Input assistance needed for design

Tarponstalker

At the time of construction back in 2006, I laid pex tubing on 12” centers throughout my entire basement floor with the intent of eventually installing a boiler for radiant heat.  There are 2 loops in the garage(to keep total loop lengths less than 300’- 2 @ 200’), a bathroom zone, a foyer zone, 2 loops in a rec room similar to garage, and a zone for each bedroom. The loops to the bedrooms are terminated at their own junction box just outside the bedrooms and would need to be feed with a supply and return line from the boiler closet via the drop ceiling cavity. All other loops come up through floor in boiler closet. 

The house is located in Delaware County, NY.  The basement floor is 4000 psi concrete with added fiber for strength. The pex is tied down to wire mesh in concrete and there is plastic sheeting and 1” thick insulation foam under the concrete. 

The loops were run to distribution bars that were pressurized to 6-10psi 15 years ago. The gauges still read this amount and I haven’t done anything with the radiant heat since pouring slab, but I’m ready to add a boiler. 

I have a closet in the basement that is 38” wide, around 10’ long, with about 12’ of ceiling height. The boiler could go on either end of the closet. The loops run up through the floor mid closet about 12” off back wall, with the exception of the two bedroom loops 30’ away.

The basement was built using an ARXX wall system. Kind of like foam LEGO blocks with 2” of foam on each side, and 8” of reinforced vertical concrete within the foam walls. The interior basement is finished in Sheetrock, and has a 9’ drop ceiling throughout with coffer lighting. The entire exterior basement is covered with half-inch textured hardy board. There are HI-E argon filled Andersen casement windows in the walls throughout the basement. Overall dimensions of the basement is 78’x28’. Two 14’x14’ bedrooms on one end with low pile carpet, an L shaped garage on the other end with existing concrete. The bathroom is approximately 10’x12’ with linoleum. The foyer is 12’x12’ with linoleum over concrete. And the rec room makes up the rest of square footage with a laminate floor. Again, all rooms 9’ high with 2’x2’ drop ceiling tiles. 

Regarding boiler, I’m not sure what to get nor do I know much about the different brands. My entire upstairs is heated by an oil fired forced hot air furnace. I have an existing 500 gallon above ground oil tank that I put kerosene in because it’s outdoors for the winter time and I use about a half tank throughout the winter. The entire downstairs is heated by electric radiant baseboard heat at the moment and for the last 15 years.

I’d like to be able to put a direct vent boiler in this 3 x 10 closet I have downstairs. It’s going to be a pain to drill a hole through the existing wall, but there’s plenty of space above the drop ceiling because the basement walls are actually 13 feet high. I currently have a propane stove supplied by a 100 gallon propane tank just outside the basement walls, but I’m considering getting rid of it and going with an electric stove because it just doesn’t heat water or heat the oven quick enough with propane. I can usually get two years or more out of 100 gallon propane tank just using it for the stove/oven. But I would consider getting larger propane tanks if a propane boiler was recommended. Just not sure what size propane tank/s. I would have to fill the tanks in the Fall and be sure the amount of propane would last until at least March as our driveway is 1000’ uphill as it pertains to propane delivery. 

So I suppose question #1 is what type of boiler would you recommend considering my layout and scope of work. I think a direct vent system would probably be the easiest and very efficient. There is a wraparound deck going around the entire house separating the basement from the upper level so the direct vent would be just underneath the deck, however I don’t see that being a problem at all. We never open the basement windows. Ever. But, there is a chase just above the intended boiler closet in a bedroom upstairs that I could penetrate through the roof for a traditional double wall b-vent chimney if need be. There is no access to the attic at this time as this is a modular home. I believe there’s 18 inches of insulation just above the ceiling on the second floor into the attic and I’ve never been up there nor have seen it. But there is a 2’ x 2’ jog in the bedroom just above this boiler closet downstairs that I could utilize to run a chimney pipe if necessary.

The house is very well insulated downstairs and there is a set of stairs going up with a stairwell to a door that I usually leave open so the heat can go upstairs to keep everything from freezing in the event I have a problem with the oil furnace upstairs. I ran out of oil one year. I usually set the upper heat at 50 with the hot air furnace and I set the electric baseboard heat downstairs to 45 when the home is not in use in the winter. There is usually activity at the home at least monthly as this is a vacation home. And I’ve never had a problem in 15 years. The basement is like a meat locker in the summer often 20° cooler then outdoors during the summer. The walls are very well insulated.

I have a plumber friend and a furnace friend that would help me set up everything with some simple instruction and pointers. However, neither have done a radiant system.  Basically at this point I’m looking to see what size boiler I should get, how it should be fueled whether by propane or oil, and how to set up the zone valves and circulators etc. Any input would be greatly appreciated. Thanks guys. Looking forward to any constructive input.

