Please help me repair this panel heater.. - Page 1
Forum section: electronics / repair

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 08, 2017, 03:35:13 am
content: Hi, we have a panel heater that just gave up suddenly. We did not use it for the past ten months and then when we used it quite often now, it just stopped heating suddenly.Basically when I flip the main switch, the first relay inside the timer module clicks/turns on, but then the second relay on another board, which turns on the heater element does not turn on.I followed the first rule in repairing stuff of course (thou shall check voltages).First I checked the line voltage, and the 230v was coming in. Then when I checked the output from the timer module, I also read 230v. But when I checked the output of the second relay board, it gave nothing. I also checked the 24VDC that should power the relay but it was only giving 14V.I disconnected the second board from the panel heater itself and then I made a schematic (image below). I noticed that there was one electrolytic cap and so I thought it might have died because of the heat. I measured that but it was still in spec.But there was this 220nf (x class cap I think) too. I checked its capacitance and it was only measuring 150nf. Should I replace this thing?..or does it matter if I will not?

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2017, 03:45:10 am
content: If I'm not mistaken that's a capacitive divider PSU for the relay winding. Check the 47uF isn't cooked and the relay winding is OK.You can probably power the relay from a bench PSU just to check it's functionality and contact resistance is OK.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 08, 2017, 04:06:06 am
content: Yeah, the 47u electrolytic cap isn't cooked and I also powered the relay from a power supply and checked its contact's continuity and it was ok.Thanks.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 08, 2017, 04:14:56 am
content: But why do I measure only 14vdc on the relay coil when it is supposed to have 24v?

author: Armadillo
author_rank: Super Contributor
timestamp: July 08, 2017, 07:23:02 am
content: Hi,You should check the resistor. Power off and measure the Ohms.Also, the circuit is suppose to be full wave rectified, one diode may be open resulting in drop of dc voltage, put meter to diode mode and check both diodes.Your diagram don't appear to be complete. The neutral should be return to the AC-neutral source is it?

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 08, 2017, 08:28:45 am
content: Hi, the resistor in parallel with the x-class cap has already been checked it and it was 47k, which was also said by its colour code. I also checked the two diodes and it had a typical diode drop voltage (around 0.6V) which meant it was fine.For the schematic diagram, its just a crude simplified version so I can give you guys an idea.Thanks.

author: mikerj
author_rank: Super Contributor
timestamp: July 08, 2017, 08:42:01 am
content: Quote from: bjcuizon on July 08, 2017, 03:35:13 amX class capacitors do degrade over time and lose capacitance, it's quite possible this may be affecting the circuit. One question, what plugs into the small two pin connector?

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 08, 2017, 08:58:24 am
content: Good question, I don't really know...but I think it's some kind of thermocouple. I measured the resistance between the two pins that go into that connector and I got 0 ohms. Is that normal for a thermocouple? (if it's indeed a thermocouple/sensor)

author: Armadillo
author_rank: Super Contributor
timestamp: July 08, 2017, 09:12:47 am
content: Has the resistor been changed before. Is it original?The relay needs at least35mA16mA.Its way on the high side.

author: jdraughn
author_rank: Regular Contributor
timestamp: July 08, 2017, 09:14:33 am
content: I can't help but wonder if the second relay is bring down the voltage to 14v because it's going out and shorting the 24v.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 08, 2017, 09:32:28 am
content: Quote from: Armadillo on July 08, 2017, 09:12:47 amAll the components are the original ones. They have not been changed or altered.Thanks.

author: Armadillo
author_rank: Super Contributor
timestamp: July 08, 2017, 09:39:39 am
content: Quote from: bjcuizon on July 08, 2017, 09:32:28 amWell, then I think as the components became seasoned [mechanical relay], previous bare bare bare minimum just became not enough.Cursory calculation deduced that the resistor is way high. Anyone here has a different opinion?What brand is this design or circuit?Edit: Any dry joints developed?Edit: Datasheet of Relay say minimum pick up voltage is 80% = 19v. So if you measure 14V, its not enough.

author: Armadillo
author_rank: Super Contributor
timestamp: July 08, 2017, 10:43:15 am
content: Quote from: bjcuizon on July 08, 2017, 03:35:13 amYeap, you need to change this Cap, voltage divider which is in parallel with the rather high resistance. miss it out initially.This one is responsible to give it the kick to contact.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 08, 2017, 04:10:07 pm
content: Yeah, 14v is really not enough to turn the relay on. By the way, no dry joints were develped either.And yeah...I should look for another cap. Are aliexpress ones good enough?

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 08, 2017, 04:21:08 pm
content: The weird thing was that we had two of these panel heaters at home. We just started using them both because our heatpump died...but now, they're both dead too with the same problem!?

author: Armadillo
author_rank: Super Contributor
timestamp: July 08, 2017, 04:24:13 pm
content: Why don't you try ebay;http://www.ebay.com/itm/10pcs-Lot-CBB-Polypropylene-film-capacitor-10nf-22nF-47nF-100nF-220nF-1uF-etc-/222484178631?var=&hash=item33cd1726c7:m:m_zd8A49wxkVNVSQulDvqqQPolypropylene type should do it. 220nf, the bigger the voltage, the bigger the footprint.

author: tautech
author_rank: Super Contributor
timestamp: July 08, 2017, 04:30:51 pm
content: Quote from: bjcuizon on July 08, 2017, 04:10:07 pmPop along to Jaycar in a few hours for RG-5238.X2 220nF ~$1.50

author: Armadillo
author_rank: Super Contributor
timestamp: July 08, 2017, 04:35:42 pm
content: Quote from: bjcuizon on July 08, 2017, 04:21:08 pmHeat is the killer for that "X" thing.The replacement caps, don't go below 400V.

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 08, 2017, 06:00:41 pm
content: Quote from: tautech on July 08, 2017, 04:30:51 pmAlright, I'll be in jaycar soon. Thanks

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 10, 2017, 07:45:00 am
content: Here's an update of the repair:Every time I go to a local electronics shop, I always check if there are some parts in my junk bin...And fortunately, there was just one cap with the same rating (X2 220nf @ 275V) which I pulled out from an old, junked Sony CRT TV I rescued from the roadside. This did not have the same footprint for the heater's circuit board and so I just bodged it up. (Some pics below.) I tucked all the things in neatly...And finally, the heater came back to life! - But only one heater though (cause I only had one salvaged cap).

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 10, 2017, 07:47:17 am
content: Thanks guys for all your advice and assistance!It is very much appreciated.Now we can enjoy the heat during this winter.

author: tautech
author_rank: Super Contributor
timestamp: July 10, 2017, 07:54:01 am
content: Quote from: bjcuizon on July 08, 2017, 06:00:41 pmSo you went through your junk pile instead.All that's missing to close off this thread is the brand and model # of the heater, you know it could really help someone else out.

author: Armadillo
author_rank: Super Contributor
timestamp: July 10, 2017, 08:00:23 am
content: ehm!, that could be a good way to remove that heat [surface mount it on the panel].

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 10, 2017, 08:06:52 am
content: Quote from: tautech on July 10, 2017, 07:54:01 amOh...yeah, good tip right there!The panel heater is anARLEC PEH209T Series 2...my dad bought it from the local bunnings warehouse

author: bjcuizon
author_rank: Frequent Contributor
timestamp: July 10, 2017, 08:09:55 am
content: Quote from: Armadillo on July 10, 2017, 08:00:23 amWell, yeah, I did that because that was the only space I could think of... Anyway, the more you go higher (the more you go outside the edges), the less heat it gives.