HTP phoenix light duty repair or something better?

[BDrivenByDemons]

So... My HTP light duty heat exchanger (NG) developed a leak. Took it apart and found the burner tube full of water. Cleaned it out and it slowly refilled. I was pretty happy with this unit and was using it for radiant heat in my basement floor and it seemed to do fine. So here's my weird idea...

I found a 50 gallon HTP light duty but it's LP. It's 700 bucks brand new old overstock. Manufactured date was 2014. I'm thinking I could buy it and put all my old natural gas guts on it and have a good unit again. It would be fairly easy to install as all my venting and plumbing is pretty much already there. Or...

Do I bite the bullet and do something better? I don't think my use as radiant caused this thing to fail early as it seems to be designed for it but I don't know. Do I get one of those cool kid Combi boilers I see people talk about? Those have a much higher turndown ratio and would cycle a lot less. The guy in HTP tech support said this is an unusual failure and didn't think much of it except it was out of the ordinary.

I don't necessarily mind spending money and redoing everything if it's going to be better and last longer. But I'm only running the heat floor, maybe 4 months out of the year. Not even that cuz I only turn it on if I think we're going to be down there which isn't very often. So I really don't know what to do. I see a lot of guys complain about using a DHW tank like I am for radiant but I also see people say combis are usually way too oversized or you don't get hot water for multiple fixtures.

Thanks for any opinions

 

[Fitter30]

The existing heater has a stainless tank? Are you using glycol and what type is it and %?

 

[Sponsor]

 

[BDrivenByDemons]

The old and new unit are the same except LP/NG. Yes stainless tanks. No glycol this is for DHW. The burner is some sort of coper/nickel alloy.

 

[Fitter30]

So tour using it for both dhw and radiate? I'd take the gamble on the lp. It would be interesting to weigh both heaters to see how much difference there is do to mineral buildup. Ever flush the heater?

 

[BDrivenByDemons]

So tour using it for both dhw and radiate? I'd take the gamble on the lp. It would be interesting to weigh both heaters to see how much difference there is do to mineral buildup. Ever flush the heater?

I flush yearly but it's very clean every time.

 

[BDrivenByDemons]

So tour using it for both dhw and radiate? I'd take the gamble on the lp. It would be interesting to weigh both heaters to see how much difference there is do to mineral buildup. Ever flush the heater?

Gamble paid off so far. Hope I don't jinx myself by posting about it. Only real difference was a few gaskets and the main controller. I re-used the whole natural gas fan/valve/intake assembly from the old one because it had a tube between the intake PVC and gas valve that the new LP one didn't. Goes right to a port by the offset adj. I did some quick searching but didn't find much so kept it simple.