 151-200k boilers! From what I know these are grossly oversized and will short cycle.

I'd like help with boiler sizing, also laying out my system. I've read through all of: https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_19_na.pdf
and I just want to make sure I'm not making any grave piping errors before tackling this job.

I would like to use a ModCon boiler and want to make sure it's condensing and modulating properly.

So, how would you set this system up for best results? Which circulators would you use? What size piping for the primary loop?

I also have some Nest thermostats on hand if they're going to be useful.

I really appreciate any and all help you can give me.

Zman

@Magnus042
You are probably correct that the contractors are overestimating the heat loss. I would recommend performing a room-by-room heat loss to double-check the boiler sizing and help you determine the design water temps and panel rad sizing.

I would recommend designing a one-temp system. Panel radiators will perform well at the lower temps if they are sized correctly. You will spend extra on the radiators, but save money on mixing components and controls.

Ironman

If you have an older house, particularly one with solid brick walls, a radiant floor may not produce sufficient heat in colder weather.

How large is the house and what type of construction?

A Nest thermostat is the absolute worst choice for a radiant floor or a modulating boiler. Use a Honeywell T6100AF or similar that’s designed for radiant floors.

Magnus042

Ironman said:

If you have an older house, particularly one with solid brick walls, a radiant floor may not produce sufficient heat in colder weather.

How large is the house and what type of construction?

A Nest thermostat is the absolute worst choice for a radiant floor or a modulating boiler. Use a Honeywell T6100AF or similar that’s designed for radiant floors.

The house is an older cape cod style home. 2x4 construction with an outer brick wall. The brick is separated from the interior framing with a layer of Gypsum board. The exterior walls have no insulation, but as I renovate room by room, I have been filling the walls with R-15 rockwool. In 2-3 years I’ll have insulated the entire home. 

My first floor square footage is 800 square feet. 

Ironman

If either one of your heat loss numbers is correct, you’re looking at 36-43 btus per square foot. A radiant floor with good heat transfer plates will give you about 20 btus per square foot. No where near enough to heat the house in colder weather.

You can do the floor if you want somewhat better comfort, but you’re gonna need to supplement it.

Magnus042

Could supplementation be done via an extra panel rad in each room?

Magnus042

Zman said:

@Magnus042 You are probably correct that the contractors are overestimating the heat loss. I would recommend performing a room-by-room heat loss to double-check the boiler sizing and help you determine the design water temps and panel rad sizing. I would recommend designing a one-temp system. Panel radiators will perform well at the lower temps if they are sized correctly. You will spend extra on the radiators, but save money on mixing components and controls.

How does one go about using a one temp system while protecting the tile floors? 

My understanding is that the wood floors will require a higher temp than the tile.

leonz

Hello Magnus042,

Take this from a homeowner that wishes he had steam heat instead of the 3/4" fin tube baseboard heat he has AND HATES.

There is no need to make what you are doing so much more complicated and the work so much more expensive when it is not needed.

Upgrading your current heating system will provide you with better heat and more of it and your steam system will work less. I would only do the following things in your situation as it will cost you much less
to do and you will have a faster return on a smaller investment and better heat.

The basic rule is to remember dry steam is huge heating power in a small drop.

One drop of water will expand 1,700+ times to make wet steam, adding a drop header to the twin tappings-or single tapping in your boiler steam chest will increase the speed the dry steam reaches your header pipe, a secondary drop header will let this single drop of wet steam dry even further and travel even
faster to your header pipe hanging in the ceiling joist.

If I remember Dan saying this correctly; the more steam tapping's you have in your steam chest the more steam heat your boiler will make much more quickly.

Growing up we lived over my parents grocery store and we had a very, very, small steam boiler smaller than a rolling typewriter table with wings that heated the apartment in a single pipe heating system without a drop header. We had a warm home and warm floors and we were never cold.

I hated the forced air heating systems in the houses we grew up in after that because of the dust and drafts and it caused my youngest brothers asthma as well as the wheezing I had to live with at times.

