Hydronic Radiant Heating

Robert_7

Which boiler works best with a residential hydronic radiant heating system: Polaris or MZ Boiler (MZ25C)?

Is an Open Direct System (recommended by Radiantec) the best application for a residential installation?

Need any info and recommendations in order to make an informed decision.

Alan(CaliforniaRadiant)Forbes

Radiant

The MZ boiler is a perfect fit for medium to large sized jobs; Polaris water heaters have shortcomings (see thread further down below).

As far as Radiantec's open direct system, I guess you got their flyer, too. Most of the professionals here on The Wall do not subscribe to these kinds of systems because of the chance of Legionella growth.

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Troy_3

Buy a boiler

IMHO A water heater should be used to heat domestic water. The MZ is a fine boiler. Not even in the same league with the water heater. Or rather- No water heater is in the same league with MZ, Munchkin or Viessmann. A Yugo is an automobile but doesn't resemble a Mercedes Benz and won't last as long. We use boilers for space heating and indirect water heaters with lifetime warrentee for domestic water. The incrimental additional cost will payback many times.

Troy_3

Buy a boiler

IMHO A water heater should be used to heat domestic water. The MZ is a fine boiler. Not even in the same league with the water heater. Or rather- No water heater is in the same league with MZ, Munchkin or Viessmann. A Yugo is an automobile but doesn't resemble a Mercedes Benz and won't last as long. We use boilers for space heating and indirect water heaters with lifetime warrentee for domestic water. The incrimental additional cost will payback many times.

hr

Pros and cons

First off stay away from a combined system, in my pro opinion.

The MZ is a fine piece of equipment, I have one in my shop. I install them with buffer tanks if the system is zoned much. They heat up so quickly that they tend to short cycle when low loads are applied. They have an excellent track record for dependability, and great support from Pete Caruso.

Polaris's work also. Using them on dedicated radiant may voild warranty if this is an issue, and some code bodies do not accept them when used a stand alone heat sources. Although I'm not sure that MZ has ASME listing, if the local codes require that?

MZ's are available with a small DHW flash tank. Works well with low flow DHW needs. It will keep up with a small garden hose when I wash my truck in the shop.

I have used Polaris's with a flat plate HX to provide both dhw and radiant. They work well, but are more ignitor failure prone, than the MZ. Learn how to change them if you go this route. Be sure to put the Polaris's up at least a foot, or you will stand on your head to change ignitors.

Be very careful with fluid quality in the MZ. With aluminum in the HX they, as are all aluminum HX's, are very sensitive to ph. A narrow ph range is required for the long term health of the unit. Check it yearly, would be my advise.

hot rod

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bill clinton_3

ditto hot rod

The case against open (direct) combination systems is that Legionella bacteria are widespread and that such systems provide several of the conditions that have been found conducive to rapid multiplication of that bacteria. Why gamble with the lives of yourself and your family/friends when it's so easy to isolate heating from potable systems. Use a separate water heater or boiler or install a heat exchanger. You'll sleep better.

Bill

Mark Eatherton1

I never thought I'd see the day...

that Bill Clinton said that. Boy, was I WRONG.

Well said Bill. It's an honor to call you my friend.

Well said!!

Now, if we can convert that Luttrell guy;-) (I'm holding my breath Mike, OKay:-))

ME