Radiant Boiler & DHW, Help me pick my best option.

wiscousonian

Hello everyone! New here and my first post. I've got lots to learn and I'm looking for some advice. Were a pretty young family and this is a pretty big investment in our property. I want to make sure I'm making the best possible decision for as many years as possible to come. Lets have a discussion on the options and help walk me through some questions, pretty please!

Background:

I live in a house built in 1957 in southern Wisconsin, 2400 sqft, Radiant in floor copper mixed with some baseboard radiant for areas of additions. 3BR 2.5 BA, Family of 3 (toddler under 1 included). The house is constructed of cinder block, with a insulation gap. LOTS of windows (most of which have been recently updated to new thermo-panes) and a flat roof. My current boiler is a Weil-McLain cast iron which dates nearly 30 years. I've got a standard natural gas water heater for DHW, and a old electric heater that is not being used and is to be removed. My plumbing is a disaster because of what looks like years of patches and bad plumbing. I dont have any heat loss numbers yet (Contractor #4 ran them i just don't have them yet).

The Update:

I'm hoping to update to something that can increase efficiency as well as save space. Updating all plumbing and making it as clean and out of the way as possible. For this reason I've been requesting bids for wall mount units with a DHW ability. Still natural gas fired.

Zones, pumps, and thermostats, and other details aside I'm having a hard time determining my best option. This is especially true for brand reliability, maintenance costs, and indirect vs combi units.

The Options

I've received 3 bids, and I'm waiting on the 4th to come in (its been more than a month and I'm thinking i should just pass on that contractor at this point). Below are my options.

Option 1: Weil McLain 97+ 110 with a 45 gallon indirect tank.

Option 2: HTP Elite FT 110 with 60 gallon Indirect tank

Option 3: IBC Combi Boiler DC33-160. 4GPM DHW delivery

Option 4: This bid has yet to come in, but the contractor works with Viessman 200 or maybe 220, and we had discussed a indirect tank and a modulating pump ( i think that is what it's called?)

I've done some reading about combi units vs an indirect tank, and although the appeal of the combi is enticing, I'm worried about longer term reliability with a unit like this. Ideally I'm looking long term and high quality. Should i be looking at a single modulating pump, or a single pump for each zone?

Can anyone help me?
-Ian

hot_rod

I would steer away from a Combi unit. I have a 120 combi for my wife and I, it is not a crowd pleaser. I'm in SW Missouri with well water around 55° year around.

If you are on a public water systems in WI you will probably be much colder water tempertures in winter months, that needs to be considered when looking at expected delivery with combos or tankless.

A load calc is critical, maybe perform one yourself for some comparison.

I assume the system you have now keeps the home comfortable at design conditions?

Determine how the best emitters match the heat load. Also as important is determining if the heat emitters you have can operate at lower temperatures. For the highest efficiency, you want condensing equipment that can and will modulated down to cover the loads as needed. Outdoor reset will be part of that.

All the brands mentioned are good choices, really the installer is the most important part.

Ask for and call references.

wiscousonian

Bob,
Thanks for the reply...

I kind of felt the same about the combi unit, especially with the more often need to fire for on demand DHW heating. Assuming an indirect tank could potentially need to fire less often while the reserve in the tank gets used up until a specific temperature drop. In theory reducing the strain/use of the boiler a little, as well as a single point of heating vs the proposed combi dual element heating unit with the DHW coil....

The current setup does keep things comfortable, although i do have issues with 2 remote zones, which is caused by poor plumbing and actual flow rates through the baseboards setup now AND the fact that one thermostat is controlling both zones, located at opposite ends of the house. We have no reason to believe that an update to the plumbing, including another pump and thermostat to split each zone independently wont solve our issues. That along with the water temp actually going to baseboards being lower than ideal, and update should go a long way to making things more predictable in each of the 3 Zones.

hot rod said:

Determine how the best emitters match the heat load. Also as important is determining if the heat emitters you have can operate at lower temperatures. For the highest efficiency, you want condensing equipment that can and will modulated down to cover the loads as needed. Outdoor reset will be part of that.

Can you explain what your talking about here a little more? If i'm reading correctly your saying to look into each boiler to match my heat load, as well as the temperature rise of my winter water temps? I'm really not sure how i can calculate my heat load accurately, that's why i was hoping for contractor #4 to come in with some numbers. He measured, asked questions and looked through the whole house in what I'm assuming was an attempt to calculate my heat load. Even he said he'd try the best he could to be accurate. I'm assuming that's because of my individual house and setup? (cinder block walls inside and out, flat roof, 70 windows, cement floors, etc...)

