steel boilers and snow melt

Stan_5

I'm looking for suggestions on the correct way to pipe multiple waste oil fired, steel boilers. Three boilers will serve hot water to five snow melt manifolds. Each manifold was designed to have a four way valve, reset control and circulator. There is also a circulator in the main supply to the manifolds. Tekmar shows piping the boilers reverse-return but we are dealing with a savy customer and I thought primary-secondary would be better. Should I be concerned with low return water temperatures with four-way valves in the system? At this time, I"m not sure how the salesman wants to control the boilers. The five Tekmar controls are far from the boiler so I do'nt think he will control the boilers with the reset controls. Any advice would be appreciated!

Al Letellier

steel boiler with snowmelt

Unless your boiler is steel composite and comes from Germany, I would pipe them P/S. It's the best way to protect against flue gas condensation, which can be a REALLY BIG problem with steel boilers. And with waste oil, I'd want cast iron...what boiler are you thinking of using and is it rated for waste oil???

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Stan_5

Al, these boilers are built specifically for burning waste oil from automobiles. I belive they are called Black Diamond. They are in a car dealership. They come with a specific type of oil pump that mounts on the boiler jacket, an adjacent wall or can be mounted on an oil tank provided by the manufacturer. The boiler also comes with its own filter and oil heater. At first glance the boiler looks like a locamotive. The boilers may be a steel composite from Germany. They are in a BMW dealership and I noticed the floor tile in the service bays was imported from Germany.

hr

Watch

your pump spec if you glycol some of those steel tube boilers. I have used the Clean Burn and they have a pretty healthy pressure drop thru the 1-1/4" coil tube HX. For sure use PS WITH a return protection device.

One weird thing with Clean Burn is they need to use that onboard 10 minute post purge feature. Without this they WILL overheat and kick the high limit. They get worse as they fill with ash that hold even more heat in the HX.

With PS piping the post purge gets more complicated as you need to fire the boilers pump, the primary loop pump and SOME pump somewhere to dump that heat to. At least 3 pumps would need to operate with that purgwe relay.

I have seen installers wire around the factory post purge and try to handle it with a snowmelt control. Good luck

If you have multiple boilers you need to make all these pumps communicate so any or all boilers can post purge as needed.

The tekmar multi stage boiler controls get real close to making all this happen. You may need additional relays, with the tekmar, to handle the size pumps you will be running with that much glycol laden HP.

You might consider seperating the boilers from the glycol with a plate HX. Cut down on the glycol capacity and ease the boiler pump requirement. I'd look at an Ergomax as a snowmelt glycol HX and buffer tank. Get their permission, I've done it with Triangle Tube Phase 3 tanks. This would double duty as a buffer for that dump issue, and a nifty, powerful HX, you can shove a lot of BTUs through Ergomax tanks. Bigger sizes come with 2" taps!

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hr

Also look into

a mini tube application. You may be able to feed remote location manifolds, VS, with 3/4 or 1" pex lines. Skip the multiple 4 ways and leverage that delta tee to the max. Gotta run those oil boilers at least 160 anyways. Use those temperatures to your advantage. Cut way down on pipe sizing, and insulation costs.

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