Help understanding SlantFin boiler schematics to diagnose a few things

enviousjl

Howdy. I am not a professional by any means, but simply a DIYer with a basic understanding of how things work.

I have this SlantFin boiler in a house I just bought and I'll start by saying that it seems to be working fine in the sense that the house is heating and the boiler appears to be operating normally at face value. However, there are some things I'd like to work out, and to do that, I need some help to better understand why things are set up the way they are here.

Things that I would like to address:
- Water hammer occurs when both valves are open, and then one closes
- I believe there may be some air in the system, as I can hear "rushing water" noises in certain areas of the house
- The pressure gauge always reads 0psi



In the image below with my markup, I am having a hard time understanding why there are drain valves (yellow) upstream of the zone valves, with another main valve (green) upstream of them. It was my understanding that to bleed the system, I would need to shut off flow to the boiler on the return side and bleed upstream from that, but there are no drain valves on the return side. There is a shut off valve upstream from the recirculator pump.



So I guess the main questions are:
1. How the heck do I bleed this thing? There are no valves on the radiators anywhere.
2. The water hammer - am I SOL with the way this is configured? Do I try the spring removal hack at the zone valves? I know the top one is a Honeywell, as I just replaced the head (the motor died).
3. Is 0psi at the boiler normal? Could the pressure gauge simply be toast?
4. Is there something I should do with the expansion tank? The little valve cap at the top is loose, but I have not done anything with it, and I don't know how it affects the system.
5. What is the purpose of the very upmost pipe running from the supply side of the boiler to the cold water inlet of the water heater? It looks like the flow runs from right to left based on the pressure regulator, but why?

More overalls:





Thanks in advance!

HomerJSmith

The red valve (boiler cold water shutoff) should be open and the green valve (pressure regulating valve) may have failed and needs replacing.
Having the boiler cold water shutoff valve connected to the water heater cold water feed is OK. If the pressure regulating valve has failed, you may have 0 pressure at the boiler gauge and noisy water flow sound in the piping. The gauge (tridicator) could be plugged and failed. Check the sys pressure with a garden hose bibb pressure gauge screwed on the boiler drain valve. The readings between the two should read the same.

If you have 0 psi, I would replace the boiler cold water feed valve with a Caleffi cold water feed valve (PRV) with gauge. I would check the air pressure in the expansion tank (Ex-tank) with the boiler water drained from the tank. Check the air pressure with a cheap digital tire pressure gauge. The air charge should be between 12-15 psi. There is a tire valve under the cap on the bottom of the tank. Set the new Caleffi PRV valve to the pressure that is in the air side of the Ex-tank.

If the tridicator (temp and pressure gauge) is faulty replace the gauge.

Do all this first.
https://www.supplyhouse.com/Caleffi-553642A-1-2-NPT-AutoFill-Boiler-Feed-Valve-w-Pressure-Gauge?_br_psugg_q=caleffi
https://www.supplyhouse.com/Zurn-HGI-25-Hose-Bibb-Pressure-Gauge-with-Maximum-Pressure-Indicator
https://www.homedepot.com/p/Husky-4-in-Digital-Tire-with-Gauge-AAA0138J/205937751?

enviousjl

Okay so after thinking things through a bit, I almost wonder if I've got this whole thing wrong... are the zone valves on the return side, and the pump on supply? Is this whole thing backwards? I also believe one of the zone valves is backwards, and which one would depend on whether or not the whole thing is backwards! Argh.

enviousjl

@HomerJSmith - okay thank you for that info! I will check pressure at the boiler drain valve. So is the boiler getting its main cold water supply from that line that you marked up? If that's the case, then what exactly is the other line that goes in (or comes out?) at the back left corner of the top of the boiler?

Pressure release?

pecmsg

Safety Relief. 

HomerJSmith

A boiler pressure relief valve that lets water out of the boiler if the sys pressure goes above 30 psi.
One of the zone valves may be install backward (lower one). The ZVs are installed on the supply side. The pump is installed on the return side. Everything look ok except for the possible ZV.
An argh is not required at this point in time wait for something more serious.

pecmsg

Where is this house ?

enviousjl

pecmsg said:

Where is this house ?