I can send pictures and a layout of the basement if necessary the next time I go to the home.

Ironman

Have you done a Manual J heat loss calculation? That’s the FIRST step and the FOUNDATION for sizing and designing everything.

Tarponstalker

Negative. Can you provide a link or some direction as to where I might find that? I can probably have my buddy who is an HVAC guy who is going to help me with this do a loss calculation

Alan (California Radiant) Forbes

I have a plumber friend and a furnace friend that would help me set up everything with some simple instruction and pointers.

A recipe for disaster.

Boiler selection, fuel choices, distribution piping, zoning decisions.............. In your case, they all require the input of someone with experience - on site - as there is nothing simple about what you are about to undertake.

Have you tried finding a radiant contractor in your area?

Alan (California Radiant) Forbes

There's a "Find A Contractor" link at the top left of the page. I'd also go to a local plumbing and heating supply house to see if they can recommend someone. Local architect or builder may have some recommendations. Neighbors? Online: Yelp!, NextDoor.

The heat loss calculation from your HVAC guy is a great place to start!

Tarponstalker

As I assumed, the nearest “contractor” is over 125 miles away. The property is in very rural upstate NY. And I live 225 miles from this home.  I thought I’d give this forum a whirl for input. And I certainly do not want to over complicate things. I’m a civil engineer, and have a very good grasp on understanding general system operations. I certainly don’t mind over-specing the boiler, but I’m more concerned with input regarding oil vs. propane. And I should mention that I may wish to add a ceiling hung fan operated radiant heat unit, along with the pex under the floor while I’m up there for more than a week. 

Also, I mentioned I have a wraparound deck along the entire upper floor. I will be closing in a 28’x20’ section of this deck where I have French Doors off the kitchen on one end of the home. The entire understructure is open with 2 x 12 joists on the deck. And I could easily run pex in these cavities and then insulate and cover with AZEK or plywood. This room is going to be an outdoor kitchen with sliding glass doors that could open up during the Summer. We want to maintain the view from this room with mostly glass. 

That said....I need a boiler that can handle future zones anyway, however these things aren’t even built yet. They are just ideas. So any heat loss calculation I do, or try to do, is merely guessing. 

But any input on kerosene vs gas would greatly be appreciated. As well as considerations from my original post, and then considering these additional futures. 

Thank you

pecmsg

You start by sizing the boiler to what's there NOW, not what the future holds.
Any new construction is going to be very tight and need a small percentage of what there. If that many more BTU's are needed then there are other options.

Ill add being that far from a contractor is a major issue. What do you do "WHEN" something breaks or fails?

PerryHolzman

I'm one of the homeowners who posts on this forum - mainly about my specific boiler and some things I know as an engineer who has spent their life working in power plants.

It sounds like you did some great planning in advance.

But, at this point you need a professional to take over. How much is your heat loss. Did you use the right spacing on your tubing layout - or are you going to have to run a higher than normal temperature to make it work. Which type of boiler is best for your situation (regardless of fuel type), what kinds of controls, manifolds, pumps, etc. are you going to need to make it work well, who is going to service it long term, etc.

There are a lot of "Heating Contractors", plumbers, etc. that work in the industry that really don't know or are unwilling to do what they know is actually right on how to build and set-up a system. This forum deals with homeowners stuck with those systems all the time. I assure you - that you don't want to become one of those homeowners.

There are other Heating Professionals who are truly knowledgeable and will get you a system that works up front which is long term reliable.

I'd recommend that you start by looking for contractors listed on this site that work - or are willing to work - in your area. Then search for postings where they are mentioned in this site; and read a series of posts to determine if they sound like the kind of expert you want.

I'd love to say that you could just use a local heating contractor. They may or may not do a good job for you.

I wish you well with this,

Perry

Tarponstalker

pecmsg said:

You start by sizing the boiler to what's there NOW, not what the future holds. Any new construction is going to be very tight and need a small percentage of what there. If that many more BTU's are needed then there are other options. Ill add being that far from a contractor is a major issue. What do you do "WHEN" something breaks or fails?

Go back to Plan A until I can correct it. Plan A being existing electric baseboard. I am doing this improvement because I installed pex throughout the whole floor 15 years ago. I’m just getting around to, hopefully, installing a more comfortable and efficient method of heat.

PerryHolzman

Did you install oxygen barrier pex? If not, you will likely need more expensive components to prevent degradation.

Rich_49

What currentlt provides your domestic hot water ?

