Help coming up with plans for radiant loop off wood boiler.

RED4012

Hello.

I have a outdoor wood boiler.

Currently have 1" pex line coming into house, goes through 20 plate 5x12 heat exchanger, then water to air exchanger in propane furnace plenum.

Only half the house has forced air vents, kitchen has 2 electric baseboard heaters, and 2 bedrooms upstairs also have electric baseboard heaters.

I want to get rid of the electric baseboard heaters and put in hydronic baseboard heaters.

I plan to add another plate exchanger in the boiler loop, and run the hydronic loops off of that.

Could anyone help me come up with a plan for this?

I was thinking have the plate exchanger go to a pex manifold and have 1/2" (or maybe 3/4"?) pex from there go to each room and have a thermostat and zone valve in each separate room so flow can be cut off when heat is not required.

Things I am not sure of are

• Where should the circulator pump be plumbed? Or should each loop have a separate pump?
• How do I fill the system? And how do I bleed air?
• Where in the system would I put the pressure tank and air bleeder?
• What should I fill the system with? Glycol and water 50/50?

Is there anything I am overlooking or forgetting here?

hot_rod

The 1" pex from the OWF will usually be the bottleneck in how much heat you can get to the building. What is the distance between the HX and the OWF.

Any idea the size of the forced air coil or required BTUs?

It may be easier to upsize the HX you have instead of another complete separate system with expansion tank fill etc.

Plate HXs can be fairly inexpensive on E bay, etc.

The piping inside should not need glycol? Nor should the OWF if the loop pump stays running.

So a bigger HX with two separate circulators for the baseboard and FA coil.

What are you using for hot water, a separate HW tank?

RED4012

I have no shortage of available btus. The boiler doesn't have any trouble keeping up, and furnace fan doesn't run very often. When the furnace fan isn't running, and the hot water isn't running, there are lots of btu's to be had by the new baseboard project.

The 1" pex in theory should be a bottleneck, but seems to run just fine. I am getting about 8gpm flow.

I figured it would be easier to have the boiler loop just be 2 plate exchangers and 1 air exchanger then back to the outdoor boiler.

I am using a 40gal electric domestic water heater being fed by water warmed by the plate exchanger. I have the breaker shut off and the water is hot hot. Use electric in the summer when the boiler isn't running.

DCContrarian

Is there any chance the existing plate heat exchanger has enough capacity for the loops too? That would be simplest.

hot_rod

if there is a name and model on that hx you could get some better answers

assume you can get 8 gpm through the A side. At a 20 delta you have 80,000 btu/hr

If the B side could run 160/ 140 and pumped accordingly you may have enough for the AH and addition on one hx

It would be good to know what those loads are, or it is just a WAG.

20 plate sounds a bit small.

Certainly you could have two Hx in parallel