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Plumbing

Should A "Cross Pipe" Connecting The CH Inlet & Outlet Pipes Be Left Open Or Closed?

Anonymous user 03/03/2024 - 3.26 PM

My new place has what seems like a fairly old boiler (Ferroli Modena 102). A few months back, when decorating we ended up kinking a radiator's pipe, meaning I had to shut the water, boiler etc off and get someone in to mend it... When shutting everything off I made sure to take note of the state that the various valves were in, one of which was a closed valve with a hand wheel, in the middle of a pipe that went from the central heating inlet and outlet pipes (from what I can tell at least), under the boiler. These pipes form a H shape under the boiler. When the lad who helped us sort the radiator left I went to check everything, and found that valve left open. I closed it figuring it didn't need leaving open. Is that correct? I've been having troubles with my hot water in general recently, with my showers reliably going back and forth between hot a cold... I'm wondering if this is playing a part, and am curious in general. Many thanks in advance!

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3 Answers

Heron Gas Services

Rating: 5 out of 5

Solihull

Hello, the set-up in question sounds like a by-pass. This is used to allow a minimum flow if all other paths are blocked and prevents overheating and damage to the boiler. The manual for your boiler states on page 10 paragraph 3 that if thermostatic radiator valves are fitted then a bypass must be fitted as far away from the boiler as possible. At least you have one but it's too near the boiler, making too small a circuit. if you open it fully then you will likely find it turns something like 3 and a half revolutions. Close it fully, then open it half way or less. eg. 1.5 turns or so. If this valve is open too much, then the water will take the easiest route and whiz round this small loop rather than going through the far away radiators. If it's closed too much then the boiler could overheat and, worst case, split its heat exchanger, ruin the boiler and cause property damage. In short - leave it open a little bit. Thanks.

Answered12 December 2019

Browns Plumbing Services

Rating: 5 out of 5

Stafford

As heron gas services above as stated this is a bypass. Your hot water problem is a separate issue.

Answered18 December 2019

Anonymous user

The cross pipe as you call it is a bypass you can put a automatic bypass valve on the cross piece which will alleviate any circulation issues, as for the hot water that’s not affected by the bypass, if it’s intermittent it could be the plate hex is sludged up , but without seeing it that’s an educated guess

Answered7 December 2022