Mastertemp 200 - 3 cracked manifolds!!

[ajw22]

We have not seen your entire pool plumbing and equipment. You have a setup that is non-standard.

If when the circulation pump is off there is water pressure in the heater that makes the heater think the pump is running when it is not so the heater starts running, that would cause your problem.

 

[ajw22]

And by "check valve" do you mean the flow switch that others are recommending?

No, the check valve shown in the heater bypass article.

 

[alleycats]

We have not seen your entire pool plumbing and equipment. You have a setup that is non-standard.

If when the circulation pump is off there is water pressure int he heater that makes the heater think the pump is running when it is not so the heater starts running, that would cause your problem.

Haha, everything in Guatemala is non-standard! I'm laughing.

I understand what you are saying but it's so strange, because I've never noticed the heater to run when the pump doesn't.

But I suppose one possibility is that my caretaker, who is supposed to filter the pool while guests are there, may be doing so while the water is hot. If he either turned those valves while to bypass either while the heater was running, or even right after turning the circ pump off, then that WOULD trap hot water in the heater. You would think it would shut off at that point for lack of flow, but I guess that's what the flow switch is for(!) and why are you are telling me that the heater may still be heating itself?

It's interesting to note that the way he described the problem recently was that he turned on the pump to filter, and everything was normal, and then a little while later he heard the water gushing out of the manifold.

 

[alleycats]

No, the check valve shown in the heater bypass article.

So am I correct in understanding that the check valve allows water to flow one way but not back flow the other?

Because that check valve is where my technician said he would put the flow switch. Or rather he would put something there that I gathered would be wired back into the heater (flow switch). But it had to do with the flow switch.

 

[ajw22]

Yes the check valve allows water to flow one way but not back flow the other.

You would put the flow switch between the heater and the check valve. The flow switch would only turn on if water is flowing out of the heater.

 

[JamesW]

I guess what I mean to say is that in theory the heater only turns on when water runs through it, and water only runs through it when I switch the valves so they run through heater instead of looping directly back into the jacuzzi (by passing heater to filter).

This is not correct. The heater has no way to tell if there is any flow. It only senses pressure. If the pump is on, the heater can sense the pressure from the pump even if the valves are closed. This is why you need a flow switch. I would put the flow switch near the heater outside and connect it to the wires that go to the pressure switch. Remove the wires from the pressure switch and connect them to the flow switch

I would also add a remote switch that is connected to the fireman's switch so that you can turn the heater off from the pump room without having to go outside.

It a simple on/off switch with two wires going from the switch to the heater and connected to the heater's fireman switch.

Turn the heater off any time that you don't want it to run.

How do the guests turn on the hot tub now?

 

[alleycats]

How do the guests turn on the hot tub now?

Right now the guests turn on the hot tub simply by flipping one switch, which is the circ pump switch. The valves are left in position so that the water circulates through the heater, and, critically, the heater is left "on" all the time, so that all they have to do is flip that switch and the heater ignites onces the water runs through it.

I was told I could do this by a non-Pentair technician here, but I'm starting to think not only is this wrong, but it might be responsible for my problem.

I did talk to my carataker and he told me that, indeed, when he switched the pool to filter the heater had been hot/running. So I am concerned that whether or not he turned off the circ pump before switching the valves, the heater would have been filled with hot water in either case, and then when he turned the valves he essentially locked that in, then ran the filter by-pass --- but, and here's the critical but, if as you say the heater will sense the pressure EVEN IF THE VALVES are off, then it absolutely could have heated already hot water and have that be the thing that broke it.

Is the "fireman's switch" the main on/off switch of the heater? I'm inquiring now with the Pentair folks here if they can install such a thing.

 

[JamesW]

These heaters were designed 50 years ago when pools were simple.

You had a pump, filter, heater and then back to the pool.

In that situation, the pressure switch makes more sense.

If there was pressure, there was probably flow.

Today, pools are much more complicated. You have pools, spas, bypasses, fountains, solar, heat pumps etc.

So, it's much more likely that the heater can get pressure with no flow.

In my opinion, it's irresponsible to manufacture and sell a heater that does not include a flow switch.

 

[JamesW]

Here is the fireman's switch. You use it to turn the heater on and off but it's not a power on/off switch.

All you need is a simple on/off switch like a light switch. The switch is called a SPST-NO (Single Pole, Single Throw, Normally Open) switch.

I would put the switch next to the circulation switch.

Turn off the heater one minute before turning off the pump or before turning the valves.

Turn the heater back on only after turning on the circulation pump and only when valves are set correctly.

Install the flow switch in the line going to the heater and connect it in series with the pressure switch or in place of the pressure switch.

 

[alleycats]

Install the flow switch in the line going to the heater and connect it in series with the pressure switch or in place of the pressure switch.

Thank you. So this is interesting, because I'm nearly certain the pentair guy here said he would put the flow switch in the outgoing line from the heater! I guess it makes sense that if there's flow coming in there will be flow going out, but it seems intuitive to me that the incoming line would be the priority.

 

[JamesW]

You can put it on the line going in or out.

 

[JamesW]

I would also change the valves to the three way valve and a check valve on the line coming out of the heater.

Any time you change the valves, the pump should be off to avoid pressure spikes.

If you close a valve quickly while the pump is on and water is flowing, you will create something called "Water Hammer", which is a pressure spike from instantly stopping tens to hundreds of pounds of water.

 

[JamesW]