Tarponstalker

Electric. I have a 50 gallon electric upstairs and a 50 gallon electric downstairs. Don’t forget it’s a vacation home and I turn them off when not in use. My electric bill during the warmer months is never over $40 a month. The electric heat downstairs is where I get hit from September through early May. And I’ve never had one over $350/month. I’d actually like to heat my garage so that it doesn’t freeze and I can work in there on equipment in the winter. Currently I’m using patio heaters but a nice warm floor heated by the previously installed pex is what I would be looking for. But while I’m at it, I figured I could eat the whole downstairs since all loops are already in place. Just have never been used in 15 years

Tarponstalker

PerryHolzman said:

Did you install oxygen barrier pex? If not, you will likely need more expensive components to prevent degradation.

I have no idea. It was 15 years ago so whatever the product was at that particular time. One of my friends who is a plumber who did all the Tyann’s for the modular above suggested putting radiant heat in prior to pouring the floor for a future use. I don’t even think he would know. What I can tell you is it still holding pressure from 15 years ago

pecmsg

Tarponstalker said:

pecmsg said:

You start by sizing the boiler to what's there NOW, not what the future holds.
Any new construction is going to be very tight and need a small percentage of what there. If that many more BTU's are needed then there are other options.

Ill add being that far from a contractor is a major issue. What do you do "WHEN" something breaks or fails?

Go back to Plan A until I can correct it. Plan A being existing electric baseboard. I am doing this improvement because I installed pex throughout the whole floor 15 years ago. I’m just getting around to, hopefully, installing a more comfortable and efficient method of heat.



That works when your there, what happens when your not? Yes it can be done, auto switchover to electric but you'll need a great controls guy.

TAG

Getting a heat load done should not be very hard .... Pay someone (that's what I do). Then you need to map out what you have in each space and see what each needs -- being a slab and decent construction -- the PEX will deliver enough BTU's. I would also check to see what you are getting (BUT) from each of the current sources (oil and electric). That will give you an idea as well.

There are small Japanese designed oil fired boilers around -- Toyotomi. I have only seen one used .... Since you already have oil that may be the way to go.

See if you can read the name on the PEX

I don't see the issue ... map it out and get the manifolds. Use large enough pipe to connect up the remote manifold. I'm sure you will have to do a proper primary/ secondary ... maybe a Low loss header with the amount of radiant you need. My guess is the load will be lower then any boiler out there ....


My current project is 5000sf and the smallest Viessmann is too big;

PerryHolzman

Please keep in mind that all mod/cons have turn-down ratios. The boiler are rated maximum rating, and list a turn-down range. Ideally you want a boiler that the lowest turn-down output for continuous operation will meet your heat load at the worst winter weather. Other times the boiler cycles on and off. Adding a surge tank may reduce cycling (how big..??).

The main boiler ratings are often presented as heat input numbers. You are looking for the output heat numbers: NET AHRI Rating

An example is that a Vitodens 200 W model 94 has an NET AHRI Rating (the heat output) of 77, and a turndown ratio of 6.5. Thus its minimum constant output is 11.85 MBH (Millions of BTUs per Hour). Note that the Flyer rounds this up to 12 MBH in its summary subtitle claim.

I find it hard to believe that a 5000 square foot home would use less than that in the coldest winter days.

Perry

TAG

Why would you want to design so the boiler firing on the lowest output on the coldest day -- you want the boiler to be putting out all it can on the coldest day. That is the design load ... in my neck of the woods it may happen a few times a decade ... but it can happen and has for a few days. The rest of the time you need the modulation. A 5000sf spray foamed house can easily be heated with less than 60k on the cold design day.

PerryHolzman

I believe that you misunderstood my intent: IF you are using a mod/con boiler you want a boiler that will operate within its range for at least the coldest day of the year - and hopefully more than that.

You also misunderstand sizing of boilers. I suspect that the Vitodens 200 model 9, or similar models from other mfrs, is actually not to big for your house.

First off the heat load you calculate is not exactly accurate. It's likely off by at least 10%, and possibly 20%. So you want a boiler that has the capability to provide 120% of your calculated heat loss (Other people will give you slightly different numbers; but the concept is the same).

Second; mod/con boilers are most efficient at partial loads - and not full loads (if you decide to go with a mod/con). So, if you are looking for efficiency - you need to just be in the range of the boiler. A normal non-condensing boiler fires only at 100% and will cycle a lot more for most of the year. My boiler (the predecessor to the current smallest Vitodens 200 W has more capacity and less turn down ratio with a minimum output of 22 MBH due to changes in the burner and control technology over the last 18 years (it actually has the same design and size and heat exchanger as the smallest Vitodens 200 W).

Boilers tend to have minimum sizes; and its likely that if you really have a very well insulated and air sealed house that virtually every boiler will have more capacity than you need. The market for very small boilers is small and its often not considered worthwhile to develop and market a smaller variant than one with a decent turn-down ratio (the boiler will not cost much less).

Extra boiler capacity also helps for Domestic Hot Water - which often requires a higher capacity boiler than the heating load for much of the year.

