New OWB Install Planning

Have you had success installing fintube first?

 

I don't actually have any cast iron rads, it's all fintube. I would really like some but wifey can't get past the look of them for some reason. Three of our 4 zones have a bathroom at or near the end of the zone run - I'd really like to put them there. Also pretty sure I know others who mix them up - have been in houses around here that did similar to what I'd like to do. I think they can look pretty good.

 

I won't say it can't be done, but it will take some careful planning.
This may make your bathrooms colder, not warmer!

The fintube heats up fast and will warm the bedroom(s) quickly, satisfying the thermostat. (I'll assume the bedroom is where the thermostat is located). The water then goes to the radiator which takes a lot of hot water to warm up. The radiator needs a lot more time/hot water to get up to temp than fintube. If the slantfin warms the bedroom(s) before the radiator is hot (and shuts the loop off), your bathroom may not get enough hot water to get the radiator up to temp.

(Fintubes can be heated with a single loop of pipe. Radiators always had a supply loop and a return loop and a venturi/valve on each rad. so the rads would all heat up at the same time.)

 

All comes down to the system design. Cast rads can usually heat with lower temp water than fin tube usually specs - they are great radiant heaters. So in my case the water would be cooler entering them than would be entering the fintube at the start of the zone. My flows are slow and more constant and my supply water is on the cooler side. Usually in the 160-170 range, vs some fintube systems that run 180 all the time. Actually they spend a fair amount of time running even cooler than that - I usually don't light up until the temps get down to the 140 range, at which point flow is pretty well all the time. If I did have cast rads, they do hold quite a bit of water yes vs. fintube, but all that water will keep giving up heat if the flow gets stopped by a stat, for a while after the flow stops. Whereas when the flow stops in fin tube, the heat from them pretty well stops then too.

 

Ok, so if I've 2400 sq that means 60K BTU if I read that correctly?

 

Pretty proud of my boys who are 8, 12, and 13. They got the trench dug for the underground pex lines while I was out of town this week. Payday for them tomorrow.

 

There are all kinds of variables, house by house & area by area. To get a decent handle you'd have to run a heat loss calc on your place & it also would take into account your climate. I think there are online calculators for that that you'd plug some of your situation variables into, but I've never done it. We're in a 22 year old 2700 sq.ft. two story (standard 2x6 construction for the time, fairly well insulated) with an unfinished 1500 sq.ft. basement under it, on an open hilltop, and going by how much burning I do each day over the course of a winter I think we are at around 30,000btu/hr. That's in a fairly moderate climate, for this country at least - I'm thinking MI would be colder.

 

I didn't use the baseboard formula as l have forced air. Added insulation this year again & putting tyvek & siding on now. I've got 3 100k btu exchangers in here on separate t stats. I'm pretty certain l can make plenty of heat. New boiler that's never been fired. Can't wait to see how this goes.

 

Well, according to this logic, my house is way, WAY overdone with baseboard. Now this is not fin-tube, but radiant panels. Not sure if that makes a difference.

My living room is 12x24. According to this formula it needs 12.6 feet. I pretty sure I have 4x8' sections in there for 32' total. Same for dining room/kitchen.

 

Overdone baseboard isn't a bad thing. That usually means you could heat your house with lower supply temps. Lower boiler/supply temps usually means lower standby & piping heat losses and maybe increased boiler efficiency depending on the boiler & situation. Pretty sure mine was overdone (I didn't do it) which is why I can keep the place warm with 140 water & fintube.

 

I haven't used my boiler much in the time we've lived here. I'm trying to remember right after we moved in and before the wood stove....the system would hardly ever hit 160*. I wonder if I should think about mixing down the baseboard heat some? Hmmm.... Nothing I'm going to do this year...but maybe when I redo all the panel supply lines I'll mix them down a little lower and have the ability to adjust for each zone.

 

160 isn't too bad efficiency wise. There used to be a habit of designing to require 180 water - that hot can leak some heat. Very much especially if you also use the boiler to heat DHW in the summer and leave it set at 180 year round.

 

Got the underground PEX punched through the basement wall and the power pulled out to where the power boiler where sit. I'm going to wait to backfill the pex until I have the boiler set in place. That Thermopex is wicked stiff and hard to work with (and it's 80* outside and I let it sit in the sun all day) so I expect it to be a challenge to feed it up into the boiler.

Getting close. Boiler gets here Sunday.

 

Found out my baseboard heat exchanger has different port sizes that what I was expecting (1.25 vs 1.00). Menard's didn't have any reducing elbows so I had to order online. Not a big deal but I was hoping to get that thing plumbed in Sunday evening. Oh well, still have plenty of stuff to keep me busy until parts arrive.

Kind of weird feeling that's there's nothing I can do on this project right now. Actually, I need figure out some shims to level the boiler...my slab has quite a bit of fall to the south. I've got some black locust boards I can mill down to fit...those should last a while.

 

Boiler is supposed to deliver this evening. Heat index will be about 105 when we set it in place.

 

How you getting a Sunday delivery?

 

Dunno. It was his idea.