Aquastar 125VP Turns on but not up

[Grinchy]

This is sort of an unorthodox installation. The heater was modified more than 8 years ago by following the suggestions from Controlled Energy Corp. (the former owners/distributors in the US) to use the heater as a boiler for a hydronic radiant floor heating system (one zone). Several years ago I had to replace a diaphragm because it wasn't turning on, at all. The current problem is not as clear-cut.

My ex failed to pay her gas bill, over the summer, and it was shut off at least three separate times. After the third time having it turned back on, these symptoms began. The heater has not come up to "full blast" when it turns on. It still turns on when there's a demand, but not enough to heat the floor, anymore. It runs in this 'half-way' mode for long periods of time. The system is also used for domestic hot water. It's been working just fine for the last 8+ years. Of course, now that it's winter, suddenly I have to fix it.

Anyone have an idea of what to look for? There's a knob, on the front of this unit that is supposed to modify the intensity of the flame. It has no apparent effect, anymore, though. Also, this is the older version of the Aquastar - it has a pilot light instead of the piezo start.

[hvacdrd]

These tankless units have gas valves that modulate. A common problem is scale buildup in the heat exchanger causing restricted flow. Here is a tune up sheet for your model that should get you started with some basic checks & servicing. As far as the gas being turned on & off, check the gas pressure to rull that out first.

One thing to note is that these tankless units require regular maintenance, they are not like a regular water heater that you install & forget about.

[Grinchy]

OK.... let me see if I can explain a little better, then you can tell me if I'm just being dense, or if I've got some other problem. The Aquastar does fire up when the recirc pump kicks in. It does not, however, fire up to the degree it used to. The flame(s) used to be about an inch and a quarter high (guess-timate). The max they get to, now, is about 1/3 inch. PLUS.... the flames on the burner are all a nice blue color. I've got 3 other appliances fed from the same gas main, and they're all getting gas and burning (well.... except the dryer, but that's a valve problem I've already got info to fix), so I don't think it's a matter of gas pressure.

Also, it IS firing up, and if allowed to work just for the domestic hot water (storage tank in the form of an (unwired) 80 gallon electric water heater), it gets plenty hot... So I don't think it's a problem with the heat exchanger, either.

I've had to do some maitenance on it, over the years, so your point about it needing that is well taken. I think it's something to do with the gas valve. I don't know if something got caught up in it the last time the gas service was turned back on. It didn't start acting up until then (so I'm told).

Thanks for letting me ramble on.

 

[hvacdrd]

[user=18142]Grinchy[/user] wrote:

This is sort of an unorthodox installation. The heater was modified more than 8 years ago by following the suggestions from Controlled Energy Corp. (the former owners/distributors in the US) to use the heater as a boiler for a hydronic radiant floor heating system (one zone).

Do you have a copy of this modification so I can see what changes were made? I couldn't locate a copy. 

To confirm your last post, it works fine when used for the domestic hot water? Flames look "normal" size and heat output is ok?

Follow the link I posted for gas pressure, it also contains information on testing the manifold pressure (output). If it passes this test we can rule out the gas issue.

[Grinchy]

Here's the instructions. I'm really surprised I was able to locate them in such a short amount of time. Sorry about the splotches - they're rust stains! I initially did this modification in 1998. In 2002 or 2003 I had a problem and called Controlled Energy Corp. They sent me the replacement parts already modified, so that's what's in there now.

While it DOES heat up the domestic water, it does NOT produce "normal" flames. The Aquastar is part of the initial loop. The recirc pump kicks on whenever the storage tank water temp drops below it's pre-set limit. This can happen if either domestic hot water use OR the heating system draws enough hot water from the tank to lower its temp. It cycles water through the Aquastar and back to the tank. There's a separate pump to move heated water through the floor tubing.

I hope I've given you enough detail, but if not, I'm happy to give more. I don't have a manometer to check gas pressure.

[hvacdrd]

The unit is supplied with an external regulator on the gas line. It is possible this has jammed when the gas was turned on too quickly. Try this...

[align=left]To unjam a regulator, remove the nickel size screw[/align]

[align=left]plug on the front. Inside you will see another large[/align]

[align=left]screw. Draw a line down the threads to mark the[/align]

[align=left]location of the screw. Remove the screw and push[/align]

[align=left]on the bottom of the hole with the eraser side of a[/align]

[align=left]pencil or similar object. This will release the diaphragm.[/align]

[align=left]Reinsert the screw and screw it down[/align]

[align=left]to the end of the mark you made.[/align]

[Guest ahammer48]

Hello

 

Since the problems started after the gas was turned off/on, I woulsd start there. Call the gas company and have them check the gas pressure coming thru their meter to the house. Most utilites will do this for free. For a small charge most will check the pressure down at the furnace. Since its winter, their regulator at the meter may not be opening fully. 

