Settling a disagreement: steam boiler + passive water tank

dnb

Hi-
Would love to hear your opinion about this because I am receiving contradictory information from my plumber and the manufacturer and I'm not sure what to do.

Our portion of the house is heated by a steam boiler. Hot water is provided via an Amtrak WH7Z (Boliermate) which stores and distributes water that gets heated by a loop through the boiler via a conduction pump. This loop/pump runs close to the floor and connects to the water heater at the bottom of the tank.

After 13 years, the tank has started to develop a pinpoint leak, and like its predecessor (which lasted at least as long), Amtrol is willing to replace it under warranty. The bad news is they stopped making the WH line a year and a half ago and only make a CH line where the fittings are entirely found at the top of the tank. Here's where things get tricky for me.

My plumber is absolutely convinced that re-piping things from the bottom of the tank to the top of the tank (water would travel up from the boiler, down into the tank, back up, and then down back to the boiler loop again) is asking for trouble on a steam boiler because of water levels, specifically in the form or air locks. The manufacturer tech support is absolutely convinced there should be no trouble at all, the pump should have no problem circulating the water, even on a steam boiler. They feel that even in the unit I have now, the loop ran half way up the tank internally so this would not be a big change.

I'm not sure what to think in this case. Any ideas?

— dNb

Jamie Hall

Should be no problem at all. Just make sure the connections to the boiler are below the water line, and pump away from the boiler.

STEAM DOCTOR

And proper isolation and purge valves

EBEBRATT-Ed

@dnb

I would suggest pushing the water into the boilermate with the pump on the supply coming from the boiler. Keep the pump down as low as possible to the floor,

All the connections have to be tight

dnb

Thanks for the replies!

Can I just check my understanding of the advice here?

Currently the loop is entirely (at least visually) at the same height near the floor. It leaves the boiler, goes to a pump and enters the tank and from the tank there's a return segment (no pump). One big circle at the same altitude.

The proposal would be to replace the pump->tank segment with something that climbed up ~4' then went down into the tank instead of being at the same level. The return would then have a small climb up and then a ~4' drop into the previous return segment.

In this scenario there would be no change to the boiler connection, relationship to water line, flow direction, or valves (I think). Just an extra climb up, down, up, and then down again. I think there is some concern about the water line that could lead to air lock on the part of the plumber, but I don't quite understand why or how this extra piping would change that (sorry if I'm being so dumb about this). Does that sound still fine to you, @Jamie Hall ?

Would this change necessitate new/different valves, @STEAM DOCTOR ?

— dNb

Jamie Hall

Your understanding is fine. Shouldn't have a problem. On valves and unions. They cost money, so don't get carried away -- but it's nice to be able to close valves or open them to do things like maintaining pumps or draining parts of systems, and unions are very handy when trying to thread things together or unthread. them.

KC_Jones

If your plumber has a lack of understanding do you really want them hooking this up? Maybe that's just my paranoia speaking.

You could also let your plumber know it's possible, if done correctly, to pipe the hot water loop up over 30' and it will still work without losing water. Again it must be done correctly, the most important part, don't allow any air into that loop. It needs to be very tight.

Grallert

There is no issue with piping your water heater the way you propose.

dnb

Thanks again everyone for the response.

@KC_Jones I think my plumber is actually pretty good, which is why this has been a bit nerve wracking. I think he believes that there may come times because of the water level in the boiler that air will get into that loop and that won't be a lot of fun. I don't think he's concerned about distance.

— dNb

dopey27177

IF THE PUMP OS LOW TO THE GROUND (BELOW THE BOILER WATER LINE) THE PUMP IS ALWAYS PRIMED.

Because the pump pumps away from the boiler water will always flow into the coil.

Because you have an open loop system any air or steam that may be in the water will be pushed out to the boiler.

Jake

STEAM DOCTOR

> @dopey27177 said:
> IF THE PUMP OS LOW TO THE GROUND (BELOW THE BOILER WATER LINE) THE PUMP IS ALWAYS PRIMED.
>
> Because the pump pumps away from the boiler water will always flow into the coil.
>
> Because you have an open loop system any air or steam that may be in the water will be pushed out to the boiler.
>
> Jake

Not neccesarily. The loop runs above the boiler water line. Will only work if loop is properly primed before turning on the circulator.

dopey27177

once the loop is primed air will be no problem. It still is an open loop system.

When the pump is sized properly I do not see a reason why the pump will not force entrapped air or steam through the loop.


Jake

dnb

(btw, if it would be helpful, happy to post pictures)

STEAM DOCTOR

> @dopey27177 said:
> once the loop is primed air will be no problem. It still is an open loop system.
>
> When the pump is sized properly I do not see a reason why the pump will not force entrapped air or steam through the loop.
>
>
> Jake

Agreed

EBEBRATT-Ed

Loop primed or not doesn't matter. If the pump is below the boiler water line (the lower the better) the pump will never loose it's prime as long as it pushes toward the boiler mate