Northern Nevada

HomerJSmith

Elko, Reno, Ely, Lovelock?

enviousjl

HomerJSmith said:

An argh is not required at this point in time wait for something more serious.

Haha, I know. The argh was more me frustrated with trying to understand why the ball valves are where they are

enviousjl

HomerJSmith said:

Elko, Reno, Ely, Lovelock?

Carson City

HomerJSmith

The capitol of Nevada, you don't say. You can try JackRabbit Plumbing they have a lot of experience with boiler stuff or call or mosey over to Western Nevada Supply near Costco and talk to the hydronic dept for a recommendation.

enviousjl

HomerJSmith said:

The capitol of Nevada, you don't say. You can try JackRabbit Plumbing they have a lot of experience with boiler stuff or call or mosey over to Western Nevada Supply near Costco and talk to the hydronic dept for a recommendation.

Thanks for the recommendations. I will try your suggestions first and go from there. Any reason to attempt an air bleed at this point? I keep seeing that come up as something to do first.

HomerJSmith

Purging air should be done if you break into the sys. So make any repairs first then fill and purge the air.

enviousjl

HomerJSmith said:

Purging air should be done if you break into the sys. So make any repairs first then fill and purge the air.

Sounds good. Last question (for now) - how would I purge the air with no hose connection anywhere on the return side, and only the two valves upstream of the zone valves? It doesn't make sense to me.

HomerJSmith

Easy-peezy! Close the white handled ball valve to closed. Then open the ZV for the zone you want to purge and connect a garden hose to the boiler drain and a garden hose to the hose bibbs before the ZV you want to purge. Flow the water into the boiler drain to the hose bibb you're purging.

Those two hose bibbs should have been installed after the ZVs. Use street pressure to force water thru each zone. Of course I would do that with a high pressure pump.

If I would break into the sys I would put two Webstone valves beyond (after) the ZVs for circuit shut off and purging while the sys is down. It would make purging so easy. https://www.supplyhouse.com/Webstone-50613-3-4-Sweat-PRO-PAL-Full-Port-Ball-Valve-w-Drain

enviousjl

HomerJSmith said:

Easy-peezy! Close the white handled ball valve to closed. Then open the ZV for the zone you want to purge and connect a garden hose to the boiler drain and a garden hose to the hose bibbs before the ZV you want to purge. Flow the water into the boiler drain to the hose bibb you're purging.

So it really doesn't matter exactly where the water comes in and goes out does it? As long as there's water going in somewhere in the loop, and out somewhere in the same loop. So basically run a hose from a spigot somewhere INTO the boiler drain, and then discharge the other hose?

HomerJSmith

The zone valves closes against the flow. Pumping thru the boiler drain will put pressure on the ZV seal pushing it more tightly closed. Pumping thru the hose bibbs that are before the ZVs can push water past the ZV seals if the pressure is too high.

I would install the Webstone isolation valves with a hose drain. That would make things much more easy.

enviousjl

Okay so here's my situation. Pressure showed ~11-12psi on the hose bib gauge connected to the boiler drain. Looks like the tridicator is toast (although it does show correct temps). Anyway, while doing this, the boiler drain leaked for a while until I could find the sweet spot to shut it off.. too tight and it still dribbled. I feel like it sucked some air in, because then last night, throughout the night, I could hear a lot more gurgling and bubbling noises.

With that said, I'm pretty sure I need to purge this thing now and then evaluate what needs to be replaced/added.

Thoughts?

Grallert

I would suggest you go ahead and replace the components that are required to fill and purge the system. Otherwise you're likely to find that they are faulty one at a time wasting hours and making a mess over and over. So they're are the PRV the relief valve the gauge any boiler drain that drips. Then you can accurately test the expansion tank. To make you life easier have a couple of purge stations installed just after the zone valves perhaps. Air vents also maybe. These things will make life so much easier.

HomerJSmith

Use the following hose bibb caps to prevent drips from the boiler bibb. You can get one at Home Depot or Lowes.