If all checks out, then your problem is in the unit. Gas lines can be very dirty inside. Turning the gas on/off like that may have brought alot of this dirt down your supply line and into the house. You may have dirt blocking the inlet screen of the units gas valve or it may not be allowing the valve to open fully.

I don't like to tell laymen to do there own gas work so I would call a company in to check the manifold (after the gas valve) pressure to the burner and compare it to OEM specs.

Hope this helps:)

 

[Grinchy]

Thanks! The dirt in the inlet is "kind-of" what I was thinking it was. I'm not exactly what I would call a "layman", although I readily admit I don't have the knowledge level you "pros" do. I did the initial installation of this unit by myself and made the modifications with only a piece of paper to guide me. I plumbed in all the gas piping for this house. I've also undertaken the repair of the gas valve on my dryer with guidance from this forum... with great success, I might add!

If you don't feel comfortable posting directions/instructions on this forum, perhaps you'd be more likely to advise me by regular email? I tried un-sticking the diaphragm on the inlet regulator (per the instructions, above) and it didn't change things a whole lot, although it has seemed to make a bit of a difference. I'm pretty sure this is a dirt-related issue. I'd just like to disassemble things once, rather than a whole bunch of times, if you know what I mean!

Thanks again!

[Rrey199]

I don't think the problem is with the gas supply, but I could be wrong. I do a lot of the Bosch w/h's and a few of the new aquastars.

I think you aren't going into high fire because it isn't sensing enough water flow. Find the water flow sensor, remove and clean the screen. If it's not dirty, look for other reasons for insufficient flow or a bad flow sensor.

Hope this helps:dude:

[Grinchy]

Well! Right you were! It WAS a problem with water flow. The diaphragm in that part of the sensing circuit was hard as a rock AND there was calcification around the pushrod that actuates the gas valve. I found this out quite by accident, though. Because it eventually shut completely down. Having replaced that diaphragm once before, I was quickly able to recognize it when it shut completely down. The time before this, though, it hadn't gone to a lower setting like it did this time. Weird. The previous diaphragm was wasted.... holes in it and thin. This time it was hard and stiff.

[Powerws]

[user=18142]Grinchy[/user] wrote:

Well! Right you were! It WAS a problem with water flow. The diaphragm in that part of the sensing circuit was hard as a rock AND there was calcification around the pushrod that actuates the gas valve. I found this out quite by accident, though. Because it eventually shut completely down. Having replaced that diaphragm once before, I was quickly able to recognize it when it shut completely down. The time before this, though, it hadn't gone to a lower setting like it did this time. Weird. The previous diaphragm was wasted.... holes in it and thin. This time it was hard and stiff.

It is a problem with water flow! But you should never do the modification to the water piston. This is a band aid fix to your problem. The real problem is the diaphram located in the brass clamshell. The reason you don't want to drill out the piston is that due to thermal expansion it will pre-maturally fire thus sending the unit off in high limit. I have serviced these units for 35 year when we originally imported them from france. I will be able to help you, but you should replace the water piston. 

[Powerws]

[user=11813]Rrey199[/user] wrote:

I don't think the problem is with the gas supply, but I could be wrong. I do a lot of the Bosch w/h's and a few of the new aquastars.

I think you aren't going into high fire because it isn't sensing enough water flow. Find the water flow sensor, remove and clean the screen. If it's not dirty, look for other reasons for insufficient flow or a bad flow sensor.

Hope this helps:dude:

yes the screen was in the original units and should be checked. The newer units had a flow restricter in the and should be removed, but only the inside. Retain the white outer part of the flow restricter and re install.

[Powerws]

[user=18142]Grinchy[/user] wrote: 

There's a knob, on the front of this unit that is supposed to modify the intensity of the flame. It has no apparent effect, anymore, though. Also, this is the older version of the Aquastar - it has a pilot light instead of the piezo start.

This is because the thermostat is bad. Once you replace the water piston and diaphram, you will probably have a problem with the unit going out on high limit, because the either based jelly in the capillary tube has lost it's properties, thus allowing the unit to overheat.