From Tankless to Boiler

BCook

Now that I got some guidance on the tankless radiant debacle I started with, I'm ditching that and moving towards a propane boiler. I looked at the Navien NHB 55 Condensing Boiler because it was the first low BTU Boiler I saw. Seems that there are some negative reviews with this one. Are there other makes and models that are better suited for my application.

What I have at this point: One room shop, Closed System, 1000 LF 1/2" PEX divided into 4 250lf circuits, 12" OC. 30% Prop. Glycol. 15FT. ceiling. 2" Poly Bd. under and wrapped around a 5 inch slab. walls R-19, ceiling R-40. No windows, 1 door.

I'm figuring 25000 BTU. 1 GPM = 11,000 BTU = 2.27 GPM = .57 GPM for circuit.

According to PPI pressure/head loss calculator I have:

Calculating with the PEX site with chart I'm getting 3.5 feet of Hd. and 2.27 GPM. Can someone tell me if I'm close to being on track or help me with more direction?

Awesome Site!

Thanks in advance.

Kaos

HTP modcons seem to be popular for propane shop around me.

As for the actual swap, not sure how much sense it makes to fix a $200 undersized pump problem with a brand new modcon install.

hot_rod

With that 30% glycol you will need to pump that a bit harder notice the head difference between water at 4.6’ and the glycol at 10’

I used .85 gpm it isn't turbulent until 1 gpm I think you'll be ok

So 3.4 gpm at 10’ maybe add some piping loss, you are getting to the high end of an Alpha

I have a Lochinvar Knight 55,000 in my shop it has a lot of nice control features and is one of the top brands

I have owned 5 Lochinvars now and not a single problem with any, including two combi

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BCook

I did contact a company rep to get an opinion on upgrading to a stronger pump and was told that although they do mention it's use with radiant floor heat the unit would die an early death. They couldn't give me specifics.

I started with a higher percentage of glycol in the beginning knowing that this (budget) project was going to take time and I was sure I would be breaking into the system some time or another. It was insurance more or less. A frozen pipe in a slab scares the hell out of me. After the latest low temps, (3 degrees) I realize that with only a standup freezer making minimal heat in the shop, the temp saw a low of 29 degrees. Not bad. I might go to 20% which should give me 18F. I don't think I can just go to water.

I'll look into the Lochinvar Knight 55,000.

Thanks you both for the help.👍️ 

hot_rod

I think the newest Alpha 15-58 would be about right.
The second number in Grundfos lingo is the head in decimeters.

58 decimeters is about 19’ head

kcopp

This is what I would install. I have A LOT of them in the field.

Simple, reliable. Its made in a 50k btu option.

HC Series – IBC Technologies Inc. USA

GroundUp

Do NOT go to 20% glycol. 25% and below is prime grounds for bacterial growth and it does deteriorate over time, so I'd stick with 30-35% if you're not going to use just water.