Hayward H250 Heater. Starts by jumping across TH on gas valve.

cschnurr

Silver Supporter
LifeTime Supporter
Sep 21, 2007
94
Guelph, Ontario, Canada
We had our pool installed 16 yrs ago with a Hayward H250 heater (millivolt system). We actually only use it 2-3 times a year and each time is a struggle.
At the beginning of the year it takes about 5 minutes of holding the gas valve on 'PILOT' to keep the pilot light from extinguishing,.

Whenever I do turn the heater ON, its seems a struggle. Tonight I approached it systematically. I followed the troubleshooting guide in the manual. Pool pump ON, Pilot light lit, gas valve ON, thermostat set higher than pool water. When I jumper across the TH terminals on the gas valve, the burner lights. When I remove the jumper wire, the burner STAYS LIT. My understanding is that jumping across the TH terminals on the gas valve jumps across all components. The troubleshooting continues to determine which of the components is defective by jumping across each component until the burner stays lit.
My burner stays lit without jumpers, it just didn't start until I jumpered the all the components.

Given the rare times we use the heater, I have no problem starting the heater every time this way, but if I did want it fixed where would I start? Is this a safety concern?

Thanks,
Carl
 
Last edited:

swamprat69

Well-known member
Mar 30, 2019
601
Las Vegas, NV
Not quite understanding what you mean by "jumper across the TH terminals"? The three terminals on a Robertshaw millivolt gas valve are labeled TH - TH/TP - TP and on a Honeywell millivolt gas valve are labeled TH - TH/PP - PP. TP or PP are common from the thermopile/powerpile directly to the gas valve. TH/PP or TH/TP are the other lead from the thermopile/powerpile which then goes through all of your safeties and operating controls back to TH to supply voltage to your gas valve to operate. If you are jumping from TH to TH/PP or TH/TP and the burners then stay lit, it would seem to indicate that the problem is not with an individual safety or operating control but rather with marginal minimum voltage ( in DC millivolts ) needed to operate the gas valve. This can be due to an old/weak thermopile/powerpile or excessive resistance ( due to dirt/corrosion of contacts or poor wiring connections) in the circuit (safeties and operating controls ) from TH/TP or TH/PP to TH. This guide along with a multimeter should help you isolate the problem https://gdainfo.com/Resource1049853HJDUFOS023X/Touble Shooting/Robertshaw Millivolt Tests.pdf You can see a general millivolt wiring diagram on page 15 of this manual https://www.hayward-pool.com/assets/documents/pools/pdf/manuals/h-series-millivolt-owners-manual.pdf
 

swamprat69

Well-known member
Mar 30, 2019
601
Las Vegas, NV
Forgot to mention that thermopile/powerpile output can also be effected negatively (reduced) by a weak pilot flame due to a dirty pilot orifice or low gas pressure. Also (rarely) incorrect positioning of the thermopile/powerpile in the pilot flame as the voltage is created by a temperature differential between the hot junction and the cold junction.
 

cschnurr

Silver Supporter
LifeTime Supporter
Sep 21, 2007
94
Guelph, Ontario, Canada
Thanks swamprat69. Sorry for the slow reply, I was out of town for a couple weeks.
'Jumper across the TH terminals' is the description given in the troubleshooting flowchart on p36 of the manual you attached. I interpreted this to mean TH to TH/PP.

Its getting time to close the pool. I'll wait for a warm day to troubleshoot, or just close it and troubleshoot next spring.
 
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