Two Stage T-stat with Hydrocoil...

PJO_2

Wallies,

Part of the system improvements that have management approval this summer include adding a hydrocoil to the first floor of our home. I will post other stuff as it comes, but this issue needs the most planning.

After trying to convince her (management, that is) that two or three panel rads in certain spots would be better for the family room (cathedral ceiling, lots of windows...you know what happens at design temps) she says "Can't you just make the air conditioner put warm air in here? The boiler could do something, right?"

This statement made me both proud (she's come a long way as far as hydronics goes...) and a little upset (kind of like when the kid hits a baseball really far...into a window!). I said that "Yes, it's certainly possible and it would have a quick recovery, but it won't be as nice as the radiant floor and panels..", well that was all she needed to hear and it's a done deal.

Egads! I am adding FHA to my home :-)

Anyway, I think I need to get a two stage thermostat and a coil to attach to the front/inside of my Bryant (heat pump) air handler. Can I find a t-stat that will do this at a 3 degree differential or so to recover from setback? Then when the temp. is satisfied it just runs the radiant circulator? I've seen this discussed before but please excuse my ignorance. Bill W, are you there? How about a Tekmar?

Can anybody recommend a coil...I only need about 6kBTUh in the area mentioned, but to add it to the handler would put it in the entire first floor...15 or 20k is about as big as I'd like. I've seen information on a few that would seem to work well. Are they difficult to install, any issue with hanging them, ductwork, etc? I can give more specifics as needed.

I normally run the boiler at 170F design temp. and when I re-pipe this summer, this connection will probably be just after the two baseboard zones (upstairs) in a P/S configuration...160F is likely. I'm thinking another 007 circ and a flow check, unless there's a better way.

Glenn is my tech and he's really good, but I think his experience here is limited. I'm hoping the vast knowledge and experience from the Wall will come through.

TIA...Take Care, PJO

flange

why do you want a two stage stat, use w1 to control the zone. use a circ relay powered from the end switch in a zone vale, and add a relay to parallel your g to your fan.

Tony_8

Does your HP fancoil have elec. heat installed ? If so, you could stage the circ. 1st and the fan 2nd off the sequencers. This would prevent the "cold draft" startup. Connect this to w1 instead of the condenser being w1 and disconnect w2 as you no longer need it as back up. Summer operation will stay the same.

David_5

second stage

I did this in my home with a Robertshaw thermostat. The differential is adjustable. Don't know about Honeywell. You will probably end up with an oversized hydro coil. How about installing a thermostatic mixing valve to the coil to reduce water temp and btu output?
In my house the 2 stage thermostat didn't work well for me. My Radiant can only cover the load down to about 20º outside. With the 3º diff the second stage came on too late to be comfortable. Changing the diff to 1 or 2º cauused the hydro to come on, overshoot, and shut off both stages. In January I installed a Tekmar thermostat just for the radiant. It works better but I don't think it is an acceptable solution if I was a paying customer.

David

PJO_2

Thanks for the responses, guys...

and also to Bigugh for the "off the Wall" discussion.

I will present the issue to Glenn (my tech), but I still want to go with panels...and may install a small floor convecter in the loop as well (great suggestion Gary).

Interesting comments on the t-stat wiring, and I may use it as well. I have electric back-up on the unit, which I didn't mention before (sorry) and will not be used...the meter's velocity may cause it to spin off it's axis :-)

A new presentation will be made to management with the Wallies help!

This is the best place around...'nuff said.

Take Care, PJO