Help: I did something really stupid.. Heat Exchanger Plumbing

[rdelisa]

I was doing a very simple repair - replacing an o-ring to seal a very minor link in my heat exchanger, Model RayPak RP2100. I closed off the valve to the pool jets and forgot to open it back up when I ran the pump. I heard an explosion and of course an ensuing flood of water. Since there was no where for the water to go the back pressure caused the plug to blow off, possibly damaging the internal threads.

The Retainer plug and gasket completely blew off. I am afraid the thread on the inside of the plumbing may be damaged, but I would like to order some new parts and try it anyway. My problem is that I do not see the old U.G which is shown in the picture. I am unsure if I need it. It is called, a unitherm governor. I assume this is some sort of thermostat? I am unsure if I need this part. I do not see where the old one landed when it exploded or is it possible I never had one at all? I can get these parts on Amazon for about $79.00.

My next question is: Is there a cheap fix for damaged internal plug threads if they truly are damaged and won't seal? Otherwise, this would be a very costly and time consuming repair to replace the entire housing unit where the plug and output pipe goes.

Thanks in advance for your help,

Rob

 

[jongig]

Sorry about that, I can't imagine how you'd fix bad threads without drilling and tapping out for the next size up.

I just bought a gas heater and noticed that the unit would run without water going through it because the pressure switch gets activated by pressure in the system. With it connected correctly as it is I guess this won't happen but I was surprised that it doesn't have a flow switch. If yours had a flow switch you wouldn't have had the mistake ruin the unit.

 

[rdelisa]

Thanks for the reply. I just went ahead and ordered the parts. It's possible only the part itself has stripped threads. I might just wrap some teflon tape around it and see if it will tighten and seal up.

It's also possible it had nothing to do with the valve being closed. The plastic threads look very corroded and worn.

 

[CJadamec]

Don't use Teflon tape on the plug. It has an o-ring seal and the Teflon will not help anything seal.

 

[rdelisa]

As you can tell, I don't know a dang thing about plumbing. The inside thread looks a little warn, but it seems to me it should still hold a plug.
The gasket blew off completely. Could that be what the problem is?

It just seems there should be something I can do to insure that the new gasket and plug are secured tightly when I replace them. Replacing the entire header looks very tedious and expensive. Tapping to a bigger sized plug would require that I can actually find a bigger sized plug. I would like to go the easier route if there is one!

 

[CJadamec]

You blew the plug out with water pressure there is a good chance something is broken. Best thing to do now is get the replacement plug and gasket and see if it holds water first. Cross your fingers you might be lucky and that will fix it.

 

[rdelisa]

My other question is whether or not I need the governor and spring that is pictured to the left. I don't see any indication that I ever had this. I scoured the floor and shelves of the pump room to see if it landed somewhere, but no signs of it. I ordered the spring and governor anyway, just in case.

Either way, I should have the new plug in a couple of days and I will see if I can get it to plug securely and hold water.
If not, then I might just have to unscrew the panel and see if replacing the header part is a job I can handle myself. It's going to be a hot summer without the pool to enjoy.

 

[CJadamec]

If for some reason you can't get the heater to hold water you can always plumb a bypass around it so you can still use your pool.

Not sure about the spring generally if its in the parts manual it should be in the unit. Unless it only goes on some units or you don't have the right parts sheet.

 

[rdelisa]

That's an interesting alternative. Thanks. Meanwhile, I read about the unitherm governor and apparently it keeps the heat of the unit in an acceptable range. From what I read it sounds like I should have it and use it. Just odd that I cannot find the old one or maybe it was never installed.

Having looked at the parts a little more closely. I think I might be able to handle a DIY replacement of the entire header which costs $179.00 on Amazon. This comes with gaskets. Do I need a particular type of grease or silicone lubricant for these?
Thanks again,
Rob

 

[ajw22]

Sorry about that, I can't imagine how you'd fix bad threads without drilling and tapping out for the next size up.

I just bought a gas heater and noticed that the unit would run without water going through it because the pressure switch gets activated by pressure in the system. With it connected correctly as it is I guess this won't happen but I was surprised that it doesn't have a flow switch. If yours had a flow switch you wouldn't have had the mistake ruin the unit.

Flow switch on your heater will prevent the heater from turning on but not prevent water from flowing through the heater core. The OP turning on his pump while his return valve was closed meant it pressurized the pipes between the pump and the closed valve, which included the heater, and the weakest link gave way. That happened to be in the heater.

 

[JamesW]

The pump can't generate enough pressure to cause the parts to blow out like that.

Did the heater fire up?

