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?

ThatBurnhamGuy

Old post, but I'll weigh in anyway as there seem to be unanswered questions, and a few comments that open additional points the OP didn't ask. Others have commented on some low hanging fruit here such as pump orientation, which I will not comment on other than to say I recommend referring to the pump manufacturer's install instructions. Regarding the rest-

1-Agree with many of the previous comments. I would not normally install a combi and indirect for the following reasons. 1-More moving parts that are not necessary for the intended application. 2-Higher cost. 3-If the indirect is not exposed to high levels of contaminants that will rot the tank out, the DHW feature of the combi may never come into play. 4-If the house is better suited to an indirect, when the indirect goes it will likely just be replaced. However…

2-Regarding the install of the Combi 200, this happens often. The contractor markets a combi with the intent of using the DHW circuit if and when the indirect fails. They offer the 200 because "bigger is always better." Untrue in the A/C world, and most often untrue in hydronic heating as well. However it is dangerous to comment without knowing the full scope of the project. How many bathrooms? What fixtures? What is the maximum regular continuous desired DHW flow? This may be why they chose a 200 combi. Although the house will likely never need close to the CH output of the boiler, they might have three bathrooms or many teenage children that may fully utilize the DHW feature of the combi if and when it is ever connected. Again, not making excuses or saying I would do this, but believe in affording the contractor the benefit of doubt. One side point- the DHW could be connected as an auxiliary source, if and when the indirect goes south, a few turns of some valves would restore DHW service.

3-Regarding the DHW tapping's, there is no need to cap them, and in fact they should not be capped as another poster has correctly stated. Considering they now have press caps new adaptors will be required (available as a parts kit) should the DHW feature ever be connected. Additionally, these should not capped as although unlikely, it is possible pressure can build up and damage the combi block. Simply loosen one of the nuts to resolve the pressure issue.

4-A previous post commented on efficiency being compromised. I have no desire to debate this but will offer the following perspective. If the minimum heat distribution capacity of the smallest zone is equal to or greater than the minimum firing rate of the boiler (20kbtu/h), my opinion is there is no efficiency penalty here. One could say you have more heat exchanger than you need, and the boiler will likely spend the majority of it's life at lower firing rates. This means there is proportionally more surface area of the heat exchanger relative to average firing rate allowing more heat transfer. This boiler will likely condense like crazy, indicating you are getting the full benefit of condensing/latent heat absorption. Most 3/4" zones are engineered around 4-5 gpm @ 20 degree delta. So I think your OK here unless the heat emitters on the CH loops have less than 20kbtu/h transfer capacity (read excessively short). Also, no idea if this is fin tube, hydro-air, etc. In any case, your probably ok. If fin tube baseboard, measure the length of all ACTIVE radiation, meaning only the parts with the aluminum fins. Multiply length in feet by 550 to get the average heat output of the loop. If the number for each zone is =or>20K, all set. If not, not the end of the world. The boiler can be programmed to compensate to some degree.

5-The Alta boiler allows adjustment of the maximum firing rate. There are separate adjustments for AUX and Central Heat. If desired, your contractor can come back and turn the CH max firing rate down to whatever the house needs. If you have 2 3/4" zones, 80K will probably do the trick.

5-You pose the question about rate-based reset. This is an amazing feature and one the really distinguishes the Alta. The boiler will adapt to the needs of your home using the coolest water possible to maintain setpoint. This is the most efficient way to operate the boiler. As long as the contractor wired the indirect aquastat to the boiler AUX input the boiler will use RBR for central heating, and immediately go to max DHW setpoint when the IWH aquastat closes. Easy way to figure this out is to turn the thermostats all the way down (50 degrees) and run the hot water until the boiler turns on. If you see the faucet icon illuminated during a DHW call, your GTG. If you see the radiator icon during DHW demand, post back here. It's an easy fix for the contractor if this is the case.

6-Check where the condensate line drains. The condensate from the boiler is highly acidic and must be managed properly, most often with a neutralizer containing lime chips.

I have no desire to argue or debate any of these points. I offer them only to help a homeowner who seems anxious about his purchase. I will be happy to DISCUSS as a gentleman any points you find interesting or have a different perspective on. I am limited as to what I can discuss or advise with non-professionals due to liability, so some conversations may have to take place on another part of this site. I will respond to all genuine questions but will not respond at all to any challenges or confrontational content. Life is too short. Throw rocks on your own time…

In closing, looks like a pretty good job with a few small exceptions. They gave you a very expensive air separator and installed a mag strainer on the return to protect the boiler from any system debris, which Burnham recommends but many installers do not provide. The piping orientation is pumping away from the PONPC, and the feeder is connected in the optimal location. Picture doesn't show the vent, so no comment there. I will not get into pricing, but I would not feel any buyer's remorse regarding the product you got nor the installation. Enjoy your new boiler! Feel free to post here and I will answer whatever questions I can. That Burnham Guy

psb75

Thanks ThatBurnhamGuy. That was a thoughtful and well-composed addition to this forum thread. I would certainly feel better if I was latent_heat AND/OR the installer.