Brazed plate HX on Greenstar

kcopp

Has anyone had luck or should I say a way to flush out the boiler side of a BPHX on a Bosch greenstar boiler?
I have one that I'm 99% has gotten gummed up.
Boiler temp is running high in DHW mode and they are getting poor hot water.
I am hoping to be able to flush it out w/o removing it...
thanks.

hot_rod

If you can isolate the boiler from the system, circulate a hydronic cleaner around the boiler and HX

 what type of system, radiant, radiators, fin tube?
Has the system been taking on fresh water?
Unusual, but not impossible for the boiler side doesn’t get gunked up

kcopp

The heat side of the system works fine. Its the dhw That is the issue. So when the 3 way valve switches the boiler water to the BPHX and it has restriction.
I have flushed out the boiler, installed a cleaner, Pulled every ferrous part out of the system and there was a magnetic filter added. Added inhibitor.
The fin tube is fed w/ 3/4" Poly butylene.

So it may take some working out of the junk in the system to get the water better.
How do I just get the BPHX boiler side flushed out instead of the boiler side? WITHOUT taking it out of the system...

hot_rod

Without an extended dhw call, I guess the cleaner will not circulate through the HX,
if there was a way to force the 3 way valve to dhw you could circulate it?

Does it have a zone valve or solenoid?

kcopp

Its a solenoid.
I was hoping someone had worked on this unit and could help me manually open the valve so I can flush out some of the junk. If you power it down it just stays in heating mode so flushing out that part is simple.

GGross

Have you cleaned and flushed the DHW side of the heat exchanger? that is usually the side that gets scaled up which will impede heat transfer and lead to lower DHW temps. If the boiler side of the brazed plate were getting gunked up I would imagine the boilers main heat exchanger would as well since it is significantly hotter there, and you would get issues on the heating side. Most of these flate plate heat exchangers in combi boilers are designed with the intent to completely remove them periodically for service. So long as this is similar you can completely remove the DHW heat exchanger and clean both sides of it.

kcopp

It’s not the domestic side w/ the issue. It’s the boiler side. When the 3 way valve switched to making hot water the pressure gauge drops and the boiler temp goes up. 

Yes I could remove… it wont be fun. 

The heat piping has a Caleffi dirt mag installed. I pulled both magnets and flushed this out today… odd enough it is not ferrous. 

hot_rod

Weird! Is it metallic like chunked up solder. Is it light weight like aluminum shavings?
Wonder if it is some drill shavings from the boiler or HX manufacturing process. Is that an aluminum block boiler?

I did see this same issue on a year old Viessmann combi. Once the contractor disassembled the HX from the block the boiler side was full of gunk like that.

The heat exchanger/ pump/ solenoid was a composite monoblock, the heat exchanger goes into the composite block with some O-ring seals. A bit of a task to get it out and apart.

The DirtMag will remove non ferrous particles like that. It is a multi pass device so some may have gotten into the HX before making it across the DirtMag.

The new XF "extra filtration" Dirt Mag was built with that in mind. The fine mesh grabs everything on the first pass. Designed to protect sensitive heat exchangers on A2WHPs.

https://video.search.yahoo.com/yhs/search?fr=yhs-ima-st_mig&ei=UTF-8&hsimp=yhs-st_mig&hspart=ima&p=caleffi+xf&type=q3000_A1BWP_set_bcrq#id=1&vid=d3a1cb863dabc4d33a534e8c35ef49db&action=click

Big Ed_4

Two screws the plate will drop out . May be easer to just replace ...Floor model piece of cake . Wall model cut a exit slot between the two support brackets on the left side . Use facet grease on instal ...

dko

While the unit is on, activate DHW mode or just turn on a hot faucet. When the diverter is on DHW side, disconnect the wire harness from the diverter valve. Then you can turn off the unit and the valve will stay on the DHW side.

kcopp

The greenstar is an aluminum block boiler. It looked more scale like.
I saved it and placed it off to the side.
Now I am wondering if the inhibitor I put in the system did one of two things... Reacted w/ the aluminum or is just scouring the 30 years of junk off the inside of the piping.

Big Ed_4

Boiler dope or sealer ?

kcopp

The previous boiler was a Trianco Heatmaker from what I understand.
It lasted about 20 yrs. I dont think they added any sealers. I did add cleaner to the system in October and it circulated for about 10 days before I flushed it out and added the inhibitor. oct 31st.
Most all the piping another contractor did 2 yrs ago.
Its 99% pro press.

Big Ed_4

Some #$% broke loose . 50+ old house ..

kcopp

So i did end up swapping out the FPHX. It was not the easiest and did require 2 sets of hands.
It was not the worst.
The only way to get the FPHX out was to drop the circulator and angle it out...
No room any other way.
I did have my silicone grease handy to have the parts go back properly.
Once that was in just a simple purge and the bleed out port.
I did add more inhibitor as I flushed out a good amount during the draining.
Im going to flush out the old FPHX w/ some vinegar.

Thanks all.

hot_rod

Did you cut open the old one with a PortaBand? Be interesting to see inside.

Big Ed_4

The left manifold may be easier . Buying a new one comes with all the o rings , gaskets and hardware ...

kcopp

I didnt cut open anything. I was actually going to try to clean it out and have for that owner to have as a back up.
I did flush it out w/ water and got a similar colored scale solution .

Big Ed_4

I like the German engineering just not their instructions ....

hot_rod

kcopp said:

I didnt cut open anything. I was actually going to try to clean it out and have for that owner to have as a back up. I did flush it out w/ water and got a similar colored scale solution .

Take it to a radiator shop, they will cook it out to brand new condition

psb75

You could "cook" it yourself by putting in in a large pot of straight vinegar on your cooking stove. Or set up a recirc. system with vinegar in a heated vessel. Household/supermarket vinegar tends to be 4% acidity. There is some vinegar labeled "cleaning vinegar" that may be stronger.