Converting back to Hot Water Radiant

[triguy128]

So I've been doing a ton of research and am leaning towards making a move to go back to radiant heating, at least for my downstairs. I'm thinking of mixed system with the following:

1) Navien Combi boiler cascaded to existing Navien tankless water heater. We actually have found situation where we're hit about a 5 gpm "limit" with current cold incomming winter water temps. So a little more hot water capacity wouldn't be bad either. You can also common vent it. I want to reroute the vents up the center chimney so eliminate all vents on the side of the house, and then install a electric fireplace for occassional use and more for ambiance. Going up the center chimeny requires routing the pipes through the existing out of service masonry fireplace. The adjacent chimeny have "kinks" that make relining or venting up then challenging.
2) Place the 2 radiators in Living room back in service
3) Place the 2 radaitors in the dining room bak in service
4) Place the radiator in the semi heated garage back in service
5) Install a floor mount fan coil in the basement and close off all but 2 very small registers.
6) Install a small unit heater in the garage.
7) Possibly install a wall mount radiator in the river room


I'm still debating about using a heat pump at least for mild weather and to heat the kitchen forced air zone, where radiators stuggle to control heating as evenly. I also have low time of use rates. The heat pump can also run together with the radiators for recovery from setbacks.

I haven't quite sorted out the best way to do the controls. I'm thinking using a zone cotnrol panel for the forced air, then use a hydronic zone panel for the boiler with the forced air as 1 zone, the radiators as a 2nd zone with TRV on each pair of radiators (pipe in series) since i have plenty of EDR, it will save a little costs and increase the temp drop a little. The hydronci coils con air handler, fan coil and unit heater, I may pipe in series with the radiator return to lower their capacity and increase temp drop. With a mod con, the name of the game is low overall temps and large delta T since the primary has a limited flow. You can't get more than 50k btu out of most condensing boilers without a delta T over 20F.


Future Options:
1) Radiant floor heat in kitchen when we replace the laminate floor and most likely go with tile.
2) Snow melt system when we replace our driveway and eventually front walks.
3) Place upstairs radiator in a sunroom type space, back in service.
4) Radiant floor heat in finished basement (if we ever finish part of it)
5) heat exchanger for hot tub heating... if we even install a hot tub. Had one at our last house , didn;t use it a lot in part due to less privacy than now... but as we get older will likely want one again.

Any opinons? Am I crazy... this might cost a fortune or not be too bad. I think it's bar far the best solution for comfort and flexibility. Hydronics open all sorts of doors for furture energy sources using indirect tanks... such as solar, wood, water to water geothermal.

[csnyder]

Hydronics certainly offer a lot of options (and a lot of expense). The forums at heatinghelp.com have a lot of knowledgeable people - that'd be a good place to learn more.

[triguy128]

I think I have it all designed including circuit lengths and size, pressure drops, pump sizes and models. Now to make a "shopping list" and see what the parts will cost, then talk to my plumber and get a feeling on the time/cost ot install it.

I'll do all the controls and wiring myself. Really with this much piping, it might be worth getting a PEX tool and tackling it all myself and just pick away at it. I probably won't buy the boiler or airhandler/AC system until October. So I could get all the piping and manifolds installed between now and then.

Actually if I install service valves on the manifolds, I could "Test" it with just hot domestic water from my tankless without a pump and take that opportunity to flush it with hot water and see how well it heats, then add chemicals ot clean the boiler. Let it circulate on just water for a while to clean things up too.

[csnyder]

I'd definitely recommend getting a PEX tool - from what I've heard, it's not too hard to do, and doing it yourself would pay for the cost of the tool many times over.

I'm uneasy with the idea of connecting the water heater to the radiant system, even for testing - connecting potable and non-potable systems without proper safeguards (backflow preventer, at the least) is never a good idea.

[triguy128]

Well, I'm at $5800 in just parts and materials including controls and zone dampers and zone controller for the forced air side. Add about $7k for air handler and heat pump with hydronic coil. I could put in a furnace and heat pump for about $7500.

What do I get?

