Aquastat Always On

donny312

I have a hot water heat system with a gas-fired boiler. Up until now, it was a 1 pump, 1 zone system. A contractor recently installed a 2nd pump to effectively create a 2nd zone, with its own thermostat, etc.

Here's the catch. The zone 2 thermostat only controls the zone 2 pump, NOT the aquastat. So the boiler wasn't firing for zone 2, and it was just pumping cold water. The boiler only fires if zone 1 calls for heat. The contractor's solution is to rewire the aquastat to be always on, IE a warm start always keeping the water in the boiler at 180°. That way, the two thermostats only turn the various pumps on and off always circulating 180° water.

Is this an acceptable solution? The contractor says not to waste money on a $100 relay or control box to keep the boiler as a cold start, and that this setup will use minimal gas to keep the water in the boiler at 180°. What are your opinions?

STEVEusaPA

i agree, don't waste any more money with this contractor.
What was the reason for the second zone?
Can you show us a diagram of the way it is piped now?
If the second zone is truly separated, it should be wired properly.
Depending on the aquastat, you might be able to just wire a zone in properly, or add a relay to make it work properly.
It's a huge waste to keep a boiler at 180° even if needed for domestic hot water.
If you could provide more info, someone should be able to point you in the right direction as to how to proceed.

Leonard

As it is currently wired sounds like the aquastat can't shut off 2nd circulator to protect against boiler falling below ~ 140 and get exhaust condensing ( rusting). Condensing might not happen if fuel nossel size is large compared to BTU load of the 2 zones.

Paul48

He's wasted your money, in his labor trying to make a peanut into a phonograph needle. It probably would have been cheaper, and certainly would have been more proper to install a switching relay.

Solid_Fuel_Man

Get us some pictures of this setup. Boiler sec9nd zone, and how the second zone is controlled. Did he use a line voltage thermostat?

donny312

He is finishing his work today, and I will take pictures tonight. Here are some photos of the aquastat wiring as is.

donny312

Sorry, images are not loading for some reason. I will try again later.

Paul48

His "fix" is not an acceptable solution. He will short-cycle the boiler, cost you more money(forever), and shorten the life of the boiler. But, he will "save" you $120.

Solid_Fuel_Man

It is my opinion that ANY boiler that is able to be cold started SHOULD be cold started. The amount of wasted heat up the chimney and into unconditioned space over the life of the boiler would scare you.

donny312

I'm going to have a different contractor install a relay or control box after I confirm this guys work is complete. I wouldn't want this one wiring it anyways.

Solid_Fuel_Man

Oops, edited it! You are correct Hat

donny312

Update

Ok, here goes. His work is done, but his work was obviously not the solution. Previously I mentioned the outdoor air temp sensor - he wired that to the aquastat's thermostat terminals to trigger aquastat always on for outdoor air temps under 60.

Problem 1: the hot boiler water is naturally circulating even though the t stats and pumps are off, drastically heating the house because it's 58 out and the aquastat is on. I turned the sensor down to 55 because the house was way too hot. He thought the pumps, when off, would impede flows. This is not happening. Solution: taco control box or relay.

Problem 2: he said pumps would mostly impede flows and is using them as check valves. Will this work if 1 pump is on? I am concerned that my cold zone will pump much longer and simply overheat the already hot zone. I'll test this out in cold weather, which may be awhile. Solution (if needed): add zone valves.

Thoughts?

Paul48

New contractor.

donny312

Yes. I already found one who said everything you all did. Thanks. Does a circulator, when off, provide literally any level of flow check like he suggests? Or do I definitely need to add them to zone this system?

Paul48

Most, if not all circ manufacturers now offer circs with internal flow checks(IFC). They do this because circs offer very little resistance to flow. If the circs you have are not of that design, you need to add separate flow checks.

donny312

It's a new pump but obviously wasn't flow checking anything since the house was getting hot with natural circulation. Odd that it should have an IFC. I'll check the specs. The mystery continues. I'd love to be able to use IFCs so I don't have to open the system again.

So, for my own knowledge how do flow checks with 2 pumps work? Are they adjustable? Wouldn't the pressure from either pump open both flow checks?

Paul48

http://s3.supplyhouse.com/manuals/1351084237747/85084_PROD_FILE.pdf
It's easier to let them explain it.

donny312

Thanks. I understand the mechanics, but Let's say you had two circs and two loops. Wouldn't pressure from pump 1 push water through loops 1& 2 and open Both check valves?

Paul48

You have to keep in mind... they are circulators. When one is running it draws through it's inlet and expels through it's outlet. If 3 gallons go out, 3 gallons must come in. Now, if that circ is drawing water past another zone(circ), there exists stratification within the pipe(different temp. layers). The hottest at the top will want to go into the other zone. Not under pressure, the running circ is still going to draw it's 3 gallons, just from the cooler(relative) layers within the pipe. A flow check with a slight weight is then enough to stop the convective flow.

donny312

Makes sense. Are the flow checks in pumps simply a check against backflow? Ie they have no weight to prevent natural convective flow?

Paul48

They operate exactly the same way.

HVACNUT

Have the new contractor put everything back the way it was, install a 2 zone control board with both circs and tstats wires into it. Wire TT leads in the boiler to XX dry contacts on the zone board. Sounds like you just got a plumber rather than a heating tech.

HVACNUT

Also, don't know where your circs are located but it might be easier to install shark bite spring checks on the returns. (Let's hear the Booo's)
If your original circ is not IFC and there's no flow valve in the piping, what prevented overheating at least a couple degrees even with a cold start aquastat? Unless your house and boiler is on a slab and piping goes down.