If your boiler has two tapping's in the steam chest and only one tapping is used you need to have a new twin tapping pipe set up installed WITH THE CORECT SIZE PIPING along with a drop header of a larger pipe size AND A second drop header of an even larger size with the correct size condensate drain back to the water line of the boiler to increase the speed of the dry steam that will reach the header pipe hung in the basement ceiling joists.

1. have your boilers fire box, flue pipe, chimney clean out emptied and burner cleaned
a. if the chimney does not have an approved chimney cap it should have one installed if allowed with the local plumbing code.

2. have the steam chest cleaned and the mud flushed out
a. make sure the header pipe hung in the ceiling joists of your basement has the correct slope to permit the steam condensate to drain back to the boiler
b. clean or install vents at the end of the header pipe or pipes if they do not have them
c. make sure the radiators are correctly sloped to allow them to drain back to the header pipe

d. install thermostatic regulator valves to allow you to control the heat in each room.

3. clean or replace the pig tail and the steamtrol cleaned or replaced

4. If you have an automatic fill valve cleaned or replaced if needed

5. have a pair of low water cut offs installed as the first electric controls in the steam boiler to protect the boiler from boiler dry and potentially destroying the boiler if water is added back-your steam boiler may not be up to national plumbing code if it does not have one or more low water cut offs.
a. Having two low water cut offs installed before the wiring reaches the steamtrol assures the boiler will be protected if the first low water cut off fails in the event of a water loss.

6. Adding a drop header sized larger than the tapping's to the twin tapping's in your boilers steam chest
and adding a second drop header of a larger pipe size with the condensate drainpipe back to the water line in your steam boiler will make heat faster and

Adding or replacing/cleaning the vents at the end of the header pipes would be the first thing to do as your boiler will make dry steam faster and your radiators will stay hotter much, much longer.

Along with that installing thermostatic radiator valves for each radiator would be done at the same time so you can control the temperature of each room in your home while venting the air out the radiators and allowing the steam to enter the radiator and hold the heat in the radiator much longer.

Having these few items done along with your installing R-15 rock wool will create a warmer home and also reduce your heating bills considerably more providing a much faster payback for your investment.

Having a steam licensed plumber do the work for you will save you a great deal of money and work and the payback will be much quicker than making a mess of your home with ripping out your beautiful steam radiators and installing radiant floor heat as your radiators will heat your home much more efficiently with thermostatic radiator control valves.

A steam radiator is a true heat sink and will suck up the heat in the steam and release it back into the home slowly.

The money you save by updating your steam heating system will give you a much quicker return on your investment let you buy radiator covers (if you do not have them) and cast iron steam kettles to set on each radiator cover to let you add more moisture back into your home in each room.
It will also add more value your home as the boiler will work much less.

I know it is none of my business what you do with your heating system but you simply need a steam licensed plumber to help you with improving your steam heating system and in the end save you so much more money in the long run.

Hire a steam plumber for an hour to look at your heating system and print out what I have written here to show him and I know your going to have a warmer home with warm floors next heating season and use much less fuel.

I hope I have not forgotten anything, but I am sure that my fellow forum members will correct any mistakes I have made in my writing as we only want to help you with your heating system as all you need are basic repairs and upgrades to the steam system plumbing that will bring it up to code and improve your steam heating system that have been proven to work and work well for many years.

I have learned from my diseased fathers past experience with his radiant floors that radiant floors can be very expensive to install and correcting the basic plumbing mistakes made by the manufactured home company that did the work was a massive and expensive undertaking as they did not install the needed radiant plating in the joist spaces to radiate the heat upward into the living space and the pex piping simply became a race track for hot water and my brother had to install foil back foam insulation board to hold the heat in to allow it to radiate upward into the living space.

It was real shame as the new construction with a wide open basement would have allowed for steam heat to be installed with a single header pipe with big mouth vents and the heating system would have been complete with no additional work.

Magnus042

I really appreciate the Steam advise, however, I want it out. Whoever installed it put it smack in the center of my unfinished basement and I desperately want to finish that basement for more living space. My steam pipes hang at head smacking height down there and the power venting on my steam boiler sounds like a jet taking off 10 times a day every winter day. I’ve had enough of it and want to switch to hydronic heating. 

