Single loop single pump snowmelt

CBRob

The typical system I've seen uses a primary secondary loop, along with a condensing boiler and glycol as needed.

With a good condensing boiler that can take very cold return temps is it any advantage to run a single loop and a single pump?

Does the viscosity of glycol require the primary/ secondary loops to keep the gpm high enough when the system starts cold?

Zman

CBRob said:

Does the viscosity of glycol require the primary/ secondary loops to keep the gpm high enough when the system starts cold?

You already know the answer

CBRob

I thought so...
was just reading some old posts about how condensing boilers love cold temps....
thanks Z

CBRob

I'm reading up on the whb from lochinvar that you mentioned a couple months ago.

The piping from the top option could be helpful for me.


Im looking at the whb 155, is this one that you have used for dedicated snow melt systems?

hot_rod

Keep the glycol percentage as low as possible, glycol cost additional pumping power and heat transfer. The boiler will be most efficient when that ;0 degree fluid hits it💰

Zman

CBRob said:

I'm reading up on the whb from lochinvar that you mentioned a couple months ago.

The piping from the top option could be helpful for me.


Im looking at the whb 155, is this one that you have used for dedicated snow melt systems?

The WHB is a good one.
The provided circulator is variable speed and controlled by the boiler. It will automatically give you the perfect delta t thus reducing the return water temps and maximizing efficiency.

HomerJSmith

PexA size is important. If you use 1/2" pexA keep your circuits less than 200' and you can use serpentine or counterflow pattern. If you use 3/4" pexA use a counterflow pattern under 300' per circuit. A counter flow pattern will have only two 180 deg bends per circuit, the other bends would be 90 deg. In a serpentine pattern all bend would be 180 deg. It's easier to bend pex at 90 deg than 180 deg. A counterflow pattern would give you a more even heating across the slab.

3/4" PexA would lessen the pumping requirement in terms of flow. Be sure and deduct the loss of flow based upon the percentage of glycol mix when looking at a pump curve. Glycol mix is harder to pump than water.

I am currently using a Lochinvar WHB-155 in a sys that I am doing. I am doing a primary-secondary sys at 40% glycol with 3/4" PexA with 4 circuits with Tekmar slab sensor and control.

CBRob

> @HomerJSmith said:
> PexA size is important. If you use 1/2" pexA keep your circuits less than 200' and you can use serpentine or counterflow pattern. If you use 3/4" pexA use a counterflow pattern under 300' per circuit. A counter flow pattern will have only two 180 deg bends per circuit, the other bends would be 90 deg. In a serpentine pattern all bend would be 180 deg. It's easier to bend pex at 90 deg than 180 deg. A counterflow pattern would give you a more even heating across the slab.
>
> 3/4" PexA would lessen the pumping requirement in terms of flow. Be sure and deduct the loss of flow based upon the percentage of glycol mix when looking at a pump curve. Glycol mix is harder to pump than water.
>
> I am currently using a Lochinvar WHB-155 in a sys that I am doing. I am doing a primary-secondary sys at 40% glycol with 3/4" PexA with 4 circuits with Tekmar slab sensor and control.

Will you be using the tekmar control to modulate the boiler?

Zman

5/8" pex is a nice compromise for snowmelt. A good target length would be 250' which works well with 1,000' roll.
Having the tekmar modulate the boiler is a nice add but not required. It tends to confuse techs that are not fluent in "tekmar".