1) Radiant heat
2) More hot water capacity for mid winter. 5.5GPM with the cold, cold inlet water temps is it in winter. That's a lot, but 2 showers at once +1 facuet and you'r short. 1 soaking tube takes all of that flow.
3) The old house "charactor" of having huge cast iron radiators back in service pumping out heat.
4) More heat for the garage, making it truely heated actively. I should be able to maintain 60-65F all winter. It's 50-55F right now, which isn't bad at all.
5) More heat in the basement
6) Our dining room won't be under condtioned all the time. In winter you have ot open all the doors and turn on all the lights to get it warm.
7) zone controls so no hot kitchen when cooking, not hot or cold dining room.
One really cool heating system.
9) during a power outage, I only need about 200 Watts to heat the downstairs, except the kitchen and provide hot water. Less if the combi will run without power to the "slave" tankless.

[csnyder]

I can't analyze your financial situation, but I'd say that it's worth it. With my limited experience with hydronics (our system is a single zone plus the combi DHW), I've been impressed with the possibilities. Water is a much better than air for moving heat around. The comfort of hydronic cast iron radiators on an outdoor-reset system is also hard to beat.

One suggestion I've learned after seeing our installation, as well as our neighbor's: Valve the hell out of it. Wherever you think you might need to shut off or reduce the flow at any future date, install a valve; this applies to both the supply and return lines.

For our neighbor's house (completely new installation, replacing a rotted-out steam system), he ran all of his PEX piping off of a manifold with individual valves; therefore, if he needs to drain a radiator, he can do that without having to drain any of the rest of the system.

For our system (kept almost all of the piping from the original gravity hydronic system), the plumbers installed valves on each supply and return pipe right before they connect into the main loop. They also replaced almost all of the valves at the radiators. Since each branch of the system does 3-5 radiators, I can drain part of the system when I need to move a radiator. This came in handy recently, as we're painting a room. One thing I learned: the radiator valves are not useful for completely shutting off the flow; the brand new valve leaked a trickle when closed, so I had to take it off and cap the supply pipe like I did the return. The radiator valves are still useful for reducing the flow to throttle back an over-producing radiator.

[triguy128]

So I took a step back and rethoguht what I was trying to accomplish. One beauty of radaitors is using TRV's for zone control. So I priced out some new wall panel radiators for the 2 rooms and center hall without a radiator. So I dumped all the zone controls, hydronic coil, forced air zoning and home run piping and specd a parallel reverse return setup that would basically run the perimeter of the basement/garage.

For the new radiators, the Myson T6 had excellent heat output, long length and slim profile along with a couple Myson Select series which hit a nice price point. I'd still kept the primary secondary loop design sicne flows on the heating loop would be around 7-8GPM depending on water temp/delta T. With only 140F water a 20F delta T probably isn't realistic. More likely is closer to 15F. I'd use a Grufundos Alpha Circulator on a constant pressure mode. I'll have to size the loop piping to keep the head under 10ft at full flow. Plus the primary pump is only 5GPM fixed speed, so to get more than 50k BTU, I need more than 20F delta T on the primary. SO that means a secondary with closely spaced T's. (I've been reading a LOT )

So that gets my total price down to around $4800 in equipment... so I shaved $1000, but gained and 100% radiant system for heating. I'll put in a slightly undersized 1.5T AC and use the blower to circulate for a bypass humidifier. I'd probably just go 14 SEER. Undersizing will effectively buy me another 1-2 SEER anyway in longer runtimes.

In the future, I can still add radiant floor heat in the kitchen too, or switch over to zone controls.

Now, can I "Sell" it to my wife.

[triguy128]

One downside of LOTS fo valves, is that it adds resistance in the piping. BUT, no more than pex fittings. I can overcome that by oversizing the piping header.... or rather using more 1" instead of 3/4. The reverse return will help balancing.

But your right, lots of isolation is great if you have a leak and want to still heat the rest of the space while you're making repairs.

[triguy128]

So the wife isn't sold on this, and the up front costs are looking pretty daunting. I'm thinking this might be a future project when/if we remodel the kitchen and go with radiant floor heat. For what I would spend on piping, pump, boiler, I can put towards a really nice zone control system that will give me more comfort overall 12 months out of the year and respond fater to varying loads and save more energy overall sinec I can setback unoccupied zones during certain times of the day. For example i get up 2 hour before my wife, but only use hte kitchen. So why heat or cool the whole 1700 sqft downstairs, when I only need about 500sqft of it conditioned.