I’ve already installed the aluminum joist track underneath the entirety of the first floor, and will be filling my joist bays with 7 inches of rockwool to force the heat up.

Ironman

Magnus042 said:

Could supplementation be done via an extra panel rad in each room?

Yes, but it needs to be sufficient to provide enough heat.

You really need to do a room by room heat loss calc to get it right.

leonz

Magnus042 said:

I really appreciate the Steam advise, however, I want it out. Whoever installed it put it smack in the center of my unfinished basement and I desperately want to finish that basement for more living space. My steam pipes hang at head smacking height down there and the power venting on my steam boiler sounds like a jet taking off 10 times a day every winter day. I’ve had enough of it and want to switch to hydronic heating. 

I’ve already installed the aluminum joist track underneath the entirety of the first floor, and will be filling my joist bays with 7 inches of rockwool to force the heat up.

=================================================================

There are a few things I would like to ask and add to this;

1. What brand of steam rated boiler is this?

2. Does it have an open fire box with a water wall or walls and a steam chest or does it use fire tubes surrounded by and covered by a deep water blanket and then the air space for steam vapor?

3. When was it cleaned last?

4. does the boiler flue pipe have a barometric damper?? If not it needs one.

5. is the flue pipe from the boilers flue breech to the power venter and to the outside vent same size all the way to the exterior of the home or is the power venter mounted in the exterior wall?

5. is there a manometer with the proper probe located in the firebox or at the flue breech?

The steam boiler you have was centrally located in the basement to simplify the installation of the header pipes to the radiators and there was no thought of using it for living space as the basement was typically used for a coal storage room by a driveway side window used for the coal chute and perhaps a root cellar and basic useable storage.

If the home is older it could very well have had a hand fired octopus coal boiler in it to make steam or a coal stoker.

If the steam boiler is making that much noise it needs to be serviced and the power venter cleaned.

Placing the boiler closer to the chimney will eliminate the need for the power venter. The previous owner did not want to move the boiler closer to the chimney obviously.

A boiler of any kind that is properly insulated and operating correctly should barely make a sound when operating as the noise should be contained within the firebox and you should barely hear a rush of air when you are outside if the chimney is relatively close.

Your power venter needs to be cleaned annually as a rule.

My old 33 year old Buderus Logana G204 boiler barely emitted a sound when running on oil as it was insulated on all sides and the rear around the flue breech as well and the dry bottom of the boiler. The five inch flue pipe was six feet from the chimneys clay flue tile

It sounds as if your basement is ceiling height at the bottom of the framed joist is less than 6 feet in height rather than 7' 6" so it is not that much of a useable living space.

a. The steam boiler can be moved to an area closer to the chimney and you will gain more useable living space in the basement.

If the pipe layout is examined further by a plumber with a steam heating license the header piping could be moved to the exterior walls of the basement using two header pipes and vents and hanging steam radiators could be mounted on the exterior walls after they are insulated or floor mounted radiators could be used with some piping work.

b. it would be worth your while to look at some you tube videos of homeowners that have used refrigerant grade soft copper pipe to run dry steam to thier radiators successfully from a header pipe which could let you run a new header pipe along one wall and the smaller soft copper pipe to each radiator.

By now you are saying to yourself: who are you to be asking all these questions???

I am a concerned homeowner that has been through a long series of bad decisions that were not mine and poor plumbing experiences involving plumbers, well drillers, being without running water for 7 months, dealing with bad realtors, carpenters, etc., over a 43 year period.

It is your money and a capital expense like replacing one heating system with another is not to be taken lightly.

Every time I hear of a steam system being ripped out and replaced with another its most always because the steam system was never taken care "PROPERLY" or the desired use of unscorched forced air used for cooling rather than using basic window mounted room air conditioners for air conditioning comes to mind.

My thoughts on this anyway.

Magnus042

leonz said:

Magnus042 said:

I really appreciate the Steam advise, however, I want it out. Whoever installed it put it smack in the center of my unfinished basement and I desperately want to finish that basement for more living space. My steam pipes hang at head smacking height down there and the power venting on my steam boiler sounds like a jet taking off 10 times a day every winter day. I’ve had enough of it and want to switch to hydronic heating. 