Please do a proper heat loss, and consider domestic hot water (or perhaps a hot tube tank); and then see what heat load you need after accounting for potential error.

Anyway - I wish you the best with this.

If I were to do it again with the current boilers on the market though, I'd currently go with a Viessmann Vitocrossal 300 CU3A; which was not available in 2006 when I put a Vitoden WB2 6-24 in my house (the 1st generation Vitoden boiler).

Perry

TAG

Manufacturers seem to be listening to the market -- smaller output boilers and modulating furnaces have been coming out. My boilers output is above my projected heat loss -- not by much. Looking over efficiency ratings I don't see breakdowns regarding efficiency at different fire rates. Return water temp is important -- but, at design the BTU are going to the house and the return is cold enough. In PA we get a wide range of temps .. on my new build there are many times when I need to 12k output .... otherwise it's on/off ... how is that better? DHW needs to be factored .... how fast the tank will recover and how mush draw will occur at any one time. A typical 40 gallon tank is only around 26k at 80% .. so even a 60k boiler is 2x that delivery

The OP has the problem of adding to a heat source -- the current system being oil and he is remote location. He could use an oil boiler and do a fan coil and indirects ...or keep the furnace and still use oil. Or go Propene for the new radiant w/ wall boiler.

The Viessmann 300 looks like a great replacement for high mass systems or mixed systems where you need higher temp .... for all radiant I don't see the benefit ...maybe someone can chime in. I have always had a winter weekend place and it's always a challenge to save some $$ when not there but have comfort when you are.

hot_rod

Certainly I would not oversize on purpose, but a large BTU boiler at low return and low firing is most efficient. You are exposing a lot of HX surface to a small flame so plenty of condensation surface area.

That is a benefit of a combi boiler, they size for the DHW load, are often oversized for heating, but the low turndown maximizes that HX. Viessmann talks about that concept in their boiler efficiency seminars.
A 150K combi for example could provide 3 gpm or more dhw, with a 10-1 turndown you have a 15K heating boiler.

TAG

HR -- That's interesting ... so the question becomes. Why make small boilers? What's the efficiency with a 60k boiler at design w/ 140 output and 120 return water? I guess the other items would be --- If design is 60k. How many steps will the 60k boiler have vs the 150 at 15/30/45/60 .. and does it really matter that much?

Jon_blaney

What is your goal with this project? Is it to lower cost, improve comfort, or save the environment? All of these factors can effect equipment/system choice.

hot_rod

TAG said:

HR -- That's interesting ... so the question becomes. Why make small boilers? What's the efficiency with a 60k boiler at design w/ 140 output and 120 return water? I guess the other items would be --- If design is 60k. How many steps will the 60k boiler have vs the 150 at 15/30/45/60 .. and does it really matter that much?

Here is a good Coffee with Caleffi that Jody presented in regards to efficiency that better explains the concept. Jody went back to Viessmann shortly after this, same materials regardless. It's had 10,000 views, must be a topic that generates interest.

https://www.youtube.com/watch?v=6mNECDHgDrg&list=PLuuV0ELkYb5VE0I4evUZ30b5U78CRlRdg&index=30&t=7s

Tarponstalker

Jon_blaney said:

What is your goal with this project? Is it to lower cost, improve comfort, or save the environment? All of these factors can effect equipment/system choice.

My intent is to lower cost because the downstairs is currently heated by electric baseboard heat. And it works great. But since I have pex in the floor already, I figured I might as well install a boiler in this vacant closet I have and get the benefit of comfort as well. I always have the electric baseboard as a back up. If I go to the house, upon arrival it’s 45° in the winter as this is where I set my thermostats. If I turn up my two thermostats in the rec room, within a half hour the room has met temperature and the electric baseboards maintain the heat no problem. My primary objective right now is to get heat in the garage where I have pex underneath as well as in the bathroom downstairs where I’m using an electric oil filled Delonghi. Both bedrooms have electric baseboard heat as well, and it works perfectly. But I also have packs under the floor there as well so I’m figuring why don’t I just use it.

Jon_blaney

A vacation house has challanges that a normal residence does not have. Under floor heat is going to be slow to raise the temperature to a comfortable level. Significant set backs are generally discouraged. I think it is inconsistent with a vacation house. I would look to replace the electric heat with some kind of hydronic heat maybe baseboard, radiators or the like. This will respond faster. Get a hydronic space heater for the garage, a fancoil type unit. You can turn that on or off as needed. I would install a conventional low mass boiler with buffer tank. You need a lot of btus to make the jump from 55 to 70 and then you are over sized. The buffer tank will help with that. You might think about a high output water heater. For fuel I suspect oil is the most economical. This simplifies your systems. Pare down to oil and electric. You could replace the furnaces in the future with air handlers.