Alta Boiler Model Install Question

latent_heat

Hi, I recently got a Burnham Alta ALTAC-200 installed, with 2x CH zones, as well as a 38 gallon IWH tank. These replaced my inefficient 195 KBTU boiler and 45 gallon water heater.

My simple question is why one would use the ALTAC-200 rather than the ALTA-150, as both have the same performance numbers, but the combi is ~$1K more expensive:

• DOE Heating Capacity (141 MBH)
• Net AHRI (123 MBH)

I noticed the ALTA-150 manual's piping install diagram looks nearly identical to my install, but the ALTAC-200 manual has no such IWH diagram (I&O manuals). Not to second guess professional plumbers, but does a IWH tank with a combi boiler make sense?

SuperTech

No reason to use a combi with an indirect water heater. Makes no sense whatsoever.

Do you really need 195-200K BTUs? Did the installer do a heat loss calculation? That determines what size boiler you need.

HVACNUT

Unless there's something else going on, that's ridiculous. The Combi IS a direct fired water heater. So why would there also be an indirect fired water heater, plumbed directly off the direct fired water heater?

What's connected to the Hot and Cold on the Combi, anything?

If it helps, I've been seeing a lot of really weird stuff lately. Like, mind boggling.

GGross

A combi with a tank makes no sense to me. I have had customers install combi boilers with tanks and it has always been because they overthink a simple problem and wasted the end users money, or they sold the end user on the combi and then they hated the tankless aspects of it.

no matter how this is installed you aren't getting the efficiency you paid for. Either they plumbed it as a zone and now can't use the outdoor reset, or they plumbed it to the DHW ports and have to recirculate to maintain tank temperature, 1 extra heat exchanger in that setup = less efficient. I would call your plumber back, to me this is a really big deal

hot_rod

lets see how it is piped with some pics? Maybe the indirect is being used as a buffer for some reason?

latent_heat

Thanks, everyone.

I'm still feeling a bit incredulous here as I agree it makes no sense. But the manual is for a combi, the energy sticker says ALTAC-200, and it looks like there are unused taps on the bottom. When I bid it out, I asked for prices for both combi and indirect setups. Maybe they made a copy paste error?

Here's the bottom hookup @HVACNUT .

WRT to load sizing @SuperTech , I had 5 bids that came in around 150 to 200 KBTUs. Everyone said they did Manual-Js when asked.

Thanks, @GGross , I'll ask them.

latent_heat

@hot_rod here's the full piping setup.

EdTheHeaterMan

WOW, That was a dumb choice to select a combi and cap off the DHW side and install an indirect DHW tank

Someone does not understand basic common sense.

GGross

The pump for your indirect is also installed with the motor shaft vertical which the pump manufacturer will tell you very plainly not to do. If they used rotating flanges it's a super easy fix. They did ok with the piping, and there are drain points which is nice, though they could have more for better purging. Pump needs to be fixed, and I would be asking for the difference between the heat only and the combi boilers to be refunded to me at a minimum ideally they swap it out with a correctly applied heat only boiler. Other than that keeping this boiler will mean you probably can't use outdoor reset and just have to set a setpoint temp. I don't know of any combi boilers that will take an indirect water heater signal to boost the supply temp on a DHW call so you are kind of stuck with an 80-85% efficient boiler

mattmia2

Capping the hx for the combi isn't the right way to abandon it, at least one side of it needs to be open to prevent the unlikely conditions that could cause it to be filled with water and heated and explode.

GroundUp

Simply put, you did not get what you paid for. The efficiency is poor, the indirect circ is mounted wrong, and you had to pay for a lot more boiler than you needed. I would be getting them back ASAP to replace the boiler with the correct one and repipe accordingly (essentially a complete repipe) as well as refund the difference. This is horrible, I wish you the best in dealing with them.

I have to ask: was this the lowest bidder, by any chance?

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1815997#Comment_1815997

Not sure about Grundfos, but Taco allows motor up if pressure is at least 20 psi. Motor down is a no no.

HVACNUT

I'm thinking that's what was in stock? That doesn't make it right. A combi is often times sized for the domestic demand, not the heat loss. So the boiler is likely oversized for the application.

Have you asked the installer why?

FWIW, I saw a combi with an attached water heater yesterday. The hot and cold on the Combi is piped to an electric water heater, looped with a 006 stainless. Tank thermostat energizes the 006. Flow activates the boiler. It also has a recirc line with a strap on aquastat. Again, why not a boiler and an indirect?

latent_heat

Thanks, @HVACNUT . I'll ask.

You're right that while the ALTA-150 and ALTAC-200 have the same central heating output, the DHW output is 200K, which is completely unnecessary if the DHW inlet and output have been capped.

latent_heat

Have you asked the installer why?

 @HVACNUT, currently I'm hearing that this was a "free upgrade!" in case my IWH ever failed and I wanted to go back to using it as a combi. I'm pessimistic that trying to use the abandoned DHW loop/heat exchanger in 10 years will work well. This feels like a Jedi mind trick.

What I'm really trying to understand is how this can be made to work efficiently? Since the DHW loop is abandoned, that means there is no way to call for hot water or utilize a different DHW and CH set point, right? Since the IWH loop is just seen as another CH zone, it also means that Outdoor temperature reset would just mess with that IWH loop, as you want that to be a constant HW setpoint, but want CH to be variable (e.g. don't give me cold showers on warm spring days).

Or, does the ALTA's rate based reset magically account for all of this?