4Johnpipe

Not be be a party pooper...We have dealt with copper radiant in "slab" floors here. They are destined for disaster. The concrete will eventually deteriorate the copper. Is your home on slab or do you have a basement / crawl space?

wiscousonian

4Johnpipe,
Unfortunately i get it... it's the problem of the era and how it was made at the time (1957). Short of waiting for my 30 year boiler to die and leave me stranded in the winter i'm not sure what else i can do.

No basement, on slab....

hot_rod

Probably you have little to any insulation under the slab if it was installed in 1957? So that will be a fuel hog. You may look into other options for heating like panel rads, but that slab will be a cold surface to live on once the radiant is gone.

Retrofitting any hydronic system to a slab on grade can be a challenge. Either attic piping or boxing in some chases.

I agree with John that it is not a matter of IF that copper in the slab will fail, but when. It might pay to come up with a plan B for heating.

Does the home have AC of any sorts? A ducted system maybe?

wiscousonian

Bob,
I have all the original plans for the construction so i can look, but i think your right... i doubt the slab is insulated. As it is now, it's working great and is very enjoyable. I'm not sure i have many other options... No attic or even crawl space of any kind.

No A/C either, but the slab and a fine tuned sense of the weather and open windows keeps the house plenty cool for the majority of the summer except for a week or so every summer with extended high heat periods.

I agree that the slab in floor will fail at some point, but who knows when? I really am failing to see what my other options are.

4Johnpipe

Darn! I would seriously, seriously consider the life of the in slab tube...New Pex can be run to the ceiling, walls or possibly over the existing floor with minimal ceiling height loss if that is an issue. I hope that this possibility was discussed with at least one of the contractors that looked at the job?
I have been called in to jobs that leaked right after new equipment installed by others. The copper gets so thin it gets displaced when purging the system. Then begins the decline of the new equipment. It picks up the concrete by products into the water and destroys itself from the inside out.
This is one case where I would not rush to change equipment without first having a major discussion with the inevitable situation...

Gordy

Not to give to much hope however my home was built in 52, and my copper in the basement slab is still fine. So there is 5 years of hope. A lot depends on the concrete mix design. High content fly ash being the culprit. Also soils of high cinder content if the copper is not fully embedded in the concrete.

Gordy

Also chances are in your area your slab sits on sand which is a better insulator so long as it's dry than clay, or other soils.

wiscousonian

Ok so i quickly looked at the original plans... the 4" floor slab is reinforced and has a 1" perimeter insulation.

Additionally:
"Piping: Complete copper-piping system for floor panel shall be of dimension shown in drawing by H. A. Thrust Co. and shall be copper-piping as manufactured by "Chase" co. or approved equal"

"Base Board: Furnish and install low-silhouette C.I. baseboard with necessary air vents as indicated"

"Soldering. Soldered fittings shall be used to join tubes. Soldering shall be 95% tin and 5% antimony, or equal. Use non-corrosive flux"

"Testing: The entire piping system shall be pressure tested with a water pressure of 200 pounds per sq. in. for at least 6 hours, make careful inspection of joints"

"Boiler: Furnish and install hot-water boiler "kewaunee" GW-3U (or approved equal) gasfired, output 10800 BTU, in conjunction with domestic hot water storage tank, with wiring for one circular, complete unit"

I Also have complete plans of the heating system... details that i can see are:

"All floor coils to be 1/2" I.D. copper tubing placed 6" on centers. Maximum length for any coil 200'"

"Installed radiation: 95,000 aprox. BTU's (this is minus the additions that have the baseboard heat)."

Updated details about the perimeter boarder, 1" insulation inset into interior 24" wide with a vapor barrier on top. set 2" below surface of floor. Gravel below (no cinders) System designed for an average water temp of 130 degrees.

Gordy

Nice design for the period. 6" on center nice.

rick in Alaska

I don't know how much it would affect the heat transfer, or the head pressures, but you might look in to the companies that do relining of pipes. They pump an epoxy coating through the lines, which should give you much longer life.
It would be nicer if the pipes had been 3/4 instead of the 1/2 inch though just to have more room inside.
Rick

wiscousonian

So it sounds like everyone advises against an update to the heating system instead holding out on what i have now until it fails?

hot_rod

wiscousonian said:

Ok so i quickly looked at the original plans... the 4" floor slab is reinforced and has a 1" perimeter insulation.