I’ve already installed the aluminum joist track underneath the entirety of the first floor, and will be filling my joist bays with 7 inches of rockwool to force the heat up.

=================================================================

There are a few things I would like to ask and add to this;

1. What brand of steam rated boiler is this?

2. Does it have an open fire box with a water wall or walls and a steam chest or does it use fire tubes surrounded by and covered by a deep water blanket and then the air space for steam vapor?

3. When was it cleaned last?

4. does the boiler flue pipe have a barometric damper?? If not it needs one.

5. is the flue pipe from the boilers flue breech to the power venter and to the outside vent same size all the way to the exterior of the home or is the power venter mounted in the exterior wall?

5. is there a manometer with the proper probe located in the firebox or at the flue breech?

The steam boiler you have was centrally located in the basement to simplify the installation of the header pipes to the radiators and there was no thought of using it for living space as the basement was typically used for a coal storage room by a driveway side window used for the coal chute and perhaps a root cellar and basic useable storage.

If the home is older it could very well have had a hand fired octopus coal boiler in it to make steam or a coal stoker.

If the steam boiler is making that much noise it needs to be serviced and the power venter cleaned.

Placing the boiler closer to the chimney will eliminate the need for the power venter. The previous owner did not want to move the boiler closer to the chimney obviously.

A boiler of any kind that is properly insulated and operating correctly should barely make a sound when operating as the noise should be contained within the firebox and you should barely hear a rush of air when you are outside if the chimney is relatively close.

Your power venter needs to be cleaned annually as a rule.

My old 33 year old Buderus Logana G204 boiler barely emitted a sound when running on oil as it was insulated on all sides and the rear around the flue breech as well and the dry bottom of the boiler. The five inch flue pipe was six feet from the chimneys clay flue tile

It sounds as if your basement is ceiling height at the bottom of the framed joist is less than 6 feet in height rather than 7' 6" so it is not that much of a useable living space.

a. The steam boiler can be moved to an area closer to the chimney and you will gain more useable living space in the basement.

If the pipe layout is examined further by a plumber with a steam heating license the header piping could be moved to the exterior walls of the basement using two header pipes and vents and hanging steam radiators could be mounted on the exterior walls after they are insulated or floor mounted radiators could be used with some piping work.

b. it would be worth your while to look at some you tube videos of homeowners that have used refrigerant grade soft copper pipe to run dry steam to thier radiators successfully from a header pipe which could let you run a new header pipe along one wall and the smaller soft copper pipe to each radiator.

By now you are saying to yourself: who are you to be asking all these questions???

I am a concerned homeowner that has been through a long series of bad decisions that were not mine and poor plumbing experiences involving plumbers, well drillers, being without running water for 7 months, dealing with bad realtors, carpenters, etc., over a 43 year period.

It is your money and a capital expense like replacing one heating system with another is not to be taken lightly.

Every time I hear of a steam system being ripped out and replaced with another its most always because the steam system was never taken care "PROPERLY" or the desired use of unscorched forced air used for cooling rather than using basic window mounted room air conditioners for air conditioning comes to mind.

My thoughts on this anyway.

Thanks again for your steam advice, but its coming out. I have it serviced yearly so its in decent shape, its right next to the chimney but the town forced the previous owner to put in a power vent before i could take ownership of the home. my basement height is 7.5 feet, plenty of space for me to comfortable enjoy a mancave. I have not taken this decision lightly. again i thank you for your advice but id like to stick to discussing my new radiant system. The steam boiler and everything attached to it is being taken to the scrap yard as soon as i can.

leonz

You can sell you radiators to someone who will use them for
steam heating or an architectural salvage yard as they simply
need cleaning.

Magnus042

Anyway, according to the slantfin app and an entire afternoon of measuring and googling, my total heatloss for the radiant in floor portion of my home is 16,697 putting me right at 20 btu per square foot on the first floor. Ill calculate and size the btu for the second floor panel rad separately. Its tricky because the walls are angled and im unsure of the insulation between the panels and the roof.