 

[ajw22]

RayPak RP2100 has a flow switch. Manual here http://www.royalswimmingpools.com/rp2100manual.pdf

Page 7 -

WATER PRESSURE SWITCH
A water pressure switch is provided in the heater to
shut off the burners in the event that water supply is
interrupted. It is very important to verify that the switch
electrically opens and shuts off the gas valve when
water flow to the heater is interrupted. Otherwise,
rapid and severe damage will likely occur to the
heater. (The water pressure switch should be checked
and adjusted for proper operation by a qualified service
person at the time of installation and periodically
checked thereafter. Refer to Pressure Switch
Adjustment on pg. 38 of this manual).


Actually, thinking about it, the heater flow switch likely did see some initial water flow to fire the heater while the return valve was closed. Although the flow should have been momentary as the pressure built in the line when the flow stopped.

 

[JamesW]

The heater doesn't have a flow switch, it has a pressure switch. The heater can't tell if there is any actual flow.

Notice that the manual says pressure switch and not flow switch.

 

[ajw22]

The heater doesn't have a flow switch, it has a pressure switch. The heater can't tell if there is any actual flow.

Notice that the manual says pressure switch and not flow switch.

Do all heaters have pressure switches and not flow switches or does it vary by manufacturer?

 

[JamesW]

Most have pressure switches. There are some commercial heaters that come with flow switches or you can retrofit a flow switch.

In my opinion, all heaters should have a flow switch. SWGs have a flow switch, so it's not like it's a big problem to have a flow switch on equipment.

 

[ajw22]

Most have pressure switches. There are some commercial heaters that come with flow switches or you can retrofit a flow switch.

In my opinion, all heaters should have a flow switch. SWGs have a flow switch, so it's not like it's a big problem to have a flow switch on equipment.

I never focused on the difference between a flow switch that a SWG has and a pressure switch that heaters have. I looked at the Pentair Mastertemp Heater manual and see it also has a pressure switch.

 

[rdelisa]

Flow switch on your heater will prevent the heater from turning on but not prevent water from flowing through the heater core. The OP turning on his pump while his return valve was closed meant it pressurized the pipes between the pump and the closed valve, which included the heater, and the weakest link gave way. That happened to be in the heater.

Your explanation seems logical and most likely. The gas to the heater was not yet turned on so it didn't have a chance to even fire up before the plug exploded. I also have an SWG between the heater and return valve so hopefully it didn't do any damage to that. From what I can see it is okay. The wear on the threads appear to be from gradual corrosion more than from a sudden jolt so it is probably likely that it was only a matter of time before it became problematic. Shutting the valve just happened to be the final straw to set it off. The pool chemistry of my pool was very poorly maintained by the previous owner and pool guy. I educated myself a few years ago here on TFP and now do the BBB method, but years later I am still paying for some of the poor chemistry. I also had the heat exchanger replaced to the tune of $750 about years ago. It seems to me more and more that I will probably have to replace the header. I am going to remove the panel and see if this is something I feel comfortable doing before I pay $179.00 for the part. At what point do I judge this entire unit is getting old and make the huge investment into brand new?

My stupid mistakes, though costly, always teaches me new things about the pool and equipment I inherited with this house purchase several years ago.

 

[ajw22]

I also had the heat exchanger replaced to the tune of $750 about years ago. It seems to me more and more that I will probably have to replace the header. I am going to remove the panel and see if this is something I feel comfortable doing before I pay $179.00 for the part. At what point do I judge this entire unit is getting old and make the huge investment into brand new?

My guideline is if the repair approaches 50% of replacement cost I buy a new unit. I would have bought a new heater instead of spending $750 on the heat exchanger.

Do you know how old the heater is? You need to assess the internal condition and what parts you have recently repaired to decide if it makes sense to keep investing in it. Owning pools and heaters for over 20 years I have seen many ways heaters fail. Insulation gets worn until internals melt. Electronic board fry. Pool heaters live in a very inhospitable environment.

 

[rdelisa]

I think an installed replacement for this unit would be $2400. Had I spent that on a new heater I'd be 9 years into it already. The $750 was probably worth it as the heater has been maintenance free up to this point. So, it hasn't been too much of a money pit over the course of that time. If I was going to get something new I might invest in one of those ultra energy efficient units.

 

[ajw22]

I think an installed replacement for this unit would be $2400. Had I spent that on a new heater I'd be 9 years into it already. The $750 was probably worth it as the heater has been maintenance free up to this point. So, it hasn't been too much of a money pit over the course of that time. If I was going to get something new I might invest in one of those ultra energy efficient units.

I didn't realize the $750 repair was 9 years ago. I have yet to get 9 years out of any heater I have owned.