Additionally:
"Piping: Complete copper-piping system for floor panel shall be of dimension shown in drawing by H. A. Thrust Co. and shall be copper-piping as manufactured by "Chase" co. or approved equal"

"Base Board: Furnish and install low-silhouette C.I. baseboard with necessary air vents as indicated"

"Soldering. Soldered fittings shall be used to join tubes. Soldering shall be 95% tin and 5% antimony, or equal. Use non-corrosive flux"

"Testing: The entire piping system shall be pressure tested with a water pressure of 200 pounds per sq. in. for at least 6 hours, make careful inspection of joints"

"Boiler: Furnish and install hot-water boiler "kewaunee" GW-3U (or approved equal) gasfired, output 10800 BTU, in conjunction with domestic hot water storage tank, with wiring for one circular, complete unit"

I Also have complete plans of the heating system... details that i can see are:

"All floor coils to be 1/2" I.D. copper tubing placed 6" on centers. Maximum length for any coil 200'"

"Installed radiation: 95,000 aprox. BTU's (this is minus the additions that have the baseboard heat)."

Updated details about the perimeter boarder, 1" insulation inset into interior 24" wide with a vapor barrier on top. set 2" below surface of floor. Gravel below (no cinders) System designed for an average water temp of 130 degrees.

Any other homes in the area built with the same systems? Often times a builder or architect spreads a bunch of the same systems around an area.
There are so many variables to the life expectancy. If the tube is completely encased in the slab, and it stays dry, it could have many more years. It is usually wet areas and exposed tube that cause failures. Hows the drainage around the home? Does all the roof and in water drains away quickly?

Do you have access to a manifold that you could isolate a failed loop if need be? With 6" spacing and loops 200', you should have a number of loops, maybe several manifold locations.

All of these play into your decision to keep going with the radiant slab, or consider options.

SWEI

Don't forget the local water quality, most especially pH.

Alan (California Radiant) Forbes

If that were my house, I would gamble and stay with the existing radiant distribution system and update the boiler and indirect. I have many old radiant systems on my route and even when people start having leaks, they find, expose and fix the leak. Any other system will not be as comfortable and they don't want to give that up.

wiscousonian

Based on the plans there is a waterproof membrane installed above the gravel and below the tubing & Insulation so it should help to keep things dry.

Drainage is good... there are a few areas that do not drain as well, but this is an area that does not have in-floor radiant.

I do have access to the manifold, and the plans for the system should really help if i ever do have issues. I should be able to either find the loop or have plans to the areas and route the plumbing takes.

So stepping back to the initial question, what should i know to select a unit & installer?

Gordy

Did any contractor do a detailed heat loss?

I would use option 1 with elite ft.
Or option 4 which you may find pricey when it comes in.

Two boilers not listed I would give a hard look at would be the htp UFT. Since one installer seems familiar with htp. 10:1 turn down.

Another is the Lochinvar KHN series. Another 10:1 turndown.

With 6" centers on the slab I would be inclined to get the water temps down. Once a outdoor reset control strategy is implemented which comes with any of those boilers. Your water temps can be lowered quite a bit. What makes a mod/con really sip the fuel is getting return temps as low as possible.

hot_rod

You may need a two temperature system with that cast iron baseboard.

This is where a true hydronic pro come in. With a load calc and review of the heat emitter, he would come up with a plan for supply temperatures required, zoning, equipment selection and more. All of this is important to get the system and efficiencies you want.

Gordy

Your installer should do a radiation survey on your higher temp base board emitters. Usually it ends up being ample baseboard to utilize lower supply temps. This comes to light either by ample emitter being installed originally, and or envelope improvements which in turn now make the emitter to large. A good thing because then lower water temps can be used.

Either way you utilize ODR because you do not need the same supply temp at -10 as you do at say 20-30 degrees.

Just so you understand mod/cons. If you can get the return below 130 most of the time it will condense, and be more efficient. You will not get advertised efficiencies until your in the low 90's high 80's return water temps.

wiscousonian

THanks for the help guys,

I connect with #2 and ask about the htp UFT. This contractor also just mentioned that they have started installing IBC's also but that htp UFT looks pretty nice.

I'm also having contractor 3 quote another unit thats not a combi with an indirect tank. Should hear back next week.

TO answer a few other questions:
No detailed heat loss was done, Contractor 4 did some work but i still have yet to hear from them with an estimate. It's not saying much about their services to be honest.

I dont have cast iron baseboard, just copper. BUT you are correct i should aim for lower temps in floor, and higher baseboard temps. I'm guessing that this can easily be managed by the zone pumps and the water temps. THanks for the details on this.

I agree a ODR should really help.

hot_rod

I think you have an idea now of how the process should go. The load calc is easy to perform and should be done.

Every installer will have a different idea how to pipe and control the system.

Another option is the Lochinvar, some models offer 3 temperature control, along with ODR for those, built into their control.

If you do determine that two temperatures are required, that is a nice feature.

With copper 6" OC in a slab, you should, and want to run low supply temperatures, possibly below 100° Floor covering will also dictate supply temperature. Carpet and pad for example need higher supply temperature than bare concrete, tile, etc.

The fin tube zone will need higher temperature than that, probably.

Only the numbers can help you make the best decision.