Bock 50sk no flow through cool

Fender74

I replaced a Bock 50sk indirect hot water heater under warranty the old one leaked . When I installed the new I put it back in exactly the way it came out . I wasn't exactly thrilled with the way it was installed but I figured it worked before. I filled the tank purged it out and threw the switch boiler came on and the circ as well brand new 007. I have no flow through the coil it doesn't get hot not even though the feed repurged it nothing. The pump feels like it's struggling like I left the return valve off. It's piped off the top of the boiler off the heat zones and it returns on the right side of the boilerweil Mclain 68 where there was originally the 3/4" boiler drain. Off the feed it's reduced from 1 1/2 to 1 1/4 comes up goes into the air scoop expansion tank comes out the bottom and there's a BG flow check and then 4 Ts that feed zones all on zone valves on the return . The heating circ is on the return. At the end of the manifold the last zone a 3/4 t feeds the tank with the cir on the inlet of the tank there is about 20 feet of pipe to the inlet and 10 elbows. Is it possible the head pressure is too for the 007 to circulate or the distance from the manifold is to great and it's causing the pump to cavitate the pump is really loud it's pulling thought the BG flow check there's another on the return so between the 2 checks the other 3/4 and the first one 1 1/4 about 20 elbo 3/4 and 2 ball valves from best I can tell I have at least 10 feet of head . And all I hear is the old one worked for 15 years. The original installer came back and he purged it for hrs and he said it's what he did when he installed it the first time. It worked when we left and dead headed later. I know it needs to get repiped with the pumps on the return and close to the manifold but all I keep hearing is it worked before.I have my money and time tied up in this thing . The home owner keeps having the oil company that first installed it come back and I'm not sure he's doing anything but purging it more . Any ideas

Fender74

I meant to say no flow through coil

LRCCBJ

The Bock specifications show a requirement for 14 GPM through the coil to meet the specifications for first hour delivery. You cannot get the 007 to flow anywhere near that level with 3/4 piping. Even 1" is marginal and you probably will not get 14 GPM through it with a 007. However, the performance will be adequate at 11 GPM.

In addition to insufficient pipe size, you probably have a problem with one of the flow checks that is failing to open. I'd replace both of them first.

Fender74

Thanks the one on the return is new the old one off the feed is old and it leaks around the backing I tried talking to the home owner into changing it

LRCCBJ

You are between a rock and a hard place. Even if you do get flow though the coil, your current setup probably won't deliver more than 4 GPM. That's going to take forever to get the tank up to temperature and it certainly will not keep up with a shower, despite the size of a boiler.

I suspect this customer is going to be dissatisfied no matter what you do to it…………..unless you repipe it properly, which I suspect he's not going to do.

Fender74

I think I'll push for the flow check the problem is he's trying to get the oil company he has a contract with to do as much of the work as he can and he's taking his time he doesn't want to give away free parts and labor but Im into for $500 in parts and the time I have into it and I want to get paid . Thanks for your advice

hot_rod

That was the tank that Caleffi used as a solar tank, the large 1-1/2" , 30' long coil.

We ran them with 1-3 collectors so 1-3 gpm typically and they would heat fine, with that low flow, low supply temperature.

We did performance testing at the Bock lab and could flow that large diameter coil up to 40 gpm if you want super performance.

Bock has a second company that winds those steel coils, in a few different lengths. Those coils and tanks show up with a bunch of different names, Laars, Bradford, some Lochinvar versions, and other solar OEM brands. Same coil goes into the CombiCor type water heaters.

The coil gets a AO Smith Permaglass coating like the tanks.

It takes a lot of flow to get a good clean purge in that large diameter coil. A slow 1/2" fill valve may not be enough fizz to get a clean purge.

EdTheHeaterMan

It worked that way before so it will work that way again. What circulator was on the old water heater zone? From your explaination it appears that the Taco 007 for the DHW zone is new. and if the old circulator was not a 007, that may be your problem.

From your description this is the picture in my mind of your piping system.

With the circulator pump on the DHW tank zone on the pipe between the last zone valve and the tank's boiler water inlet. If you want to keep the Taco 007, then I would suggest this minor piping change.

This will get you up and running as long as there is some way to drive that air out of the DHW HX coil.  By connecting the DHW zone before the 1-1/4" B&G Flow Valve and placing a 1-1/4" full port valve between the boiler outlet and the Tee that feeds the DHW circulator, there will be a good way to power purge the DHW HX coil.   If all the CH zones are closed, then the only direction that water can flow from the feed valve under the air scoop is towards the boiler.  With the full port valve on the boiler supply closed, the water must flow thru the DHW HX coil and out the boiler drain at the bottom. 

HVACNUT

Post some pics. It worked with the old tank. No reason it shouldn't work now.

Fender74

The picture up above is a real accurate drawing of what's going on. The oil company that has the service account with the customer and did the original install purged it again with a hose on the bottom of the boiler to super feed it and got the air out I've only personally had to do that few times and it was usually when I had either a High elevation and the feeder was slow. Any way he got it it's been ok for about 3 days . If it's a problem I'll suggest he re pipes it like the lower picture thanks again for all of the insight you have given