New Radiant Installation

Isi

I'm installing staple up radiant heat through my house. 3 loops in the second floor @ 300' each run using Pex-AL-Pex and 2 loops in the first floor at 280' each run. I'm thinking of purchasing a prefabricated panel wanted to see if anyone has done this and which they recommend, also a good combi boiler, heating space is 1200sqf, I have 3 showers, washer machine and dishwasher. Do you recommend one pump and manifold or should I get the 2 manifolds and separating the zones. Someone told that if I get a buffer tank of 30 gallon so the boiler does short cycle is this correct? What would you recommend Thanks

GroundUp

I'm personally not a fan of combi units, as they're almost always WAY oversized for space heating to meet the DHW load. Yes, this can be remedied with a buffer tank but once you spend the coin on that and forever have a scaled up HX in the combi, you could've purchased a heat only boiler and indirect tank for the same cost and less headache. The prefabricated panels are also a waste of money IMO, as you can hire someone who actually knows what they're doing for a similar price and know the job is done right. With your small zones, you'll want something with a high turndown ratio to meet the load of your small zones- I am really liking the HTP UFT-80W the last couple years and would recommend it here for you, but I think a more appropriate choice would be to find a local contractor who has his/her own recommendation and is familiar enough with it to be able to service it in the future. If your tubing is all homerun to the mechanical room, you would save a few bucks and have a cleaner install by using a single 5 loop manifold with actuators versus a 2 and 3 loop setup with either 2 circs or 2 zone valves to separate the zones. If your manifolds are remote mounted, you don't have much choice in the matter on manifolds but you will still have the choice of zone valves versus zone circs- I would go with the zone valves myself

Lance

I have three types of radiant in my home. Be careful how you build it. Your runs may be too long. How you control flow and temperature is a must. Too hot and some floors can be damaged. Floor temps must be controlled with direct floor contact.
If you want to sacrifice a little efficiency and let the boiler run at 110F - 190F you can run radiant by suspending the tubes mid joist and install radiator fins on the tube and than seal up the joist space. No matter how hot you get the water, the floor will never overheat. This way you can mix uses between radiators and radiant and not have to use mixing valves to control zone temps.
If you don't want to do it twice, get the tube length and manifolds right. Also use a T-stat with a floor sensor for better control.
Check out http://www.ultra-fin.com
Make sure different zones have separate controls or you may find uneven heat from uneven radiation built.