Pump question, Grundfos 15-58


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Old 02-01-15, 07:01 AM
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Pump question, Grundfos 15-58

For starters I have Lochinvar WHN055 boiler with one zone split with two zone valves and a Squire 40 gallon indirect set for priority. When it was installed the tech put the boiler pump (15-58) to speed 3, upon further reading of the manual and outside input I see it should be on speed 1. So I've used speed 1 for all but the first few days of this, about a month since install.

Everything has been running just fine until yesterday, after two back to back showers the boiler did its tank recovery like normal then when satisfied it switched back over to heating and nothing happened besides the boiler temp shot up to 200* and triggered a Lockout, MRHL and ARHL.

After things cooled I reset it and it started but the 15-58 didnt turnover and temps started to climb through the 140's to the 170's so I flipped it to speed 2. After setting it on speed 2 the boiler temps fell back to normal temps and carried on the rest of the day. Is it possible all of a sudden speed 1 doesn't have the gumption to feed the boiler?

Could a pump fail in one speed only?
 
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Old 02-01-15, 10:00 AM
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Hi CT,

I don't quite understand your description.

Are you saying that you have one pump with two zone valves for the central heating, and a SEPARATE pump for the indirect?

OR, is the indirect on a zone valve also?

It may be possible for the pump to fail on one speed, though I've never seen that. I'm guessing that the selector switch could possibly crap out.

It's also possible that the pump is 'sticky'... and speed 1 doesn't have enough OOMPH to get it going.

Does it work on speed 1 when you switch it back again?

I don't think speed 1 is correct either... not sure why the manual led you to believe that (but I haven't looked at it yet) ... highly likely that speed 3 is too high... put it on Goldilocks porridge speed... just right... and I think you'll be fine.
 
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Old 02-01-15, 06:32 PM
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http://www.lochinvar.com/_linefiles/WH-I-O-Rev%20R.pdf


See page 36

I have the 15-58 as the boiler pump, Alpha as a supply pump which pumps into two zone valves. The indirect has its own Alpha and it's set to priority. When the indirect fires the boiler pump stops, once the indirect is satisfied the boiler pumps restarts...there is the problem, speed 1 all of a sudden isn't enough to get the thing going.

Speed 1 has satisfied everything since day one, why all of a sudden is it Locking out? Yes speed 2 works, but is it necessary to pump that much? Once things get going yes I can switch to speed 1 and it works. It even works when it just cycles heat on/off...only locks out when it comes off of firing the indirect.

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Last edited by CT-Homebody; 02-01-15 at 08:16 PM.
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Old 02-01-15, 08:08 PM
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You need to correct your boiler link.
 
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Old 02-01-15, 08:18 PM
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Thanks...corrected - I think.
 
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Old 02-02-15, 07:52 AM
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CT, haven't we discussed that pump previously? I thought you were running that on medium?
 
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Old 02-02-15, 09:23 AM
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http://www.doityourself.com/forum/bo...questions.html. See post #6

You might not see much delta T difference changing the speed of the boiler pump, but you do want to maintain the proper minimum flow through the boiler with that... I doubt that it needs to be on HIGH, only the '155' model calls for High speed... The 55 and 85 models call for LOW, the 110 for medium.
 
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Old 02-02-15, 10:49 AM
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Ahhh, yes, now I remember! So many boilers, so few brain cells.

works when it just cycles heat on/off...only locks out when it comes off of firing the indirect.
That there is the odd part.

If the pump were 'sticky', it should have a problem all the time...

My thinking cap is on...........................
 
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Old 02-02-15, 12:38 PM
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Understood, can only imagine the setups you try to analyze over a PC.
 
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Old 02-08-15, 08:48 AM
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NJT, I've got the senior tech coming out this week to troubleshoot the pump. What should I expect?

Would I be out of bounds if I offer to pay for a 0-10v variable speed pump, one that the Lochinvar can maximize its efficiency?
 
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Old 02-08-15, 10:10 AM
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Would I be out of bounds if I offer to pay for a 0-10v variable speed pump, one that the Lochinvar can maximize its efficiency?
I don't know 'out of bounds', but it seems like a lot of expense for little gain.

Where is this tech from? Grundfos? Lochinvar? Installing company?
 
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Old 02-08-15, 10:32 AM
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Installing company, hopefully they have an answer without getting reps involved.
 
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Old 02-08-15, 10:52 AM
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Pretty sure they'll just cut their losses and install a new pump... without troubleshooting or analyzing. It's all about the profit margin these days.

Probably will tell you to run it on medium or high anyway, in spite of what the manual says!
 
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Old 02-18-15, 10:36 AM
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After a few tries to simulate my problem he agreed something is wrong with the pump, put on a new 15-58 and worked it a few times. Fixed.
 
 

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